Phosphorus leaching from soil cores from a twenty-year study evaluating alum treatment of poultry litter
Citation
Anderson, K.R., Moore, P.A., Miller, D.M., DeLaune, P.B., Edwards, D.R., Kleinman, P.J.A., Cade-Menun, B.J. (2018). Phosphorus leaching from soil cores from a twenty-year study evaluating alum treatment of poultry litter. Journal of Environmental Quality, [online] 47(3), 530-537. http://dx.doi.org/10.2134/jeq2017.11.0447
Plain language summary
Poultry manure (PM) is high in nitrogen (N) and phosphorus (P), so can be a valuable alternative to chemical fertilizer. However, the ratio of N/P in PM is low compared to crop needs for N and P. This means that adding PM to meet crop N requirements will add too much P to soil. This extra P can be lost from soil to water, causing algal blooms and other water quality problems. When alum is added to PM, it stabilizes the extra P in soil, reducing P loss to water. However, the long-term stability of P from alum-treated and untreated PM is unknown. A 20-year study was conducted with different levels of alum-treated and untreated PM. After 20 years, cores were taken from the plots and subjected to a one-year leaching experiment, with and without added fertilization. Alum treatment significantly reduced P losses in leachate compared to untreated cores, including dissolved reactive P and total dissolved P. This indicates that alum additions to PM will have a legacy effect, preventing P loss in leaching in future years.
Abstract
Adding alum to poultry litter is a best management practice used to stabilize P in less soluble forms, reducing nonpoint-source P runoff. However, little research has been conducted on how alum additions to litter affect subsequent leaching of P from soil. The objective of this study was to evaluate the effects of alum-treated versus untreated poultry litter on P leaching from soil cores receiving long-term poultry litter applications. Two intact soil cores were taken from each of 52 plots in a long-term study with 13 treatments: a control, four rates each of untreated and alum-treated litter (2.24, 4.49, 6.72, and 8.96 Mg ha-1), and four rates of ammonium nitrate (65, 130, 195, and 260 kg N ha-1). One core from each plot received the same fertilizer as for the previous 20 yr, whereas the other was unfertilized in the study year, resulting in a total of 25 treatments. Cores were exposed to natural rainfall, and P leaching was measured for 1 yr. The average soluble reactive P concentrations in the leachate varied from 0.16 to 0.44 mg P L-1 in fertilized alum-treated cores, whereas leachate from cores fertilized with untreated litter ranged from 0.40 to 2.64 mg P L-1. At the highest litter rate (8.96 Mg ha-1), alum reduced total dissolved P and total P concentrations in leachate by 83 and 80%, respectively, compared with untreated litter. These results indicate that alum additions to poultry litter significantly reduced soluble and total P fractions in leachate.