Cover cropping for nutrient runoff reduction and the benefits of

high-frequency water samplingBen Bruening, Catherine O’Reilly, Shalamar Armstrong, Bill Perry

Problems with Nitrate and Phosphorous pollution

• Nationally and Internationally: • Oceanic Dead

Zones

• Locally: polluted drinking water• Can lead to Methemoglobinemia

Illinois Nutrient Loss Reduction Strategy

Aims for 15 % reduction of nitrate, 25% reduction of phosphorous by 2025

• Ultimate goal 45% total nitrate and phosphorous export reduction

• Encourage voluntary nutrient reduction practices such as:

• Spring-only fertilizer application

• Efficient Fertilizer use

• Constructed Wetlands

• Woodchip bioreactors

• Fall seeded Cover crops

Cover Cropping• Crops such as oats, rye, and tillage

radish planted in fall on row cropped fields

• Benefits:• Prevent nutrient leaching (Dean and

Well 2009, Fraser et al. 2013)• Reduce soil erosion (Kaspar et al. 2001)

and suppress weed growth (O’Reilly et al 2011)

• Reduces soil compaction and increases soil organic matter

• Improve efficiency of applied fertilizer by preventing runoff (Lacey and Armstrong 2015)

• Don’t require land to be removed from cropping rotation

Our Study:

Towanda

• Cover Crops (mainly mix of rye and tillage radish) planted via airplane on 48% of 1000- acre tile-drained watershed.

• Another 700 acre tile-drained watershed was left without cover crops

• Nutrient runoff compared between two sites

• Unlike other studies, our study is on a watershed scale, not a field scale

Water Sampling Methods: Autosampling equipment

Rain gauge

Solar Panel

Sampling tube

Equipment box

Discharge Probe and Sampling nozzle

Autosampling equipment (interior)Autosampler Datalogger

Discharge Module

Batteries

Sample collection bottles

Methods: Autosampling equipment at non cover cropped watershed

Photo by Victoria Heath

Water sampling methods (cont.)

• Water samples tested for nitrate and phosphorous concentrations in the ISU LEA

• Using these concentrations combined with our discharge measurements, we can determine the total amount of nitrate and phosphorous running off from a system (loading).

Photo by Victoria Heath

Cover Crop Planting

Cover Crop Planting Cont.

Cover crop termination- First week of April

Results: Nitrate Concentrations

EPA mandated limit

EPA mandated limit

Cover Cropped Watershed

Non Cover Cropped Watershed

Feb 15 May 9 July 20

Non cover cropped Cover Cropped

Results: Nitrate Loading

May 9 July 20Feb 15 May 9 July 20Feb 15

1.3 lbs/acre daylost

.017 lbs/acre daylost

.6 lbs/acre day lost

.06 lbs/acre daylost

Non cover cropped Cover Cropped

Results: TP Loading

May 9 July 20Feb 15 May 9 July 20Feb 15

.027 lbs/acre daylost

.025 lbs/acre daylost.000085lbs/

acre day lost

.000025lbs/acre day lost

Loading Trends Summary

• Both nitrate and phosphorous loading are strongly linked with storm events• Phosphorous is especially closely linked to these storm events

• This emphasizes the importance of high resolution sampling

• Nitrate peaking during the May 9th storm event was more severe at non-cover cropped site than the cover cropped

• More data and analysis will be performed to determine with certainty whether more whether cover cropping is having an influence on runoff

Other work: Spring soil SamplingCover Cropped

Graphic Courtesy of Shalamar Armstrong

Spring Soil Sampling (Cont)

• Soils planted with rye and tillage radish were found to have higher levels of nitrogen as NH4 than soils planted with oats or no cover crops

• This is good, because NH4 isn’t carried by runoff as easily, meaning it is available for crops

Courtesy of Shalamar Armstrong

Soil NH4 at cover-cropped site

Spring Soil Sampling (cont.)• Soils planted with

rye and tillage radish were found to have lower levels of nitrogen as nitratethan soils planted with oats or no cover crops

• This isn’t good, because nitrate is carried by runoff as easily

Conclusions

• The cover cropped watershed seems to have less severe nitrate runoff during storm events than the non-cover cropped watershed

• Cover cropping with cereal rye and tillage radish increases the amount of NH4 in the soil in the spring

• Cover cropping seems to be having a positive impact on the nutrient behavior of our study site

Acknowledgements

• Thanks to NREC and the Illinois EPA for funding this project

• Thanks to Victoria Heath, Allyson Hanlin, Joe Miller, Danny Dallstream Lucas Chabela, Jeremy Neundorff, Eric Deck, and Mark Dreher for helping with Field and lab work

• Questions?

Preliminary Water Sampling results: Loading at Cover Cropped Site

Nitrate Phosphorous

Feb 15

May 30March 31 May 9May 1 Feb 15 May 30March 31 May 9May 1

Preliminary Results: Reference site, autosampler 2

Feb 15May 30March 31 May 9May 1 Feb 15 March 31 May 1 May 9 May 30

Cover Cropped site vs non cover cropped sites

• Cover Cropped• Peak is 3x average

loading

• Non cover cropped (AS 2)• Peak is 20x average

loading

Preliminary Results Control Site, Autosampler 1

Feb 15 May 9March 31 May 1 Feb 15 May 30March 31 May 9May 1