Winter Rye Cover Crop Preceding Soybean: Fall Planting Dates and Rates

Each fall, we receive questions about winter rye planting dates and rates for establishing cover crops in anticipation of soybean production next spring.

Rye cover crop planting dates can range from August to November, and planting rates may range from 20 to 90 lb/acre. Farmer goals with the cover crop are an important consideration, and likely include protection from soil erosion, weed suppression, and long-term improvement of soil productivity. A study is being conducted by the Carrington Research Extension Center, with financial support from the North Dakota Soybean Council, to help determine the optimum rye seeding rate and resulting established stand, based on fall seeding dates and following season factors affecting soybean production.

The field study commenced during the fall of 2018 with two planting dates and three planting rates of winter rye. Initial rye planting dates range from September 17 to October 2, and second planting dates range from October 8 to November 1. Planting rates are 25, 50 and 75 lb per acre. Rye was direct-seeded with a no-till drill and terminated by glyphosate near soybean planting time.

Three years of data have been collected (2019-21) and data collection continues during this current season. Data includes rye plant population, ground cover, weed suppression and soybean performance. The following is a summary of preliminary data:

• Averaged across four years, rye plant density and ground cover measured during May (prior to soybean planting) ranged from 137,800 to 598,300 plants per acre, and 9 to 27% ground cover, among combinations of rye seeding dates and rates.  The greatest rye plant density (598,300 plants per acre; 14 plants per square ft) and ground cover (27%) resulted from the first planting date and 75 lb per acre planting rate.
• Averaged across three years, green and yellow foxtail suppression ranged from 51-73% among the six rye treatments, with the greatest suppression (73%) occurring with the first rye planting date and 75 lb per acre planting rate. In 2020, kochia suppression was greatest (79-83%) with the early rye planting date and 50 or 75 lb per acre planting rates.
• Averaged across three years, soybean plant density and development, and seed yield (average of 45.2 bu per acre) and quality were similar among rye treatments.

Currently, the study data indicates planting winter rye as a cover crop during the last-half of September versus later in the fall, and at a planting rate 75 lb per acre, provides the best potential for optimizing factors measured in the study. Soybean performance will be acceptable with proper management using rye cover crop.