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Bare soil and inadequate soil tillage are emerging problems worldwide that result in soil quality impoverishment and contribute to global warming. To reverse this situation and to improve soil structure and carbon and nitrogen storage capacity, implementing sustainable land management (SLM) practices is needed. This study evaluates the combined effect of different SLM practices (tillage with/without compost addition) and cover crop types (native/seeded cover crops) and their management (mowing or grazing) on soil organic carbon (SOC) and total nitrogen (tN) stabilization in rainfed semiarid Mediterranean almond orchards under a range of edapho‐climatic conditions. To do so, the long‐term effects of different SLM practices, such as reduced tillage plus seeded cover crops (RT + SCC), reduced tillage plus native cover crops (RT + NCC) and no tillage plus native cover crops (NT + NCC) on soil water‐stable aggregates distribution and different organic carbon and nitrogen pools were estimated at a depth of 0–20 cm (plough layer) at five experimental sites. SLM practices, implemented over 5–12 years (depending on the experimental site), were compared with the traditional tillage (TT) carried out by farmers, which consisted of three‐five passes per year to maintain soil bare. Our results demonstrate the cross‐site potential of combining reduced tillage and cover crops (regardless of seeded or native) for improving SOC and tN sequestration and stabilization. However, the magnitude of the effect of SLM practices on SOC and tN stabilization depended heavily on the local environmental and management conditions. As seeded cover crops (RT + SCC) accelerated SOC and tN stabilization compared with native cover crops (RT + NCC and NT + NCC), its implementation in these semiarid agro‐ecosystems is recommended. However, no tillage implemented as an isolated practice is not recommended in soils prone to compaction, but managed in combination with other SLM practices, such as compost addition or mulching, can be effective for SOC and tN sequestration and stabilization over time. [ABSTRACT FROM AUTHOR]

The objective of this work is to evaluate the impact of regenerative agriculture alternatives in rainfed almond crops on a range of ecosystems services. A Multi-Criteria Analysis (MCA) was conducted to evaluate the different land management alternatives integrating different quantitative and qualitative indicators based on long-term field research. Three land management alternatives were analyzed: (i) conventional management, (ii) native cover crops, and (iii) seeded cover crops. MCA was able to evaluate the performance of the three alternatives considering different priorities of two groups of farmers (conventional and regenerative) and score the different scenarios. The alternative of natural cover crops had the best score in almost all the groups of ecosystem services and economic indicators. The sustainability, acceptance, and stability of the scenarios were achieved and provided an integrated view of impacts that can help decision making. [ABSTRACT FROM AUTHOR]

The growth of legumes, reduced tillage and addition of crop residues can be regarded as a good alternative in intercropping systems to increase soil organic matter, soil fertility and biodiversity while enhancing crop production and reducing the use of fertilizers. Despite the potential benefits, there is still a research gap about using the combination of cowpea and melon in intercropping to increase productivity and reduce external inputs. Thus, the aims of this study were to: i) assess if crop yield, crop quality and soil physicochemical properties can be improved by intercropping systems between melon (Cucumis melo L.) and cowpea (Vigna unguiculata (L.) Walp.) with reduced tillage and addition of crop residues, compared with a melon monoculture with intensive tillage and removal of crop residues, all grown under organic management; and ii) evaluated if cowpea grown as intercrop with fertilization reduced by 30% in the diversified plots can partially replace the use of fertilizers with no negative effects on total crop production. In this study we compared over three crop cycles monocrops with three different melon-cowpea intercropping patterns: mixed intercropping, row intercropping 1:1 (melon:cowpea) and row intercropping 2:1 (melon:cowpea). Our results, presented in this study, showed that intercropping systems, regardless of the pattern, kept soil organic C levels, while it significantly decreased in melon monoculture. Intercropping also significantly increased soil total N, available P and exchangeable K (0.13%, 62 mg·kg-1 and 387 mg·kg-1, respectively), compared to the melon monocrop (0.11%, 25 mg·kg-1 and 306 mg·kg-1). Total crop production was significantly higher under diversified systems, with land equivalent ratios > 1. Hence, the introduction of cowpea associated with melon, combined with reduced tillage and the incorporation of crop residues could be considered as a feasible strategy for sustainable agriculture, with environmental gains and economic savings for fertilizers and water. [ABSTRACT FROM AUTHOR]

