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Organic agriculture uses contracts and networks to overcome its asset‐specificity problems and to ensure compliance with its standards and norms, including environmental conservation. This study analyzed the effects of certified‐organic production on supplier failures and the potential income effects of these failures on vegetable and macadamia producers in Kenya. Using survey data and propensity score matching, the study found that organic macadamia production reduces delivery failures because its asset specificity necessitates a dedicated transport system. It also found that organic vegetable production reduces quality failures because organic consumers are often less concerned about the physical quality of organic produce. However, despite these advantages, cases of supplier failures are still rampant among both organic and nonorganic producers of macadamia and vegetables. The potential income effects of these supplier failures, especially quantity and delivery failures in macadamia, raise concerns. These problems necessitate policy interventions, especially with respect to establishing and strengthening producer organizations, which are often very instrumental in overcoming quality, quantity, and delivery failures.

Background and aim: Plant-available silicon (Si) is limited in strongly weathered tropical soils. The aim of the study was to evaluate Si fertilisation as a strategy to improve phosphorus (P) fertiliser use efficiency on acidic tropical soil, and the potential of using glacial rock flour (GRF) as a source of Si. Methods: Wheat (Triticum aestivum cv. Benchmark) plants were grown in a pot experiment in an oxisol soil. Si was supplied as either GRF or silicic acid (SiA) at low and sufficient P levels. A soil incubation study and a compartmented pot experiment were also included to assess how soil chemistry was affected by the Si sources both with and without plants. Results: Addition of Si as either GRF or SiA doubled shoot biomass under limited P conditions, and the combined treatment quadrupled it. SiA led to increased P uptake under P-limited conditions, while GRF did not. Soil incubation showed that only SiA increased P availability in bulk soil. The addition of SiA in combination with GRF led to increased root exudation of citric and oxalic acid. Localised weathering of GRF resulted in higher rhizosphere pH, but did not affect rhizosphere P availability or organic acid exudation. Conclusion: Si released from GRF can rejuvenate strongly weathered agricultural soils, improve stress tolerance in plants and ultimately increase yields but GRF does not improve P availability on acidic soils.

Rock flour (RF) is a fine‐grained material produced naturally by glacial movement and resulting bedrock abrasion. In Greenland fluvial transported RF from the inland ice sheet sediments in riverbeds and marine outflows. This fine‐sized RF (50% < 9.8 µm) has a high reactivity and may therefore potentially be used to rejuvenate nutrient poor soils and provide nutrients to plants. The aim of this study was to evaluate the ability of a RF from Greenland to supply P, K, Mg, and S to plants. A double‐pot system was used, in which ryegrass (Lolium perenne L.) could take up nutrients from both a hydroponic solution and a soil‐compartment with or without RF amendment; a soil mixture or pure sand was used in the soil‐compartment to estimate RF‐soil interaction effects. Omission of single nutrients from the hydroponic solution allowed assessment of which nutrients the RF in the soil‐compartment was able to supply. Ryegrass biomass was harvested four times during 62 days. We found that RF could supply K continuously to plants grown in soil or sand, but insufficient to fully circumvent K deficiency. During 62 days 5.8% and 4.3% of the applied K from RF was accumulated in the aboveground plant tissue in soil and sand, respectively. Mg was supplied from RF to plants in sand, but no significant effects were observed in soil, possibly due to background soil Mg availability. The amounts of P and S supplied to plants were insignificant. These results indicate the potential of Greenland RF to act as a slow release K and Mg fertilizer.

A continuous rise in the global demand for palm oil has resulted in the large‐scale expansion of oil palm plantations and generated environmental controversy. Efforts to increase the sustainability of oil palm cultivation include the recycling of oil mill and pruning residues in the field, but this may increase soil methane (CH4) emissions. This study reports the results of yearlong field‐based measurements of soil nitrous oxide (N2O) and CH4 emissions from commercial plantations in North Sumatra, Indonesia. One experiment investigated the effects of soil‐water saturation on N2O and CH4 emissions from inorganic fertilizers and organic amendments by simulating 25 mm rainfall per day for 21 days. Three additional experiments focused on emissions from (a) inorganic fertilizer (urea), (b) combination of enriched mulch with urea and (c) organic amendments (empty fruit bunches, enriched mulch and pruned oil palm fronds) applied in different doses and spatial layouts (placed in inter‐row zones, piles, patches or bands) for a full year. The higher dose of urea led to a significantly higher N2O emissions with the emission factors ranging from 2.4% to 2.7% in the long‐term experiment, which is considerably higher than the IPCC standard of 1%. Organic amendments were a significant source of both N2O and CH4 emissions, but N2O emissions from organic amendments were 66%–86% lower than those from inorganic fertilizers. Organic amendments applied in piles emitted 63% and 71% more N2O and CH4, respectively, than when spread out. With twice the dose of organic amendments, cumulative emissions were up to three times greater. The (simulated) rainwater experiment showed that the increase in precipitation led to a significant increase in N2O emissions significantly, suggesting that the time of fertilization is a critical management option for reducing emissions. The results from this study could therefore help guide residue and nutrient management practices to reduce emissions while ensuring better nutrient recycling for sustainable oil palm production systems.

Upland agricultural systems are rapidly transitioning from traditional shifting cultivation to more commercialized agriculture, i.e. annual cash crop cultivation – a trend widely observed in the uplands of Northern Lao P.D.R. and with consequences to household livelihood strategies at the village-level. The main objective of this study was to compare village and household socioeconomic standings of two upland agricultural systems varying in degree of commercialization in Northern Lao P.D.R.: i) Navene, a village with a relatively recent introduction (2010) of the cash crop, fodder maize, where it is cultivated extensively with no added external inputs or mechanization and ii) Ko Ngiaw, where cultivation was introduced in 2004 and fodder maize is now successively cultivated on ploughed upland fields with herbicide application. Participatory mapping, household surveys (during planting and harvesting), farmer activity books and ranking exercises were conducted to collect data on village and household resources, crop production (upland rice, paddy rice and maize), labour productivity (maize) and general perspectives on commercial agriculture. We show both infrastructure development and accessibility (market access, support and services) are important underlying drivers of the commercialization of agriculture in upland areas. This leads to a transition of upland livelihoods towards market–orientation, with implications to household demographics, socioeconomic standings and income portfolios. Results capture how market integration progressively decouples livelihood strategies from the ‘land’, exposing households to market volatilizations, indebtedness and socio-cultural losses. Food security is no longer perceived from a ‘producer’s’ standpoint but from a ‘consumer’s’ as commercialized upland households are more dependent on markets for their food supply. We conclude that proper services, support and access to i.e. markets or non-farm employment in conjunction with infrastructure development should be prioritized if upland households are to transition towards commercialized agriculture equally and with minimal risk to their livelihood security.

The rapid increase in global production of and demand for palm oil has resulted in large-scale expansion of oil palm monoculture in the world's tropical regions, particularly in Indonesia. This expansion has led to the conversion of carbon-rich land-use types to oil palm plantations with a range of negative environmental impacts, including loss of carbon from aboveground biomass and soil. Sequestration of soil organic carbon (SOC) in existing oil palm plantations is an important strategy to limit carbon losses. The aim of this study was to investigate SOC stocks of oil palm plantations under different management systems. Soil samples were collected from three different management systems (best management practices (BMP), current management practices typical of large plantations (CMP) and smallholder management practices (SHMP)) in north Sumatra, Indonesia. Plantations were divided into four management zones that were sampled separately with four replicate profiles in the weeded circle, frond stack, harvesting path and interrow zones. All the soil samples were collected from five (0–5, 5–15, 15–30, 30–50 and 50–70 cm) soil depths. Soil samples were analysed for concentration of SOC, soil texture, soil bulk density and pH. Calculations of SOC stocks in the soils were undertaken according to the fixed-depth and equivalent soil mass approaches. Results showed that SOC stocks of plantations under BMP (68 t ha−1) were 31% and 18% higher than under CMP (57 t ha−1) and SHMP (46 t ha−1) respectively. In the BMP system, soils under the interrow zone that received enriched mulch and frond stack positions stored significantly more SOC than the harvesting path of the BMP system (77, 73 and 57 t ha−1 respectively). BMP also had a 33% higher fresh fruit bunch yield compared to the SHMP system. This study shows that residue incorporation or retention as a part of BMP could be an effective strategy for increasing SOC stocks of oil palm plantations and confirms that these management practices could improve yields from SHMP systems.

