NUTRIMENTAL POTENTIAL OF RED DOLICHOS, BROWN DOLICHOS AND COWPEA FOR GREEN MANURE PRODUCED UNDER THREE TILLAGE SYSTEMS

Abstract

The nutrimental content of N, NO3-N, P, K, Mg, Ca, Mn, Zn, Cu, Fe, and B, was evaluated in three bean cultivars of two species with potential to be used as green manure. Cultivars were the red lab-lab bean (RL) (Lablab purpureus), brown lab-lab bean (BL) (L. purpureus) and cowpea (CW) (Vigna unguiculata). Three tillage systems were assayed: conventional tillage (CT), minimum tillage (MT) and optimal tillage (OT). Results showed that the nutrimental content of N, NO3, P, K did not evidence statistical differences (P≤0.05) among bean cultivars and tillage systems. However, the greater content of N was in BL-CT with 4.85%. The content of P varied from 0.38 to 0.41% and the concentration of K from 2.40 to 2.84%. Ca showed the highest concentration in RL-OT with 2.88%, while the lowest percentage was evidenced by CW-CT, with 2.12% (P≤0.05). The highest percentage of Mg appeared in CW-OT with 0.89% and the lowest concentration was registered for BL-CT, showing 0.52% (P≤0.05). The highest Fe concentration was observed in RL-OT with 0.15% and the lowest in BL-CT and RL-CT, with 0.10%. The Mn content was significantly greater in CW without concerning the tillage system with 0.39% and the smallest concentration was obtained in RL-MT with 0.17%. The greatest percentage content of nutriment B was observed in BL-OT, RL-CT, CW-MT and CW-OT, from 0.024 to 0.030%. In contrast, the lowest content of B was found in RL-MT with 0.015%. The content of Zn did not showed statistical differences respect to the cropping system; the lowest concentration of Zn was observed in CW-OT with 0.0026% and the highest percentage in BL-OT with 0.0040. Cu was significantly highest in BL-CT, BL-MT, BL-OT, RL-CT, RL-MT, RL-OT and CW-OT, being BL-MT and BL-OT the combinations with the highest concentration (0.0061%), while the lowest concentration was observed in CW-MT and CW-CT, with 0.0048% and 0.0044%, respectively.