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Agriculture contributes to over 20% of global anthropogenic GHG emissions and irrigated paddy fields account for 5–10% of CH4 emissions. Main organic input providing methanogenesis substrate is straw. We hypothesized that removing rice straw can mitigate CH4 emissions, and that replacing its carbon (C) input with raw or solid digestate can be a valuable alternative both for crop, soil and emission responses. A mesocosm study was setup to follow crop growth, changes in soil pore water chemistry (dissolved Fe(II) and dissolved Organic C), and CH4 emissions over one cropping season on soil treated with the combination of two straw managements (removal or incorporation) and three fertilizations (mineral, raw digestate, solid digestate). Soils not receiving straw on average emitted 38 % less than soils after straw incorporation, while the two organic fertilizers did not increase emissions with respect to mineral N application. Furthermore, straw incorporation induced a yield depression independently from the fertilization strategy, probably as a result of N immobilization, especially in early stages. This was evidenced by early SPAD observations and flag leaf length, and both grain and straw final production. Moreover, the two organic fertilizers were not fully able to sustain crop N requirements with respect to the mineral fertilizer. Straw management was therefore decisive for determining both rice yield and CH4 emissions, while the impact of fertilization treatments was crucial only for crop productivity.

Conservation agriculture (CA) involves complex and interactive processes that ultimately determine soil C storage, making it difficult to identify clear patterns, particularly, when the results originate from many experimental studies. To solve these problems, we used the ARMOSA process-based crop model to simulate the contribution of different CA components (minimum soil disturbance, permanent soil cover with crop residues and/or cover crops, and diversification of plant species) to soil organic carbon (SOC) sequestration at 0-30 cm soil depth and to compare it with SOC evolution under conventional agricultural practices. We simulated SOC changes in two sites located in Central Asia (Almalybak, Kazakhstan) and Southern Europe (Lombriasco, Italy), which have contrasting soils, organic carbon contents, climates, crops and management intensity. Simulations were carried out for the current (1998-2017) and future climatic scenarios (period 2020-2040, scenario Representative Concentration Pathway 6.0).Five cropping systems were simulated: conventional systems under ploughing at 25-30 cm with monoculture and residues removed (Conv–R) or residues retained (Conv+R); no-tillage (NT) with residue retained and crop monocultures; CA and CA with a cover crop, Italian ryegrass (CA+CC). In Conv–R, Conv+R and NT, the simulated monocultures were spring barley in Almalybak and maize in Lombriasco. In CA and CA+CC, crop rotations were winter wheat - winter wheat - spring barley - chickpea in Almalybak; maize - winter wheat - soybean in Lombriasco, together with Italian ryegrass in the +CC options.In Lombriasco, conventional systems led to SOC decline of 170-350 kg ha-1 yr-1, whereas, NT and CA prevented the decline and kept it on the slightly positive level under both climate scenarios. A low rate of SOC increase most likely stems from, in addition to climates, the low silt-clay fraction (34%), and thus, more vulnerable to mineralization and decay.In Almalybak, SOC loss in conventional systems was 480-560 kg ha-1 yr-1 under current climate, and NT prevented the loss only under current climate, but not under the future climate scenario. In contrast, CA allowed for the annual C sequestration of 300 kg ha-1 and up to 620 kg ha-1 with cover crops. Under the future climate scenario, the model predicted somewhat less C sequestration under CA, probably, due to the reduction of residue biomass. Particularly, in Southern Kazakhstan, CA has the largest potential for C sequestration under both climate scenarios, twice exceeding the objectives of the “4 per 1000” initiative. This initiative claims that an annual growth rate of 0.4% in the soil carbon stocks, or 4‰ per year, in the first 30-40 cm of soil, would significantly reduce the CO2 concentration in the atmosphere related to human activities.

The recycling of agricultural wastes, co-products, and by-products is necessary for creating circular economic (closed loop) agro-food chains and more sustainable agro-ecosystems. The substitution of N mineral fertilisers with recycled organic fertiliser promotes a circular economy, makes the agricultural system more environmentally sustainable, and guarantees food security. Results from a continuous maize experiment and four-year rotation cropping systems (maize, winter wheat, maize, and soybean) were used in a three-year study that replaced part or all mineral fertilisers with Municipal Solid Waste Compost (MSWC). In the first experiment, two different fertilisation strategies, MSWC only (M-Com) and mineral fertilisers (M-Min), were compared with zero nutrients (M-Test 0), whereas in the rotation cropping systems, mineral fertilisation (R-Min) was compared with a combination of MSWC and mineral fertilisers (R-Com + Min). Depressed yields resulted in the initial year of compost application, but by the middle term (three years), MSWC fertilisation showed a good N fertiliser value, mainly for yield summer crops and integrated with N mineral fertilisers. Different soil indicators and the N content in crop tissues and soil suggested that the scarce N availability recorded mainly during the first year is responsible for yield reduction. Due to limited supplies of MSWC, soil total N and the stable organic fraction bound tightly to minerals (MOM), did not vary significantly in the three-year experiment. Conversely, the more labile organic fraction (fPOM) increased only in the top soil layers (0–15 cm). Also in the top layer, M-Com increased the amount of organic fraction occluded into soil aggregates (oPOM). Furthermore, replacement of N mineral fertiliser with compost effectively mitigated N2O emissions in wheat and maize. Overall, the fertiliser value of MSWC was maximised when it was used repeatedly and in combination with mineral fertiliser, especially in spring and summer crops.

Organic farming has become increasingly important in recent decades as the consumer has grown its focus on the food and environmental benefits of the technique. However, when compared to conventional farming systems, organic farm system are known to yield less. Presented in this paper are the results from two organic cropping systems following six years of organic management. Fertilisation management differentiated the two systems; one was fertilised with green manure and commercial organic fertilisers, while the other was fertilised with dairy manure. A conventional cropping system, managed with mineral fertiliser as typical in the southern Piemonte region (Italy), served as the bussiness as usual crop management. The first hypothesis tested related to crop yield variation during the initial phase of organic management; we expected a sharp reduction in the early phase, then minor reductions later on. The second hypothesis tested related to soil fertility variation; we expected enhanced soil fertility under organic management. Overall, the organic system produced less, relative to the conventional system in interaction with year effect. Yield reduction seemed related to the lower soil nutrient availability of organic fertilisers that provided nutrients consequent to mineralisation. Therefore, summer crops are well-suited to manure-fertilised organic farms as mineralisation happens at higher temperatures, as opposed to winter wheat, which is largely reduced in such systems. Commercial organic fertilisers can, however, limit this effect through their high nutrient availability in the winter and early spring Also shown was that soil quality, defined as a general decrease in soil organic carbon (SOC) over time in the three analysed arable systems, can be mitigated by manure additions. Green manuring can maintain SOC and increase total N in soil, only if introduced for a sufficient number of years during crop rotation. Finally, soil fertility and Potential Mineralisable N in the different systems demonstrated that organic systems managed with commercial organic nitrogen fertilisers and green manure do not improve soil quality, compared to systems managed with mineral fertilisers.