Key points
• A three year field trial established near Darfield in 2010 examined the effects of a one-off application of compost at differing rates, in combination with nitrogen and phosphate fertiliser, on the production of five sequential crops.
• The crop rotation from the first crop established was: spring barley, winter forage oats, spring barley, winter forage oats and a vining pea crop.
• The one-off application of 36 t/ha compost led to significant increases in dry matter for the first three crops in the rotation. All rates of compost increased barley yield in the first year, but only the 36 t/ha rate increased barley yields significantly in the second year.
• The highest barley yields came from a combination of compost, P and N. As yields were higher when compost was added it was assumed that compost was supplying a limiting nutrient, possibly more P.
• Many treatments were uneconomic for the barley crops. At the end of two seasons the most profitable treatment came from applying N and P fertiliser and no compost.
The 36 t/ha treatment gave a significant increase in forage oat dry matter yield in the first season only, and showed positive returns as no further fertiliser was added. However this treatment was not economic over the cropping rotation.
• There was an increase in Olsen P during and at the completion of the trial but no changes in soil N or quality.
No. 101 Evaluation of compost in a cropping rotation
