Researchers from the United States and Zimbabwe say that in Malawian smallholders’ farms maize yields are low, resulting in low food production in the country.
The researchers compared three farming systems: no-till maize or continuous maize farming with the soil left relatively undisturbed from harvest to planting, growing maize with crops such as cassava and cowpea on soils that had previous season's residues, and planting crops such as sweet potatoes and beans on soils that had most crop residues cleared or burned.
“Incorporating crop rotations had the greatest impact on maize yields with yield increases ranging from 11 to 58 percent greater than continuous no-till maize.”
Dan TerAvest, Washington State University
According to the study published last month (20 December) in Agriculture, Ecosystems & Environment, the crop rotations were implemented in two agro-ecological zones in Malawi: Nkhotakota and Dowa districts from 2011 to 2014. The researchers assessed the effect of the three farming systems on outcomes such as soil moisture content, earthworm abundance and crop production.
“Incorporating crop rotations—whether in conventional or conservation agriculture tillage systems—had the greatest impact on maize yields with yield increases ranging from 11 to 58 percent greater than continuous no-till maize,” says Dan TerAvest, a co-author of the study and a postdoctoral researcher in soil science at the Washington State University in the United States.“This is most likely due to a combination of factors such as improved soil fertility and quality, and reduced pest and disease pressure following rotation.”
TerAvest adds that conservation agriculture could offer significant benefits to farmers in Malawi and the rest of Sub-Saharan Africa, but more effort is needed to determine what conditions are best suited to it, instead of promoting it to every farmer everywhere.
The study, he notes, also highlights the need to diversify conservation agriculture systems and incorporate crop rotations to maximise benefits, adding that the findings should help formulate interventions that are based on site-specific conditions instead of using blanket policy recommendations that may benefit only a portion of smallholders.
Francis Chilenga, a principal agricultural extension officer at the Karonga Agricultural Development Division, Malawi, agrees with the findings, stressing that different crops have different rooting depths, resulting in differences in how they draw nutrients and moisture from different layers.
“If [maize is] alternated with legumes, soil fertility is improved because legumes fix nitrogen in the soil,” says Chilenga. “This calls for farmers to adopt conservation agriculture because, among others, it improves soil structure, water retention, organic matter content and fertility. All these lead to higher and more stable yields.” Elias Tambalale, a subsistence maize farmer from Traditional Authority Msakambewa in Dowa district, Malawi, tells SciDev.Net:“We have experienced before that when we change the crops we grow on our pieces of land, we get better yields than when we grow the same crop continuously.”
Tambalale adds that agricultural extension officers have introduced conservation agriculture approaches such as minimum soil disturbance and total soil cover to smallholders.
“The findings give us more reason to believe what we are doing and that should help us boost yields,” he says.
This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.