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

[摘要] Improved agricultural management plays a vital role in protecting soils from degradation in eastern Africa. Changing practices such as reducingtillage, fertilizer use, or cover crops are expected to enhance soil organic carbon (SOC) storage, with climate change mitigation co-benefits, whileincreasing crop production. However, the quantification of cropland management effects on agricultural ecosystems remains inadequate in thisregion. Here, we explored seven management practices and their potential effects on soil carbon ( C ) pools, nitrogen ( N ) losses, andcrop yields under different climate scenarios, using the dynamic vegetation model LPJ-GUESS. The model performance is evaluated against observationsfrom 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 inthe field experiments. We found that for large parts of Kenya and Ethiopia, an integrated conservation agriculture practice (no-tillage, residue andmanure application, and cover crops) increases SOC levels in the long term ( +11  % on average), accompanied by increased crop yields ( +22  %)in comparison to the conventional management. Planting nitrogen-fixing cover crops in our simulations is also identified as a promising individualpractice 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 thepossibilities of conservation agriculture when targeting long-term environmental sustainability and food security in crop ecosystems, particularlyfor those with poor soil conditions in tropical climates.

[学科分类] 大气科学