Enhancing Maize Yields and Soil Health in Southern Africa Through Conservation Agriculture and Biochar

Effects of climate change pose a major threat to crop production in Southern Africa. In this region, agriculture provides livelihoods to over 70% of smallholder farmers, who are the main food producers. In the face of climate change and land degradation, smallholder farmers are seeking sustainable agricultural practices to improve crop yields and soil health.

“Conservation agriculture is a sustainable farming system designed to enhance soil health and agricultural productivity while minimizing environmental impact,” PhD candidate Mirriam Phiri explains.

In her doctoral thesis, Phiri has evaluated the impact of conservation agriculture and biochar on maize production and soil quality in Zambia.

“My goal was to identify practical solutions for smallholder farmers to combat the adverse effects of climate change and land degradation,” she says.

Impact of conservation agriculture on maize and phosphorus

In her thesis, Phiri has evaluated the impact of conservation agriculture on maize grain yields and phosphorus availability by comparing adjacent conservation and conventional farming practices across various regions in Zambia. It involved different land preparation methods, crop rotations, and residue management, with soil samples analysed for key nutrients and properties during and after the growing seasons.

Additionally, the effect of rotating maize with pigeon pea on phosphorus availability was assessed through both field trials and greenhouse experiments, focusing on plant uptake and soil nutrient changes.

Boosts maize yields

Phiri’s results indicate that conservation agriculture significantly boosts maize grain yields in rain-fed agriculture by 24% to 39% compared to conventional farming methods.

The yield improvements were most notable with seasonal precipitation, peaking at around 900 mm. This is particularly beneficial for Zambia's southern and western regions, which are prone to drought and have soils with limited water retention capacity.

Promising results with biochar

After five years of conservation agriculture practice, soil quality, including plant-available phosphorus, showed no significant difference between the practices.

However, the combination of conservation agriculture with pigeon pea biochar demonstrated potential to enhance plant-available phosphorus and phosphorus uptake by maize.

Economic alternative

Drought and land degradation severely impact crop production for smallholder farmers in Southern Africa.

“Declining soil fertility and productivity, coupled with acidic soils and low nutrient availability, exacerbate these challenges,” says Phiri.

Traditional soil fertility improvement methods, such as using organic matter, lime, and synthetic fertilizers, are often inaccessible to resource-poor farmers.

“My results show that conservation agriculture and biochar can help farmers improve crop yields and soil health in a changing climate,” she concludes.