article · Agriculture Ecosystems & Environment
Soil nitrogen scarcity is a major barrier to crop productivity across sub-Saharan Africa. A meta-analysis of 87 studies across 15 countries examined how climate-smart agricultural methods, specifically conservation agriculture and biochar amendments, influence nitrogen dynamics and crop productivity compared to conventional approaches. Both conservation agriculture and biochar substantially increased overall grain yields and nitrogen use efficiency. Biochar notably boosted biological nitrogen fixation, whereas crop residue retention raised soil nitrate levels and increased nitrous oxide emissions. Existing soil characteristics played a decisive role, with yield gains peaking in soils holding between 0.5 and 1.0 percent total organic carbon. Crucially, the benefits of climate-smart techniques over conventional farming were strongest when inorganic nitrogen fertilizer was absent or used at very low rates, showing that these interventions deliver their greatest relative yield and efficiency advantages in low-input systems.
Low soil fertility severely limits agricultural yields for farmers across sub-Saharan Africa who cannot afford expensive synthetic fertilisers. This analysis demonstrates that adopting biochar and conservation agriculture improves crop output and nutrient efficiency precisely in low-fertiliser conditions. It offers clear evidence on how sustainable soil management can support food security while identifying trade-offs, such as increased greenhouse gas emissions from residue retention.
The findings can inform agricultural extension programmes, biochar producers, and soil amendment developers targeting smallholder farmers who operate with minimal chemical inputs. Because this is a synthesis of existing field research from 15 countries, the underlying practices are tested and ready for field deployment. However, the abstract does not describe a proprietary technology or direct commercial product pathway.
AI-generated from the published abstract. Always read the original work before citing.
Soil nitrogen (N) is one of the most limiting factors affecting crop production in sub-Saharan Africa (SSA). Here we conducted a meta-analysis on the effect of climate smart agricultural (CSA) practices (conservation agriculture (CA) and/or biochar (BC)) application on: (1) soil nitrate-N (NO 3 -N), nitrous oxide (N 2 O) emission, biological N 2 -fixation, percent of nitrogen derived from the atmosphere (%Ndfa), grain yield and nitrogen use efficiency (NUE), (2) the role of soil properties and regions on grain yield and N cycling under CA and/or BC biochar application; and (3) the relationship between inorganic N fertilizer and NO 3 -N, N 2 O emissions, NUE and grain yield. We synthesized 87 unique papers, from 15 countries in SSA with 1643 paired observations. On average across all studies, CA and/or BC significantly increased grain yield and NUE, compared to conventional practices. Residue retention resulted in a significant increase in soil NO 3 -N and N 2 O emission, compared to conventional practices. Our analysis further indicates that BC application significantly increased biological N 2 -fixation, grain yield and NUE. Auxiliary soil parameters also affected grain yield and N cycling. Grain yield was significantly influenced by total organic carbon classes (TOC), whereby highest grain yield was recorded under CSA in soils with 0.5–1 % TOC, compared to soils with < 0.5 % TOC and > 1 % TOC. In addition, total nitrogen (TN) significantly affected the response ratio of CSA and conventional agriculture on N 2 O emission and biological N 2 -fixation. N 2 O emission increased significantly in soils with < 0.05 % TN, while biological N 2 -fixation increased significantly in soils with > 0.2 % TN. Increasing N fertilizer use significantly increased the response ratio of CSA and conventional agriculture on N 2 O and NO 3 -N while significantly reducing the response ratio of yield and NUE. The gap in yield and NUE between CSA and conventional agriculture practises was more pronounced at lower N rates of 0 kg ha −1 and narrowed as N input increased to 120 kg ha −1 ; this implies that, CSA offers more benefits compared to conventional agricultural practices under low N rates. • Conservation agriculture significantly increased grain yield and NUE, compared to conventional practices. • Residue retention significantly increased soil NO 3 -N, leading to higher N 2 O emissions, compared to conventional practices. • Biochar increased biological N 2 -fixation, grain yield and NUE, compared to conventional practices. • Climate smart agriculture offers more benefits in low N rates than high N rates, compared to conventional agriculture.
This page summarises published work. The authoritative version sits with the publisher.
DOI: 10.1016/j.agee.2024.109243
Is something wrong with this record? Report it or request removal.
Discussion
Have you built on this work, tried to replicate it, or seen it applied in practice? Share what you know. Verified researchers and MARATTO™ domain experts can open a discussion, and any member can reply. Contributions are reviewed before they appear.
No discussion yet. Open the first thread.
New to MARATTO™? Create a free account.
