Amendment type and Time of Addition Influence the Effect of Short-term Heating on Soil Respiration and Nutrient Availability

Abstract

Heating of soil influences soil respiration and nutrient availability. But little is known about how amendment type (plant residue or inorganic N and P fertilisers) or time between amendment application and heating influence the effect of heating. A sandy clay loam was incubated moist (165 g kg−1) for 8 days and amended with the same amount of total N and P as pea residue (C/N 59, C/P 435) or inorganic N and P (0.4 g N kg−1 and 0.06 g P kg−1) either 8 or 1 day before heating. On day 8, soils were heated to 60 °C for 30 min followed by rewetting to 165 g water kg−1 and moist incubation for 7 days. Soil was sampled before heating (day 8), 2 and 7 days after heating (day 10 and 15). Heating only reduced respiration when residue was added 1 day before heating. Heating had no effect on available N in fertiliser treatments. Heating increased available N on day 10 in the unamended soil by about 20% and in residue treatments about 10-fold, particularly when residue was added 1 day before heating. Heating increased phosphatase P two- to fivefold only on day 10; it increased citrate P on days 10 and 15 up to threefold compared with a greater effect in the residue treatments. Heating of soil had a greater effect of on respiration and available N and P pools after residue addition than unamended soil or soil amended with inorganic fertiliser.