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There is currently an intense debate about the potential for additional organic carbon storage in soil, the strategies by which it may be accomplished and what the actual benefits might be for agriculture and the climate. Controversy forms an essential part of the scientific process, but on the topic of soil carbon storage, it may confuse the agricultural community and the general public and may delay actions to fight climate change. In an attempt to shed light on this topic, the originality of this article lies in its intention to provide a balanced description of contradictory scientific opinions on soil carbon storage and to examine how the scientific community can support decision-making despite the controversy. In the first part, we review and attempt to reconcile conflicting views on the mechanisms controlling organic carbon dynamics in soil. We discuss the divergent opinions about chemical recalcitrance, the microbial or plant origin of persistent soil organic matter, the contribution of particulate organic matter to additional organic carbon storage in soil, and the spatial and energetic inaccessibility of soil organic matter to decomposers. In the second part, we examine the advantages and limitations of big data management and modeling, which are essential tools to link the latest scientific theories with the actions taken by stakeholders. Finally, we show how the analysis and discussion of controversies can guide scientists in supporting stakeholders for the design of (i) appropriate trade-offs for biomass use in agriculture and forestry and (ii) climate-smart management practices, keeping in mind their still unresolved effects on soil carbon storage. [ABSTRACT FROM AUTHOR]

Population growth and improving living standards are leading to a growing demand for beef. The understorey in the 19 million hectares of oil palm plantation worldwide represent a source of cattle feed, while also sparing additional land conversion for grazing. Research on cattle grazing under oil palm is novel and knowledge is lacking on long-term profitability and sustainability of the system, a major deterrent to cattle–oil palm farming system adoption. Here we review the current literature on cattle grazing in oil palm plantations, to highlight the knowns and unknowns of grazing impacts on the understorey, cattle and oil palm productivity, as well as economic implications. This review’s major outcomes are the following: (i) although understorey utilization as feed is a major advantage of cattle–oil palm integrated farming systems, declining understorey productivity under ageing plantation indicates the need for alternative solutions for sustained cattle productivity over the plantation’s lifecycle; (ii) oil palm yields were reported to increase under cattle integration but evidence was weak, both oil palm yields and the pathways through which oil palm yields are impacted by cattle grazing should be further explored; (iii) economic analyses showed cattle grazing under oil palm plantations was profitable for large-scale oil palm producers due to cattle sales, and returns were further enhanced by reductions in weeding and fertilizer costs; (iv) sustainable cattle grazing was found to be difficult in smallholder oil palm plantations due to land constraints and the current practice of free-grazing; options for improving grazing sustainability and profitability in these systems should be explored. This systematic review concluded that cattle integration in oil palm plantations has great potential but further research is required to develop locally specific productive and sustainable systems of grazed cattle integration with oil palm plantations. [ABSTRACT FROM AUTHOR]

Oil palm plantations worldwide generate vast amounts of empty fruit bunches (EFB), often disposed of as waste and left to undergo natural decomposition or incinerated, contributing to greenhouse gas emissions. However, EFB could be used as soil conditioner to improve soil properties and increase crop yields. We conducted a meta-analysis to synthesize evidence of the effect of soil amendment by different forms of EFB on crop growth and yield and how other factors moderate performance. The meta-analysis included 19 studies on the growth and yield of crops grown on EFB-amended and unamended soils. Applying EFB as mulch, biochar, or compost to soil led to a 49.2% increase in crop growth and yield compared to unamended soils. When EFB were co-applied with a second material such as mineral fertilizers, crop growth and yield was increased by 16.4% compared to unamended soils. The growth and yield advantages were affected by the location of the experiment, soil texture, or the form of EFB applied. Compared to unamended soils, crops grown on soils amended with pyrolyzed EFB, raw EFB, composted, and ash EFB recorded growth and yield increase by ~78.4%, 33.8%, 30.9%, and 21.0%, respectively. Overall, amending soil with EFB is likely to increase crop yield. Still, the benefits must be clarified by a benefit-cost analysis based on the ratio of yield advantages from its usage to the cost of accessing or using the product by farmers. [ABSTRACT FROM AUTHOR]

Crop residue management is an important agricultural practice that has a high potential to improve soil health and optimize crop production. Compared to annual crops, relatively little is known about crop residue management effects on the yield and temporal stability of perennial crop production. This study focused on oil palm ( Elaeis guineensis), an important tropical crop that had expanded rapidly over the past decades. We aimed to understand the effects of applying a major oil palm residue, the empty fruit bunch, on crop yield and temporal stability of production. We compared 15 years of crop yield performance from a field trial in Sumatra, Indonesia. The treatments included empty fruit bunch application of three application rates (30, 60, and 90 t ha year), and a reference treatment of chemical fertilizers with no addition of empty fruit bunch. Compared to the reference treatment, the cumulative crop yield over 15 years under low, medium, and high application rates of empty fruit bunch increased by 2.4, 5.9, and 4.8%, respectively. The annual crop yield and temporal stability in production were not significantly different between treatments. Soil organic carbon was significantly higher under medium application rate of empty fruit bunch compared to that under the chemical fertilizer treatment. Soil organic carbon and relative humidity were positively associated with annual crop yield with a time lag of 2 years. This study is the first to show that both crop yield and temporal variability of oil palm production can be maintained under crop residue application, compared to chemical fertilizer treatment. Furthermore, climatic conditions had strong effects on the temporal variability of oil palm production. These findings will inform the design of optimal empty fruit bunch application schemes that enhance sustainable intensification of oil palm cultivation. [ABSTRACT FROM AUTHOR]