Rapid changes in carbon and phosphorus after rewetting of dry soil

Drying–rewetting (DRW) cycles are important for soil organic matter turnover; however, few studies have considered the short-term effects on nutrient availability. The pulses in soil respiration, extractable C, P and N pools were quantified after a single DRW cycle (ten sampling times over 49 h). Soil was pre-incubated with or without glucose (2.5 g kg−1) for 10 days to induce differences in the size and activity of the microflora and then either subjected to a single DRW cycle (7-day drying period) or kept constantly moist. A resin extractable P (Presin) method was used and compared to extraction of dissolved organic (DOP) and inorganic P (DIP) with a salt solution. The pulse in soil respiration, extractable organic C (EOC), Presin, DOP and DIP was immediate and greatest in the first 2 h. The Presin pulse was two to three times that measured by solution extraction (DIP). Also, Presin quantified temporal changes in P not apparent in DIP, indicating the advantage of anion-exchange membranes in quantifying short-term changes in P availability. The Presin pulse was smaller in the soil incubated with glucose showing that P pulses will be quantitatively smaller in a soil with an active microbial biomass. In contrast to P, pre-incubation with glucose did not alter EOC concentration or the pulse in EOC after rewetting. The Presin pulse had disappeared by 49 h after DRW despite continued elevated rates of respiration. The sustained increase in DIP following DRW may have implications for plant availability or environmental losses.Clayton R. Butterly, Ann M. McNeill, Jeff A. Baldock and Petra Marschne