A major national project to evaluate the benefits of compost to vegetable production has demonstrated compost consistently increases marketable yield and improves soil quality. Its continued use will build soil nitrogen and carbon, increase soil biological activity and cation exchange capacity, increase water holding capacity, reduce bulk density and stabilise pH. This leads to increased returns and benefits for growers, the environment and the wider community.

When transplanting leafy crops good quality compost has been shown the elevate plant available nitrogen increasing yields and potentially allowing major reductions in applied fertiliser. Root crops were shown to be sensitive to compost quality and yield and ability increases were not as dramatic. To gain the full advantage of using compost on these crops it will be necessary to adjust fertiliser programs to account for the improved soil fertility.

Improved marketable yield and savings in fertiliser alone have been sufficient to return extra dollars particularly on light sandy soils. The greatest benefits arise when its regular use effectively ‘bullet proofs’ the soil against unanticipated climatic events, irrigation or equipment failure and human error that would otherwise result in loss of potential yield.

This is because compost increases soil organic matter which increases the soils ability to:

• Hold crop available nutrients and water
• Maintain and improve soil aeration and drainage
• Maintain optimal pH and reduce erosion

One of the most important findings has been the ability of compost to increase the supply of plant available nitrogen and potentially reduce the need for large amounts of inorganic nitrogen. It contains useful quantities of plant available phosphorus, potassium, and magnesium and the nitrogen it contains is retained in the soil and is available for future crop use. To achieve full benefits growers will need to incorporate the use of compost into their normal management programs and the repost acknowledges that a number of changes and evelopments are needed before growers will use compost on a large scale.

This project has been funded by Hort Innovation, using the research and development levies listed below and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.

• Vegetable Fund