Application of spent mushroom compost to a riverine silt loam at the time of pasture renewal and its effect on soil infiltration rate

Abstract

Pasture renewal is an important strategy for maintaining pasture production. While cultivation during pasture renewal can improve soil macropores in the short term, these benefits do not necessarily persist. Evidence from previous studies indicates that compost applied to agricultural soils can improve soil physical properties and increase earthworm numbers. We assessed whether adding mushroom compost at the time of pasture renewal would have further benefits on soil infiltration. We applied commercial mushroom compost to a riverine silt soil that had low soil infiltration and regularly ponded temporarily during irrigation events. The experimental treatments were assigned to replicated field plots (5m x 6m) and included: A) no pasture renewal, no cultivation, B) pasture renewal, no cultivation, C) pasture renewal, cultivated, D) pasture renewal, cultivated, 50t/ha compost applied, E) pasture renewal, cultivated, 100t/ha compost applied, and F)
pasture renewal, cultivated, 150t/ha compost applied. Soil infiltration rates measured 2 months after initiating
treatments indicated no difference between plots that were cultivated and amended with compost compared with those plots left under the original pasture (and without cultivation). However, for pastures that were renewed via direct drill (i.e., without cultivation), soil infiltration rates were significantly (P<0.05) lower than all other treatments and likely reflected surface soil damage that was caused by heavy rainfall soon after drilling new seed rather than the absence of compost.
After 14 months none of the management approaches for renewing pastures that we assessed were found to have a lasting effect on soil infiltration rate. Earthworm numbers and total earthworm biomass measured after 7 months were not significantly different across treatments across all compost rates evaluated. However, earthworm biomass tended to be lower in the cultivated soils compared with the non-cultivated treatments (P<0.10). This experiment indicates that a
single application of mushroom compost during the renewal of pasture had limited benefit in improving soil infiltration rates or increasing earthworm numbers within 14 months after pasture renewal.