Established cover crops can reduce soil erosion, improve water infiltration, and suppress weed pressure.
Delaying of cover crop termination closer to planting date can reduce soybean yield in this trial when stubble remained standing.
Introduction
Cover crops can provide a wide variety of soil health benefits and help protect against erosion. The root structure of a growing crop promotes the development of soil structure, holds soil in place to guard against wind and water erosion, and increases water infiltration. Cover crops also provide the opportunity to scavenge nutrients from the soil that are at risk of being lost and later after decomposing return nutrition to the following crop. Cereal rye has been a popular choice for a cover crop because of its ability to overwinter and grow vigorously in cooler early spring temperatures. Although there are many benefits to using cover crops, how they are managed and integrated into current management practices can have a negative impact on cash crop yields. Termination of cover crops prior to planting can be delayed due to weather resulting in a decision to further delay planting or terminate afterward planting. A better understanding of these agronomic impacts can help make the most economical decision.
2023 Rye Cover Crop-Soybean Trial
Figure 1. Early growth differences of soybean plants, 2023: A) no cover crop, B) cover crop terminated 2 weeks prior to planting, C) cover crop terminated by crimping, D) cover crop terminated with glyphosate day of planting
An Agronomy in Action Research trial was designed to evaluate the effects of fall established rye cover crop termination timing and method. Soybeans were planted into areas with or without a fall seeded rye cover crop. Within the area planted to rye, the cover crop was terminated with glyphosate either 2 weeks prior to or on the day of planting soybeans. An additional termination method using a roller-crimper just before planting was also evaluated. Termination methods were compared to a check treatment where no cover crop was established. Four soybean varieties: GH2505E3, GH2922E3, GH2610E3, GH2722XF brands were no-till planted in 30-inch rows to understand if varieties responded differently to termination method and timing.
2023 Cover Crop Trial Results
Results from this one trial showed that there were no significant soybean yield differences between terminating cover crops two weeks prior to planting or crimping the day of planting compared to no cover crop (Graph 1). Terminating with glyphosate the day of planting greatly reduced yields in this trial. At time of soybean planting, rye had reached 40-inches in height. The extra residue from delaying termination with glyphosate or crimping improved overall weed control, but also suppressed early soybean growth and development (Figures 1 and 2). Even though crimping and glyphosate termination the day of planting had equivalent amount of rye residue to contend with, crimping still showed improved soybean yields, likely by reducing in-season light competition from standing rye (Figure 2). The later termination timing and crimping method also reduced soybean emergence as result of the heavy biomass. All four soybean varieties responded similarly within termination timing and methods.
Figure 2. 2023 Trial, no cover crop (front left), crimped rye (front right), glyphosate termination day of planting (upper right) and glyphosate termination 2 week prior to soy planting (upper left)Summary
One of the additional benefits from establishing a cover crop in soybeans was a notable difference in weed suppression in areas where cover crops were planted. Allelopathic chemicals are released by rye and can inhibit germination and early growth of small-seeded plants. General recommendations suggest terminating cereal rye at least 14 days ahead of planting to avoid any allelopathic or residue management concerns although planting soybeans into rye the same day as termination is often widely recommended. While delaying termination and creating a thick layer of residue can be a good weed management strategy, these results indicate there is potential for soybean yield loss to occur.
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