Water drainage is an important mitigation option for reducing CH4 (methane) emissions from residue-amended paddy soils. Several studies have indicated a long-term reduction in CH4 emissions, even after re-flooding, suggesting that the mechanism goes beyond creating temporary oxidized conditions in the soil. In this pot trial, the effects of different drainage patterns on straw-derived CH4 and CO2 (carbon dioxide) emissions were compared to identify the balance between straw-carbon CH4 and CO2 emissions influenced by soil aeration over different periods, including effects of drainage on emissions during re-flooding. The water treatments included were: continuous flooding [C] as the control and five drainage patterns (pre-planting drainage [P], early-season drainage [E], midseason drainage [M], pre-planting plus midseason drainage [PM], early-season-plus-midseason drainage [EM]). An equal amount of 13C-enriched rice straw was applied to all treatments to identify straw-derived 13C-gas emissions from soil carbon derived emissions. The highest fluxes of CH4 and δ13C-CH4 were recorded from the control treatment in the first week after straw application. The CH4 flux and δ13C-CH4 were reduced the most (0.1–0.8 μg CH4 g−1 soil day−1 and -13 to −34‰) in the pre-planting and pre-planting plus midseason drainage treatments at day one after transplanting. Total and straw-derived CH4 emissions were reduced by 69% and 78% in pre-planting drainage and 77% and 87% in pre-planting plus midseason drainage respectively, compared to control. The early-season, midseason, pre-planting plus midseason and early-season-plus-midseason drainage treatments resulted in higher total and straw-derived CO2 emissions compared to the control and pre-planting drainage treatments. The pre-planting and pre-planting plus midseason drainage treatments lowered the global warming potential by 47–53%, and early-season and early-season-plus-midseason drainage treatments reduced it by 24–31% compared to control. By using labelled crop residues, this experiment demonstrates a direct link between early drainage and reduced CH4 emissions from incorporated crop residues, eventually leading to a reduction in total global warming potential. It is suggested that accelerated decomposition of the residues during early season drainage prolonged the reduction in CH4 emissions. Therefore, it is important to introduce the early drainage as an effective measure to mitigate CH4 emissions from crop residues.

Rice production systems are an important source of agricultural greenhouse gas (GHG) emissions. Mitigation techniques, such as alternate wetting and drying, have been developed but have often not taken into consideration the constraints imposed by the practices and preferences of farmers. Since GHG mitigation benefits are not obvious at smallholder farm level, it is essential to design site-specific mitigation technologies with the participation of local stakeholders. The purpose of the present study was to adapt a participatory approach to designing and assessing mitigation practices for the dissemination of climate-friendly rice production systems. To improve the hybridization of scientific and local knowledge, a participatory five-step approach to prototyping was applied: (i) diagnosis based on a literature review and survey of stakeholders, (ii) design of mitigation practices based on laboratory trial and local knowledge (that of farmers, agricultural advisors and regional stakeholders), (iii) testing in growth chambers, (iv) testing in farmers' fields and (v) dissemination and assessment. The study was conducted in An Luong village, Red River Delta, northern Vietnam. In the study area, rice residue burning is restricted and farmers have to incorporate residue into the soil. Current water management practices, i.e. conventional continuous flooding and adopted midseason drainage, are not enough to reduce GHG emissions from added residues. Two new water management practices (pre-planting plus midseason drainage and early plus midseason drainage) were designed in participation with local stakeholders, and subsequently tested in the laboratory and in the field with the participation of local farmers. Future mitigation practices were assessed based on the yield, GHG emissions reduction and feedbacks of local stakeholders. Early plus midseason drainage proved to be an effective and feasible mitigation option for rice production in the area. Here we show that participation of local stakeholders in co-designing process help to identify the feasible GHG mitigation options, further it facilitates smallholder rice farmers to implement mitigation practices in their fields.

Debates on adaptation in rural Africa rarely consider how responses to climate variability vary by wealth group. This study examines differences across wealth groups based on principal component analysis and cluster analysis triangulated with participatory methods. Results indicate that perceptions of weather variability and extreme events are detected by most households regardless of wealth status. The most common responses—using drought-resistant crops and changing planting dates—are also similar across groups. However, there are significant differences in the type of adaptation options adopted by wealthier and poorer farmers: the former intensify agriculture through improved seed varieties, fertiliser and manure; the latter depend on craft activities, seasonal migration and support from relatives and neighbours. Overall, our findings suggest that measuring asset holdings could allow a differentiated approach to supporting adaptation across socio-economic groups in rural regions in Ethiopia and Africa more broadly.

Conversion of shifting cultivation to rubber (Hevea brasiliensis) plantations is one of the dominant land use changes in montane mainland areas of Southeast Asia, with the area of rubber expected to quadruple by 2050. However, the impacts of this transition on total ecosystem carbon stocks are poorly quantified. We undertook a chronosequence study to quantify changes in ecosystem carbon stocks following conversion from swidden agriculture to rubber plantations in Northern Laos. We measured above-ground biomass stocks and collected volume specific soil samples across rubber plantations established between 2 and 18 years prior to the study, and fallows used in a swidden system. The carbon stock in the upper 40 cm of the soil was almost 20% lower after 18 years of rubber than in the swidden system fallows, suggesting a SOC loss of 0.74 ± 0.2 Mg C ha−1 yr−1. Rates of biomass accumulation in fallows were 1.5 ± 0.12 Mg C ha−1 yr−1 and 1.9 ± 0.14 Mg C ha−1 yr−1 in rubber plantations. When comparing time-averaged carbon stocks of swidden systems to rubber plantations with 30 year rotation periods, the stocks of swidden systems with rotation times of 5 and 10 years were 19% and 13% lower respectively; the stock of swidden systems with a rotation time of ∼15 years was approximately equal to rubber; and the stock of swidden systems with a rotation time of 30 years was 11% higher than in rubber. Therefore, we conclude that the replacement of swidden agriculture with rubber leads to soil carbon losses, but the overall effects on ecosystem carbon stocks depend on the rotation intensity of the swidden system that is being replaced.

Flooded rice production is crucial to global food security, but there are associated environmental concerns. In particular, it is a significant source of methane (CH4) and nitrous oxide (N2O) emissions and a large consumer of water resources, while arsenic levels in the grain are a serious health concern. There is also a tendency to use more organic fertilisers to close nutrient cycles, posing a threat of even higher GHG emissions and grain arsenic levels. It has been shown that alternate wetting and drying (AWD) water management reduces both water use and GHG emissions, but success at maintaining yields varies. This study tested the effect of early AWD (e-AWD) versus continuous flooding (CF) water management practices on grain yields, GHG emissions and grain arsenic levels in a split-plot field experiment with organic fertilisers under organic management. The treatments included: i) farmyard manure, ii) compost, and iii) biogas digestate, alone or in combination with mineral fertiliser. The e-AWD water regime showed no difference in yield for the organic treatments. Yields significantly increased by 5–16 % in the combination treatments. Root biomass and length increased in the e-AWD treatments up to 72 and 41 %, respectively. The e-AWD water regime reduced seasonal CH4 emissions by 71–85 % for organic treatments and by 51–76 % for combination treatments; this was linked to a 15–47 % reduction in dissolved organic carbon (DOC), thereby reducing methanogenesis. N2O emissions increased by 23–305 % but accounted for

We test the hypothesis that agroforestry improves livelihoods and mitigates climate change in smallholder farming systems simultaneously. Data were collected using household surveys and standard biomass assessment approaches using locally relevant allometric equations. Summary statistics and regression analyses reveal linkages between on-farm carbon stocks and farm- and household characteristics. With an average of 4.07 ± 0.68 Mg C ha −1 and Shannon diversity index of 3.06, farm carbon stocks were significantly associated with farm size (r = 0.453, p < 0.05), tree density (r = − 0.58, p = 0.05) and the average size of trees on farm (r = − 0.42, p = 0.05), but not by Shannon diversity index (r = 0.36, p = 0.080), species richness (r = − 0.044, p = 0.833) or the number of land use categories (r = − 0.192, p = 0.356). Timber was considered the most important use of on-farm trees before firewood and construction material. The results suggest that gaining self-sufficiency in firewood is the most important benefit with on-farm carbon accumulation. The focus on exotic species for timber production presents a considerable trade-off between livelihood options and environmental goals. Heterogeneity in local environmental conditions over very short distances, less than 12 km, significantly determine livelihood strategies and on-farm carbon stocks. These results ostensibly contradict that carbon storage in smallholder farms is determined by diversity of tree species, suggest that livelihood strategy can equally drive carbon storage and demonstrate the diversity of livelihood and environmental benefits derived from trees on farms.

