Assessing the impacts of agricultural managements on soil carbon stocks, nitrogen loss and crop production — a modelling study in Eastern Africa

Improved agricultural management plays a vital role in protecting soils from degradation in Eastern Africa. Changing practices such as reducing tillage, fertilizer use or cover crops are expected to enhance soil organic carbon (SOC) storage, with climate change mitigation co-benefits, while increasing crop production. However, the quantification of cropland managements’ effects on agricultural ecosystems remains inadequate in this region. Here, we explored seven management practices and their potential effects on soil carbon (C) pools, nitrogen (N) losses, and crop yields under different climate scenarios, using the dynamic vegetation model LPJ-GUESS. The model performance is evaluated against observations from two long-term maize field trials in western Kenya and reported estimates from published sources. LPJ-GUESS generally produces soil C stocks and maize productivity comparable with measurements, and mostly captures the SOC decline under some management practices that is observed in the field experiments. We found that for large parts of Kenya and Ethiopia, an integrated conservation agriculture practice (no-tillage, residue and manure application, and cover crops) increases SOC levels in the long term (+11 % on average), accompanied by increased crop yields (+22 %) in comparison to the standard management. Planting nitrogen-fixing cover crops in our simulations is also identified as a promising individual practice in Eastern Africa to increase soil C storage (+4 %) and crop production (+18 %), with low environmental cost of N losses (+24 %). These management impacts are also sustained in simulations of three future climate pathways. This study highlights the possibilities of conservation agriculture when targeting long-term environmental sustainability and food security in crop ecosystems, particularly for those with poor soil conditions in tropical climates.

Innovating Traditional Production Systems Through On-Farm Conservation Agriculture and Agroforestry Research

Maize (Zea mays L.), the staple crop of Mexico, is often produced by smallholder farmers on sloping terrains. Historically, little agronomic research has been performed under the conditions of these farmers to support them in the sustainable intensification of their production systems. We set up trials at two locations in the state of Oaxaca to evaluate conservation agriculture and agroforestry in collaboration with local farmers. Crop diversification through crop rotations, multicropping, relay cropping or agroforestry increased system yields the most, by up to 1.4 t ha−1 in Teopoxco and 1.7 t ha−1 in Tamazulapam. Increased input use through increased fertilization or liming did not increase profitability enough to justify their use. Zero tillage and residue retention increased yields and reduced production costs. Conservation agriculture with agroforestry was a high-yielding, profitable system that also reduced farmers' risk by providing several harvests per year. The most profitable combinations of agroforestry and conservation agriculture could produce up to $4,854 USD ha−1 in Teopoxco and $2,143 USD ha−1 in Tamazulapam, while the control treatments in the same sites and years produced $175 USD ha−1 and $92 USD ha−1 respectively. In several years the main crop failed, while the trees were able to produce due to their different growing season compared to maize. Through adaptive investigation under farmers' conditions, sustainable intensification of traditional production system is possible with low-cost changes that are locally adapted and within farmers' possibilities.

Experiences With Conservation Agriculture in the Eastern Gangetic Plains: Farmer Benefits, Challenges, and Strategies That Frame the Next Steps for Wider Adoption

While there are numerous studies that explore the agronomic and the economic benefits of Conservation Agriculture in South Asia, only few studies have explored the farmers' experiences and the drivers of its adoption. This study aims to learn directly from current users through exploration of their decision processes, evaluations, and experiences in extrapolating the concept for the broader scaling of Conservation Agriculture across the Eastern Gangetic Plains (EGPs) of South Asia. We analyzed a total of 57 qualitative and semi-structured individual interviews with the farmers who are currently implementing Conservation Agriculture practices across six locations. These farmers faced a variety of hurdles including hesitation in accepting and adopting the technology, technical performance challenges, information gaps, and subsidy/project dependence. To overcome these, respondents adopted various strategic approaches such as assuming the role of an educator by sharing their knowledge with other farmers in the community, changing mindsets for stover retention, adoption through self-investment, and opting for communal purchase of machinery to reduce project dependence. This led farmers to identify a range of benefits including improved socio-economic condition, increased respect in the community, and increased free time to pursue diverse interests and opportunities. Additionally, strengthened information networks such as improved interpersonal connection with agricultural universities, government extension systems, and local farmers groups have positively enhanced the uptake, allowing them to overcome further limitations. These findings provide novel learnings on how farmers overcome nine key friction points, and what this means for increasing the farmer uptake of new practices across the region, which are crucial for successful future interventions as implemented by the government and development organizations.

Effects of Tillage and Cropping Sequences On Crop Production And Environmental Benefits in the North China Plain

The ever-increasing trend of greenhouse gas (GHGs) emissions is accelerating global warming and threatening food security. Environmental benefits and sustainable food production must be pursued locally and globally. Thus, a field experiment was conducted in 2015 to understand how to balance the trade-offs between agronomic productivity and environment quality in the North China Plain (NCP). Eight treatments consisted of two factors, i.e., (i) tillage practices: rotary tillage (RT) and no-till (NT), and (ii) cropping sequences (CS): maize-wheat-soybean-wheat (MWSW), soybean-wheat-maize-wheat (SWMW), soybean-wheat (SW), and maize-wheat (MW). The economic and environmental benefits were evaluated by multiple indicators including the carbon footprint (CF), maize equivalent economic yield (MEEY), energy yield (EY), carbon sustainability index (CSI), etc. Compared with NT, RT increased the EY and MEEY, but emitted 9.4% higher GHGs. Among different CSs, no significant reduction was observed in CF. The lowest (2.0 Mg CO2-eq ha-1 yr-1) and the highest (5.6 Mg CO2-eq ha-1 yr-1) CF values were observed under MW and SWMW, respectively. However, CSs with soybean enhanced MEEY and the net revenue due to its higher price compared to that of MW. Although the highest CSI was observed under RT-MW, soybean-based crop rotation could offset the decline in CSI under NT when compared to that for RT. These findings suggest that conservation agriculture (CA) could enhance the balance in trade-offs between economic and environmental benefits. Additional research is needed on how to achieve high crop production by establishing a highly efficient conservation agriculture system in the NCP.