data on nitrate in groundwater and factors that …...2020/02/27 · practice details % nitrate-n...
TRANSCRIPT
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
NO3-
Fertilizers
Nitrate in irrigation water
NO3-
Nitrogen Cycle
N2O
N2
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
0
10
1
• 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
Mu
nic
ipal
Wel
l
Pri
vate
Wel
l
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
Pro
po
rtio
n o
f w
ells
Nitrate Concentration (mg/L)
10
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
Less
Nitrogen Fertilizer Added (lb/acre)
More
N-P-K
Yie
ld o
r B
iom
ass
Acc
um
ula
tio
n (
kg/h
a)
Fertilizer Added (kg/ha)
Increasing
Yield response to nitrogen
Incr
easi
ng
Maximum Yield
0
Slope = Added Yield
Fertilizer UnitEconomic Optimum / MRTN• variable from year to year depending on energy costs, fertilizer costs, price of commodities, temperature, precipitation, etc.
Yie
ld o
r B
iom
ass A
ccu
mu
lati
on
Fertilizer Added
Increasing
Incre
asin
g
100%
0
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
40 ft
~2-3 weeks
Drainage Volume X Concentration = Nitrate Leaching
X =
Flow Weighted
Mean (FWM)
Cumulative Nitrate Leaching Loss ÷ Annual Drainage = Flow-weighted Mean Nitrate Concentration
Nitrogen Leaching Losses
Nitrogen Leaching Losses
Estimating Leaching Losses Using a Nitrogen Budget
Nitrogen Leaching Losses
Accounting for spatial variability at the field scale using wells
Accounting for spatial variability at the field scale using wells
Nitrate Leaching at Arlington, WI
Nitrate Leaching at Arlington, WI
Nitrate Leaching at Arlington, WI
N
Or
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
365
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
Water
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
Nit
rate
Le
ach
ing
Po
ten
tial
Forest/Prairie/CRP
0
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
Be
st
B
ette
r
Go
od
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
Corn1
(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
32 lbs 32 lbs 32 lbs 32 lbs
32 lbs 32 lbs 32 lbs 32 lbs
32 lbs 32 lbs 32 lbs 32 lbs
32 lbs 32 lbs 32 lbs 32 lbs
20 lbs
Comparing Land-use Impacts
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
20
acr
es
20
acr
es
Assuming 10 inches of recharge
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
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
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
Comparing Land-use Impacts
32 lbs/ac x 20 acres = 640 lbs 20 lbs/septic system x 32 septic systems = 640 lbs
20
acr
es
32 lbs 32 lbs 32 lbs 32 lbs
32 lbs 32 lbs 32 lbs 32 lbs
32 lbs 32 lbs 32 lbs 32 lbs
32 lbs 32 lbs 32 lbs 32 lbs
32 lbs 32 lbs 32 lbs 32 lbs
20
acr
es
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