Effect of residue and fertiliser management on soil fertility in a long-term sugarcane trial in South Africa

Abstract

Understanding the impact of long-term continuous addition of sugarcane residues and fertiliser on soil fertility is important for development of best management practices. The experiment commenced in 1939. The fertility of the 0–10 cm soil layer was affected by the management options, but neither mulching nor fertiliser impacted significantly on soil organic carbon (SOC). However, the combination of mulching and fertiliser application increased the SOC content in the 0–2 cm soil layer significantly. It also increased soil acidity, as well as the concentration of iron, manganese, zinc and silicon, whereas reducing pH, the effective cation exchange capacity and the concentration of two of the basic cations, namely calcium and magnesium, in the 0–20 cm soil layer. Fertiliser affected yield significantly. In the absence of fertiliser, mulching had a significant effect on yield. Soil moisture and yield correlated linearly. In conclusion, increasing the addition of organic matter to continuously fertilised soils accelerated soil acidification leading to the loss of exchangeable basic cations. It is, therefore, important to take cognisance of the acidification potential of added residue under a greencane harvesting (mulching) system; this consideration emphasises the need for soil conditions to be rigorously managed on the basis of regular soil analysis.