Shifting cultivation systems of Southeast Asia are rapidly intensifying, especially through shortening of the fallow periods. It is typically assumed that intensification will result in a depletion of soil organic carbon (SOC) stocks, but existing estimates of carbon stocks in these systems are variable, and there is little certainty about the carbon outcomes of intensification. We investigated the effects of intensification on SOC stocks of a shifting cultivation system in northern Laos. Volume-specific soil samples were collected from 20 sites representing: i) various rotation intensities (fallow periods of 3–4 years and 7–10 years), ii) various stages of the rotation cycle (fallows and active fields) and iii) reference plots (old regrowth of 25–30 years). Samples were analyzed for SOC, soil texture, pH, Total Nitrogen and permanganate oxidizable carbon (POXC) – an active carbon fraction that has been suggested as an easily measured early indicator of land use induced changes in soil quality and SOC. There were no significant differences between SOC concentrations or stocks of any of the sites under shifting cultivation and the reference sites. However, the SOC stock under fallows in the intensive rotation category was significantly larger than the SOC stock under fallows in the extensive rotation category. This is likely because inputs of dead root biomass from the slashed vegetation provides an important input to the SOC pool. Fallow sites under intensive rotation had significantly higher contents of POXC in the topsoil than the active fields, which suggests that POXC captures the immediate effect of the decreased input of litter to the topsoil during the cultivation period. We conclude that in this study there is no evidence that intensification of shifting cultivation leads to a decline in total soil carbon stock, or to a decline in the more active carbon fraction measured by POXC. Therefore, narratives of shifting cultivation leading to a decline in soil carbon stocks need to be revisited, and land use policies related to the system should not uncritically be based on this incorrect assumption.

Municipal waste is usually composted with an N-rich substrate, such as manure, to increase the N content of the product. This means that a significant amount of nitrogen can be lost during composting. The objectives of this study were (i) to investigate the effect of split addition of a nitrogen-rich substrate (poultry manure) on nitrogen losses and greenhouse gas emissions during composting and to link this effect to different bulking agents (coffee husks and sawdust), and (ii) to assess the effect of split addition of a nitrogen-rich substrate on compost stability and sanitisation. The results showed that split addition of the nitrogen-rich substrate reduced nitrogen losses by 9% when sawdust was used and 20% when coffee husks were used as the bulking agent. Depending on the bulking agent used, split addition increased cumulative N2O emissions by 400–600% compared to single addition. In contrast, single addition increased methane emissions by up to 50% compared to split addition of the substrate. Hence, the timing of the addition of the N-rich substrate had only a marginal effect on total non-CO2 greenhouse gas emissions. Split addition of the N-rich substrate resulted in compost that was just as stable and effective at completely eradicating weed seeds as single addition. These findings therefore show that split addition of a nitrogen-rich substrate could be an option for increasing the fertilising value of municipal waste compost without having a significant effect on total greenhouse gas emissions or compost stability.

The nutritional responses to drying and rewetting cycles of partial root-zone irrigation still remains elusive. The effect of alternate partial root-zone irrigation (PRI) on water use efficiency and nitrogen (N) accumulation compared with deficit irrigation (DI) and full irrigation (FI) were investigated in maize (Zea mays L.) grown under three N-fertilization rates (1.5, 3.0, and 6.0 g N pot−1) and moderately and severely water-stressed levels (60 and 40% of soil water holding capacity). The plants were grown in split-root pots and exposed to FI, DI and PRI treatments from the fourth leaf to silking stage. Analysis across the N-fertilization treatments showed that both PRI and DI significantly decreased plant water use as well as plant height, stem girth, leaf area and shoot biomass, leading to similar WUE compared with the FI control. Carbon isotope composition (δ13C) was highest in PRI plants indicating a fine-tuned long-term stomatal control over gas exchange. Across the N-fertilization rates, FI plants accumulated significantly greater amount of N than deficit irrigation treatments. PRI and DI plants had similar plant δ15N, indicating the similar soil N mineralization. Plant dry biomass, which was linearly associated with plant N uptake, was similar for PRI and DI plants. Both resulted in the equivalent amount of N accumulation in the shoots of PRI and DI plants. It was noted that increased soil moisture level, e.g., from 40% to 60%, showed the tendency of increasing N uptake for PRI plants relative to DI plants. Therefore, in order to facilitate N uptake, soil water availability in the wet soil compartment of PRI treatment should remain at high water levels.

While an increasing number of large food companies commit themselves to source only certified cocoa, research on the impacts of certification on cocoa farmers is falling behind. We investigate how Rainforest Alliance (RA) certification of small-scale cocoa farmers in Ghana has affected both the financial and the natural capitals of the farmers. Across two villages, certified farmers were compared to conventional farmers, using both qualitative and quantitative data collected through farmer and key informant interviews and participatory rural appraisals. A combination of the Sustainable Livelihood Framework and the Input-Output-Outcome-Impact Framework was used for the analysis. Results indicate that the RA certification scheme has a positive influence on the certified farmers in terms of cocoa production, yield, income and farmers’ perception of changes in their natural and financial capitals. The positive influence is a result of inputs from the RA certification, including financial support, information and knowledge, technical assistance, and increased access to farm inputs and credit. However, these positive impacts are conditioned by the presence of active farmer organizations and access to agricultural inputs and credit through associations and government institutions, and may be undermined by certified farmers who sell their produce outside the premium value chain. While an increasing number of large food companies commit themselves to source only certified cocoa, research on the impacts of certification on cocoa farmers is falling behind. We investigate how Rainforest Alliance (RA) certification of small-scale cocoa farmers in Ghana has affected both the financial and the natural capitals of the farmers. Across two villages, certified farmers were compared to conventional farmers, using both qualitative and quantitative data collected through farmer and key informant interviews and participatory rural appraisals. A combination of the Sustainable Livelihood Framework and the Input-Output-Outcome-Impact Framework was used for the analysis. Results indicate that the RA certification scheme has a positive influence on the certified farmers in terms of cocoa production, yield, income and farmers’ perception of changes in their natural and financial capitals. The positive influence is a result of inputs from the RA certification, including financial support, information and knowledge, technical assistance, and increased access to farm inputs and credit. However, these positive impacts are conditioned by the presence of active farmer organizations and access to agricultural inputs and credit through associations and government institutions, and may be undermined by certified farmers who sell their produce outside the premium value chain.

The large scale conversion of extensive swidden agriculture to intensive market oriented production of maize in upland areas of South East Asia is a cause of environmental concern. This study investigates how intensive maize cultivation affects soil quality in an upland area of Northern Thailand by comparing commonly used indicators of soil quality in soils from maize fields used at various intensities. Relations between these indicators and concentration of permanganate oxidizable carbon (Pox-C) – a low cost proxy for soil quality – are also examined. The extent, type and drivers of land use changes between 2002 and 2012 are investigated by classification of high resolution satellite images, interviews, participatory mapping and questionnaires. We document a widespread change from traditional swidden agriculture to intensive cultivation of maize that is mainly brought about by economcic and political drivers. We show that the concentration of Pox-C in the top soil of the maize fields is closely related to common indicators of soil quality and to farmers' perceptions of soil quality. Most of the other soil quality indicators are negatively – albeit not significantly – related to intensity of maize cultivation. There is a strong negative correlation between intensity of maize cultivation and concentration of Pox-C in the upper 5 cm of the soil where the Pox-C concentration declines with a rate of 40 mg year under maize−1. We conclude that Pox-C is a sensitive indicator of effects of land use intensity on the soil and a useful integrative measure of soil quality. Copyright © 2016 John Wiley & Sons, Ltd.

