Enhancement of microbial nitrification to reduce ammonia emission from poultry manure: a review

Ammonia (NH3) emissions from poultry farming operations have become a crucial concern due to their potential adverse effects on performance, birds and human health, and the environment. Due to genetic improvements, current commercial poultry require high quality balanced nutrition to maintain their rapid growth and production. Amino acids are components of protein nutrition that greatly influence the growth of the birds, and methionine is the first limiting essential amino acid in the high protein diets of poultry. However, excess or misuse of amino acid supplementation to poultry diets increases nitrogen (N) excretion and emissions to the environment. Currently, there are limited numbers of research publications regarding NH3 emissions from poultry manure, and few of them address manure enhancement by microbial nitrification. Therefore, the aim of this review is to evaluate the potential of soil nitrifying bacteria to reduce NH3 volatilisation and enhance N retention in poultry manure. This review presents the current status of knowledge regarding soil nitrifying bacteria, NH3 nitrification, and summarises the strategies to enhance microbial nitrification of poultry manure, and the environmental ramifications when using different techniques to control NH3 emissions. In spite of the fact that there are few research studies on reducing NH3 volatilisation through nitrification, it has been concluded that nitrification would be a sustainable method for mitigating N excretion and NH3 emission from poultry; however, further research is needed to identify the proper nitrifying bacteria to enhance microbial nitrification.