The high use of pesticides, herbicides, and unsustainable farming practices resulted in losses of soil quality. Sustainable farming practices such as intercropping could be a good alternative to traditional monocrop, especially using legumes such as cowpea (Vigna unguiculata L. Walp). In this study, differentmelon and cowpea intercropping patterns (melonmixed with cowpea in the same row(MC1); alternating onemelon rowand one cowpea row(MC2); alternating twomelon rows and one cowpea row(MC3)) were assayed to study the intercropping effect on soil bacterial community through 16S rRNA region in a 3-year experiment. The results indicated that intercropping showed high content of total organic carbon, total nitrogen and ammonium, melon yield, and bacterial diversity as well as higher levels of beneficial soilmicroorganisms such a Pseudomonas, Aeromicrobium, Niastella, or Sphingomonas which can promote plant growth and plant defense against pathogens. Furthermore, intercropping showed a higher rare taxa diversity in two (MC1 and MC2) out of the three intercropping systems. In addition, N-cycling genes such as nirB, nosZ, and amoA were more abundant in MC1 and MC2 whereas the narG predicted gene was far more abundant in the intercropping systems than in the monocrop at the end of the 3-year experiment. This research fills a gap in knowledge about the importance of soil bacteria in an intercropping melon/cowpea pattern, showing the benefits to yield and soil quality with a decrease in N fertilization. [ABSTRACT FROM AUTHOR]

Purpose: Diversification practices such as intercropping in woody cropping systems have recently been proposed as a promising management strategy for addressing problems related to soil degradation, climate change mitigation and food security. In this study, we assess the impact of several diversification practices in different management regimes on the main carbon fluxes regulating the soil carbon balance under semiarid Mediterranean conditions. Methods: The study was conducted in two nearby cropping systems: (i) a low input rainfed almond (Prunus dulcis Mill.) orchard cultivated on terraces and (ii) a levelled intensively irrigated mandarin (Citrus reticulata Blanco) orchard with a street-ridge morphology. The almond trees were intercropped with Capparis spinosa or with Thymus hyemalis While the mandarin trees were intercropped with a mixture of barley and vetch followed by fava bean. Changes caused by crop diversifications on C inputs into the soil and C outputs from the soil were estimated. Results: Crop diversification did not affect soil organic carbon stocks but did affect the carbon inputs and outputs regulating the soil carbon balance of above Mediterranean agroecosystems. Crop diversification with perennials in the low-input rainfed woody crop system significantly improved the annual soil C balance in the short-term. However, crop diversification with annual species in the intensively managed woody crop system had not effect on the annual soil C balance. Conclusions: Our results highlight the potential of intercropping with perennials in rainfed woody crop systems for climate change mitigation through soil carbon sequestration. [ABSTRACT FROM AUTHOR]

The role of fluvial sedimentary areas as organic carbon sinks remains largely unquantified. Little is known about mechanisms of organic carbon (OC) stabilization in alluvial sediments in semiarid and subhumid catchments where those mechanisms are quite complex because sediments are often redistributed and exposed to a range of environmental conditions in intermittent and perennial fluvial courses within the same catchment. The main goal of this study was to evaluate the contribution of transport and depositional areas as sources or sinks of CO2 at the catchment scale. We used physical and chemical organic matter fractionation techniques and basal respiration rates in samples representative of the three phases of the erosion process within the catchment: (i) detachment, representing the main sediment sources from forests and agricultural upland soils, as well as fluvial lateral banks; (ii) transport, representing suspended load and bedload in the main channel; and (iii) depositional areas along the channel, downstream in alluvial wedges, and in the reservoir at the outlet of the catchment, representative of medium- and long-term residence deposits, respectively. Our results show that most of the sediments transported and deposited downstream come from agricultural upland soils and fluvial lateral bank sources, where the physicochemical protection of OC is much lower than that of the forest soils, which are less sensitive to erosion. The protection of OC in forest soils and alluvial wedges (medium-term depositional areas) was mainly driven by physical protection (OC within aggregates), while chemical protection of OC (OC adhesion to soil mineral particles) was observed in the fluvial lateral banks. However, in the remaining sediment sources, in sediments during transport, and after deposition in the reservoir (long-term deposit), both mechanisms are equally relevant. Mineralization of the most labile OC (the intra-aggregate particulate organic matter (Mpom) was predominant during transport. Aggregate formation and OC accumulation, mainly associated with macroaggregates and occluded microaggregates within macroaggregates, were predominant in the upper layer of depositional areas. However, OC was highly protected and stabilized at the deeper layers, mainly in the long-term deposits (reservoir), being even more protected than the OC from the most eroding sources (agricultural soils and fluvial lateral banks). Altogether our results show that both medium- and long-term depositional areas can play an important role in erosive areas within catchments, compensating for OC losses from the eroded sources and functioning as C sinks. [ABSTRACT FROM AUTHOR]

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The role of fluvial sedimentary areas as organic carbon sinks remains largely unquantified. Little is known about mechanisms of organic carbon (OC) stabilization in alluvial sediments in semiarid and sub-humid catchments where those mechanisms are quite complex because sediments are often redistributed and exposed to a range of environmental conditions in intermittent and perennial fluvial courses within the same catchment. The main goal of this study was to evaluate the contribution of transport and depositional areas as sources or sinks of CO2 at the catchment scale. We used physical and chemical organic matter fractionation techniques and basal respiration rates in samples representative of the three phases of the erosion process within the catchment: (i) detachment, representing the main sediment sources from forests and agricultural upland soils, as well as fluvial lateral banks; (ii) transport, representing the main channel as suspended load and bedload; and (iii) depositional areas along the channel, downstream in alluvial wedges and in the reservoir at the outlet of the catchment, representative of medium and long-term residence deposits, respectively. Our results show that most of the sediments transported and deposited downstream come from agricultural upland soils and fluvial lateral bank sources, where the physico-chemical protection of OC is much lower than that of the forest soils, which are less sensitive to erosion. The protection of OC in forest soils and medium-term depositional areas (alluvial wedges) was mainly driven by physical stabilization mechanisms, while chemical protection of OC was observed in the fluvial lateral banks. However, in the remaining sediment sources, in sediments during transport, and after deposition in long-term deposits (the reservoir), both mechanisms are equally relevant. Mineralization of the most labile OC, intra-aggregate particulate organic matter (MPOM), was predominant during transport. Aggregate formation and OC accumulation, mainly associated with macroaggregates and occluded microaggregates within macroaggregates, were predominant in depositional areas, being more protected than the OC from the most eroding sources (agricultural soils and fluvial lateral banks). Both temporary and permanent sediment deposits in the catchment have an important role in erosive areas, compensating OC losses from the eroded sources and functioning as C sinks. [ABSTRACT FROM AUTHOR]

Purpose: Soil respiration ( R) is controlled by abiotic soil parameters interacting with characteristics of the vegetation and the soil microbial community. Few studies have attempted a comprehensive approach that simultaneously addresses the roles of all the major factors known to influence R. Our goal was to explore the links between heterogeneity in R, aboveground plant biomass and belowground properties in three representative land-use types in a dry Mediterranean ecosystem: (1) a 150-year-old mixed Aleppo pine-kermes oak open forest, (2) an abandoned agricultural field, which was cultivated with cereal for several years until abandonment in 1980, when establishment of typical Mediterranean shrubland vegetation started and (3) a rain-fed olive grove, which has been cultivated for 100 years. Materials and methods: We selected two distinctive sampling periods coinciding with annual minimum or near minimum (December) and maximum (April) rates of R in this dry Mediterranean ecosystem. In each sampling period, R, temperature and moisture, aboveground plant biomass, carbon (C) and nitrogen (N) contents in both light and heavy soil organic matter fractions, extractable dissolved organic C (EDOC), as well as microbial and fine root biomass were measured within each land-use type. Results and discussion: Across sites, R rates were significantly higher in April (3.07 ± 0.1 μmol m s) than in December (1.30 ± 0.1 μmol m s). The labile soil organic matter fractions (light fraction C and N contents, microbial biomass C and EDOC) were consistently and strongly related to one another, and to a lesser extent, to the C and N contents in the heavy fraction across sites and seasons. Linear models adequately explained a large proportion of the within-site variability in R ( R values ranged from 41 to 91 % depending on land use and season) but major controls on R differed considerably between sites and seasons. Primary controls on spatial patterns in R were linked to recent plant-derived C inputs in both forest and olive grove sites. However, in the abandoned agricultural field site R appeared to be mainly driven by microbial activity, which could be sustained by intermediate or recalcitrant C and N pools derived from previous land use. Conclusions: Conversion of native woodland to agricultural land and subsequent land abandonment leads to profound changes in the relationships between R, aboveground biomass and belowground properties in this dry Mediterranean ecosystem. While above- and belowground vegetation are the primary controls on spatial variability in labile soil C pools and R in the open forest and olive grove sites, a complete lack of influence of current vegetation patterns on soil C pools and respiration rates in the abandoned agricultural field was observed. [ABSTRACT FROM AUTHOR]

Aims: Plant litter decomposition plays an important role in the storage of soil organic matter in terrestrial ecosystems. Conversion of native vegetation to agricultural lands and subsequent land abandonment can lead to shifts in canopy structure, and consequently influence decomposition dynamics by alterations in soil temperature and moisture conditions, solar radiation exposure, and soil erosion patterns. This study was conducted to assess which parameters were more closely related to short-term decomposition dynamics of two predominant Mediterranean leaf litter types. Methods: Using the litterbag technique, we incubated leaf litter of Pinus halepensis and Rosmarinus officinalis in two Mediterranean land-uses with different degree of vegetation cover (open forest, abandoned agricultural field). Results: Fresh local litter lost between 20 and 55% of its initial mass throughout the 20-month incubation period. Rosemary litter decomposed faster than pine litter, showing net N immobilization in the early stages of decomposition, in contrast to the net N release exhibited by pine litter. Parameters related to litter quality (N content or C:N) or land-use/site conditions (ash content, an index of soil deposition on litter) were found to explain the cross-site variability in mass loss rates for rosemary and Aleppo pine litter, respectively. Conclusions: The results from this study suggest that decomposition drivers may differ depending on litter type in this Mediterranean ecosystem. While rosemary litter was degraded mainly by microbial activity, decomposition of pine litter was likely driven primarily by abiotic processes like soil erosion. [ABSTRACT FROM AUTHOR]

Purpose: Selective water erosion of soil organic carbon (OC) has been reported to occur in small plots under field and laboratory conditions. However, little is known about how the process of OC erosion happens at larger scales. This study was conducted to assess the differences in the selectivity of OC between different erosion processes taking place within the same catchment. Materials and methods: A geomorphological survey of the hillslope-streambed connections within a catchment in SE Spain was conducted to determine and select the dominant erosion forms to be studied. Undisturbed sediment samples were taken from deposits derived from four different erosion processes (gully, interrill, bank and tillage erosion) and from the streambed sediment bars. Soils of the three main land uses (forest, shrubland and agricultural fields) of the drainage area were also sampled to establish comparisons with the sampled sediments and determine the enrichment ratios. Different organic carbon pools (size fractions) and particle size distribution, both dispersed and non-dispersed, were studied in soils and sediments. Results and discussion: All sediments were impoverished in OC compared to the source soils of the catchment. The largest differences were found between bank erosion and tillage erosion processes. Particle size distribution analysis indicated that soil particles were mainly being transported as aggregates. In addition, aggregates in the 250-63 μm size fraction seemed to contain primary silt and clay particles, which were positively correlated to total organic carbon. Bar sediments downstream in the streambed were impoverished in mineral-associated organic carbon, suggesting that this OC fraction can be carried further downstream by remaining in suspension longer due to its binding to smaller mineral particles. Conclusions: In general terms, there are indications that different erosion processes can result in different organic carbon enrichment ratios. Although selectivity during detachment, transport and deposition results in a complex set of interactions that need further research and field-based data, in this study, the nature of the erosion process, the characteristics of the source material and the level of aggregation of soil particles were found to be important variables. [ABSTRACT FROM AUTHOR]

The article offers information on the effect of land use change and check-dams on catchment sediment yield. A study was conduced in Spain to determine the impact of reforestation and abandonment of agricultural activities on soil sediment. It examines the extent of erosion processes at the catchment scale as effect of extensive land use change with or without sediment controlled structures, such as check-dams. The result of the study revealed that in a scenario without check-dams, the land use change caused a progressive decrease in sediment yield. About seventy sevent percent of the sediment yield was retained by the used of dams. It is showed that check-dam efficiency depends on the specific environmental condition of the area.