Winter rye is used as a cover crop in the Northeast because it is cold-hardy and grows quickly in the fall and continues to produce more biomass in the spring. Winter rye can be planted later than many other crop crops and gives farmers the opportunity to plant a cover crop even after harvesting a full season crop like soybeans. Over the past two field seasons, the UVM Extension Northwest Crops & Soils Program has conducted research trials on the impact of winter rye planting date & seeding rate on no-till soybeans. Keep reading for a summary of how cover crop planting date impacted soybean yields in these trials. Additional information, including the full research reports can be found on our website.
In 2021-2022 and 2022-2023, rye was planted at five planting dates (Table 1). Cover crop biomass was measured the following spring just before it was roller crimped and then soybeans were planted into the mulch using a no-till planter. At harvest, soybean yield was measured. Figure 1 provides a summary of the relationship between rye biomass and soybean yield in planting dates 1, 3, & 5. Rye biomass was higher in 2023, but decreased with the later planting dates in both years. Soybean yields were also higher in 2023. The soybean yield response to rye planting date was quite different. In 2022, soybean yields were highest when planted into the first planting date, and lowest in the last. The opposite trend was observed in 2023; soybean yields were negatively impacted by the increase in rye biomass, and yields were highest in the last planting date.
Winter rye produced exceptionally high biomass in 2023 due to above average temperatures in the fall and through the early months of 2023 (Table 2). In 2021, fall temperatures were also warm, but cold winter and early spring temperatures limited rye growth. Rye biomass in 2021-2022 reflects average yields for our region, approximately 2 tons of dry matter per acre. Excessive rye biomass taking up water in the soil and limited precipitation in May 2023 resulted in a dry seed bed at soybean planting. Cool temperatures persisted, and excessive rainfall during the remainder of the season resulted in above average precipitation. Sub-optimal growing conditions and high rye biomass likely resulted in soybean yield reductions in the first planting date of the 2023 trial. Temperatures were also cooler than average during the 2022 soybean growing season. But there was more precipitation in May & June 2022 compared to 2023 and this resulted in saturated soil conditions that persisted throughout the season. In this scenario, the additional rye biomass in the first planting date may have reduced soil moisture by taking up available water in the soil.
Moderate amounts of rye biomass in the spring may help reduce soil moisture in years with increased precipitation and improve soybean yields. But too much rye biomass can deplete the soil of moisture, and exacerbate dry soil conditions, resulting in yield reductions.
Table 1. Winter rye planting dates by trial year.
Table 2. Monthly average temperature & total precipitation by trial year compared to the 30-year average.
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