Proper estimation of the nitrogen (N) content of poultry manure and proper manure handling are necessary to ensure that application rates minimize emissions from the manure and nitrate leaching into the cropland. Uric acid and undigested proteins are the two main N components in poultry manure that cause ammonia emissions and nitrate leaching in the ground water. The ammonia that is applied to cropland may be 50 to 90% of total N, depending upon the way the manure has been stored or treated. Ammonia and hydrogen sulphide contents have been proven to be useful alternative measures of odour reduction. The order of importance in influencing ammonia formation is : litter pH > temperature > moisture content. Total fixation of ammonia was achieved below pH 4 and temperatures down 10°C are necessary to have a negative effect on degradation and volatilisation. Adsorbants such as sawdust and straw enable the capture some of the readily available N and enable the microbial population to start immobilizing N. The organic fraction of poultry manure had a C/N ratio that varied from 1 to 27:l. Most of the N (approximately 60 -70%) excreted in poultry manure is in the form of uric acid and urea. Total N, total Kjeldahl N (TKN), organic N, ammonium, nitrate and nitrite are significantly correlated with the amount of N mineralised as well as the fraction of organic N mineralised during incubation. Some useful equations are: Inorganic N (IN) = ammonium + nitrate + nitrite; Total N (TN) = TKN + nitrate + nitrite; Organic N = TKNammonium or TN -(ammonium + uric acid) or TN -IN; Available N (AN) = Inorganic N + 0.4 x organic N; Predicted available N (PAN) = 80% Inorganic N + 60% Organic N.

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This paper describes, under laboratory and/or field conditions, an approach that could be used to predict nitrogen (N) mineralization of poultry litter. Proper composting of poultry litter results in N mineralization, reducing or eliminating the environmentally harmful effects of ammonia (NH 3 ) odours and nitrate leaching. Addition of straw to poultry manure provides sufficient available carbon and increases NH 3 binding capacity, overruling any greater influence of diet composition on methane (CH 3 ) formation. C:N ratio ranges (6-25) vary in the amount of low N loss depending on substrates. Aerobic decomposition of manure results in formation of humified organic compounds and decreased nutrient availability, while anaerobic decomposition forms low molecular weight compounds (volatile fatty acids and NH 3 + -N). The differences in the size of the composted particles results in physical separation and decomposability of high and low C:N ratio substrates. Temperatures ranging from 14 to 35ºC did not affect the rate of N mineralization, but affected N loss from poultry manure pellets by decay nitrification at 14 and 35ºC compared with 25ºC. Uric acid and undigested proteins in poultry litter have optimal degradation rates at pH of 5.5 or higher, with the optimum pH for uricase being about 9. Variations in manure composition are seen between different species such as cattle, swine and poultry. The chemical composition of the manure and not the substrate N status influences the rate of decomposition or microbial availability. The N mineralization potential of some vegetable residues correlated better with the total and water soluble N contents than with their C:N ratios. Poultry manures are applied to agricultural soils at rates determined by the amount of available N that they are assumed to contribute to the crops. Many equations have been developed to calculate these application rates.

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