Soil water availability influences P pools in the detritusphere of crop residues with different C/P ratios

Abstract

Little is known about the effect of water availability on P pools in the detritusphere. Detritusphere was generated with two plant residues: 100% barley straw, C/N 95, C/P 255; 75% barley straw with 25% young faba bean shoot, C/N 74, C/P 200. Residues were placed between two PVC caps filled with soil at − 0.078 MPa, separating them from the soil surface with fine nylon mesh. Unamended controls were without residue between the two meshes. After 2 weeks, soil at 0–2 mm distance from the surface was collected and the soil water availability was either maintained at − 0.078 MPa or reduced to − 0.320 and − 1.700 MPa by drying in a fan-forced oven. Bioavailable P pools, available N, and microbial N were measured 1, 14, and 28 days after adjusting to different water availabilities. Soil respiration was measured over 28 days. Soil water availability had a stronger effect on respiration, available N, and microbial biomass N (MBN) in the mix than the control or barley. With the mix compared with − 1.700 MPa, cumulative respiration from day 0 to 14, available N and MBN were five, two, and three-fold higher at − 0.078 MPa. In the control or with barley, differences between the two water contents were two or less fold. Low water availability limits microbial activity and nutrient fluxes at high substrate availability as in the mix but has little effect when substrate availability is low even at high water availability as in the control and with barley.