Data on Nitrate in Groundwater and Factors that …...2020/02/27 · Practice Details % Nitrate-N...

Kevin Masarik

NR151 Technical Advisory Committee

February 27, 2020

Data on Nitrate in Groundwater and

Factors that Determine Nitrate

Groundwater Quality

Our nitrate challenge:The top foot• Current agricultural systems allow for significant

nitrate losses to groundwater – much of it can occur outside the growing season

• Soils and geologic considerations can exacerbate losses from agricultural systems

• Future management priorities/challenges:• 1) Encourage but also need to better quantify nitrate

reduction from different management strategies• Cover crops• Diversification of crop rotations• Etc.

• 2) Climate change will impact nitrate losses to groundwater

• More extreme rainfall events• Longer growing season• Increased soil temperature

• 3) Be more intentional about residential development with private wells in rural areas/subdivisions

• Proximity to agricultural areas• Density of septic systems

Groundwater 101

Source:

Merritts, Menking, & De Wet, Environmental Geology: An Earth Systems Science Approach. 2nd Edition. 2014

Modified from: https://nevegetable.org

Groundwater

Sources of Nitrogen to

Agricultural Fields

Fertilizers

Nitrate in irrigation water

Nitrogen Cycle

Runoff, Wind Erosion

Nitrate and Human HealthInfants and pregnant women• Methemoglobinemia or “blue-baby syndrome”• Central nervous system malformations (birth defects & miscarriages)

AdultsPossible correlations to:• Non-Hodgkin’s lymphoma• Various cancers (ex. gastric, bladder)• Thyroid function• Diabetes in children

Nitrate often indicator of other possible contaminants (ex. other agricultural contaminants, septic effluent, etc.)

Wisconsin Groundwater Coordinating Council, 2015; Weyer, 1999

Nitrate Nitrogen• Greater than 10 mg/L

Impacted at a level that exceeds state and federal limits for drinking water

• Greater than 1 mg/L Evidence of land-use impacts

• Less than 1 mg/L Natural or background levels in WI groundwater

• DO NOT give water to infants

• DO NOT consume if you are a woman who is pregnant or trying to conceive

• RECOMMEND everyone avoid long-term consumption

Nitrate-Nitrogen Concentrations

Considered suitable for drinking water

Nitrate exported to surface waters

http://water.usgs.gov/nawqa/sparrow/gulf_findings/delivery.html

• Excessive nutrients contribute to growth of large amounts of algae that decay and consume oxygen –hypoxia.

• Some algal blooms can be harmful to health

Algae bloom on Wisconsin’s Lake Tainter. (photo: Peg McAloon)

Decades

Private Well Nitrate Concentrations

WI Well Water Viewer, 2019

Average Nitrate-Nitrogen Concentration by Township

Nitrate-N breakdown

• 57% of private wells have concentrations less than 2 mg/L

• >40 mg/L: 0.12%*; 960 wells1

• >30 mg/L: 0.56%*; 4,480 wells1

• >25 mg/L: 1.0%*; 8,000 wells1

• >20 mg/L: 2.2%*; 17,600 wells1

• >10 mg/L: 8.2%**; 10%*, 65,600-80,000 wells1

*estimate from Center for Watershed Science and Education database, UW-Extension/UW-Stevens Point

**estimate from Agricultural Chemicals in Wisconsin Groundwater, DATCP. 2017

Based on estimate of 800,000 private wells, GCC Report to the Legislature, https://dnr.wi.gov/topic/groundwater/GCC/wells.html

Nitrate Concentration (mg/L)

Greater than 10 mg/L drinking water standard

Agricultural Lands of WisconsinAnnual Row Crops

Forage Crops/Pasture/CRP

Maps produced using WISCLAND Data Coverage. 2002. WiDNR/EDM

~20% of samples exceed the 10 mg/L nitrate-nitrogen standard when more than 75% of the area is cultivated (DATCP, 2017)

Coarse textured surficial deposits

Map created using: Groundwater Contamination Susceptibility Model (GCSM); Surficial Deposits ("sdppw95c")

The GCSM was developed by the DNR, the US Geological Survey (USGS), the Wisconsin Geological & Natural History Survey (WGNHS), and the University of Wisconsin – Madison in the mid-1980s.

Shallow carbonate rock aquifers

Photo credits: Ken Bradbury, WGNHS

Wisconsin Karst Potential

Nitrate Variability in Wisconsin’s Groundwater

Nitrogen Fertilizer Added (lb/acre)

Fertilizer Added (kg/ha)

Increasing

Yield response to nitrogen

Maximum Yield

Slope = Added Yield

Fertilizer UnitEconomic Optimum / MRTN• variable from year to year depending on energy costs, fertilizer costs, price of commodities, temperature, precipitation, etc.

Fertilizer Added

Increasing

Yield Optimum

Economic Optimum / MRTN

• variable from year to year

depending on energy costs,

fertilizer costs, price of commodities

Nitrogen Recommendations

Environmental Optimum

• depends on climate, soils, geology, etc.

• What is our goal…MCL, PAL, zero?

• depends on who you are…infant, parent, farmer, etc.

Alternative Field Crops Manual, 1989. University of Minnesota and University of Wisconsin -MadisonNutrient application guidelines for field, vegetable and fruit crops in Wisconsin. A2809. 2012. University of Wisconsin-Madison

Miscanthus and switchgrass recommendations: Anderson et al., 2013; McIsaac et al., 2010; Vogel et al., 2002; Arundale et al, 2014

Nitrogen fertilizer recommendations for common crops

* Legumes have symbiotic relationship with N fixing bacteria

Estimating Nitrogen Leaching Potential

From Meisinger, J.J and Randall G.W. 1991. Chapter 5: Estimating Nitrogen Budgets for Soil-Crop Systems. In Managing Nitrogen for Groundwater Quality and Farm Profitability, editors: Follett, Keeney, and Cruse. Soil Science Society of America.

Potential N Leaching = N Inputs - N Outputs (excluding leaching) - Change in N Stored

Runoff, Wind Erosion

Measuring nitrate leaching below an irrigated field in the Central Sands Region

2016 2017 2018 2019

X 4Installed 2016

~2-3 weeks

Drainage Volume X Concentration = Nitrate Leaching

Flow Weighted

Mean (FWM)

Cumulative Nitrate Leaching Loss ÷ Annual Drainage = Flow-weighted Mean Nitrate Concentration

Nitrogen Leaching Losses

Estimating Leaching Losses Using a Nitrogen Budget

Nitrogen Leaching Losses

Accounting for spatial variability at the field scale using wells

Nitrate Leaching at Arlington, WI

Water (inches) x Nitrate-Nitrogen Concentration (mg/L) x 0.226 = Pounds of Nitrogen per Acre(8 in.) x (10 mg/L) x 0.226 = 18.1 lbs N/acre

1 2 3 4 5 10 15 20 30 40

Inches of

Irrigation

1 0.2 0.5 0.7 0.9 1.1 2.3 3.4 4.5 6.8 9.0

2 0.5 0.9 1.4 1.8 2.3 4.5 6.8 9.0 13.6 18.1

3 0.7 1.4 2.0 2.7 3.4 6.8 10.2 13.6 20.4 27.1

4 0.9 1.8 2.7 3.6 4.5 9.0 13.6 18.1 27.1 36.2

5 1.1 2.3 3.4 4.5 5.7 11.3 17.0 22.6 33.9 45.2

6 1.4 2.7 4.1 5.4 6.8 13.6 20.4 27.1 40.7 54.3

7 1.6 3.2 4.7 6.3 7.9 15.8 23.7 31.7 47.5 63.3

8 1.8 3.6 5.4 7.2 9.0 18.1 27.1 36.2 54.3 72.4

9 2.0 4.1 6.1 8.1 10.2 20.4 30.5 40.7 61.1 81.4

10 2.3 4.5 6.8 9.0 11.3 22.6 33.9 45.2 67.8 90.5

Nitrate-Nitrogen Concentration (mg/L)

lbs of Nitrogen per acre

Estimating nitrogen from irrigation or leaching losses using concentration

Water in inches

Graph of root depth: http://www.bae.ncsu.edu/programs/extension/evans/ag452-1.html

Picture of corn roots: http://www.soilandhealth.org/01aglibrary/010137veg.roots/010137ch2.html

