Runoff Phosphorus Loss Immediately after Poultry Manure Application as Influenced by the Application Rate and Tillage

Authors: KAISER, DANIEL - University Of Minnesota; MALLARINO, ANTONIO - Iowa State University; HAQ, MAXHAR - Iowa State University; Allen, Brett

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2008
Publication Date: 1/13/2009
Citation: Kaiser, D.E., Mallarino, A.P., Haq, M.U., Allen, B.L. 2009. Runoff Phosphorus Loss Immediately after Poultry Manure Application as Influenced by the Application Rate and Tillage. Journal of Environmental Quality. 38: 299-308.

Interpretive Summary: Excessive application of poultry manure to cropland may result in significant risk of P loss with surface runoff. This study assessed P loss from surface-applied poultry manure for runoff events shortly after manure application and using a rainfall simulation technique. Runoff was analyzed for concentrations of sediment, dissolved reactive P (DRPC), bioavailable P (BAPC), and total P (TPRC). Manure application increased runoff DRPC, BAPC, and TPC at five of eight sites, and increases were consistently greater when the manure was not incorporated into the soil compared with manure incorporated by tillage. Although tillage to incorporate manure usually increased sediment concentration in runoff, this effect was not high enough to surpass the higher amount of P lost when the manure was not incorporated. Also, the relationship between MWSP applied and DRPC was highly significant and linear for both incorporated and non-incorporated manure, although the rate of DRPC increase was approximately 10 times steeper for non-incorporated manure. Results for runoff DRPL, BAPL, and TPRL usually followed those of concentrations. Treatment effects on TPRL were significant only in two sites, probably because of inconsistent and more variable effects on both surface runoff volume and sediment concentration. Overall, manure incorporation with tillage was very effective at reducing P loss during runoff events shortly after poultry manure application.

Technical Abstract: Excessive or N-based application of poultry manure for crops may result in significant risk of P loss with surface runoff. This study assessed P loss immediately after poultry manure application to soybean [Glycine max (L.) Merr.] residue with and without tillage at eight Iowa fields. Manure from chickens (Gallus gallus domesticus) or turkeys (Melleagris gollopavo) was applied at intended rates of 0, 84, or 168 kg total N ha–1 (total P was 0, 21–63, 50–123 kg P ha–1, respectively) with three replications. Simulated rainfall (76 mm h–1) was applied to 3-m2 sections of larger field plots with 2 to 7% slope, usually within 2 d of application, to collect runoff during 30 min. Runoff was analyzed for concentrations of sediment, dissolved reactive P (DRPC), bioavailable P (BAPC), and total P (TPRC). Non-incorporated manure consistently increased (P 0.10) concentrations of all runoff P fractions in five sites, but there were increasing trends at all sites, and on average manure increased DRPC, BAPC, and TPRC 32, 23, and 12 times, respectively, over the control. Tillage to incorporate manure reduced DRPC, BAPC, and TPRC by 88, 89, and 77% on average, respectively, although in non-manured plots tillage seldom affected DRPC or BAPC and often increased TPRC. Tillage increased sediment concentration in runoff but not enough to offset the benefits of manure P incorporation. Runoff P loads generally followed trends of runoff P concentrations but were more variable, and significant treatment effects were less frequent. Overall, incorporation of manure by tillage was very effective at reducing P loss during runoff events shortly after poultry manure application under the conditions of this study.