Synergistic effect of a tropical earthworm Balanteodrilus pearsei and velvetbean Mucuna pruriens var. utilis on maize growth and crop production

Abstract

Many Mexican and Central American farmers use the legume cover crop Mucuna pruriens (velvetbean) to reduce weed growth, enhance soil fertility, and reduce the use of irrigation, tillage and herbicides. This cropping system can also maintain abundant native earthworm populations, such as of the endogeic species Balanteodrilus pearsei, although the functional significance of these earthworms, particularly their effects on litter decomposition and plant growth are still mostly unknown. Therefore, a completely randomized 2 × 2 factorial was set up to investigate the effects of B. pearsei and M. pruriens litter on maize growth under controlled conditions. One maize plant was grown in each bucket for 120 days and each treatment was replicated 10 times. Treatments consisted of: soil without B. pearsei and without M. pruriens residues (S); soil with B. pearsei and without M. pruriens litter (SB); soil with M. pruriens and without B. pearsei litter (SM); soil with B. pearsei and M. pruriens residues (SBM). In SBM, biomass, abundance and sexual maturity of B. pearsei were, respectively, 1.6, 1.4 and 2.4 times higher than in the treatment lacking M. pruriens (SB). B. pearsei presence significantly reduced the amount of M. pruriens litter mass remaining on the soil surface. Maize root biomass and grain yields were significantly higher in SBM than in SM, S and SB. Grain yield was significantly related to B. pearsei abundance and biomass, as well as to M. pruriens litter breakdown. The positive yields effects of SBM in this experiment appear to be due to a synergistic effect of B. pearsei and M. pruriens. These findings point to the importance of providing adequate conditions for earthworm activity in tropical agroecosystems, together with organic residue management, to enhance soil fertility, crop yields and agricultural sustainability.