There is a growing body of literature documenting higher productivity of the System of Rice Intensification (SRI) than conventional practices; however, few studies have been conducted to explore the factors explaining this higher productivity. This paper investigated key factors influencing yields in a rain-fed lowland rice ecosystem in Cambodia under farmer’s SRI and conventional management practices (CMP). Rice yields from 70 plots with recorded management practices (36 plots under farmer’s SRI and 34 plots CMP) were measured. Composite soil samples (210 in total) were collected from the harvested plots and analyzed for physical and chemical properties. Stepwise multiple regression analysis was performed to identify important predictors explaining rice yield variability. Variables contributing significantly to yield variation included: number of cattle (access to farmyard manure [FYM]), farmer’s SRI practices, planting density and soil organic carbon (SOC). These four variables explained 39% of variance in rice yield. Keeping other variables constant, rice yields were increased by 14% (458 kg ha−1) by shifting from CMP to farmer’s SRI practices. The change of one unit in cattle (head), hill density (hill m−2) and SOC (g kg−1) results in an increase of rice yield by 5% (153 kg ha‐1), 2% (66 kg ha‐1) and 9% (289 kg ha‐1), respectively. The higher rice yield obtained by transplanting with narrower spacing suggests that the wider spacing recommended by SRI is not likely advisable, especially in nutrient-poor soil. Although the application of manure did not emerge as a key variable, three out of the four key variables (farmer’s SRI, access to FYM, and SOC) are directly linked to its use. Farmer’s SRI was strongly associated with the use of FYM, and the plots that received more FYM and belonged to farmers with more cattle had higher total soil N. Total soil N was positively correlated with SOC. The results highlighted the important role of livestock in crop-animal integration and the contribution of animal manure to increase agricultural productivity within smallholder farmers on infertile sandy Cambodian soils.

A considerable growth in the maize (Zea mays L.) sector in Southeast Asia has resulted in a rapid expansion and intensification of maize monoculture on sloping uplands. This practice entailed the heavy use of fertilisers, leading to environmental degradation and farmers' indebtedness. Intercropping of legumes with maize could complement or replace fertiliser inputs; however legume adoption by smallholder maize farmers remains low. This study investigates the constraints and potentials to integrate legumes in maize-based cropping systems in such environments. A comparative study between maize monocropping and maize/legume relay cropping was carried out in two villages of Thailand, using surveys, participatory rural appraisal (PRA) tools and interviews. The results demonstrated that both cropping systems were equally profitable, although the maize yield in maize/legume relay cropping was lower than that in monocropping. Low selling price was the most cited reason by the non-adopters for not introducing legumes. Selling price of legume grains, ease of harvesting, marketability and ease of growing were the four main criteria that determined the adopters' choice of legume species. Among the cultivated legumes, ricebean (Vigna umbellata L.) best fulfilled the criteria for the choice of legume species. Establishing maize/legume relay cropping as an alternative to maize monocropping under rainfed conditions can decrease risks, due to reduced expenses for farm inputs and similar economic returns. This study generated useful information for agricultural policy makers and development practitioners in identifying the barriers and facilitating factors that influence farmers' decision to adopt legumes and the conditions that shape the farmers' decision-making environment. Copyright © 2016 John Wiley & Sons, Ltd.

Rice production systems are the largest anthropogenic wetlands on earth and feed more than half of the world's population. However, they are also a major source of global anthropogenic greenhouse gas (GHG) emissions. Several agronomic strategies have been proposed to improve water-use efficiency and reduce GHG emissions. The aim of this study was to evaluate the impact of water-saving irrigation (alternate wetting and drying (AWD) vs. soil water potential (SWP)), contrasting land establishment (puddling vs. reduced tillage) and fertiliser application methods (broadcast vs. liquid fertilisation) on water-use efficiency, GHG emissions and rice yield. The experiment was laid out in a randomised complete block design with eight treatments (all combinations of the three factors) and four replicates. AWD combined with broadcasting fertilisation was superior to SWP in terms of maintaining yield. However, seasonal nitrous oxide (N2O) emissions were significantly reduced by 64% and 66% in the Broadcast-SWP and Liquid fertiliser-SWP treatments, respectively, compared to corresponding treatments in AWD. The SWP also significantly reduced seasonal methane (CH4) emissions by 34 and 30% in the broadcast and liquid fertilisation treatments, respectively. Area-scaled GWPs were reduced by 48% and 54% in Broadcast-SWP and Liquid fertiliser-SWP treatments respectively compared to the corresponding treatments in AWD. Compared to AWD, the broadcast and liquid fertilisation in SWP irrigation treatments reduced yield-scaled GWPs by 46% and 37%, respectively. In terms of suitability, based on yield-scaled GWPs, the treatments can be ordered as follows: Broadcast-SWP < Broadcast-AWD = Liquid fertiliser-SWP < Liquid fertiliser-AWD. Growing-season water use was 15% lower in the SWP treatments compared with the water-saving AWD. Reduced tillage reduced additional water use during land preparation. The conclusions of this study are that improved water management and timely coordination of N fertiliser with crop demand can reduce water use, N loss via N2O emissions, and CH4 emissions.

Thermal drying is an increasingly common post-treatment for digestate-solids, but prone to N losses via ammonia (NH3) volatilization. Acidification with strong acids prior to drying may retain ammonium (NH4+) in the solids. Natural zeolites can provide adsorption sites for exchangeable cations as ammonium and porosity for free ammonia, which has the potential to contribute to higher N retention in the dried solids. The present study investigated whether the zeolite addition increases NH4+-N retention during thermal drying of two digestate solids (manure based, MDS; sewage sludge based, SDS), and whether any synergistic effects of combining acidification with sulfuric acid and the addition of zeolite exist. Operating conditions included four pH levels (non-acidified control, adjusted to 8.0, 7.5, 6.5 with concentrated sulfuric acid), four zeolite addition rates (0%, 1%, 5% and 10%), fixed drying temperature (130 °C) and fixed air ventilation rate (headspace exchange rate of 286 times hour−1). Zeolite addition significantly increased NH4+-N retention from 18.0% of initial NH4+-N in the non-acidified control up to a maximum of 57.4% for MDS, and from 76.6% to 94.5% for SDS. No positive synergistic effect between acidification and zeolite addition was observed, with acidification being the dominant. Nevertheless, zeolite has the potential to be a safe and easy-to-handle alternative to concentrated sulfuric acid.

Shifting, or swidden, cultivation remains an important land use across Southeast Asia and other parts of the tropics, albeit under pressures from other land uses. The swidden cycle of cultivation and regrowth creates mosaic landscapes with regrowing fallows of various age interspersed with active fields and patches of mature forest. Quantifying tree biomass in these landscapes is limited by the availability of reliable allometric models, hindering accurate carbon stock estimation and thus quantification of GHG emission associated with land use transitions. We therefore developed new allometric models for the prediction of both above- and below-ground woody biomass in swidden systems based on a destructive harvest of 150 trees in Luang Prabang Province, Laos People’s Democratic Republic (PDR). This study is the first to develop allometric models of root biomass for swidden landscapes in this region, which we hypothesised would be a major carbon pool given that resprouting, and associated high root biomass, is a common physiological/morphological trait in regularly disturbed ecosystems. We found that a general model including tree diameter (DBH, cm) and height (H, m) was best for estimating aboveground biomass (AGB, kg) for both resprouts and trees growing from seed (AGB = 1.09 + 0.027D2H) though the inclusion of H only resulted in a marginal increase in model performance meaning a DBH-only model is acceptable to use in the absence of height data (AGB = 0.1286DBH2.134). Tree height was less important for estimating root biomass, with models including only DBH performing best. Re-sprouting trees exhibited greater root biomass (BGB = 0.355DBH1.732) compared to those growing from seed (0.016DBH2.597) meaning different root allometric models were developed for each tree type. Thus, we suggest that field efforts should be directed towards checking resprouting status over the estimation of tree height. We also found that models fit using non-linear regression provided equally good fits to the data compared to the traditional approach of log-transforming the data. Our models were subsequently applied to 12 nearby plots spanning a chronosequence of fallows to examine the impact of re-sprouting allometry on biomass estimation. Root biomass stocks were on average 58% higher after accounting for the allometry of resprouting trees, resulting in an average 9% increase in total biomass stocks, highlighting the importance of choosing root allometrics based on growth form in swidden fallows. If re-sprouting status is unknown, a stand-level root:shoot ratio of 0.32 can be applied. Our analysis suggests that using our models will substantially improve the accuracy of estimates of tree biomass and its distribution among different pools in swidden fallows. This information is crucial in better quantifying carbon stock changes resulting from the conversion of swidden land to other land uses.

