NUTRIENT DYNAMICS DURING THE FIRST 3 YEARS OF AN ALLEYCROPPING AGROECOSYSTEM IN SOUTHERN USA

An alleycropping system (AC), using Albizia julibrissin as the tree sp ecies, was compared to an annual legume-based cropping system (NA) ove r a three-year period. In both AC and NA, a crop rotation was implemen ted with the following sequence: Mucuna deeringiana, Trifolium incarna tum, Sorghum bicolor, Triticale aestivum, and Sorghum bicolor. Abovegr ound biomass of crops was analyzed for C, N, P, K, Ca, and Mg. A soil fractionation method was used to determine P dynamics in different tre atments through time. Aboveground net primary productivity (NPP) was h igher in the AC than in the NA. Nutrient input-output balance of N, P, K, Ca, and Mg from January through November 1991 was higher for AC th an for NA, Area-based sorghum yield in 1991 was lower in AC than in NA . comparative sorghum yield in 1991 at 1 m distance from the hedgerow was lower than NA sorghum, In a three year period, the alleycropping s ystem seemed to be more efficient in tapping unavailable forms of soil P, and achieved a higher P stock than the annual legume-based croppin g system.