Agronomic effectiveness of vermicompost in grassland systems

Abstract

Vermicompost is the proccess of organic waste breakdown by red worms (Eisenia foetida) and other microorganisms. Vermicompost increases the bioavailability of nutrients which encourages the growth of plants and germination of seedlings, thus acting as an organic fertiliser. The objective of this trial was to assess and quantify the agronomic value of vermicompost applied to six different soils with respect to perennial ryegrass uptake of applied nitrogen, phosphorus, potassium and sulphur. The vermicompost was collected from the Tuaropaki Trust, in Mokai, along with six different soils collected from their sheep and beef farm, recently converted forestry block and dairy farm. A pot trial comparing perennial ryegrass response to vermicompost and equivalent soluble nutrients was set up at the Lincoln University glasshouse in May and was harvested in September 2017. The perennial ryegrass was analysed for dry matter yield and total nutrient uptake. Results showed, the relative agronomic performance of vermicompost at 6 and 12 t/ha was low in comparison to soluble nutrient uptake, especially for nitrogen (6-7%) and sulphur uptake (8-11%). This was suggested to be linked to the nutrients held in organic form, which was unavailable for immediate plant uptake. On the other hand, phosphorus (16-22%) and potassium uptake (25-26%) increased steadily with vermicompost application, which was associated with nutrients mainly present in inorganic forms. These trends were evident across six soils and with higher vermicompost applications of 24 to 96 t/ha. The findings of this experiment clearly demonstrated, Tuaropaki vermicompost was a relatively poor short-term source of major nutrients for perennial ryegrass compared with nutrients added in soluble form. However, Tuaropaki vermicompost could potentially be a viable slow release nutrient source and a soil conditioning agent.