Abstract
Conservation agriculture (CA) as a system is still evolving on many of the smallholder farms in sub-Saharan Africa (SSA) and questions on the impact of individual components and pathways toward adoption still require answers. A short-term study was conducted to investigate the effect of tillage, crop rotation, and crop residue management, including maize residue biochar on above ground biomass, cumulative carbon (C) input, soil organic carbon (SOC), and maize grain yield. A split–split plot design was used to evaluate two tillage operations (conventional tillage (CT) and no-till (NT)), three crop rotations (maize–fallow–maize (MFM), maize–oat–maize (MOM), and maize–vetch–maize (MVM)), and three-crop residue management (retention (R+), removal (R−), and biochar (B)). The cumulative above ground biomass produced in the MOM rotation was significantly higher by 78.9% and 88.7% relative to MVM and MFM rotations, respectively. The cumulative C input under residue management treatments ranged from 10.65 to 12.16 Mg ha−1. The highest SOC was observed under R+ (1.10%) followed by B (1.0%) and the lowest was in R− (0.96%). Crop residue management significantly affected grain yields in 2015/2016 (p < 0.05) and 2016/2017 (p < 0.01) summer seasons. Biochar did not result in an obvious improvement in both C input and crop yield. Smallholder farmers can potentially switch from CT to NT without any significant yield penalty, as well as adopt MOM and R+ practices for increased biomass and C input.
Highlights
The poor adoption of conservation agriculture (CA) is a result of several socioeconomic and biophysical factors like availability, cost and knowledge associated with use of herbicides for purposes of weed control, lack of adapted implements for direct sowing and residue management tradeoffs in crop–livestock farming systems [1,2]
This study showed that the adoption of crop rotations and residue management practices results in an increase in crop biomass, which is positively correlated C input
Changes in soil organic carbon (SOC) due to management practices occurred too slowly to reflect in maize grain yields in the short-term
Summary
The poor adoption of conservation agriculture (CA) is a result of several socioeconomic and biophysical factors like availability, cost and knowledge associated with use of herbicides for purposes of weed control, lack of adapted implements for direct sowing and residue management tradeoffs in crop–livestock farming systems [1,2]. Description of smallholder farmer practice of CA by many authors (e.g., [1,4,5]) shows that many adopt one or two of the principles but rarely all three [6]. Evaluation of interaction of factors involved in CA may reveal the best practices to promote a combination or steps that will assist to enhance improvement in early phases when there might be little visible evidence of change at field level. In this regard, a component omission experiment could be a useful tool. This approach can lead to the identification of informed and sustainable key entry points for potential adoption by the farmers [7,8]
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