Safe Utilisation of Feedlot Manure and Effluent

Summary

In Australia, estimated manure production by the intensive cattle, poultry and pig industries is of the order of 1-1.5, 1-1.2 and 1.2 million Vyear, respectively. Cattle feedlot manure contains a high amount of organic matter, as well as macro and micronutrients essential for plant growth, although the release rate of nutrients is dependent upon the nature of the manure, the nutrient concentration and form and climatic conditions. This manure resource has, in the past, been considered a "waste product" that had to be disposed of. This project investigated ways to turn this "waste product" into a valuable nutrient' and organic matter source and to produce guidelines to define Best Management Practices (BMP's) for manure reutilisation.. This was achieved through field trials located on the Darling Downs of Queensland and on the Northern Tablelands of New South Wales.

This project monitored crop production, and nutrient and water dynamics, when feedlot manure was applied to soil. A one-off application of 60 t/ha manure supplemented with nitrogen fertiliser produced 57.5 t dry matter/ha of hay over a 3 year period compared to 55.2 t/ha when annual applications of 20- 25 t/ha of manure ( the normally recommended rate), plus nitrogen fertiliser were made. These yields compare to 14.0 t/ha without manure and fertiliser. Surface and sub-surface water runoff was lower with the higher manure application rate and nutrient loss in runoff was similar, and environmentally safe, between the two manure treatments.

The results indicate that a single large application of manure, together with applications of inorganic fertilisers to balance the nutrition of the crop, is the most productive and environmentally safe way to profit from manure reutilisation. Relay cropping with minimal cultivation maintains soil surface structure, which enhances water infiltration and so provides more water for the crop and reduces water and nutrient loss. These findings have been incorporated into recommendations for Best Management Practices for feedlot manure reutilisation.