Nitrogen cycling in conventional and no-tillage agroecosystems in the Southern Piedmont

ABSTRACT:

Nitrogen (N) dynamics in conventional and no-tillage agroecosystems of sorghum (1978-1979) and soybeans (1980-1981) in the Southern Piedmont were compared. Measurements of ecological processes, including crop and weed production, litter decomposition, and crop consumption by insects, along, with solution chemistry of soil, precipitation, and groundwater, provided the data base for generating annual N budget models. Data represented four annual cropping cycles (two sorghum/rye and two soybean/rye). Crop residue placement practices (i.e., tillage or its absence) were identified as major regulators of N cycling in these agroecosystems. Soil tillage accelerated rates of plant residue decomposition as well as the total amount of N transferred between several agroecosytem components. Decomposition of plant and animal residues under continuous no-tillage practices mimics that found in natwal terrestrial ecosystems. By immobilizing N at or near the soil surface, no-tillage systems recycle N more slowly but also more efficiently (as measured by cycling indices) than conventional tillage.