Submitted to: Transactions of the ASABE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/1/2006
Publication Date: 3/6/2007
Citation: Baker, B.J., King, K.W., Torbert III, H.A. 2007. Runoff Losses of Dissolved Reactive Phosphorus From Organic Fertilizer Applied to Sod. Transactions of the ASABE. 50:449-454. Interpretive Summary: Application of manure to agricultural land can lead to detrimental levels of phosphorus in runoff water causing the deterioration of the surface water quality. This research compared the phosphorus losses from manure sources with different initial P concentrations to determine how initial P concentrations of manure affected losses of P in runoff. Results showed that the higher the initial P concentration in the applied manure the greater the loss of P in runoff. In fact the losses were disproportionately higher with high initial P concentrations when compared to lower initial P concentrations manures. People planning on applying manure need to take extra care when applying manures with high initial P concentrations because these materials if applied carelessly can have deleterious environmental impacts especially on surface water bodies.
Technical Abstract: Fertilizers are often applied on a nitrogen requirement basis; however, recent evidence suggests that phosphorus (P) may pose as much if not more of an environmental threat. The objective of this research was to quantify the differences in PO4-P losses in runoff from two organic fertilizer sources (poultry litter and composted dairy manure) applied at a uniform nitrogen rate (187.3 kg ha-1) and one inorganic fertilizer control. Initial P concentration in the poultry litter (PL) was 2.5% while the initial P concentration in the composted dairy manure (CDM) was 0.5%. The two organic and one inorganic fertilizer were applied to run-over troughs filled with an Austin clay soil planted with ‘Tifway’ Bermuda grass (Cynodon dactylon L. Pers.). The troughs were fitted with water dispersion devices that supplied an even distribution of runoff at a rate equivalent to 125 mm hr-1. Runoff was simulated for 30 minutes every 7 days for a period of 10 weeks. Runoff water was collected and analyzed for quantity and PO4-P concentration. The results from both the PO4-P concentration and load data show the high P concentration fertilizer (PL) had the greatest loss during the first simulated runoff event while the low P concentration fertilizer (CDM) did not vary significantly (p>0.05) from the control. This pattern continued for the first 9 weeks of runoff events but during the10th week none of the treatments showed a difference. Comparison of cumulative losses over the 10 weeks showed the high P fertilizer lost a larger proportion of its initial P application than did the low P fertilizer. The low P fertilizer did not have a greater cumulative loss compared to the control until day 56, when the low P fertilizer began to outpace the loss of the control. The PL with its high initial P concentration lost a disproportionately larger amount of PO4-P in runoff compared to the CDM with its low initial P concentrations.