Improved Cover Crop Options for Corn Belt Farmers

Improved Cover Crop Options for Corn Belt Farmers

Summary

Seventeen cover crop treatments (nine sole-crops, five binary mixtures, two trinary mixtures, and a no-cover-crop control) were planted in two environments in Iowa in October 2013 and three environments in October 2014 following harvest of soybean. Establishment was excellent in four environments, however, cover crops at one environment did not emerge prior to winter conditions arrival in 2014. Winter rye (“cereal rye”), winter triticale, Camelina sativa, and hairy vetch overwintered in 2013-2014, but Brassica napus, B. rapa, spring oat and barley entries did not. Cover crops differed significantly for stand density, accumulation of aboveground biomass, C and N in fall and the subsequent spring of 2014. The C:N ratio of cover crop aboveground biomass and weed density did not vary among cover crop entries at termination in spring 2014. Winter rye, and mixtures with winter rye, produced greater amounts of biomass and accumulated more N than other cover crops or cover crop mixtures. Corn stand density, grain moisture at harvest, and weed community prior to the first in-crop herbicide application, did not vary for cover crop entry in 2014. However, corn yield following triticale cover crop was less than corn production following Brassica rapa cover crop. Weed community in cover crops was dissimilar to weed community in subsequent corn in the first completed cycle of this study.

Objectives/Performance Targets

1 – Compare establishment, winter survival, biomass production, N accumulation, and weed community in 17 cover crop treatments. Plant 17 cover crop treatments at three locations (envrionments) following soybean harvest annually. Over two years, the cover crops were planted in five environments following soybean harvest (Table 1). We were unable to plant the cover crops at the Sutherland environment in 2013 due to excessive rains, which resulted in delayed planting and harvest of soybean that year. Stand establishment and density were assessed in the fall at each of the five environments, with data collected at four of five. Due to late soybean harvest at Boone in 2014 and cold conditions, cover crops did not emerge following planting on 30 October. It was noted that most cover crop seed had germinated, but none had emerged by 11 November.   Fall biomass, N, and C accumulation were determined for cover crops at one of two planted environments in November 2013 and one of three planted locations in November 2014 due to limited cover crop growth. Biomass, N, and C accumulation in cover crops were assessed from samples harvested from both environments in May 2014 prior to termination of cover crops.         

2 – Compare corn establishment, growth, N status, grain yield, and weed community following 17 cover crop treatments.   

3 – Mr. Seth Appelgate was recruited as the M.S. candidate supported by this project. He completed his B.S. in Agronomy at Iowa State University and began employment in the second week of May 2014.  

Accomplishments/Milestones

Cover crop establishment

1 – Initial plant stand and winter survival data of Camelina sativa appear promising, however, we are not yet close to recommending its use as a cover crop in the upper Midwest Corn Belt.

2 – Both Brassica napus canola varieties and B. rapa turnip established well, and survival was initially good at the Curtiss Farm site (near Ames) due to snow cover when temperatures fell to 7 F. However, these three crucifer entries suffered nearly total stand loss from the 7 F encountered at the Atlantic site in early November. None of these three entries survived the winter of 2013-2014 at either location.

3 – Prior to termination in May 2014, 2013 fall-seeded cover crop entries differed for C and N concentrations (results not presented) and accumulations (Table 2) in aboveground biomass.

Corn following cover crops

Corn was planted in May 2014 following termination of cover crops (Table 1). Cover crop entry did not influence corn stand density (Table 2) or grain moisture at harvest. Data were collected on corn leaf chlorophyll concentrations and corn growth and development (results not presented). Corn grain yield differed following cover crops from the Armstrong Farm environment (Table 2).

Weed community

Weed density did not vary in April 2014 among cover crop entries that were planted in October of 2013 (Table 2). The weed community in association with corn was composed of 24 species (results not presented). However, tall water hemp (Amaranthus tuberculatus) accounted for 95.4% of total individuals of the weed community. Marestail (Conyza canadensis) had the second highest density, and accounted for less than 1.1% of the total number of individuals observed. Cover crop entries did not significantly influence total weed density in corn prior to the first in-crop herbicide application, when mean density for total weeds in corn across cover crop treatments was 224 m^-2 (Table 3).

Table 1. Planting dates and locations for 17 cover crops and subsequent corn, 2013-2014.  

†Corn at the Curtiss Farm was abandoned in 2014 after the site suffered severe flooding on the third of four occasions.

Table 2. Cover crop biomass, carbon and nitrogen concentration, and carbon and nitrogen content from two locations, May harvest, 2014

† Means within a column followed by different letters differ at P= 0.05 using Tukey’s HSD test following analysis of variance.

‡Means of 0 not included in statistical analysis of biomass, C, or N data.

Table 3. 2014 corn grain yield from Armstrong Farm.

† Means within a column followed by different letters differ at P= 0.05 using Tukey’s HSD test.

Impacts and Contributions/Outcomes

Impacts and Contributions/Outcomes

The project was started in October 2013. Insufficient time has passed for our project to have had large impacts and outcomes. However, funding of our project and description of cover crop treatments was presented at two cover crop meetings in fall of 2013. Outputs for 2013 include planting cover crops at two sites in October 2013 and three sites in October 2014.

Collaborators: