Evaluating Corn Varieties in Pure and Mixed Stands for Organic Crop Production across Three States in the Corn Belt
Results of corn organic variety trials conducted in Iowa, Wisconsin, and Ohio in 2007 – 2008 were analyzed and summarized. Varieties evaluated in these trials included organically produced hybrids, open pollinated varieties, and untreated conventionally produced hybrids marketed in each state. Up to five evaluations of varietal blends were performed in each state using replicated on-farm strip tests. Data collected included grain yield, emergence, seed germinability and vigor, stalk lodging, grain protein, oil and starch. Results have been presented online, at field days, and publicized in newsletters and the popular farm press for distribution to organic farmers. Two papers summarizing results of the study were presented at the 2009 American Society of Agronomy Meeting.
1. Evaluate the agronomic performance and grain quality of organic certified varieties in pure stands.
2. Investigate differences in grain yield and quality among corn hybrids planted in pure and mixed stands.
Objective 1: Organic variety performance trials were conducted at three test locations in each state. Varieties evaluated included organically produced hybrids, open pollinated varieties, varietal blends, and conventionally produced hybrid (untreated seed). Seed companies marketing organic seed in Iowa, Ohio and Wisconsin were invited to enter organic varieties in the trials. The organic variety performance trials evaluated the agronomic performance and grain quality of 20 to 30 varieties in pure stand at field sites in each state that were certified organic or transitional organic. Each variety entry in the trials was evaluated using four replications per site in a randomized complete block design. Data collected included grain yield, emergence, seed germinability and vigor, stalk rot and lodging, grain protein, oil and starch.
Objective 2: Organic and conventionally produced hybrids (untreated seed) were planted in pure and mixed stands in organically certified fields at five on-farm sites per state. Pure and mixed hybrid plantings were evaluated in strip trials in which two hybrids were planted on each side of a center strip where the two hybrids were mixed by alternating rows or seed of each hybrid. Mixing was accomplished by filling alternate planter boxes on a conventional corn planter or mechanically mixing seed for planters with central seed hopper delivery systems. Strips were a minimum of 250 feet in length. The hybrid treatments (pure vs. mixed hybrids) at each on-farm site were replicated three times in a randomized complete block. Ear samples were collected to determine if hybrid mixing affects kernel set (pollination success), tip fill, kernel abortion, etc.. Ten ears from a 50 foot length of row in the center of each strip plot were collected to ensure minimal pollen contamination. In plots planted to hybrid mixtures, ears were collected from 10 plants of each hybrid component. Data collected included grain yield, test weight, emergence, seed germinability and vigor, stalk rot and lodging, grain protein, oil and starch. Farmer collaborators determined yield using weigh wagons or on-farm scales. A one to two pound grain sample from each plot was collected from the combine hopper during the harvest operation for grain moisture and grain composition.
Impacts and Contributions/Outcomes
The organic variety trials increased organic farmer access to research-based information on varietal performance in pure and mixed stands. The results increased the ability of organic growers to apply research based information in variety selection. The results may also benefit to seed companies starting to market organic seed, thereby providing organic growers with more options in their selection of seed.
Before the implementation of the National Organic Program, organic farmers generally used untreated corn seed of conventional varieties they knew and trusted from years of trial and error on their farms. Since the implementation of the NOP in October 2002, this situation has changed, and now certified organic farmers must use certified organic seed unless it is not available. Although several seed companies have started to market organically produced, untreated corn seed in accordance with the new organic production guidelines, many organic growers continue to use untreated seed of conventionally produced hybrids. A recent survey conducted by the Organic Crop and Improvement Association – Research and Education indicated that about one third of the organic corn farmers in Iowa, Wisconsin, and Ohio plant untreated seed of conventionally produced hybrids.
Some organic corn growers have expressed reservations concerning the yield potential seed, and grain quality of organically produced corn compared to conventionally produced corn. Some contend that the organically produced hybrids currently available do not have as high yield potential as conventionally produced hybrids. Results of these 2008 multistate organic variety tests indicate that organic hybrids are available with yields comparable to conventional corn hybrids commonly planted in organic cropping systems. Test results also indicate that seed germinability and vigor of organic and conventional seed was similar. Grain protein and oil of organic and conventional hybrids was slightly less than open pollinated hybrids. However, the latter generally produced yields only 1/3 to ½ those of the organically and conventionally produced hybrids.
The on-farm blend study results indicate that mixed stands provided little yield advantage over pure stands. Effects of blending hybrids on grain composition were variable but relatively small. The protein content of grain from the mixed hybrid plantings was either similar to that of the hybrid with the higher protein content in pure plantings or intermediate that of the two hybrids in the pure plantings. Oil content of the grain from the mixed plantings was intermediate that of the grain for the two hybrids in the pure planting. Differences in the starch content of grain from the hybrid blends and the hybrids in pure plantings were negligible.
Iowa State Univerity
Department of Agronomy
2104 Agronomy Hall
Ames, IA 50011
Office Phone: 5152946655
The Ohio State university
201 Thorne Hall
Wooster, OH 44691
Office Phone: 3302023534
Iowa State University
Dept. of Agronomy/Horticulture
106 Horticulture Hall
Ames, IA 50011
Office Phone: 5152947069
The University of Wisconsin
1575 Linden Hall
Madison, WI 53706
Office Phone: 6082637438