Soil Temperature and Fumigation Effects on Plant Phosphorus Uptake and Related Microbial Properties

Early season problems with growth of corn (Zea mays L.) under cool, wet conditions prompted a study of the effects of soil and environmental conditions on mineralization and plant uptake of phosphorus (P). Our objective was to determine the effect of soil test P, temperature, and soil fumigation on soil P availability and uptake during early corn growth. Corn was grown in growth chambers at temperatures of 14°C or 25°C. Soils were a high-P Hastings silty clay loam (fine, montmorillonitic, mesic Udic Argiustoll) and a low-P Sharpsburg clay loam (fine, montmorillonitic, mesic Typic Argiudoll). Plants grew for up to 42 d either in soil which had been fumigated with methyl bromide to reduce microbial populations or left unfumigated. We harvested whole pots for soil and plant analysis at 1, 14, 28, and 42 d after planting. Biomass carbon (C) and biomass P were lower in fumigated soils and biomass C increased with time. Fumigation increased Bray Pl-extractable P at all times. Phosphatase activity and mycorrhizal colonization were both reduced by fumigation. Cumulative plant P uptake was highest in Hastings at 25°C. Higher temperature and higher initial P status increased plant P uptake during early growth. Plants grown in fumigated soil did not take up more P, despite greater extractable P