Carbon, Nitrogen, Phosphorus, and Sulfur Mineralization in Plow and No‐Till Cultivation

Abstract

Abstract Conversion to reduced‐tillage management systems by winter wheat ( Triticum aestivum L.) producers may cause changes in soil organic‐matter transformations. This study was conducted to monitor C, N, P, and S mineralization differences between soils with notillage and conventional‐tillage winter wheat/summer fallow management histories. Intact soil cores were taken from research plots that had been in no‐tillage and conventional tillage for 16 yr. Cores were incubated at 25 °C and 350 g water kg −1 soil for 84 d. Carbon dioxide evolution, NO 3 ‐N, NH 4 ‐N, PO 4 ‐P (as NaHCO 3 ‐exchangeable P), SO 4 ‐S and recoverable plant‐residue (>2 mm) content were determined for soil depths of 0 to 2.5 cm, 2.5 to 5 cm, and 5 to 15 cm at 0, 7, 14, 28, 56 and 84 d of incubation. No‐till soils accumulated greater NO 3 ‐N, SO 4 ‐S, and PO 4 ‐P at the 0‐ to 2.5‐cm soil depth than did year‐old plow (preplow) and recently plowed (plow) soils. Tillage did not influence net N, P, and S mineralization below the 5‐cm soil depth. No‐tillage soils peaked at 26 kg ha −1 SO 4 ‐4 in the top 15 cm compared with 19 and 15 kg ha −1 SO 4 ‐S for plow and preplow soils, respectively. A nonstoichiometric accumulation of soil NO 3 ‐N, PO 4 ‐P, and SO 4 ‐S was observed within and among tillage treatments, indicating that N, P, and S transformations were partially controlled by separate processes associated with the tillage operations.