Comparing an Annual Row Crop to Perennial Ecosystems

http://soils.usda.gov/sqi/management/files/RSQIS6.pdf

Mixed Native Perennial

http://www.soilandhealth.org/01aglibrary/010137veg.roots/010137ch2.html

Nitrogen fertilizer use efficiency for Midwestern corn systems

37%(Cassman et. al. 2002)

http://www.bae.ncsu.edu/programs/extension/evans/ag452-1.html

Effect of cropping systems on nitrate leaching loss in the Midwest

Cropping

systemsN Inputs

Nitrate-N

Leaching

DrainageData Source

kg N ha-1 yr-1 kg N ha-1 yr-1 mm yr-1

Annual

Corn-Corn 138 55 193 Randall et al., 1997 (1)

180 37 399 Masarik et al., 2014 (2)

151-221 17-32 63-187 Thomas et al., 2014 (3)

202 63 590 Weed and Kanwar, 1996 (4)

202 43 280 Randall and Iragavarapu, 1995 (5)

Corn-Soybean 136-0 51 226 Randall et al., 1997 (1)

168-0 34-46 ND McIsaac et al., 2010 (6)

168-0 34 470 Weed and Kanwar, 1996 (4)

171-0 10-35 ND Cambardella et al., 2015 (7)

Mixed C-S-O/A-A 171-0-57-0 8-18 ND Cambardella et al., 2015 (7)

Perennial

Alfalfa 0 2 104 Randall et al., 1997 (1)

CRP 0 1 160 Randall et al., 1997 (1)

Switchgrass 0 <1-4 ND McIsaac et al., 2010 (6)

112 2-11 52-156 Thomas et al., 2014 (3)

Miscanthus 0 2-7 ND McIsaac et al., 2010 (6)

112 <1-1 52-147 Thomas et al., 2014 (3)

Prairie 0 <1 122 Masarik, et al., 2014 (2)

Pasture 0 1-10 ND Cambardella et al., 2015 (7)

*16 -37X greater nitrate loss below continual corn cropping systems compared to perennial systems

Forest/Prairie/CRP

Alfalfa Soybean Corn Potato

Corn-Soybean

Economic Optimal Nitrogen Rates

Water Quality/ Nitrate Concentration

Less Greater

Masarik, UW-Extension

Nitrate Leaching Potential

Long-term nitrogen reduction strategies for agricultural areas

Practice Details % Nitrate-NReduction (StDev)

Reduction potential

Uncertainty

Timing

Fall to Spring Pre-plant 6 (25) Low High

Spring pre-plant/sidedress 40-60 split compared to fall applied

5 (28) Low High

Sidedress – Soil test based compared to pre-plant 7 (37) Low High

Nitrification InhibitorNitrapyrin – Fall – Compared to applied w/out nitrapyrin

9 (19) Low Medium

Cover CropsRye 31 (29) Medium Medium

Oat 28 (2) Medium Medium

PerennialBiofuel Crops (ex. switchgrass, miscanthus) 72 (23) High Medium

Conservation Reserve Program 85 (9) High Low

Extended RotationsAt least 2 years of alfalfa or other perennial crops in a 4 or 5 year rotation

42 (12) Med-High Low

Iowa Nutrient Reduction Strategy, 2014

Septic systems and nitrate

Robertson and Harman 1999

• Designed to dispose of human waste in a manner that prevents bacteriological contamination of groundwater supplies.• Do not effectively remove all contaminants from wastewater: Nitrate, chloride, viruses?, pharmaceuticals?, hormones? • One person excretes 11 pounds of nitrogen per year (Tchobanoglous, 2010)

Comparing Land-use Impacts

(per acre)Prairie1

(per acre)Septic 2

System

Total Nitrogen Inputs (lb) 169 9 20-25

Nitrogen Leaching Loss (lb) 32 0.04 16-20

Amount N lost to leaching (%) 19 0.4 80-90

1 Data from Masarik, 20142 Data from Tri-State Water Quality Council, 2005 and EPA 625/R-00/008

32 lbs 32 lbs 32 lbs 32 lbs

20 lbs

32 lbs/ac x 20 acres = 640 lbs14 mg/L

20 lbs/septic system x 1 septic systems = 20 lbs1/32nd the impact on water quality

0.44 mg/L

Assuming 10 inches of recharge

Using these numbers: 32 septic systems on 20 acres (0.6 acre lots) needed to achieve same impact to water quality as 20 acres of corn

32 lbs/ac x 20 acres = 640 lbs 20 lbs/septic system x 32 septic systems = 640 lbs