Black wattle (Acacia mearnsii, De Wild.) is a fast growing tree species introduced into South Africa in the nineteenth century for commercial purposes. While being an important source of timber and firewood for local communities, black wattle is an aggressive invasive species and has pervasive adverse environmental impacts in South Africa. Little is known about the effects of black wattle encroachment on soil carbon, therefore the aim of this study was to investigate the impact of black wattle encroachment of natural grassland on soil carbon stocks and dynamics. Focussing on two sites in the Eastern Cape, South Africa, the study analysed carbon stocks in soil and litter on a chronosequence of black wattle stands of varying ages (up to >50 years) and compared these with adjacent native grassland. The study found that woody encroachment of grassland at one site had an insignificant effect on soil and litter carbon stocks. The second site showed a clear decline in combined soil and litter carbon stocks following wattle encroachment. The lowest stock was in the oldest wattle stand, meaning that carbon stocks are still declining after 50 years of encroachment. The results from the two sites demonstrate the importance of considering changes in soil carbon when evaluating ecosystem effects of invasive species.

Greenhouse gas (CH4 and N2O) emissions from rice paddy fields amended by differently treated manure and crop residue inputs [fresh manure (FM), composted manure (CM), liquid biogas digestate from manure (D), D mixed with biochar (D + B) or D mixed with rice straw and composted before application (CD + RS)], were compared in a field experiment, also including two mineral nitrogen fertiliser controls (N1, N2). The trial was performed on a degraded soil in Bac Giang Province in northern Vietnam with a three-crop per year rotation (summer rice–maize–spring rice). CH4 and N2O fluxes from the two rice crops were measured using static chambers. Fluxes of N2O were below or close to the detection limit at nearly all sampling times in both seasons and therefore considered negligible. However, the CH4 emissions were significant and their temporal pattern differed markedly between the rice seasons. In the summer rice season, the D + B + N1 and D + N1 treatments had significantly lower cumulative CH4 emissions (156 and 162 kg CH4 ha−1 crop−1) than CM + N1, CD + RS + N1 and FM + N1 treatments (217, 283 and 288 kg CH4 ha−1 crop−1, respectively). In the spring rice season, CH4 emissions were generally much lower, and the D + B + N1 and D + N1 treatments emitted significantly less CH4 (44 and 72 kg CH4 ha−1 crop−1) in comparison with treatments amended with FM + N1, CD + RS + N1 and CM + N1 (89, 124 and 137 kg CH4 ha−1 crop−1, respectively). Treatments amended with D + B + N1 or D + N1 therefore had the lowest emissions of methane per unit of rice grain yield.

In Xishuangbanna, China, rubber production has spread rapidly, resulting in extensive land use changes and an increasing influx of migrant workers who have come to find work on the plantations. These migrant workers have limited access to subsidies and the local collective forest due to the household registration system in China called hukou. To assess how these policy-based restrictions on access affect wood consumption and local communities, a case study was conducted in Manlin village, Xishuangbanna, undertaking a household and weight survey with local and immigrant households. The results show no significant difference in firewood consumption between the subpopulations, despite predominantly more local than immigrant households have access to subsidised alternative energy sources. On the other hand, limited access to the collective forest is found to influence the choice of housing materials and living standards in immigrant households as they cannot access timber or afford brick houses. This paper highlights rural issues connected to the hukou system and suggests that rural energy and resource policies should take the growing population of immigrant workers into consideration in future to expand the reach of the polices to the de facto and not only de jure rural population and thus optimise policy efficiency. (C) 2015 Elsevier Ltd. All rights reserved.

Global rice production systems face two opposing challenges: the need to increase production to accommodate the world's growing population while simultaneously reducing greenhouse gas (GHG) emissions. Adaptations to drainage regimes are one of the most promising options for methane mitigation in rice production. Whereas several studies have focused on mid-season drainage (MD) to mitigate GHG emissions, early-season drainage (ED) varying in timing and duration has not been extensively studied. However, such ED periods could potentially be very effective since initial available C levels (and thereby the potential for methanogenesis) can be very high in paddy systems with rice straw incorporation. This study tested the effectiveness of seven drainage regimes varying in their timing and duration (combinations of ED and MD) to mitigate CH4 and N2O emissions in a 101-day growth chamber experiment. Emissions were considerably reduced by early-season drainage compared to both conventional continuous flooding (CF) and the MD drainage regime. The results suggest that ED + MD drainage may have the potential to reduce CH4 emissions and yield-scaled GWP by 85–90% compared to CF and by 75–77% compared to MD only. A combination of (short or long) ED drainage and one MD drainage episode was found to be the most effective in mitigating CH4 emissions without negatively affecting yield. In particular, compared with CF, the long early-season drainage treatments LE + SM and LE + LM significantly (p < 0.01) decreased yield-scaled GWP by 85% and 87% respectively. This was associated with carbon being stabilised early in the season, thereby reducing available C for methanogenesis. Overall N2O emissions were small and not significantly affected by ED. It is concluded that ED + MD drainage might be an effective low-tech option for small-scale farmers to reduce GHG emissions and save water while maintaining yield.

The continuous rise in the global demand for palm oil has resulted in large-scale expansion of industrial oil palm plantations - largely at the expense of primary and secondary forests. The potentially negative environmental impacts of these conversions have given rise to closer scrutiny. However, empirical data on the effects of conversion of forests to industrial oil palm plantations on soil organic carbon (SOC) stocks is scarce and patchy. We evaluated the changes in SOC stocks after conversion of tropical forest into oil palm plantations over the first and second rotation period in Sarawak, Malaysian Borneo. Soil samples were collected from three age classes of oil palm plantations converted from forest (49, 39 and 29 years ago respectively) with three replicate sites and four adjacent primary forest sites as reference. In each site under oil palm, the three management zones, namely weeded circle (WC), frond stacks (FS), and between palm (BP), were sampled separately. All soil samples were collected from five soil layers (0-5, 5-15, 15-30, 30-50 and 50-70 cm). Samples were analysed for SOC concentration, soil bulk density, pH and soil texture. Results showed SOC stocks declined by 42%, 24% and 18% after 29, 39 and 49 years of conversion respectively. Significant differences in SOC stocks were found among different management zones in the oil palm plantations, and the trend was similar for all age classes: FS > WC > BP, demonstrating the necessity of considering within-plantation variability when assessing soil C stocks. The largest differences between SOC stocks of the reference forest and converted plantations were found in the topsoil (0-15 cm depth) but differences were also found in the subsoil (>30 cm). Our results will contribute towards future modelling and life cycle accounting to calculate the carbon debt from the conversion of forest to oil palm plantations.

