Phosphorus and cation dynamics of components and processes in conventional and no-tillage soybean agroecosystems

Abstract

Phosphorus (P) and cation (K, Ca and Mg) dynamics in conventionally (moldboard) plowed and no-tillage soybean agricultural systems are compared on the Georgia Piedmont. Data are presented on crop and weed biomass and elemental content in these components over a 2-year period as well as seasonal dynamics of elemental concentrations in litter, soil, throughfall and soil water. Final accumulation of above-ground soybean biomass was greater in conventionally plowed treatments. Grain yields were significantly greater in the no-tillage treatments during 1 year of the study. Soybean root biomass was greater under conventional tillage management. Weed biomass was consistently higher with the no-tillage practice. In both tillage treatments, weed tissue had higher elemental concentrations than did soybean tissue. With P, Ca and Mg, there was a trend toward higher concentrations of these elements in no-tillage than conventional tillage litter. In the upper soil stratum (0–10 cm), K, more than the other three elements, varied the most markedly with tillage treatment. In the lower soil stratum (30–40 cm), P concentrations were consistently higher in the conventionally tilled soil. Concentrations of elements in soil water collected with porous-cup lysimeters indicated higher amounts of Ca, K and Mg in samples from the conventionally tilled systems, indicating that the no-tillage system was more conservative of these nutrients than the plowed system.