Establishment of Permissible Levels of Residue Removal for Corn, Wheat, and Sorghum Fields as Biofuel Feedstocks

Establishment of Permissible Levels of Residue Removal for Corn, Wheat, and Sorghum Fields as Biofuel Feedstocks

Summary

As it may show in the SARE reporting system, this project was transferred from Kansas State University to University of Nebraska-Lincoln in late December 2012. This project is assessing the positive and negative impacts of corn stover removal on soil quality and crop production in Nebraska. Field and laboratory activities were successfully executed in 2013. Three experiments (two existing experiments and one new) of corn stover removal are being used to accomplish the goals of this study. As specified in the proposal, the first site is at Brule (west central NE), while the second site is at Clay Center (south central NE). The third site was established near Lincoln, NE (Rogers Memorial Farm) in fall 2013. This experiment consisted in removing stover after harvest at five different levels (0, 25, 50, 75, and 100%) from rainfed no-till continuous corn. This new experiment will allow the establishment of permissible levels of stover removal in the long term. Grain and biomass yields, soil organic carbon pools (total C, organic C, and particulate organic matter), and soil hydrologic, compaction, structural, and fertility parameters were measured at the two existing sites. In addition to the above soil and crop parameters, greenhouse gas (CO2, CH4, and N2O) are being measured using the LICOR system at the new site near Lincoln. Results from the existing sites showed that corn stover removal at high rates increased wind erosion potential and altered the soil properties near the surface. Removal below at low rates appear to have small or no adverse effects. Grain yield was not significantly affected by stover removal.

Objectives/Performance Targets

This regional project assessed corn stover removal impacts on soil and crop production on a regional scale in Nebraska.

In 2013, we collected data on the following:

1. Organic matter and nutrient pools, compaction, hydrology, and structural parameters of soils.
2. Corn grain and biomass yield as indicators of crop sustainability.

 The ultimate goal is that farmers, researchers, and energy industry groups will; 1) gain knowledge about the positive and negative impacts of crop stover removal on crop yields, and soil and environmental quality, and 2) determine how much stover can be safely removed from their fields without adversely affecting soil, environment, and crop production.

Accomplishments/Milestones

1. Assessment of Soil Physical Quality

In spring 2013, soil samples were collected from the two existing two large-scale experiments (Fig. 1). At each site, soil samples were collected to assess structural, compaction, and hydraulic parameters using standard methods. Laboratory determinations included soil bulk density, wet aggregate stability, and water retention capacity. Plant available water as a difference between field capacity and wilting point were computed.

At Clay Center, data collected in 2013 show that residue removal (85%) reduced soil aggregate size and stability expressed as mean weight diameter of aggregates (Fig. 2). These results also show that effects of removal are only significant in the 0 to 2.5 (0 to 1 inch) soil depth (Fig. 2A). Results thus indicate that residue removal at high rates may degrade soil structural properties near the soil surface (Fig. 2A) but not at deeper depths (Fig. 2B). Reduced aggregate size and stability near the soil surface may increase risks of water and wind erosion. Results in Fig. 2A also indicate that use of cover crop and manure may reduce the negative effects of residue removal on soil properties.

At Brule, residue baling and grazing may affect soil water storage (Fig. 3A). Baling and grazing may also tend to reduce soil aggregate stability (Fig. 3B) and increase amount of wind erodible fraction (aggregates less than 0.84 mm in diameter; Fig. 3C). The large variability in data on aggregate stability and wind erodible fraction warrant a more intensive monitoring to discern spatial and temporal effects of residue baling and grazing at Brule.

2. Soil Organic Carbon and Nutrients and Their Relationships with Soil Physical Properties

We also determined soil organic C concentration for both sites for near-surface layers (Fig. 3). At Clay Center, residue removal reduced slightly soil organic C concentration near the soil surface but addition of cover and manure offset the small residue removal effects (Fig. 4A). At Brule, residue baling and grazing had not effects on soil organic C, but baling tended to reduce soil organic C (Fig. 4). Relationships of soil physical properties with total soil organic C were studied. These relationships will allow us to better understand the value of soil organic C for improving soil physical properties. Data on soil fertility and chemical properties along with data soil physical properties were also evaluated. Figure 5 shows some photos taken during soil sampling in spring 2013.

• Changes in soil organic C due to corn residue removal
• Photos of plots during soil sampling in spring 2013
• The three study sites.
• Effects of residue removal and cover crop and manure on aggregate stability.
• Effects of residue baling and grazing on soil water loss and soil structural properties

Impacts and Contributions/Outcomes

1. Corn stover removal at high rates (>60%) can increase wind erosion.
2. Corn stover baling (about 50%) may not have negative effects on soil physical properties and soil organic carbon.
3. There is a trend for increased risks of wind erosion and degradation of soil structural properties with >50% removal.
4. Cover crops may not offset wind erosion under excessive residue baling.
5. Stover baling from irrigated corn may not reduce yields.
6. Partial removal of residue (about 50%) may be sustainable.

 These significant and rapid effects of crop residue removal were reported in the following outreach opportunities in 2012:

1. Soils School. Title of presentation: “Crop residue removal and soil physical properties* Audience: Farmers. Grand Island, NE. (March 5, 2013).
2. Extension presentation. Title of presentation: “Crop residue management” Mid Plains Beef Session. Audience: Farmers. Mead, NE. December 16, 2013).
3. Professional presentation. Title of presentation “Corn stover removal effects on soil properties” 2013 ASA, CSSA, and SSSA Annual Meetings, ASA, CSSA, and SSSA, Tampa, FL. Audience: Researchers and Extension Specialists. November 4, 2013.
4. Soil and Water Conservation Society, 68th International SWCS Annual Conference. Title of presentation: “Assessment of soil response to corn residue baling and grazing” Audience: Researchers and Extension Specialists. Reno, NV. (July 23, 2013).
5. NC-1178 (Crop Residue Removal and Biofuels). Title of presentation: “Crop Residue Research in Nebraska” Madison, WI, (June 5, 2013)

Jon King, a graduate student, has been helping with the execution of this project in Nebraska. His graduate assistantship is partially funded through this project. The title of this thesis is “Impacts of Corn Stover Removal on Soil and Environmental Quality: Greenhouse Gas Emissions and Water Erosion Parameters”.

Collaborators: