Effect of Enrvironmental Variables On Crop Yield along a Climatic and Soil Gradient in Zambia.

Crop yield with biochar in conservation agriculture along climatic and soil gradients in Zambia

Lydiah Gatere (1), Robert Delve (2), Peter Hobbs (1), Steve DeGloria (1), Johannes Lehmann (1)(1) Department of Crop and Soil Sciences, Cornell University, Ithaca, USA; (2) TSBF-CIAT, Uganda

Soil degradation and nutrient mining is one of the most important challenges for agriculture in sub-Saharan Africa. Crop responses to fertilizer additions, should they be available, are often limited due to low nutrient retention and poor soil structure. Conservation agriculture is a strategy to improve soil fertility, often by using a combination of reduced tillage, crop residue retention, and organic amendments. Integrated in conservation agriculture, biochar may offer an approach for sustainably increasing organic carbon in soils that are typically poor in organic matter such as in Southern African savanna woodlands. However, it is not known under what climatic and soil conditions biochar additions will be effective in increasing crop yields. This study investigates yield of maize in conservation agriculture with biochar additions across a climatic gradient from about 500 to 1500 mm annual precipitation, and from sandy to clayey soils. Field experiments were installed on about 300 farmers fields in Eastern Zambia, comparing biochar as an alternative to animal manure (both with full fertilization) as an addition to planting holes both at rates of 6 ton C ha^-1 DM. Biochar was prepared locally from rice husks using mounds covered with grass and soil. Data from two seasons indicate overall similar yield increases with either animal manure or biochar additions, suggesting that maximum yield can be achieved with biochar as a soil conditioner as well as with manure as a fertilizer. Preliminary data indicate different yield responses to either biochar or manure additions with varying rainfall regimes and soil properties that warrant further investigation.