SOIL SOLUTION COMPOSITION AS INFLUENCED BY TILLAGE AND TIME OF NITROGEN-FERTILIZATION

Tillage practices impart physical changes to the solum that may alter patterns of nutrient availability in soil profiles. The soil solution composition may be indicative of altered patterns of nutrient availabi lity. Soil solution compositional analysis was used to compare the eff ects of 7 years continuous no-tillage (NT) vs. conventional tillage (C T) management of corn (Zea mays L.), and differing times of N fertiliz ation, on solute distribution in a Loring (fine-silty, mixed, thermic Typic Fragiudalf) soil subjected to continuous CT for >20 years. Tilla ge plots received 168 kg N ha-1 as NH4NO3, broadcast either at plantin g (Early) or 5 weeks after planting (Late). Soil solutions obtained by vacuum displacement for three sampling dates (3 April, 8 May, and 24 June) were analyzed for pH, electrical conductance (EC), dissolved org anic C (DOC), and total concentrations of K, Na, Ca, Mg, NO3, Cl, SO4, and Al (24 June only). Tillage and time of N application frequently i nteracted to influence solute distribution in the soil profile. Compar isons of CT Early and CT Late with NT Early and NT Late, respectively, consistently indicated higher EC, NO3, Ca, and Mg for subsoils (>30 c m) sampled under CT. The imposition of NT on a soil that had been in l ong-term continuous CT resulted in altered patterns of nutrient distri bution as reflected in the composition of soil solution sampled throug hout the growing season.