Integrating erosion and phosphorus runoff assessment with nutrient management planning in SnapPlus

Transcription

1 Integrating erosion and phosphorus runoff assessment with nutrient management planning in SnapPlus L Laura Ward Good Department of Soil Science University of Wisconsin-Madison

2 What is nutrient management planning? Planning fertilizer and manure applications to cropland and pastures to meet crop needs and protect surface and ground water quality Nitrogen (N) Phosphorus (P 2 O 5 ) Potassium (K 2 O)

3 Why do we need surface water quality protections? Wisconsin Impaired Waters (2014 listing, WDNR) Stream miles Impairment P Sediment Lakes # Surface blooms of cyanobacteria (Microcystis aeruginosa) in lakes Mendota and Monona, Madison, Wisconsin Stephen R. Carpenter PNAS 2008;105:

4 Sediment and phosphorus move from agricultural land via erosion and runoff

5 RUSLE2 Soil Loss Calculation Revised Universal Soil Loss Equation 2 Daily time-step version of USLE Erosion ton/acre/yr = R x K x LS x C x P R= Erosivity K= Soil erodibility LS = Slope % and length C = Crop and tillage (management) P= Practices (e.g. contouring, terraces)

6 What goes into C-factor? Canopy cover (vegetation that intercepts raindrops) Ground cover (reduces waterdrop impact and runoff) Surface roughness (increasing infiltration, deposition, slows runoff) Ridge height (ridges parallel to flow lead erosion, cross flow increase deposition) Soil biomass (live and dead roots, buried residue) Soil consolidation (soil becomes less erodible over time after disturbance)

7 Wisconsin Phosphorus Index P Index is an estimate of the average annual P delivery from field to surface water Field Stream

8 P Index: Field-Specific Estimate of Total Average Annual Runoff P by Source and Transport Pathway Rotational runoff P losses are a function of amount of P in soil and surface amendments and the amount of runoff and erosion

9 Planning for a small dairy farm 70 milk cows + 70 calves/young cows Manure 2600 tons per year 1800 tons collected and spread on fields 800 tons deposited on pasture

10 Soil maps 220 acres cropland 78 acres pasture

11 Routine soil tests ph, organic matter %, Soil P and K

12 Field by Field Management Crops grown in sequence Corn, oats, alfalfa in rotation, some wheat on rented fields Tillage Chisel plowing and field cultivation Manure 13 tons/acre on corn, daily haul (some stacking ability) Fertilizer Spring, to meet recommendations

13 Farm level: Nutrient supply vs crop need balanced each year 1800 ton manure 90 acres corn need Last year s alfalfa provides N High P and K soils lessen needed additions

14 Conducting this balancing act every year can be challenging Don t want to put manure on alfalfa No winter spreading Watch out for well Soil high in phosphorus already

15 Soil and phosphorus runoff protection requires a multi-year perspective These fields all have acceptable erosion rates Tolerable soil loss

16 Rotational Phosphorus Index Field 8 does not meet P Index standard

17 P Index can often be fixed by lowering erosion For example, by changing crop rotation Soil loss 3.7 ton/acre/yr Soil loss 2.1 tons/acre/yr Same field, more years of alfalfa, fewer years of corn

18 P Index now meets standard But farm still needs to grow enough corn to feed the cows

19 Multiple ways to reduce erosion Erosion decreases with reduced frequency and intensity of tillage Crop: Continuous corn silage Soil loss in T/acre/yr Moldboard 3-pass Chisel plow 3-pass Chisel plow 2-pass Field cult Strip-till No-till

20 P Index for continuously tilled crops Tillage: Fall chisel, spring disking, field cultivation

21 P Index for continuous no-till crops

22 P Application Crop Needs Increasing soil P increases dissolved and particulate P in runoff Soil test P :

23 P loss from runoff following manure applications Example field: 15,000 gal/acre dairy manure applied by tillage and season Fall chisel, spring disk & field cult. Depends on: Amount of manure P on surface in water-soluble form Runoff in seasons after application (Runoff/precipitation) No-till

24 No practice is always Best Does this help reduce runoff P losses?

25 Take home: SnapPlus allows farm and field-specific management solutions for reducing erosion and phosphorus in runoff