Measuring Benefits of Hairy Vetch Cover Crop for Corn Production and Evaluating a Portable Soil Nitrate Test Kit

Final Report for FNC95-108

Project Type: Farmer/Rancher
Funds awarded in 1995: $1,815.00
Projected End Date: 12/31/1996
Region: North Central
State: Ohio
Project Coordinator:
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Project Information


The family farm is 600 acres of corn, soybeans, soft red winter wheat, rye and hairy vetch. We also finish hogs but not currently.

In the mid 1980’s we started cutting back on purchased inputs of fertilizer and pesticides. Growing of cover crops has been a key to adding nitrogen, improving soil health, and controlling wind erosion on our sandy-loam soils. We have tried both herbicide burn down with no till and conventional field tillage with cultivation and are still seeking the best practice for our farm.

The goal of this project is to quantify the benefits of nitrogen contribution which a hairy vetch cover crop supplies. More farmers may be willing to use cover crops if they understand the benefits that have been scientifically tested. Also, a key tool in using cover crop is measuring the amount of nitrogen supplied to the soil by using a nitrate test kit. The accuracy and reliability of this kit as compared to the test performed by and analytical lab on the same soil samples. If farmers can conduct their own nitrate testing, then more accurate nitrogen applications will result as compared to not doing a nitrate test.

On august 5, 1995 a wheat stubble field was seeded to hairy vetch in the following manner. Randomized 30 foot wide, field length strips replicated 6 times across the field were disked and then planted with a grain drill at a rate of 23 lbs/acre of hairy vetch seed. The comparison beside each hairy vetch strip was not planted to hairy vetch and was mowed twice that fall for weed control. The following shows the plot pattern – v = hairy vetch and c = control, each strip is 30 feet wide by 1300 feet long (nearly 1 acre).

Border V C V CC VV CC V C V Border

Significant growth of the hairy vetch (1 foot in height) occurred before winter. Regrowth of the hairy vetch began in April of the following year. The entire field was incorporated with a disk on May 22, 1996. The hairy vetch had grown well over one foot in height. It worked into the soil easily and did not cause planting problems. Pioneer 3525 seed corn was planted at 32,000 seeds per acre. Frontier herbicide was broadcast at planting at a rate of 20 oz./acre for grass control. No fertilizer was applied. Soil nitrate samples were collected weekly throughout the spring until July 1, 1996. Side dress nitrogen (liquid 28%) was applied on June 19, 1996. based on soil nitrate test results of 15.6 ppm nitrate on the hairy vetch strips and 4.5 ppm nitrate on the control strips, 60 lbs/acre actual nitrogen was applied to the hairy vetch strips and 150 lbs/acre nitrogen was applied to the control strips. This was the only nitrogen applied to the field. Tissue tests and stalk nitrate tests were also collected from each strip. A weigh wagon was used at harvest on October 29, 1996.

A flag marked a location 300 feet into the field in the center of each 30 foot strip. When collecting samples during the growing season, the flagged location was the exact spot where these soil samples, tissue samples, and stalk samples were collected. In this way, data collected represented a true difference between strips and not just field variation.

Other people who assisted in this project include:
- Alan Sundermeier – Ohio State University Extension
- Ed Zaborski and Dr. Ben Stinner – Ohio Ag. Research and Development Center
- Eric Shank – Natural Resources Conservation Service
- Jan Burkhard – Henry County Soil and Water Conservation Service
- Keith Dix – Innovative Farmers of Ohio

Evaluating a soil nitrate test kit –
48 soil samples were used to compare nitrate nitrogen readings. The results from the analytical lab at the Ohio Ag. Research and Development Center was compared to a soil nitrate tester (model 955001) purchased from Hawk Creek Lab. The average nitrate reading from all 48 samples were –

Analytical lab , Portable tester, Difference
9.625 ppm N , 10.275 ppm N , .65 ppm N

Individual test results were variable for both units with up to 9 ppm difference between the analytical lab and the portable tester. However, when comparing the average of 6 strips hairy vetch vs. control for each date, differences were not significant. The convenience and cost savings of using a portable nitrate kit seem to out way the loss of accuracy of results.

Measuring nitrogen benefits of hairy vetch cover crop for corn production – soil nitrate – 12 inch soil cores were taken in each strip for the test and during the growing season they were taken at the exact same location. The average was taken of the six strips of hairy vetch vs. the average of six strips of control at each date. The following results were from the analytical lab.

