a1 Feed and Nutrition Laboratory, College of Natural Resources, Taegu University Gyong San, 712–714, South Korea, e-mail: NahmKH@Daegu.ac.kr
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 27:1. 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 = TKN – ammonium or TN – (ammonium + uric acid) or TN – IN; Available N (AN) = Inorganic N + 0.4 × organic N; Predicted available N (PAN) = 80% Inorganic N + 60% Organic N.
(Received March 21 2002)
(Accepted March 23 2003)