Effects of tropical legume cover crops on soil quality at dryland farming area in Bali, Indonesia

Two field experiments were conducted to study the effects of tropical legume cover crops on soil quality in dryland farming areas at Angantaka village, Badung regency, Bali Province of Indonesia from June to November 2013. In the first experiment, three tropical legume cover crops (LCC) (Centrosema pubescens L.(Cp), Mucuna pruriens L.(Mp) and Pueraria javanica L. (Pj)) and one control (without LCC) were arranged in a randomized complete block design with four replicates. Variables measured were the quality of LCC biomass, C-absorbed and fixed-N by LCC. The LCCs were harvested after three months, which were then incorporated into the soil according to the treatments set for the second experiment. Design for the second experiment was a Split-plot with four replicates, where residues (biomass) of three LCC (results of the first experiment) were assigned as the main plot and four times of biomas incorporation (0,10, 20 and 30 days) as the subplot. Results showed that Pj was the best LCC crop among others (Cp and Mp) due to its highest quality. Pj also had the highest absorbed-carbon (58.50 t ha-1), fixed-N (490.21 kg ha-1), biomass FW and DW (304.83 and 116.99 t ha-1) among LCC species. The treatment of Pj with 30 days biomass incorporation significantly improved the soil quality as indicated by the highest soil moisture content (40.25%) and porosity (79.90%), organic-C (1.95%), total N (0.09%), available-P (15.71 mg kg-1), exchangeable-K (2.07 mg kg-1) and soil respiration (63.94 meC-CO2 kg-1day-1).