Nitrogen mineralization trends of applied Mucuna pruriens var. utilis

Abstract

The effect of method of applying Mucuna pruriens var. utilis on the release of mineral nitrogen in an acid soil was investigated in the laboratory. The above-ground parts of M. pruriens were dried, milled and applied at a rate of 0.3 g 100 g-1 of field moist soil. Two methods of applying milled M. pruriens were used, namely surface application (T2) and incorporation (T3). The control treatment (T1), involving soil only, was also used. The treated soil samples were incubated at room temperature for periods ranging from 0 to 90 days while maintaining their contents at 60 per cent water holding capacity. At the end of the appropriate incubation period, the mineral N contents of the soil samples were measured by extracting soil with 2 M KCI, filtered and the filtrates were then steam-distilled. The mineral N released increased with increasing incubation period. The T1, T2 and T3 had cumulative NH4+-N values of 5, 5 and 8 kg ha-1, respectively, after the 90 days’ incubation period. The incorporation treatment had the largest amount of NO3-N (66 kg ha-1), followed by the surface application treatment (54 kg ha-1). The control treatment had the least (10 kg ha-1). The soil into which M. pruriens was incorporated (T3) had larger cumulative amount of mineral N (74 kg ha-1) than either T2 (59 kg ha-1) or T1 (15 kg ha-1). The efficiency of mineral N released from M. pruriens was 45 per cent for T2 and 61 per cent for T3. The results indicated that M. pruriens var. utilis, when applied to the soil, could be a potential source of mineral N for crop production