EDITOR’S NOTE: This is the second in a four-part series highlighting different cover crop seeding techniques. This article discusses broadcasting. Our first article began running January 5 in the “Find it Now” section, and covered over-seeding. Next month: aerial seeding.

Cover crops continue to be a popular conservation practice discussed at meetings, conferences and field days. They are a critical tool listed in the Iowa Nutrient Reduction Strategy for their ability to retain both nitrogen and phosphorus in the field. One important decision is how to select a seeding method from the variety of options: over-seeding, broadcast seeding, aerial seeding, drilling and more.

SEEDING RATE: It’s important to seed the right rate per acre when seeding a cover crop. If you want to establish a small test plot, Iowa Learning Farms has a Test Strip Calculator Tool available on ILF’s cover crop resources web page.

 Broadcast seeding helps extend the fall growing season for cover crops when the seeding is completed prior to cash crop harvest. As with over-seeding and aerial application, adequate soil moisture is needed with broadcast seeding for good germination and quick establishment of the cover crops.

Innovative ways to broadcast seed into standing corn, soybeans
Broadcast seeders may be mounted to ATVs, tractors, or other implements to help cover large areas of ground. It is important to calibrate the seeder to meter the seed at the desired rate and pattern of dispersal. If using a mixture of cover crops, it is important to remember that the species have different weights which will impact the spread pattern. Heavier seeds will spread further than lighter seeds.

SEEDING INTO CORN: If you are seeding into corn, mid-August is generally a good time to do it, although there could be some germination issues due to a lack of sunlight getting down through the corn canopy.

Hand broadcast seeding is a great technique to establish small plots to try seeding cover crops at different times or to observe how different species perform. This method is used in an Iowa Cover Crop Working Group (ICCWG) USDA-NRCS Conservation Innovation Grant project that evaluates the impacts on soil and water quality as well as crop yields under cover crop mixtures, single species cover crops and no cover crop check treatments.

Guidelines for establishing cover crop plots
Between Aug. 25 and Sep. 4, 2015, ICCWG staff traveled the state to broadcast seed cover crops and collect water samples. The broadcast seeding was done by hand. This was the third seeding season at six Iowa State University Research Farms located near Sutherland, Kanawha, Nashua, Crawfordsville, Chariton and Lewis.

Before heading to the field, a seed packet for each row was weighed out and labeled. Weighing out a packet for each row helps ensure the desired seeding rate, similar to calibrating a mounted broadcast seeder. For the grant, the seeding rate is 1 million seeds per acre, so the seed packet weight is calculated based on the single species or mixture being used.

SEEDING INTO SOYBEANS: If you seed a cover crop into an existing soybean field, sew it about a week before the leaves drop, which typically occurs in late August or early September.

After arriving at the field and double-checking the plot map, the team prepared to seed the cover crop into the standing soybeans. The packet bundle was loaded into a tool pouch, and one person took the end of a tape measure while another held on to the other end ready to announce when the first person had reached 25 and 50 feet, respectively. 

ILF has a Cover Crop Test Strip Calculator Tool
Ripping off one corner of the packet, we walked backwards down the row, sprinkling out seeds as we went. At the end of the plot, we would reach for a new packet and return down the next row until the plot had been seeded. After checking the map again and loading up the next packets of seed, the process begins again until all the seed packets have been dispensed.

If you are interested in establishing a small test plot, Iowa Learning Farms has a Test Strip Calculator Tool available on our Cover Crop Resources webpage (extension.iastate.edu/ilf/content/cover-crop-resources). The cover crop test strip seeding rate calculator allows the user to input the dimensions of the plot, select the seeding method, and choose from 14 cover crop options. The tool automatically calculates the amount of total seed needed based on the plot size and reports the seeding rate per row for easy measurements.

Juchems is events coordinator for the Iowa Learning Farms program, based at Iowa State University in Ames.