Crop straw return is recommended as an effective management practice to alter soil organic carbon (C) content Understanding the effects of straw return rate on changes of soil organic C (SOC) is helpful for improving soil quality and sustaining crop productivity To determine the short-term responses of SOC content and grain yield to different annual straw return rates, a 2-year field experiment with a random block design was carried out in a rice–wheat rotation system Seven gradient rates of straw return, including 0%, 25%, 50%, 75% and 100% of total straw from previous crop returned in rice and wheat seasons, and 100% of straw returned only in rice or wheat season were set Both rice and wheat yields were investigated and SOC pools and C pool management index (CPMI) were measured The soil total organic C (TOC) and labile organic C fraction contents were higher under the straw return treatments compared to the no straw return treatment (0%S) at a 0–21 soil depth The 50% annual straw return rate (50%S) had significantly higher soil TOC, dissolved organic C (DOC), easily oxidizable C (EOC), and microbial biomass C (MBC) contents than the 0%S treatment at a 0–21 cm depth All of the straw return treatments had a significantly higher DOC content than the 0%S treatment at a 0–21 cm depth, except for the 100% only rice straw return treatment (100%RS) Compared to the 0%S, the 25%S and 50%S treatments had a significantly higher SOC lability (L), lability index (LI), C pool index (CPI) and CPMI at a 0–21 cm soil depth With the increase of straw return rate, the crop yields first increased and then decreased, and the 50%S treatment had the highest crop yields There were significant and positive correlations between the soil TOC and the annual crop yield We concluded that the 50% annual straw return rate is the best option for improving SOC sequestration and crop productivity in the rice–wheat rotation system of China

Short-term responses of soil organic carbon and carbon pool management index to different annual straw return rates in a rice–wheat cropping system

Long-term effects of tillage and straw management on soil organic carbon, crop yield, and yield stability in a wheat-maize system

The needs of healthy soils for a healthy world

Conservation agriculture, which is based on minimum tillage, permanent soil cover and crop rotations, has widely been promoted as a practice to maintain or improve soil quality and enhance crop productivity. To a large extent, the beneficial effects of conservation agriculture are expected to be provided by permanent soil cover with crop residues. Surface crop residues play an important role for crop growth through their benefits on soil-related structural components and processes in the agro-ecosystem, referred to in this study as agro-ecological functions. Through a meta-analysis of the literature, we have studied the relative effects of surface crop residue levels on the performance of a set of agro-ecological functions compared with a no-till bare soil, i.e., without surface residues. The selected agro-ecological functions were soil water evaporation control, soil water infiltration, soil water runoff control, soil loss control, soil nutrient availability, soil organic carbon (SOC) stocks and gains, weed control and soil meso- and macrofauna abundance. The potential effects of crop residue cover were quantified using boundary line models. Our main findings were (1) 8 t ha−1 of residues were needed to decrease soil water evaporation by about 30% compared to no-till bare soil. (2) To achieve the maximum effect on soil water infiltration, water runoff and soil loss control, residue amounts of at least 2 t ha−1 were required. (3) The effect of increasing the amounts of surface crop residues on soil nutrient supply (N, P and K) was relatively low; the boundary line models were not significant. (4) The average annual SOC gain increased with increasing amounts of residues, with a mean of 0.38 t C ha−1 year−1 with 4 to 5 t ha−1 of residues. (5) Weed emergence and biomass can be reduced by 50% compared to a no-till bare soil with residue amounts of 1 t ha−1 or more. (6) There was a weak response in soil meso- and macrofauna abundance to increasing amounts of surface crop residues. The maximum effect corresponded to an increase of 45% compared to a no-till bare soil and was reached from 10 t ha−1 of residues. Our findings suggest that optimal amounts of surface residues in the practice of conservation agriculture will largely depend on the type of constraints to crop production which can be addressed with mulching.

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Agro-ecological functions of crop residues under conservation agriculture. A review

Responses of soil carbon pool and soil aggregates associated organic carbon to straw and straw-derived biochar addition in a dryland cropping mesocosm system

Crop residue management and soil health: A systems analysis

Accurate and economically sound soil fertility recommendations are critical for ensuring profitable food production for smallholder farmers. However, such recommendations are lacking in many areas due to insufficient soil and crop response data. This study was conducted between 2016-2022 using boundary line analysis to evaluate crop response to soil fertility on 644 farms in Guatemala. We identify optimal soil property conditions for maize (Zea mays L.), common bean (Phaseolus vulgaris L.), and coffee (Coffea arabica L.) production in Guatemala and use crop price information to develop economically sound fertilization recommendations. We also analyzed the drivers of yield outcomes and assessed their relative importance with machine learning (ML) models. Results demonstrate that a majority of country-level data currently have sub-optimal soil nutrient levels and by optimizing nutrients, yields and profits could be improved in 64%, 51%, and 69% of maize, common bean, and coffee crops, respectively. In addition, ML underscored the central role of climate in shaping yield outcomes. Variable importance rankings from random forest indicated climate and water balance variables increased predictive accuracy more than soil parameters, highlighting the critical need for climate-smart adaptations in the region. The pairing of boundary line with ML analysis provided unique and complementary information about factors that drive yield of major crops in Guatemala. This is an effective approach for developing fertility recommendations in Guatemala and could be replicated in other countries where critical nutrient recommendations are currently lacking for closing yield gaps and identifying yield response to climatic stochasticity. This article is protected by copyright. All rights reserved 

Marie-Soleil Turmel

Papers

Crop residue management and soil health: A systems analysis

Boundary line analysis and machine learning models to identify critical soil values for major crops in Guatemala