Crop uptake of nitrogen, phosphorus and potassium from soil amended with chicken manure and green waste compost

Organic amendments can be a useful source of nutrients for vegetable crops. A two-year field trial on a Levin silt loam compared the uptake of nitrogen (N), phosphorus (P) and potassium (K) from uncomposted chicken manure and green waste compost. Each year three crops, (silverbeet, sweetcorn and winter cabbages) were grown in rotation. Two rates of both uncomposted chicken manure (5 and 15 tlha) and green waste compost (50 and 300 t/ha) was applied annually in a replicated trial. Application of organic amendments increased crop yields. N in uncomposted chicken manure appeared to be more available for plant uptake than N in green waste compost. Applying green waste compost at 300 t/ha increased soil organic carbon content from 2.7% in the control to 3.6%. As the amounts of N, P and K applied in this rate of compost were in excess of crop requirements, a surplus of N, P and K in the soil was