Improved Simulation of Soil and. Manure Phosphorus Loss in SWAT

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1 Improved Simulation of Soil and Manure Phosphorus Loss in SWAT SWAT Conference October, 2015 at Purdue University Amy S. Collick, Pete J. Kleinman, Tamie Veith, Daren Harmel, Mike White, Pete Vadas, USDA-ARS Doug Beegle, Jennifer Weld, Penn State Daniel R. Fuka, Zachary M. Easton, Virginia Tech

2 Outline Reasons behind the addition of new P routines into SWAT Basic differences between initial P routines and new routines (history of P in SWAT) Manure management issues Testing the routines in WE38 and Riesel watersheds

3 Introduction Excess phosphorus leads to eutrophication in biologically and economically important waterways across the world Heavy reliance on modeling to enhance our understanding of P transfers in the environment especially from agriculture Manure management concerns in heavy livestock areas because of drive to decrease impact of manure through various management practices (BMPs, export, etc.) Modeling again relied upon to assess the consequences of agricultural nutrient management practices on phosphorus (P) loss in runoff and to simulate introduction of mitigation practices and processes

4 Phosphorus cycling in SWAT Soil P is divided into 6 pools (3 organic, 3 inorganic) Dynamic organic pools (Stable, Active and Fresh: mineralization, decomposition and immobilization represented) Inorganic pools (Stable, Active and Solution) subject to modifications in SWAT Initial Solution pool is adjustable in SWAT (labile p in *.chm files)

5 Soil P cycling in SWAT White, M. J., D.E. Storm, P.R. Busteed, M.D. Smolen, H. Zhang, G.A. Fox A quantitative phosphorus loss assessment tool for agricultural fields Environmental Modelling & Software 25(10):

6 Incorporation of Manure Routines Discrete layer of manure on the soil surface Based on the APLE equations of Vadas et al. (2007, 2012) Surface-applied manure partitioned into four interactive pools: water extractable inorganic P (WEP I ), water extractable organic P (WEP O ), solid-phase inorganic P, and solidphase organic P (sum of these four pools equals manure total P (TP)) Manure WEP I and WEP O are leached from manure to runoff or infiltrated during storms Manure P and Runoff Model Initial pools and interactions Vadas PA, Gburek WJ, Sharpley AN, Kleinman PJ, Moore PA Jr, Cabrera ML, Harmel RD A model for phosphorus transformation and runoff loss for surface-applied manures. J Environ Qual.36(1):

7 Manure Management Practices on the Farm Field Maximizing crop benefit and downstream water quality dependent on manure application rate, solubility of P in the amendment, and application method and timing are critical factors Effective nutrient management and stewardship also requires attention to these four interdependent factors 4Rs : Right placement, Right timing, Right rate, and Right form (IPNI, 2014)

8 WE38 Mahantango Creek Klingerstown, Pennsylvania Ridge and valley physiographic region of PA within Chesapeake Bay basin Restrictive layers underlying near-stream areas generate runoff Forest and cropland (rotations of corn, soybean, small grain, and grass or alfalfa hay) Dairy, beef, and swine manure applications Weather and hydrological monitoring since 1968

9 Testing of the 4Rs in WE38 Timing of application: Application of manure at 1, 5, 10 days prior to runoff generating event Form of Application: Chemical fertilizer or manure applied at same rate Method of Application: Manure incorporated (tillage) or not incorporated after application Rate of Application: 6,000 gal/ac (common rate) or 9,000 gal/ac (high rate) applied Results at HRU/field-level and subbasin scales

10 New P routines Soluble P, kg Standard P routines Soluble P, kg Precipitation, mm VirginiaTech In the standard routines, there is no difference in loss whether the Timing manure of was Application applied the day or ten days 0 before a storm 10 Manure doesn t degrade in standard routines since 20 the storm before any manure applications shows P losses exceeding those after application` 40 Dairy manure applied 1 day before_std P routines Dairy manure applied 5 days before_std P routines Dairy manure applied 10 days before_std P routines Standard P Routines /11/06 01/15/06 01/19/06 01/23/06 01/27/06 01/31/06 02/04/06 02/08/06 02/12/06 02/16/06 02/20/06 New P Routines Dairy manure applied 1 day before_new P routines Dairy manure applied 5 days before_new P routines Dairy manure applied 10 days before_new P routines /11/06 01/15/06 01/19/06 01/23/06 01/27/06 01/31/06 02/04/06 02/08/06 02/12/06 02/16/06 02/20/06 Collick et al., 2015 JEQ

11 Fertilizer Soluble P, kg ha -1, from new P routines VirginiaTech A. Manure Soluble P, kg ha -1, from new P routines routines Form of Application B. C. Manure Soluble P, kg ha - 1, from standard P Fertilizer Soluble P, kg ha -1, from standard P routines Fertilizer Soluble P, kg ha -1, from standard P routines Soluble P losses from commercial fertilizer applications are relatively similar in both new and standard P routines in SWAT Manure and commercial fertilizer result in the same soluble P losses in standard P routines in SWAT Greater losses are predicted from manure applications than from commercial fertilizer in new P routines in SWAT Fertilizer Soluble P, kg ha -1, from new P routines Collick et al., 2015 JEQ

12 Method of Application 40 Organic P Soluble P Sediment-bound P 35 P loss, kg ha No incorporation with std P routines Immediate incorporation with std P routines No incorporation with new P routines Immediate incorporation with new P routines Collick et al., 2015 JEQ

13 Total P Loss, kg Standard New Standard New Standard New Standard New Standard New Standard New Rate of Application Total P, kg Field 1 Field 2 Field Field 4 Field Spring Fall Winter Dairy slurry applied at rates of 6,000 and 9,000 gallons per acre Collick et al., 2015 JEQ

14 Riesel Experimental Watershed Riesel, Texas Each subbasin composed of field Moderate to rapid surface flow after storm events Houston Black clay vertisol soils Grassland and cropland (cotton, grain sorghums, corn, wheat, oats, and hay) Chicken litter applications Long-term management records and flow and water quality measurements since 1938 (Harmel et al., 2014)

15 Soluble P loss, mg L-1 Soluble P loss, mg L-1 VirginiaTech Field scale assessment of new P routines Commercial fertilizer Corn-Hay New P routines overlay measured data more frequently than the std routines, but tend to over estimate P loss during lower flow periods Observed Std P routines New P routines Commercial fertilizer and poultry litter Corn-Hay Observed Std P routines New P routines /26/04 5/6/06 6/1/07 3/3/08 4/18/09 10/27/09 3/25/10 1/10/13 Photos courtesy of Daren Harmel and USDA-ARS

16 No manure application Precipitation, mm 0 P loss, mg L -1 P loss, mg L /1/2010 2/20/2010 4/11/2010 Poultry litter/manure application in January (2 tons per ac) Observed Std P routines New P routines Observed Std P routines New P routines 0.0 1/1/2010 2/20/2010 4/11/

17 Ongoing Work Determine why there is the overestimation (sometimes extreme) of P loss especially at heavier storms soon after manure applications More in depth look at the new P routines predicted P loss together with the observed data following manure applications and various storms Closer look at the soil P-cycling to be able to track soil test P measurements