The use of agricultural waste for soil amendment is limited in developing countries. Competition between fuel and feed is the major cause for the insufficient application of agricultural waste on cropland. The aims of this study were therefore (i) to investigate variation in agricultural waste allocation between groups of farmers with different livelihood strategies and link this allocation with the nutrient balances of their production systems, (ii) to identify farm characteristics that influence utilisation of agricultural waste for soil amendment, and (iii) to assess demand for urban waste compost. A total of 220 farmers were selected randomly and interviewed using standardised semi-structured questionnaires. Four groups of farmers, namely (i) field crop farmers, (ii) vegetable producers, (iii) ornamental-plant growers, and (iv) farmers practising mixed farming, were identified using categorical principal component and two-step cluster analyses. Field crop farmers produced the largest quantity of agricultural waste, but they allocated 80% of manure to fuel and 85% of crop residues to feed. Only

Efforts have been made in recent years to improve knowledge about soil greenhouse gas (GHG) fluxes from sub-Saharan Africa. However, data on soil GHG emissions from smallholder coffee-dairy systems have not hitherto been measured experimentally. This study aimed to quantify soil GHG emissions at different spatial and temporal scales in smallholder coffee-dairy farms in Murang'a County, Central Kenya. GHG measurements were carried out for one year, comprising two cropping seasons, using vented static chambers and gas chromatography. Sixty rectangular frames were installed on two farms comprising the three main cropping systems found in the area: 1) coffee (Coffea arabica L.); 2) Napier grass (Pennisetum purpureum); and 3) maize intercropped with beans (Zea mays and Phaseolus vulgaris). Within these fields, chambers were allocated on fertilised and unfertilised locations to capture spatial variability. Cumulative annual fluxes in coffee plots ranged from 1 to 1.9 kg N2O-N ha− 1, 6.5 to 7.6 Mg CO2-C ha− 1 and − 3.4 to − 2.2 kg CH4 -C ha− 1, with 66% to 94% of annual GHG fluxes occurring during rainy seasons. Across the farm plots, coffee received most of the N inputs and had 56% to 89% higher emissions of N2O than Napier grass, maize and beans. Within farm plots, two to six times higher emissions were found in fertilised hotspots – around the perimeter of coffee trees or within planted maize rows – than in unfertilised locations between trees, rows and planting holes. Background and induced soil N2O emissions from fertiliser and manure applications in the three cropping systems were lower than hypothesized from previous studies and empirical models. This study supplements methods and underlying data for the quantification of GHG emissions at multiple spatial and temporal scales in tropical, smallholder farming systems. Advances towards overcoming the dearth of data will facilitate the understanding of synergies and tradeoffs of climate-smart approaches for low emissions development.

BackgroundAgricultural production is challenged by the limitation of non-renewable resources. Alternative fertilizers are promoted but they often have a lower availability of key macronutrients, especially phosphorus (P). Biological inoculants, the so-called bio-effectors (BEs), may be combined with these fertilizers to improve the nutrient use efficiency.MethodsThe goal of this study was to assess the potential of three BEs in combination with alternative fertilizers (e.g. composted manure, biogas digestate, green compost) to promote plant growth and nutrient uptake in soils typical for various European regions. Pot experiments were conducted in Czech Republic, Denmark, Germany, Italy, and Switzerland where the same variety of maize was grown in local soils deficient in P in combination with alternative fertilizers and the same set of BEs (Trichoderma, Pseudomonas, and Bacillus strains). Common guidelines for pot experiment implementation and performance were developed to allow data comparison, and soils were analyzed by the same laboratory.ResultsEfficiency of BEs to improve maize growth and nutrient uptake differed strongly according to soil properties and fertilizer combined. Promising results were mostly obtained with BEs in combination with organic fertilizers such as composted animal manures, fresh digestate of organic wastes, and sewage sludge. In only one experiment, the nutrient use efficiency of mineral recycling fertilizers was improved by BE inoculation.ConclusionsThese BE effects are to a large extent due to improved root growth and P mobilization via accelerated mineralization., info:eu-repo/semantics/published

We studied the effects of water regimes and nutrient amendments on CH4 and N2O emissions in a 2 9 3 factorial, completely randomised growth chamber experiment. Treatments included continuously flooded (CF) and alternate wetting and drying (AWD), and three organic amendments: no amendment-control, rice straw (RS) and biochar (BC). Compound fertiliser was applied to all treatments. Rice was grown in columns packed with a paddy soil from Cambodia. Results revealed faster miner- alisation of organic carbon (RS and BC) when applied in water-saturated conditions lasting for 2 weeks instead of flooding. This resulted in lower total CH4 emissions in treatments under AWD than those under the CF water regime, namely 44 % in RS treatments and 29 % in BC treatments. Nitrous oxide fluxes were generally non- detectable during the experimental period except after fertilisation events, and the total N2O-N emissions accounted for on average 1.7 % of the total applied mineral fertiliser N. Overall, the global warming potentials (GWPs) were lower in treatments under AWD than those under the CF water regime except for the control treatment with only mineral fertiliser application. Grain yields were slightly higher in treatments under AWD than the CF water regime. Hence, the yield-scaled GWP was also lower in the treat- ments under the AWD water regime, namely 51 % in RS, 59 % in BC and 17 % in control treatments. Control treatments had the lowest GWP, but provided the highest yield. The yield-scaled GWP under these treatments was therefore lower than under the other treatments.

The reduction of CH4 and N2O emissions from rice paddies is of utmost importance in minimizing the impact of rice production on global warming. A field experiment was therefore conducted in farmers' field in Hanoi, Vietnam to examine whether the use of straw compost or straw biochar, in combination with the safe alternate wetting and drying (AWD) has the potential to suppress both CH4 and N2O emissions from rice paddies while maintaining the rice yield. The study compared the proposed strategies with local farmers' practice of permanent flooding (PF) and farmyard manure (FYM) incorporation, respectively. A control treatment without organic matter incorporation in both AWD and PF water regimes was also included in the study; all treatments received equal amounts of mineral fertilizer. Gas emissions were monitored using the closed chamber method at seven-day intervals during the first 50 days and at 15-day intervals thereafter. Addition of FYM, straw compost and biochar increased CH4 emissions by 230%, 150% and 38%, respectively, when compared with the control treatments in both the AWD and PF water regimes. Within AWD, FYM increased N2O emissions by 30%, straw compost and biochar displayed similar amount of N2O emissions as the control treatment. Within PF, N2O emissions under FYM and straw compost were 40% and 35% higher than the control treatment, respectively, and biochar once again displayed similar amount of N2O emissions as the control treatment. Yield difference was not significant (p > 0.05) between any of the treatments. These results indicated that the straw compost incorporation might not reduce the global warming potential (GWP) and yield-scaled GWP of rice production, whereas biochar in combination with AWD has the potential to maintain the GWP and yield-scaled GWP of rice production at lower level than the farmers' practice.

We investigated the effects of bulking agents (BA) and mixing ratios on greenhouse gas (GHG) and NH 3 emissions from composting digested solids (DS), separated from anaerobically digested manure and other bio-wastes, in small-scale laboratory composters. BA evaluated were plastic tube pieces (PT), woodchips (WC), bio-char (BC), barley straw (BS) and lupin residues (LR) and were included at a DS:BA of 3:1 or 6:1, resulting in nine treatments: CT DS (control, DS only), PT 3:1 , PT 6:1 , WC 3:1 , WC 6:1 , BC 3:1 , BC 6:1 , BS 3:1 and LR 3:1 . Depending on treatment, C losses via CO 2 and CH 4 emissions accounted for 41.2–65.3 g C kg −1 initial total solids (TS) and 4.4–191.7 mg C kg −1 TS (8.4–16.1% and 0.001–0.05% of initial total-carbon), respectively, while N losses as N 2 O and NH 3 emissions comprised 2.1–13.6 mg N kg −1 TS and 2.7–4.8 g N kg −1 TS (0.01–0.04% and 9.1–13.0% of initial total-nitrogen), respectively. Most of the CH 4 emissions occurred during the thermophilic temperature phase, which had little or no effect on N 2 O emissions. BS addition to DS resulted in the lowest cumulative NH 3 -N and N 2 O-N losses. BC was as effective as BS in reducing cumulative NH 3 -N losses, but had non-significant effect on CH 4 -C emissions. Decreasing the mixing ratio from 6:1 to 3:1 reduced losses of CH 4 -C and N 2 O-N (except for BC) without any increase in NH 3 -N losses. BC and BS proved most effective in reducing emissions of total GHG (as CO 2 -equivalents). Composting of DS with C-rich BA can thus be an effective means of conserving N in DS, while also reducing GHG emissions.

