The use of additives in livestock slurries to improve their flow properties, conserve nitrogen and reduce odours

Abstract

In recent years there has been increased interest in using additives in livestock slurries to alleviate management problems, to reduce the risk of air or water pollution and to improve their fertilizer value. The limited amount of independent research undertaken with bacterial or enzymic preparations for accelerating decomposition, so making semi-liquid slurries easier to store and pump, suggests that these products are frequently ineffective or too expensive. More favourable reports have come from some farms. A number of chemicals have been shown to reduce loss of nitrogen (N) by ammonia volatilization but each may have adverse side effects and the economics of their use is questionable.

Nitrification inhibitors have proved to be effective in reducing losses of N by both denitrification and nitrate leaching, especially when used with autumn or winter slurry applications to freely drained soils; agronomic experiments on both grassland and arable crops have given inconsistent results. Chemical additives have proved more effective for reducing odours than bacterial or enzymic preparations. Some success has also been reported for certain re-odorizing or masking agents and for materials with a large sorptive capacity such as bentonites and zeolites. With oxidizing agents, large quantities are normally required to achieve a significant, long-term effect.