QUALITY AND DECOMPOSITION OF BLACK LOCUST (ROBINIA-PSEUDOACACIA) AND ALFALFA (MEDICAGO-SATIVA) MULCH FOR TEMPERATE ALLEY CROPPING SYSTEMS

Black locust and alfalfa mulch quality were characterized over a 9-wee k period of decomposition. Both mulch materials were harvested with a forage harvester. The black locust material was harvested from trees a nnually coppiced for four years, the alfalfa from a pre-florescent sec ond cutting. Two identical, adjacent experiments were conducted, one o n each mulch source. A randomized complete block design was used with four replications for this single factor experiment. Fifty grams fresh weight of both mulch types were placed in litter bags, made of 98% sh ade cloth, a woven plastic with holes approximately 1 x 0.5 mm. The tr eatments included two placements of the mulch material, surface and bu ried. Sampling took place on weeks 0, 1, 3, 6, and 9. The incorporatio n of mulch materials appears to accelerate dry weight loss. From an in itial dry weight of 44.25 g, the buried black locust mulch averaged 4. 58 g, while the surface mulch averaged 7.41 g by week 6. The alfalfa m ulch initially weighed 40.99 g, with buried mulch averaging 1.75 g and surface mulch averaging 4.08 g by week 9. Carbon concentration of alf alfa mulch increased with time in both mulch placements from 43.6% to 57.6% and 51.8% in surface and buried mulch, respectively. Black locus t, with an initial carbon concentration of 46.9% increased to 55.9% fo r the buried mulch and to 53.89% in surface mulch. Nitrogen concentrat ions increased as well in buried mulch. Lignin concentrations increase d dramatically over time for both species of mulch. Black locust ligni n concentrations rose from 13.11% to 51.0% (buried) and 32.9% (surface ); alfalfa mulch lignin concentrations rose from 6.67% to 31.4% (burie d) and 47.7% (surface).