Optimizing Sweet Sorghum Production in Marginal Lands Through Conservation Agriculture: A Case Study from Eastern Cape, South Africa

The use of marginal soils is fundamentally important in the implementation of the biofuel strategy in South Africa. However, the anticipated increase in production, particularly in the former homelands may present several challenges. For instance marginal soils are highly susceptible to soil degradation. Therefore, benefits achieved through carbon sequestration are erased by the negative effects of intensification of production and land use change. Moreover, annual biofuel crops may deplete soil organic matter (SOM), cause soil erosion, nutrient depletion and soil pollution through associated direct and indirect land use change. Consequently, the application of conservation agriculture (CA) was identified as a potential sustainable production system for producing bioenergy sweet sorghum in South Africa. Several studies conducted in South Africa attest to the benefits of CA in improving soil fertility and crop productivity. This chapter seeks to highlight the potential of CA to sustain sweet sorghum production on marginal soils. The work summarizes main finding on the effect of tillage, crop rotation and residue management on physical and chemical soil properties in a study done in Eastern Cape marginal lands, South Africa, in a sweet sorghum production system. The highlighted findings show that CA significantly improved the major aggregate binding agents. Mean weight diameter (MWD) and selected binding agents (soil organic carbon (SOC) and glomalin-related soil proteins (GRSP)) were significantly influenced enhance by NT compared to CT. NT also increased Bulk density and penetrometer resistance while all the treatments did not influence infiltration rate. NT and residue management at 30% increased soil nutrient availability. In addition, NT+ 30% residue retention interaction increased NH4+-N and potassium (K) availability. The application of NT + 30% treatment combination was identified as a potentially sustainable production system that can enhance soil quality indices in marginal soils of Eastern Cape under sweet sorghum as a biofuel feedstock.