Vermicompost Influences Soil P Pools and Available N—Effect of Placement and Combination with Inorganic Fertiliser

Abstract

Compost application can increase plant nutrient availability. But the effect of compost on nutrient availability may depend on a number of factors. In this study, the effect of application method (mulch layer or mixed into the soil) and combination with inorganic fertiliser on soil P pools and available N was investigated. Soil was filled in microcosm with six treatments, including control, vermicompost layer with or without fertilisers (CL, CL/F), bulk soil mixed with inorganic fertiliser alone (F), vermicompost alone (CM) and both of inorganic fertiliser and vermicompost (CM/F). The microcosms were incubated in the dark for 3 weeks. Citrate P, HCl P and resin P were the highest in F, but MBP was higher in CM and CM/F. Citrate P and HCl P were about three- and six-fold higher in CM and CM/F than in CL and CL/F. Available N was the highest in CL/F and 20% higher in CL than in CM. Vermicompost mixed into soil slightly increased soil nutrient availability compared to unamended soil but had little effect when placed on the soil surface. Vermicompost mixed into soil with inorganic N and P could be used to minimise loss of N and P after inorganic fertiliser addition and thereby provide a longer-lasting nutrient supply for plants.