|Donoghue, Ann - Annie|
Submitted to: Transactions of the ASABE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/23/2007
Publication Date: 4/17/2007
Citation: Toor, G.S., Haggard, B.E., Reiter, M.S., Daniel, T.C., Donoghue, A.M. 2007. Phosphorus solubility in poultry litters and granulates: Influence of litter treatments and extraction ratios. Transactions of the ASABE. 50(2):533-542. Interpretive Summary: The amount of water soluble phosphorus in poultry litter is an important determinant in its potential to be released into runoff water during rainfall events. This study evaluated the amount of soluble phosphorus in raw poultry litters and poultry litters that have been through a granulation process and mixed with other nutrients. First, the granulation process did not increase the total amount of soluble phosphorus in the poultry litters at high extraction ratios, i.e. one gram of poultry litter to 200 milliliters of water. However, at the lower extraction ratios granulated litter did have increases in the amount of soluble phosphorus compared to raw [unprocessed] litters. When we evaluated other soluble factors that were related to soluble phosphorus, we found that soluble magnesium was most strongly correlated. The addition of nitrogen during the granulation process increased the nitrogen to phosphorus ratio in the poultry litter making it a more balanced fertilizer to meet crop needs.
Technical Abstract: Phosphorus (P) loss from soils receiving manure has been strongly correlated to the water extractable P (WEP) applied in the manure. Our main objective in this study was to assess the effects of different treatments (granulation alone and with urea, urea plus dicyandiamide, or hydrolyzed feathermeal) on WEP of poultry litter. We obtained poultry litters from two poultry farms located in the Northwest Arkansas and selected litters were granulated in commercial granulating plants. During granulation, urea, urea plus dicyandiamide, and hydrolyzed feathermeal were added to poultry litters, which increased total N to P ratio of litters up to 8.51. Results showed that granulated litters had greater amounts of WEP than raw and ground litters when measured at lower extraction ratio (<1:100). However, the WEP was similar for all litters (raw, ground, granulated) at 1:200 or 1:250 extraction ratios. This suggests that granulation of poultry litter does not influence total amount of WEP in poultry litters. The extraction ratio had the greatest effect on WEP in the litter while filter paper and method of P determination had minor effect on litter WEP. Of all water extractable elements, Mg was strongly correlated (R>0.87) with P in these poultry litters and granulates, suggesting Mg-P minerals might control aqueous P concentrations in litter extracts. In conclusion, this study shows that (i) granulation of poultry litter does not increase WEP of the poultry litter as given by 1:200 or 1:250 extraction ratios, and (ii) addition of urea during granulation made the poultry litter a balanced fertilizer (N:P = 8:1) compared with raw litter (N:P = 1.35:1), which would help decrease P surpluses in intensive animal production areas.