The present field study investigated the effects of the system of rice intensification (SRI) on greenhouse gas emissions and rice yield, in the first field trial of its kind in Cambodia. The study was a 2 × 4 factorial design, including SRI and conventional management practices (CMP) with the following treatments: control, composted farmyard manure (FYM), mineral fertiliser (MF) and FYM + MF. The results indicated large seasonal variations of CH4 patterns during the growing season with a peak emission of about 1,300 mg CH4 m−2 day−1 under both production systems 2 weeks after rice transplanting. There was large temporal variability of CH4 fluxes from morning to midday. Emission of N2O was below the detection limit in both systems. Under each production system, the highest seasonal emission of CH4 was under the FYM + MF treatment, namely 282 kg ha−1 under CMP and 213 kg ha−1 under SRI. Total CH4 emission under SRI practices was reduced by 22 % in the FYM treatment, 17 % in the MF treatment and 24 % in the FYM + MF treatment compared to CMP. There was no effect of water management on CH4 emission in the non-fertilized treatment. Grain yields were not significantly affected by the production system. Thus the yield-scaled global warming potential (GWP) was lower under SRI than CMP, namely 21 % in FYM and FYM + MF treatments, and 8 % in MF treatment. The application of mineral fertilisers moderately increased CH4 emission but significantly increased rice yields, resulting in a significantly lower yield-scaled-GWP compared to farmyard manure.

Solid-liquid separation of animal slurry, with solid fractions used for composting, has gained interest recently. However, efficient composting of separated animal slurry solid fractions (SSFs) requires a better understanding of the process dynamics in terms of important physical parameters and their interacting physical relationships in the composting matrix. Here we monitored moisture content, bulk density, particle density and air-filled porosity (AFP) during composting of SSF collected from four commercially available solid-liquid separators. Composting was performed in laboratory-scale reactors for 30 days (d) under forced aeration and measurements were conducted on the solid samples at the beginning of composting and at 10-d intervals during composting. The results suggest that differences in initial physical properties of SSF influence the development of compost maximum temperatures (40-70 degreeC). Depending on SSF, total wet mass and volume losses (expressed as % of initial value) were up to 37% and 34%, respectively. After 30 d of composting, relative losses of total solids varied from 17.9% to 21.7% and of volatile solids (VS) from 21.3% to 27.5%, depending on SSF. VS losses in all composts showed different dynamics as described by the first-order kinetic equation. The estimated component particle density of 1441 kg m-3 for VS and 2625 kg m-3 for fixed solids can be used to improve estimates of AFP for SSF within the range tested. The linear relationship between wet bulk density and AFP reported by previous researchers held true for SSF.

State-of-the-art predictive models of soil organic carbon (SOC) dynamics associated with land use changes are unable to reflect the diversity of tropical soil types as the knowledge of contrasting site-specific factors in mediating the response of the SOC pool is sparse. This paper examines the influence of soil type and management on SOC dynamics following the conversion of forests to annual cropping in Ghana. Soil from primary forests and from areas with short (2–7 years) and long (20 years) histories of maize cultivation was sampled from a Vertisol dominated by smectite and Ultisol dominated by kaolinite. Wet sieving was used to separate soil fractions below and above 250 µm. SOC concentrations and δ13C signatures of SOC in soil fractions and bulk soil were determined. SOC stocks were calculated by the commonly used fixed depth approach and by the equivalent soil mass approach. After 20 years of cultivation of the Vertisol, the total SOC content was 40 per cent lower than under forest, and about 95 per cent of the forest-derived SOC had been lost. After 20 years of cultivation of the Ultisol, total SOC content was only about 20 per cent lower than under forest and merely 30 per cent of the forest-derived SOC had been lost. Both soil types were managed as they would typically be in small scale farming systems, thus the higher SOC losses and the substantial loss of forest-derived SOC from the Vertisol question the conventional concept of smectite having a higher SOC-stabilizing potential than kaolinite under field conditions. Copyright © 2013 John Wiley & Sons, Ltd.

This paper aims to understand the relationship between households’ livelihood strategy and soil management using commonalities among rural households. We grouped households into four distinct types according to similar livelihood diversification strategies. For each household type, we identified the dominant income-generating strategies as well as the main agronomic activities pursued. The household types were: (I) households that pursue a cereal-based livelihood diversification strategy (23 %); (II) households predominantly engaged in casual off-farm-based strategy (15 %); (III) households that pursue an integrated livelihood strategy (38 %); and (IV) households with a potato-based strategy (24 %). We then explored the relationship between these household types and improved soil management practices. The results showed that households generating their income primarily by growing potatoes (Type IV) were not only economically “better off” but also more likely to undertake improved soil management practices than those pursuing less economically rewarding, cereal-based (Type I) or casual off-farm-based (Type II) livelihood diversification strategies. This was largely attributed to differences in access to institutional capital that determined the degree of agronomic orientation, rather than household assets, such as age, education level of the head, and family labour. Orienting lower income households toward input and output markets through improving their access to institutional capital may help build livelihood strategies with high-economic return that in turn provide incentives to undertake improved soil management practices. The identified household types may guide entry points for development interventions targeting both food security and agricultural sustainability concerns in the central highlands of Ethiopia. The approach can be applied to different geographical regions with similar livelihood circumstances. Development actors need to take into account the specific contexts of their regions and resources needed to develop a typology when designing pathways for any targeted interventions.

In the past decades a significant change in composition of urban organic waste products has occurred in many first world countries, due to cleaner technologies as well as outsourcing of heavy industries. However, the societal perception of organic urban waste has become increasingly negative, leading to widespread advocacy of incineration. Therefore we established the ‘CRUCIAL’ long-term field trial in 2003, with the rationale that by approaching the known limits for a number of heavy metals below which no profound disturbance should be observed on key soil ecological functions, it should be possible to discern if some of the many unknown components in the composite urban waste as well as agriculturally based fertilizers have measurable impacts. The following treatments were established: human urine, sewage sludge (normal N-level and accelerated level aiming at three times normal N-level), degassed and subsequently composted organic municipal waste (normal and accelerated level), deep litter, cattle slurry, cattle manure (accelerated level), NPK fertilizer, unfertilized but with clover undersown and an unfertilized control. After 4 years the soil organic matter (SOM) C content, basal CO 2 respiration and soil microbial biomass (SMB) C was significantly affected by treatments. All soils having received organic fertilizer had higher SMB C than those with no added fertilizer (unfertilized and unfertilized with clover undersown) and inorganic fertilizer. The treatment effect on q CO2 (CO 2 /SMB C) was not significant, but the unfertilized treatments showed the highest values. Treatments with accelerated levels of composted household waste and sewage sludge had the highest number of colony forming heterotrophic bacteria. Sole carbon source utilization in EcoPlates indicated a very robust microbial community in the treatments. Cumulative input of heavy metals was less than that required for reaching the heavy metal ecotoxicological limits, even after accelerated loading with sewage sludge corresponding to approximately 55 years of normal application. This could indicate that it is possible use organic urban waste for an extended period on a given site, without compromising soil functioning as long as ecotoxicological guidelines for heavy metal content are observed.

Dissolved organic carbon (DOC) has recently been proposed as an indicator of compost stability. We assessed the earthworms' effect on DOC content and composition during composting, and linked compost stability to greenhouse gas emissions and feeding ratio. Earthworms reduced total DOC content, indicating larger stability of vermicompost than of thermophilic compost. The concentrations of humic acid and fulvic acid were reduced by earthworms, whereas there was no significant effect on hydrophobic neutrals and hydrophilics. The humic acid fraction was depleted more quickly than the other compounds, indicating humic acid degradation during composting. The optimum feeding ratio decreased DOC content compared to the high feeding ratio. The lowest N2O emissions were also observed at the optimum feeding ratio. Our study confirmed the use of DOC content and composition as an indicator of compost stability and suggested that feeding ratio should be considered when assessing the earthworms' effect on stabilisation and greenhouse gas emissions.

