Amending Soil With Biochar From Available Agricultural Wastes to Improve Sustainability of Cotton Production in Mali

Improving the sustainability of cotton production in Mali can be achieved by returning organic matter and nutrients to degraded soils. Amendment with biochar prepared from locally available feedstocks has been suggested as a pathway to sustainability. A greenhouse study was conducted to evaluate the effect of biochar prepared from two feedstocks readily available in Mali, cotton field residue and rice hulls, on cotton plants grown to six weeks. A composted municipal biosolid was included for comparison with the more carbon-stable biochars. Four soils of contrasting properties were included in the study. Plants were measured for shoot height and mass, root length and mass, whole plant tissue nutrients, and arbuscular mycorrhizal fungi (AMF) colonization in roots. Shoot height was often improved by amendment in all soils. Root mass was improved by amendment only in the soil with the greatest clay content. Nitrogen (N) uptake was significantly depressed, and phosphorus (P) uptake was increased under biochar and compost amendment in the most coarsely textured soil. No effect on N and P uptake was observed in the soil with the greatest clay content. Ridge regression analysis showed that AMF root colonization was positively related to the P content of the amendments (1.411*P amend ), negatively related to soil P (-0.486*P soil ) and positively related to both soil pH (2.153*pH) and clay content (1.129*clay%). Results indicate that degraded soils may be restored through amendment with biochar created from locally available feedstock to improve sustainability of cotton production. Soil properties will determine the degree of benefit.