Quality as a factor influencing the possible utilization of eight exotic legume species as mulches

Abstract

Invasive exotic legumes need to be controlled by amongst others, mechanical control methods. Residues such as twigs and leaves of felled trees can possibly be utilized as a low cost, organic fertilizer. The quality of the organic materials influences their behaviour as mulches. In this study eight exotic legume trees were compared in terms of quality parameters such as C:N ratio, lignin, polyphenol, cellulose and hemicellulose contents. Additionally, a decomposition trial in pots was executed and three selected species were compared in terms of in vitro mineralization of C and N. Clear distinctions in terms of mulch quality could be drawn. Paraserianthes lophantha and Chamaecytisus palmensis produced mulch of a high quality, whilst Acacia pycnantha, A. saligna and A. melanoxylon produced mulch of a low quality. The mulch quality correlated well with the decomposition rates of the species in the pot experiment. The in vitro mineralization experiment supported the results of the other experiments and showed that mulch of a poor quality has an extended initial immobilization period. However, it can be used to protect soil against erosion, soil moisture depletion and weed establishment. The application of a mixture of low and high quality mulches will probably result in the most positive response by crop plants.

Key words:

• Exotic legumes
• low-cost fertilizer
• mulch quality
• small-scale farmers
• utilization