Overview of Nitrogen Management and Groundwater: Considerations for manure irrigation

Transcription

1 Overview of Nitrogen Management and Groundwater: Considerations for manure irrigation Kevin Masarik Center for Watershed Science and Education Through the University of Wisconsin-Extension, all Wisconsin people can access University resources and engage in lifelong learning, wherever they live and work.

2 History of N Use N and agriculture Ancient civilizations farmed flood plains Animal manure Crop rotations (legumes) Industrial fixation of N leads to commercial fertilizer and dramatic increase in N applications Begin to treat manure as waste product N, P, K

3 US & Wis. fertilizer nitrogen use ( ) 3 13 Wis. Sales (10 ^5 tons). US 2 Wis US (million tons)..

4 Nitrogen Cycle Nitrogen is neither created nor destroyed

5 Nitrate-Nitrogen Concentration Greater than 10 mg/l Greater than 2 mg/l UNSAFE - for infants and pregnant women or women trying to have a baby; everyone should avoid long term consumption. Impacted by local land use activities but suitable for drinking. May indicate other contaminants. Sources Agricultural fertilizer Lawn fertilizer Septic systems Animal wastes Decomposing wastes Less than 2 mg/l Close to natural or background levels

6 What can I do to reduce my nitrate levels? Possible Long-term Solution: Reduce or eliminate nitrogen inputs Short term (Lewandowski et. al. 2008) Change well depth or relocate well (not guaranteed) - $7,200 Bottled water - $190/person/year Water treatment devices - $ /yr Reverse osmosis Distillation Anion exchange

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9 Average Nitrate-N concentration by section. Wood County Nitrate-N Summary Table

10 Comparing Land-use Impacts Corn 1 (per acre) Prairie 1 (per acre) Septic 2 System Total Nitrogen Inputs (lb) Nitrogen Leaching Loss (lb) Amount N lost to leaching (%) Data from Masarik, Economic Optimum Rate on a silt-loam soil, Data from Tri-State Water Quality Council, 2005 and EPA 625/R-00/008

11 Comparing Land-use Impacts 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 20 lbs 20 acres 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 20 acres 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs/ac x 20 acres = 720 lbs 16 mg/l 20 lbs/septic system x 1 septic systems = 20 lbs 1/36 th the impact on water quality 0.44 mg/l Assuming 10 inches of recharge - Masarik, UW-Extension

12 36 lbs/ac x 20 acres = 720 lbs Water table Stream Water table Stream 20 lbs/septic system Masarik, UW-Extension

13 Comparing Land-use Impacts 36 lbs 36 lbs 36 lbs 36 lbs 20 lbs 20 lbs 20 lbs 20 lbs 36 lbs 36 lbs 36 lbs 36 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 acres 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 36 lbs 20 acres 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 36 lbs 36 lbs 36 lbs 36 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 20 lbs 36 lbs/ac x 20 acres = 720 lbs 20 lbs/septic system x 36 septic systems = 720 lbs Using these numbers: 36 septic systems on 20 acres (0.55 acre lots) needed to achieve same impact to water quality as 20 acres of corn Masarik, UW-Extension

14 36 lbs/ac x 20 acres = 720 lbs Water table 720 lbs Stream Water table 720 lbs Stream 20 lbs/septic system x 36 septic systems = 720 lbs Masarik, UW-Extension

15 Nutrient Management Provides guidance on the amount of nutrients (N, P, K) needed to achieve economic optimal production Provides recommended rate of nitrogen application for given crop and soil type. 4R s Right Amount Right Source Right Time Right Placement

16 Low Nutrient Management and Nitrogen Recommendations Nitrogen Fertilizer Added (lb/acre) High

17 Fertilizer Response Curve Yield or Biomass Accumulation (kg/ha) Increasing 0 100% Increasing Fertilizer Efficiency = Added Yield Fertilizer Unit Fertilizer Added (kg/ha)

18 Fertilizer Efficiency Fertilizer Efficiency 100% Increasing the amount of fertilizer decreases the efficiency of the fertilizer. 0% Increasing Fertilizer Added

19 Low Nutrient Management and Nitrogen Recommendations Nitrogen Fertilizer Added (lb/acre) High Yield Optimum

20 Low Nutrient Management and Nitrogen Recommendations Nitrogen Fertilizer Added (lb/acre) 160 lbs/ac High economic optimum that maximizes profitability

21 Fertilizer Response Curve Yield or Biomass Accumulation (kg/ha) Increasing 0 100% Increasing Yield Optimum Economic Optimum Fertilizer Added (kg/ha)

22 Plants are not 100% efficient at removing nutrients from the soil Corn ary/010137veg.roots/010137ch2.html Studies show efficiency typically about 30-50% for maize systems (Cassman et. al. 2002) For Comparison: Mixed Native Perennial

23 Nitrogen Fertilizer Added (lb/acre) Low High Nitrogen Leaching Loss What is the ability of nitrogen nutrient recommendations to meet groundwater performance standards?