Soil Nitrate readings
Date , Vetch ave. ppm, Control ave. ppm
8/1/95 , 4.3 , 4.6
11/28/95 , 3.5 , 3.9
5/6/95 ,0.9 , 1.3
5/14/96 ,2.6 , 2.5
Incorporate 5/22/96
6/5/96 , 8.9 , 2.4
6/11/96 ,9.4 , 4.1
6/17/96 ,15.4 , 6.4
Side dress N
6/24/96 ,29.7 , 15.6
7/1/96 , 18.8 , 11.6
7/16/96 ,28.7 , 18.7

It can be seen how hairy vetch releases a significant amount of nitrogen. If it is assumed that 8 lbs actual nitrogen is equal to 1 ppm soil nitrate difference and 25 ppm soil nitrate is sufficient for 150 bu/acre corn production then on 6/17-96 side dress nitrogen was reduced by 90 lbs/acre on the hairy vetch strips vs. control of full rate of 150 lbs nitrogen. The hairy vetch strips also showed a higher response to side dressed 28% nitrogen with higher nitrate readings after 6/17/96.

Tissue tests –
On 8/4/96 the corn had emerging silk and tassel pollen shedding. The ear leaf was removed from 10 consecutive plants in each strip and analyzed for nitrogen content at the OARDC Research Extension Analytical Lab.

Tissue test readings
Strip , Vetch % N ,Control % N
1 , 2.89 , --
2 , -- , 2.94
3 , 2.88, --
4 , -- , 3.06
5 , -- , 2.74
6 , 2.78, --
7 , 3.02, --
8 , -- , 2.90
9 , -- , 2.95
10 , 2.72, --
11 , -- , 2.94
12 , 2.86, --
Average , 2.86 , 2.92
Sufficient range (2.9-3.5)
The comparison of the tissue test results does not show a significant difference between hairy vetch and control strips.
Falk stalk nitrate test – on 10/2/96 the corn had reached black layer maturity. At the flagged location in each strip, soil samples were collected an 5 consecutive corn stalks were cut off 6 inches above the ground, then the bottom 8 inches of each stalk was cut off. These corn stalk samples were sent to the OARDC, REAL lab for nitrate analysis. The control strips averaged 2666 ppm stalk nitrate vs. 933 ppm in vetch strips. Control strips were in the excessive range for stalk nitrate with the vetch being optimum. When comparing to the soil nitrate readings, all strips showed no significant levels of nitrate remaining in the soil. One may conclude that too much nitrogen was applied to the control strips.
Yield test – the corn was harvested on 10/29/96 with grain moisture from 21-25%. A weight wagon was used and each strip was measured for length. Yields were corrected to dry corn yields.

Yield results:
Strip , Vetch bu/acre , Control bu/acre
1 , 114.8, --
2 , -- , 112.8
3 , 104.4, --
4 , -- , 99.8
5 , -- , 100.7
6 , 101.1 , --
7 , 107.5, --
8 , -- , 108.8
9 , -- , 106.4
10 , 105.8, --
11 , -- , 109.1
12 , 97.9, --
Average, 105.25 , 106.27

With dry weather in July and August, these yields were comparable to neighboring farms. The strips of hairy vetch did not differ significantly from the control strips even with 90 lbs/acre less nitrogen applied to the hairy vetch strips.

To compare the cost savings of purchased nitrogen vs. the cost of growing hairy vetch the following was compared.

Cost difference per acre
Vetch , Control
90lbs/acre additional N @ $.28/lb, --, +$25.20

Hairy vetch seed 23lbs/acre @ $.70/lb , +$16.10

Disk vs. mowing ,+$1.50

Seeding cost , +$5.00

Total special costs , $22.60 , $25.20
Savings per acre , $2.60

With no significant yield difference, this comparison shows an economic advantage with using hairy vetch. The benefits of soil erosion and improved soil quality were not accounted for. We consider the cover crop system a success.

- A field day was held on August 23, 1995 at the Rich Bennett farm. This project was included on the agenda. About 40 farmers attended.
- A poster was presented on this project at the Innovative Farmers of Ohio annual meeting in Delaware, OH on 1/20/96. Nearly 100 farmers and agency personnel attended.
- A Cover Crop Council breakfast meeting was held by the Henry County Extension agent in Napoleon, OH. The project was discussed at this meeting. About 15 farmers attended.
- A field day was held on August 28, 1996 at the Rich Bennett farm. The project field was a stop on the tour and discussed at length. About 50 farmers attended.
- The OSU Extension Sustainable Ag team toured the project field on 10/9/96. 10 people attended.
- The results of this project will be shared with the Soil and Water Conservation Service, OSU Extension and Innovative Farmers of Ohio.


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.