Climate-smart approaches have gained momentum in tropical, agricultural development. However, to date, few studies have examined whole-farm greenhouse gas (GHG) balances in smallholder crop-livestock systems. This study aimed to quantify GHG balances at farm-scale, identify GHG hotspots and assess mitigation options in coffee-dairy farms undergoing agricultural intensification in Central Kenya. In recent decades, decreasing farm size has forced the shift from extensive practices to zero-grazing systems and higher nitrogen (N) inputs. We hypothesised that different farm strategies and intensification levels determine the farm’s GHG balance. A farm typology was constructed through principal component analysis (PCA) and hierarchical clustering from 125 farms surveyed. Four farm types were identified ranging relatively from small to large farms, low to high livestock intensities, and low to high N input rates. Whole-farm GHG balances were estimated using an adapted version of the Cool Farm Tool (CFT). Farms were found to be net sources of GHG, averaging from 4.5 t CO 2 eq ha −1 yr −1 in less intensive farms to 12.5 t CO 2 eq ha −1 yr −1 in high intensive farms. Within the farm GHG hotspots identified, methane (CH 4 ) from enteric fermentation processes accounted for 26–39% of total farm GHG emissions; nitrous oxide (N 2 O) and CH 4 from manure management systems (MMS) for 26–38%; soil background and fertilizer induced N 2 O emissions for 24–29%; off-farm production of feeds and agrochemicals for 10–22%; and crop residue management (CRM) for the remaining 1–3%. Within the mitigation practices assessed, zero-grazing stalls already lowered the livestock maintenance energy requirements, reducing enteric fermentation emissions. Stall-feeding, however, brings the necessity-opportunity to manage the manure and our results showed that MMS can be a determining factor in the GHG balance. Increasing the frequency of manure collection from stalls in favour of solid storage systems can reduce N 2 O emissions by up to 75%. Furthermore, dry manure storage reduced the CH 4 emissions of liquid slurry systems by more than 70%. Further benefits in terms of carbon (C) sequestration were identified along farm types from manure and crop residues applications in soils (with averages of −1.3 to −2.3 t CO 2 eq ha −1 yr −1 ) and biomass growth in agroforestry systems (−1.2 to −2 t CO 2 eq ha −1 yr −1 ). Together, soils and woody biomass offset 25–36% of farm emissions. We conclude that reduced farm size and increased livestock density lead to higher emissions per unit area, though this increase is smoothed by larger negative fluxes in soils (by higher C inputs) and woody biomass (by higher tree densities) until a steady state is reached. Average yield-scaled emissions, or product carbon footprints (CFs), resulted in 1.08 kg CO 2 eq kg coffee berry −1 , 0.64 kg CO 2 eq kg maize −1 and 1.05 kg CO 2 eq kg milk −1 on average. CFs did not always differ between farm types and intensification levels, meaning that increases in productivity were not higher than increases in GHG fluxes from intensification. This may be due to: 1) increases in productivity are the result of more processes other than N inputs; and/or 2) emissions from N inputs are overestimated by EFs and GHG calculators. Smallholders may benefit in the near future from climate initiatives and further field characterisation, models calibration and monitoring are required to overcome critical levels of uncertainty and provide more accurate estimations of GHG balances at farm-scale.

Agriculture is one of the major sources of nitrous oxide (N2O), a potent greenhouse gas (GHG) whose atmospheric concentrations are estimated to increase with efforts to increase food production through increasing nitrogen (N) inputs. The objective of this study was to quantify N2O emissions from maize (Zea mays L.) and winter wheat (Triticum aestivum L.) fields amended with inorganic, organic N and a combination of both sources (integrated management), in tropical (Zimbabwe) and temperate (China) climatic conditions. In Zimbabwe N2O emissions were measured from maize plots, while in China emissions were measured from maize and winter wheat plots. In Zimbabwe the treatments were; (i) Control, (ii) 60 kg N ha−1 ammonium nitrate (NH4NO3), (iii) 120 kg N ha−1 NH4NO3, (iv) 60 kg ha−1 cattle (Bos primigenius) manure-N, plus 60 kg N ha−1 NH4NO3, (v) 60 kg N ha−1 cattle manure-N, and (vi) 120 kg N ha−1 cattle manure-N. In China, treatments were; (i) Control, (ii) 300 kg N ha−1 Urea, (iii) 92 kg N ha−1 Urea plus 65 kg ha−1 chicken (Gallus domesticus) manure-N, (iv) 100 kg N ha−1 Urea and (v) 100 kg N ha−1 control release Urea. Our results showed that under both temperate and tropical conditions, integrated nutrient management resulted in lower N2O emissions compared to inorganic fertilizers which had higher total and yield-scale N2O emissions. We conclude that by combining organic and inorganic N sources, smallholder farmers in both China and Zimbabwe, and other countries with similar climatic conditions, can mitigate agricultural emissions without compromising productivity Agriculture is one of the major sources of nitrous oxide (N2O), a potent greenhouse gas (GHG) whose atmospheric concentrations are estimated to increase with efforts to increase food production through increasing nitrogen (N) inputs. The objective of this study was to quantify N2O emissions from maize (Zea mays L.) and winter wheat (Triticum aestivum L.) fields amended with inorganic, organic N and a combination of both sources (integrated management), in tropical (Zimbabwe) and temperate (China) climatic conditions. In Zimbabwe N2O emissions were measured from maize plots, while in China emissions were measured from maize and winter wheat plots. In Zimbabwe the treatments were; (i) Control, (ii) 60 kg N ha−1 ammonium nitrate (NH4NO3), (iii) 120 kg N ha−1 NH4NO3, (iv) 60 kg ha−1 cattle (Bos primigenius) manure-N, plus 60 kg N ha−1 NH4NO3, (v) 60 kg N ha−1 cattle manure-N, and (vi) 120 kg N ha−1 cattle manure-N. In China, treatments were; (i) Control, (ii) 300 kg N ha−1 Urea, (iii) 92 kg N ha−1 Urea plus 65 kg ha−1 chicken (Gallus domesticus) manure-N, (iv) 100 kg N ha−1 Urea and (v) 100 kg N ha−1 control release Urea. Our results showed that under both temperate and tropical conditions, integrated nutrient management resulted in lower N2O emissions compared to inorganic fertilizers which had higher total and yield-scale N2O emissions. We conclude that by combining organic and inorganic N sources, smallholder farmers in both China and Zimbabwe, and other countries with similar climatic conditions, can mitigate agricultural emissions without compromising productivity.

Greenhouse gas (GHG) mitigation strategies are often constrained by rice farmers’ preferences, therefore an assessment of mitigation strategies taking farmers’ constraints into consideration, are important for their possible adoption. The field experiments were conducted for two continuous rice-growing seasons in northern Vietnam, to evaluate the effectiveness of drainage patterns on methane (CH4) and nitrous oxide (N2O) emissions under farmers’ variable conditions. Two improved drainage practices (pre-planting plus midseason [PM] drainage and early-season plus midseason [EM] drainage) were compared with local practices of water management (midseason drainage [M] and conventional continuous flooding (control) [C]) with full residue [F] and reduced residue [R] (local practice of residue management) incorporation. The GHG mitigation potential of water regimes was tested in two water management systems (efficient field water management [EWM] system and inefficient field water management [IWM] system). In EWM system, EM resulted an average 14% and 55% reduction in CH4 emissions compared to M with R and F respectively. The EM lowered the CH4 emissions by 67% and 43% compared to C in the EWM and IWM respectively. The EM and PM resulted in higher N2O emissions compared to M (25–36%) and C (42–43%) in both systems. The contribution of increased N2O emissions with EM and PM to global warming potential (GWP) was negligible. EM reduced the GWP by 42% compared to C with F in the IWM system, and by 20–52%, 30–62% and 66% compared to M, PM and C respectively in the EWM system. Furthermore, greenhouse gas intensity (GHGI) reduced by 22–72% in the EWM than in IWM. This study demonstrates that efficient field water management system has a positive impact on over-all GHG mitigation potential of drainage practices in farmers’ field conditions.