24 What is an Optimal Fertilization Rate? Yield or Biomass Accumulation (kg/ha) Increasing 0 Yield Optimum 100% Economic Optimum Environmental Optimum?? Increasing Fertilizer Added (kg/ha)

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26 Water quality as a function of Nitrogen Use Efficiency N Less than EON rate, same yield = increased efficiency N Applied NUE Yield N loss 120 lbs 53% 150 bu 56 lbs Studies show nitrogen use efficiency (NUE) between 30-50% (Cassman et. al. 2002) The following are hypothetical yields meant to illustrate NUE and the effect on N loss. N Greater than EON rate, no increase in yield = decrease in efficiency N Applied NUE Yield N loss 200 lbs 32% 150 bu 136 lbs N Economic optimal nitrogen rate, greater yield = increased efficiency N Applied NUE Yield N loss 160 lbs 50% 188 bu 80 lbs N Fertility-research based economic optimal nitrogen application rate N Applied NUE Yield N loss 160 lbs 40% 150 bu 96 lbs N Greater than EON rate, greater yield = no increase in efficiency N Applied NUE Yield N loss 200 lbs 40% 188 bu 120 lbs Less Water Quality - Nitrate Concentration Less More Amount of N loss More

27 How much nitrogen does it take to raise groundwater nitrate 1 ppm? The actual amount will vary based on the amount of recharge. For Wisconsin this is likely somewhere between 6 and 10 inches depending on where you live. For Spring Green we will assume that nitrogen not taken up by the plant will mineralize and nitrify. 8 in. 10 mg NO 3 -N 43,560 ft 2 1 ft liters 1 g 1 kg 2.2 lbs liters 1 acre 12 in. 1 ft mg 1000 g 1 kg = 18.1 lbs N per acre Nitrate-Nitrogen Concentration (mg/l) N Inches of Recharge lbs of Nitrogen per acre

28 Generalized Nitrate Leaching Potential Nitrate Concentration 0 Forest/ Prairie/ CRP Economic Optimal Nitrogen Rates Alfalfa Soybean Corn Potato Corn- Soybean Masarik, UW-Extension

29 Generalized Nitrate Leaching Potential Nitrate Concentration 0 Forest/ Prairie/ CRP Economic Optimal Nitrogen Rates Alfalfa Soybean Corn Potato Corn- Soybean Masarik, UW-Extension

30 Water Quality/ Nitrate Concentration Good Poor UW Nitrogen Guidelines get us to a baseline Level of nitrate concentration in groundwater ~ Right Amount Nitrate Concentration 0 Forest/ Prairie/ CRP Economic Optimal Nitrogen Rates Alfalfa Soybean Corn Potato Corn- Soybean Masarik, UW-Extension

31 GW NO3-N = f(crop N Requirements, Excess N, Soils, Geology) Nitrate Concentration 0 Forest/ Prairie/ CRP Economic Optimal Nitrogen Rates Alfalfa Soybean Corn Potato Corn- Soybean Masarik, UW-Extension

32 Water Quality/ Nitrate Concentration Good Poor Improved Nitrogen Use Efficiency through right form, right time and right place techniques Nitrate Concentration 0 Forest/ Prairie/ CRP Economic Optimal Nitrogen Rates Alfalfa Soybean Corn Potato Corn- Soybean Masarik, UW-Extension

33 Water quality as a function of crop N recommendations No Inputs Water Quality/ Nitrate Concentration Good Poor Medium Inputs Amount of nitrogen applied High Inputs

34 Water quality as a function of watershed area in production 0% 50% Percent of land base in production 100% Water Quality - Nitrate Concentration Low High

35 Factors affecting nitrogen loss to groundwater Within our control Limited ability to adjust Out of our control Amount of nitrogen applied As a function of cropping system Nitrogen application rate relative to economic optimum right amount Percent of land base in production Nitrogen use efficiency Right form, right time, right placement Geology Soil Type Precipitation / Climate

36 Slide from presentation by Becky Larson, Manure Irrigation Workshop Liquid contains greater percentage of plant available N (i.e. ammonia/ammonium), ammonium readily converted into nitrate in aerobic conditions and susceptible to leaching.

37 Slide from presentation by Becky Larson, Manure Irrigation Workshop

38 What UWEX Nutrient Guidelines Do and Don t Do: Do save farmers money by ensuring nitrogen is used efficiently Do allow farms to maximize profitability while holding everyone accountable to some standard Do prevent fields from being treated as dumping grounds for manure and other bio-solids Do help prevent excessively high concentrations of nitrate in groundwater Don t prevent nitrate from leaching into groundwater Don t ensure groundwater quality meets drinking water standards Don t ensure that groundwater quality in areas that already apply at economic optimum rates will get better over time Masarik, UW-Extension

39 Irrigation of manure Potential Benefits Less risk of catastrophic loss then when applied all at once Able to apply during times when root system is more developed. Reduced transportation costs Less equipment on roads Potential Concerns or Questions to Ask Are rotations being adjusted to maximize how much nitrogen can be applied? Will nitrogen rates be lowered below current recommended levels to account for potential benefits? What to do during wet years when irrigation isn t needed ~ where does it go, how do you get rid of it? How is the system set up to deliver manure backflow prevention, separate system from existing wells? Ammonia volatilization

40 Conclusions Nutrient management is a first step that creates a baseline concentration of nitrate in groundwater that reflects crop rotation and geology/soils. Significant nitrate leaching can occur even when nitrogen recommendations are followed no environmental optimum rate Nutrient management and crediting of N will help reduce extreme nitrate concentrations in groundwater May take years or decades for groundwater quality to reflect changes in land-use practices Kevin Masarik Center for Watershed Science and Education 800 Reserve St. Stevens Point, WI kmasarik@uwsp.edu

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