Crushed cotton gin compost effects on soil biological properties, nutrient leaching losses, and maize yield

There is currently interest in the use of industrial by-products to reduce the use of synthetic fertilizers; however, most organic wastes contain relatively low N levels. Our objectives were to: (i) determine the effect of incorporating crushed cotton gin compost, with and without inorganic fertilizers, on soil biological properties during three maize crops (Zea mays L., cv. Tundra); (ii) study nutrient leaching losses from soils receiving these fertilizer treatments; and (iii) to evaluate the effect of these fertilizer treatments on nutrition and yield of a maize crop. Compost was applied at 0, 20, and 40 t ha(-1) rates with and without 400 kg N ha(-1) (as NH4NO3 80 kg P ha(-1) [as (NH4)H2PO4], and 120 kg K ha(-1) (as K2SO4) on a Typic Xerofluvent located near Sevilla (Andalusia, Spain) for 3 yr. At the end of the study, soil microbial biomass was 32% higher in the treatment including inorganic fertilizer than in the compost-only treatment. Soil biochemical properties were greater in the fertilizer treatment than the compost-only treatment (by 61, 50, 36, and 32% for dehydrogenase, N-alpha-benzoyl-L-argininamide protease, arylsulfatase, and phosphatase activities). Macronutrient losses were greatest in the treatment including inorganic fertilizer, where increases of 24% for inorganic N, 31% for P, and 18.5% for K over the compost treatment were noted. Lowest N/P ratios were produced by the treatment including inorganic fertilizer, which suggest a lower eutrophication risk in drainage waters from soils treated with this fertilizer. The mineral nutrition, grain protein, and maize yield indicate that the compost plus inorganic fertilizer is adequate and has a good potential for use.