Submitted to: Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2001
Publication Date: 11/1/2001
Citation: QAFOKU, O.S., CABRERA, M.L., WINDHAM, W.R., HILL, N.S. RAPID METHODS TO DETERMINE POTENTIALLY MINERALIZABLE IN BROILER LITTER. ENVIRONMENTAL QUALITY. 2001. Interpretive Summary: Although broiler (chicken, Gallus gallus domesticus) litter has long been used as a fertilizer, estimation of the rate required to supply a desired amount of plant available N is still hampered by the lack of rapid methods to estimate potentially mineralizable N (PMN). Previous research has suggested that near infrared (NIR) reflectance spectroscopy and certain poultry litter characteristics, such as water soluble organic N (WSON), may be useful for estimating PMN. The objectives of this study were to evaluate NIRS and WSON as tools to estimate PMN in broiler litter. Sixty sieved and freeze-dried broiler litter samples were mixed with Cowarts sandy loam soil and incubated at 25 C for 112 days. Cumulative net N mineralized with time was fitted to a single- pooled exponential model to determine PMN for each broiler litter sample. The PMN values were regressed against NIR (780 to 2500nm) and WSON measurements. We found strong relationships between measured- and NIRS-predicted PMN (R2=0.82), and between measured PMN and WSON (R2=0.87). These results demonstrate the feasibility of using any of these two methods to estimate PMN in broiler litter. Future work should further test both methods for their ability to estimate mineralized N in whole, moist broiler litter under filed conditions.
Technical Abstract: Poultry litter, a mixture of broiler manure and bedding material, is recognized as a valuable source of plant nitrogen (N), phosphorous (P), and potassium (K) fertilizer. However, the availability of N in poultry litter is variable, which makes it difficult to estimate plant application rates. Over-application of N may lead to contamination of water resources, whereas under-application may result in reduced plant yields. Classical chemical methods for determining N are time-consuming and generate hazardous wastes - a major concern for analytical labs. In this report we describe the prediction of potentially mineralizable N (PMN) content of poultry litter by near-infrared (NIR) reflectance spectroscopy. The speed, accuracy, and convenience of the method compared with classical chemical methods suggest that NIR is appropriate for determination of PMN in dried poultry litter.