Evaluating Canola and Winter Cover in Alternative Cropping Systems in Iowa

Evaluating Canola and Winter Cover in Alternative Cropping Systems in Iowa

Summary

Adding winter cover crops to crop rotations in the form of winter annuals and perennial legumes serves to reduce soil erosion, improve nutrient management, and break weed life cycles. Both spring and winter varieties of canola are being evaluated for their suitability to fit in an Iowa crop rotation. Winter annual crop species (canola or wheat) as well as a perennial legume species (red clover) will also be included in the different planned rotations. This project modifies the common corn-soybean rotation to evaluate alternative crop rotations. The rotations being evaluated are as follows: A) corn-soybean-corn-soybean; B) corn-spring canola/winter wheat (red clover)-corn; C) corn-spring wheat/winter canola (red clover-corn. The ecological and economic impact of the alternative systems will be determined using an ecological footprint model and enterprise budgets, respectively. Portions of this research are being conducted at University research sites and at the farms of two cooperating Iowa farmers as part of the Practical Farmers of Iowa and ISU On-Farm Research Program.

Objectives/Performance Targets

The objectives of this research are to 1) to investigate the viability of canola as an alternative oilseed or ‘third’ crop in Iowa, 2) to investigate the viability of winter cover crops in Iowa, and 3) assess the ecological and economical impact of alternative cropping systems. The project will monitor different crop rotations in order to further gather information about growing and managing canola and winter cover crops in Iowa.

Accomplishments/Milestones

In fall 2011, presentations were given at the field day of farmer Paul Mugge and at the ASA-CSSA-SSSA joint meetings. The presentation at the field day answered questions from farmers regarding winter and spring canola yields, end-uses, and production. The presentation at the joint society meetings concerned yields, N-dynamics, and weed pressure associated with the corn phase of the three rotations. Furthermore, journal articles and university extension publications are tentatively planned at the outcome of the experiment to comply with our expected goals and end ‘deliverables’. In addition, both Dr. Wiedenhoeft and Mr. Gailans have been featured in local and regional press articles and radio programs discussing this project.

Impacts and Contributions/Outcomes

In 2011, grain yield of corn in the common rotation, A (12.3 Mg/ha), was significantly greater than the alternative rotations, B and C (10.8 and 11.5 Mg/ha, respectively). The lesser yields in B and C were not due to insufficient available nitrogen as evidenced by stalk nitrate tests (excess levels observed in corn in B and C; optimal observed in A). Indeed, above ground red clover cover crop biomass preceding the corn in B and C contained over 100 kg N/ha with the potential to be mineralized and become plant-available. However, corn was slower to emerge in rotations B and C owing to persistent and slow-to-terminate red clover cover crop causing the lesser yields of corn in these plots compared to the common rotation, A. Additionally, weed pressure in Rotations B and C (0.7 and 3.4 g/sq-m) was significantly lesser than weed pressure in Rotation A (8.8 g/sq-m). These differences can likely be attributed to the red clover mulch resulting from chemical termination in Rotations B and C. Measures in 2012 were taken to rectify the corn emergence problem: following chemical termination of red clover cover crop, strip tillage was employed with the corn planted directly into the strips in the alternative rotations.

Wheat yield in Rotation B (3.6 Mg/ha) were greater than that of Rotation C (2.3 Mg/ha). This is expected as winter wheat grown in Rotation B has a greater yield potential than spring wheat, grown in Rotation C. Likewise, canola yield in Rotation C (2.5 Mg/ha) was greater than that of Rotation B (0.9 Mg/ha) for the same reason: winter canola in Rotation C vs. spring canola in Rotation B. Interestingly, the combined yields of wheat and canola are similar between Rotations B and C (4.6 and 4.8 Mg/ha, respectively).

Winter cover crops (red clover, winter wheat, and winter canola) have been establishing well and providing ample, living soil cover post-October (50-90% cover) and pre-May (60-80% cover). Implications concerning soil, water, and weeds will be explored with respect to these data. Of primary comparative interest is the oil production among the three rotations. Oil yield in Rotation C (1.2 Mg/ha; winter canola) was greater than oil yields in Rotation B (0.7 Mg/ha; soybean), which was greater than Rotation A (0.5 Mg/ha; spring canola). This is encouraging given the fact that much less weed pressure was observed in soybean (6.7 g/sq-m) than in winter canola (24.8 g/sq-m) and in spring canola (207.1 g/sq-m). It should also be noted that soybean was treated twice with herbicide (glyphosate) during the growing season while neither winter or spring canola was treated with herbicide.

Preliminary costs-of-production analyses have been conducted. Only costs of field operations (tillage, fertilizer application, planting, harvesting, etc.) have been analyzed with no inclusion of costs of farming inputs (seed, fertilizer, chemicals, etc.). As such, cost of production for Rotation A was $31.13/ha less than the costs associated with both Rotations B and C. Rotations B and C entail more passes over the field due to the inclusion of inter-cropping and double-cropping systems in these rotations.

• Stefan Gailans standing by winter canola and winter wheat in April 2012
• Winter canola cover crop in late March 2012

Collaborators: