Principal Investigator: Ed Nater and Erik Krueger
Co-Investigator(s): John Baker; Deborah Allan; Paul Porter; Adam Herges
Organization(s): University of Minnesota, Department of Soil, Water, and Climate, Department of Agronomy; USDA, Agricultural Research Service
Award Amount: $249,008
Start Date: 5/26/2009 | End Date: 3/1/2012
Project Manager(s): Bob Patton (Bob.Patton@state.mn.us)
For a copy of the final report, please contact Bob.Patton@state.mn.us
Background and Introduction
Over the last century, storm events in many areas of the United States have been occurring with higher frequency and intensity. This can lead to increased soil erosion, nutrient loss, and flooding in agricultural systems. The problem may be exacerbated if large amounts of corn stalk residue are removed for the production of second generation (cellulosic) biofuels or for use on-farm as corn silage.
Winter cereal grain cover crops provide an opportunity to assist in mitigating the negative effects of climate change and the associated increase in storm intensity by covering the soil at times when it might otherwise be bare. Winter rye (Secale cereal L.) is a good choice for a cover crop in a corn-soybean system due to its cold tolerance. This allows it to fit in during the winter fallow period.
This project consisted of four studies. Three studies evaluated the potential for a winter rye cover crop following soybeans or corn silage to reduce surface runoff. A fourth study explored the effect of corn stover removal on water quality.
Project Objectives
- Evaluate three winter rye cover crop seeding methods in soybean fields for their potential to minimize the effects of high rainfall rates on surface runoff, sediment removal, and nutrient transport from agricultural landscapes under a simulated rainfall event.
- Evaluate the potential of a winter rye cover crop drilled after corn silage to minimize the effects of high rainfall rates on surface runoff and sediment and nutrient transport on a working farm under a simulated rainfall event.
- Evaluate the effect of removing corn stover on water quality using a paired watershed design.
Table 2. Effects of rye cover on total surface runoff, sediment loss, nitrate-nitrogen loss and phosphorus loss presented as a percentage of the fallow control.
| Total Surface Runoff | Sediment Loss | Nitrate-Nitrogen Loss | Phosphorous | |||||
| Fall | Spring | Fall | Spring | Fall | Spring | Fall | Spring | |
| Winter Rye Establishment Method | % | % | % | % | ||||
| Fallow (No Rye) | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Aerial | 21 | 1 | 22 | 1 | 19 | 1 | 14 | 1 |
| Airflow | 4 |
3 |
9 | 3 | 4 | 4 | 1 | 2 |
| Broadcast | 37 | 3 | 33 | 2 | 36 | 3 | 17 |
2 |
Nitrate-nitrogen (N03-N) losses in surface runoff in the fall were significantly reduced by 80% for winter rye treatments compared to fallow. However, no statistical differences were observed between the three rye treatments. N03-N losses in surface runoff in the spring were reduced by 98% in the three rye treatments compared to fallow. Total phosphorus (TP) was not significantly reduced by cover crops in the fall compared to fallow, but TP was significantly reduced in the spring. All cover crop treatments reduced sediment compared to fallow in both the fall and spring.
Study # 2: Effect of Winter Rye after Corn Silage on Surface Runoff under a Simulated Rainfall Event on a Working Farm
Study Area and Methods
A simulated rainfall event was applied to rye cover crop and fallow treatments in a corn silage system on a farm near Lewiston, Minnesota. Simulated rainfall events were applied in spring, 2010 and 2011. Treatments included standing rye, harvested rye (rye cut at 4 in above ground), and a fallow control. A rainfall rate of 2.5 inches per hour was applied for a duration of one hour to the rye and fallow treatments during the third week of May in 2010 and again in 2011. Water samples were collected every 10 minutes after initial surface runoff occurred in each simulation. Soil samples were collected to a depth of 90 cm for physical analysis, gravimetric water content, and bulk density. Winter rye was harvested to determine biomass yield in May, prior to rainfall simulations.
Results
Fallow treatments produced the highest volume of surface runoff, nutrient and sediment loads compared to winter rye treatments (table 3). Nutrient and sediment loads followed similar trends to total surface runoff for each year.
Table 3. Effect of rye cover on total surface runoff, sediment loss, nitrate-nitrogen loss and phosphorus loss- presented as a percentage of the fallow control
| Total Surface Runoff | Sediment Loss | Nitrate-Nitrogen Loss | Phosphorus Loss | |||||
| 2010 | 2011 | 2010 | 2011 | 2010 | 2011 | 2010 | 2011 | |
| Treatment | % | % | % | % | ||||
| Fall (No Rye) | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Standing Rye | 1 | 33 | 1 | 8 | 1 | 32 | 1 | 23 |
| Harvested Rye | 1 | 81 | 1 | 32 | 1 | 81 | 1 | 73 |
In 2010, soil profile N03-N concentrations to a depth of 90 cm were reduced 64% and 61% after standing rye and harvested rye compared to fallow. In 2011, soil profile N03-N concentrations were low in all treatments. Winter rye effectively scavenged excess soil profile N03-N during the spring.
Study # 3: Effect of Removed Corn Stover on Surface Runoff in a Paired Watershed
Study Area and Methods
This study took place on a farm located near Plainview, Minnesota between 2009 and 2012. Two watersheds were evaluated using edge-of-field surface runoff monitoring within adjacent paired watersheds: a treatment watershed with corn stover baled (3 acres) and removed and control watershed with corn stover not removed (10.4 acres).
Results
Prior to stover removal, ground cover in both watersheds was measured at 89% or greater. Stover removal in fall 2010 in the treatment watershed resulted in a reduction in ground cover to a level of 35%. Surface runoff increased 30% due to stover removal compared to the control. Differences in total surface runoff were observed in 10 out of 25 months. These 10 months included the four major surface runoff events in which samples were collected. Evaluating surface runoff in paired watersheds in an on farm research setting presents constraints relative to University Experiment Station lands. Flexibility had to be shared between the researchers and the farmer involved with respect to cropping management of the watersheds.
Study # 4: Effects of Winter Rye following Corn Silage on Surface Runoff in a Paired Watershed
Study Area and Methods
The study was conducted between 2009 and 2012, using edge-of-field surface runoff monitoring within adjacent paired watersheds planted to corn silage on a farm located near Lewiston, Minnesota. A treatment watershed was drilled with winter rye after corn silage removal and a control watershed was left fallow after corn silage removal. Rye was seeded at a rate of 90 lbs acre-1 using a grain drill.
The rye was planted in the treatment watershed in 2009 and 2010 and did not allow for fall tillage or manure injection to take place. In the control watershed, fall chisel-disc tillage and manure injection occurred prior to freezing of soil in the fall of both years.
Results
In 2010, corn silage yield was reduced by 30% in the treatment watershed compared to the control due to a delayed spring crop planting. Residue cover decreased in the control watershed from fall to spring whereas residue cover increased in the treatment watershed. In spring 2010, winter rye reduced soil N03-N concentrations by 30% compared to the control watershed, suggesting that the rye effectively scavenged excess soil profile NO3-N.
The treatment watershed had 60% more total runoff than the control, with a majority of runoff during spring snowmelt events. The volume of runoff in both watersheds was similar at the beginning of the snowmelt period. However, the runoff occurred for longer periods of time for the treatment watershed. The treatment watershed had higher N03-N, NH4-N, total phosphorus, and sediment loads than control watershed in two of the three events where samples were collected. The control watershed had higher loads during the summer rainfall event.
Differences in field management in fall accounted for the differences in surface runoff during snowmelt events. The snowmelt events produced 75% more runoff in the treatment watershed than the control due to snow catchment with the winter rye and the north-south aspect of the treatment watershed (compared to east-west aspect for the control) which allowed for faster snowmelt during the winter months.
Overall Project Conclusions
- Seeding a winter rye cover crop into soybeans can reduce surface runoff, sediment removal, and nutrient transport in fall and spring. The greatest environmental benefit will likely occur in the spring.
- Increasing the winter rye cover crop seeding rate beyond 112 kg ha-1 into soybeans does not improve the stand or provide increased environmental benefits.
- A winter rye cover crop planted after corn silage removal in the fall will help to prevent surface runoff, soil erosion, and off-site nutrient transport relative to fallow in the Upper Mississippi Basin.
- Corn stover removal will likely magnify soil erosion risks associated with no-till conventional practices and will negatively impact water quality due to increased surface runoff.
- Winter rye cover crops can have a negative effect on subsequent crop yields due to water and nutrient usage. Late termination of winter rye in the spring can delay crop planting.
- Winter rye cover crops should still be considered a best management practice and more years of study should be observed.
