INFLUENCE OF ORGANIC BY-PRODUCTS AND NITROGEN-SOURCE ON CHEMICAL AND MICROBIOLOGICAL STATUS OF AN AGRICULTURAL SOIL

We assessed the influence of the addition of four municipal or agricul tural by-products (cotton gin waste, ground newsprint, woodchips, or y ard trimmings), combined with two sources of nitrogen (N), [ammonium n itrate (NH4NO3) or poultry litter] as carbon (C) sources on active bac terial, active fungal and total microbial biomass, cellulose decomposi tion, potential net mineralization of soil C and N and soil nutrient s tatus in agricultural soils. Cotton gin waste as a C source promoted t he highest potential net N mineralization and N turnover. Municipal or agricultural by-products as C sources had no affect on active bacteri al, active fungal or total microbial biomass, C turnover, or the ratio of net C:N mineralized. Organic by-products and N additions to soil d id not consistently affect C turnover rates, active bacterial, active fungal or total microbial biomass. After 3, 6 or 9 weeks of laboratory incubation, soil amended with organic by-products plus poultry Litter resulted in higher cellulose degradation rates than soil amended with organic by-products plus NH4NO3. Cellulose degradation was highest wh en soil was amended with newsprint plus poultry litter. When soil was amended with organic by-products plus NH4NO3, cellulose degradation di d not differ from soil amended with only poultry litter or unamended s oil. Soil amended with organic by-products had higher concentrations o f soil C than soil amended with only poultry litter or unamended soil. Soil amended with organic by-products plus N as poultry litter genera lly, but not always, had higher extractable P, K, Ca, and Mg concentra tions than soil amended with poultry litter or unamende soil. Agricult ural soil amended with organic byproducts and N had higher extractable N, P, K, Ca and Mg than unamended soil. Since cotton gin waste plus p oultry litter resulted in higher cellulose degradation and net N miner alization, its use may result in faster increase in soil nutrient stat us than the other organic by-products and N sources that were tested.