Evaluation of Desmodium uncinatum, Fagopyrum esculentum and Brachiaria humidicola as potential green manure crops for nematode management in sugarcane

Abstract

Plant-parasitic nematodes remain a challenge to sugarcane growers in South Africa, and alternatives to chemical control are desirable. This project aimed to determine the impact of green manure crops Desmodium uncinatum, Fagopyrum esculentum and Brachiaria humidicola on nematodes and subsequent sugarcane yield. A pot trial examined the growth of these crops and their effect on plant-parasitic nematodes and subsequent sugarcane growth. Brachiaria produced the greatest biomass (to the detriment of the succeeding sugarcane crop) and significantly reduced the numbers of Pratylenchus nematodes in soil and roots. In a subsequent field trial, plots were planted to these same three green manure crops, with control plots either planted to sugarcane or left as a bare fallow. Four months later, sugarcane was replanted over the whole area. There were no significant differences between treatments in sugarcane growth or yield after growing these crops, and changes in selected nematode genera at different stages during the crop cycle were inconsistent across nematode genera and treatment. Further work is needed to investigate the nematode control potential of these crops before the system can be adopted at the field scale.