Cereal rye remains an important dual-purpose cover crop in the region due to its winter hardiness, nitrogen scavenging and high biomass potential, and feed-value as a forage crop. A cereal rye seeding rate of 2 bu/ac is typically recommended when utilizing it as a forage crop, with even higher rates (2.5 bu/ac) sown when seeding later in the fall. However, recent Penn State research has shown that lower cereal rye seeding rates are adequate when cereal rye is sown as a cover crop. Here are a few considerations for deciding on your cereal rye seeding rate this fall:Fine tuning seeding rates for forage and grain production. Seeding rate recommendations for maximizing yield potential for small grains are based on the number of germinable seeds per acre (Figure 1). Seed germination rates (%) can be found on seed tags in most cases, but seeds per pound are not always provided.Figure 1. Germinable seeds per acre
D = C x R x G
D = germinable seeds/acC = seeds per poundR = seeding rate (lb/ac)G = germination rate (%/100)The number of cereal rye seeds per pound can differ significantly between varieties and between seed lots of the same variety. For example, a recent study reported a range of 13,000 to 23,000 seeds/lb in a survey of 26 different cereal rye seed lots, including varieties (VNS, Aroostook, Danko, Wheeler) commonly used in the Northeastern region (Lounsbury et al., 2022). So depending on your seed lot, a 2 bu/ac (112 lb/ac) seeding rate may result in germinable seeding rates ranging from 1.3 to 2.3 million seeds per acre when using a 90% germination rate estimate.If growing cereal rye for grain, use of winter wheat seeding rate recommendations is likely a good starting point. Winter wheat recommendations generally start at 1.5 million seeds per acre, with increases (~20%) recommended for later sowing dates or poor-fertility soils. However, cereal rye has a longer period of vegetative growth than wheat and barley, which may allow for reduced seeding rates in some cases. For example, under optimal fertility conditions, field trials in the Southeast US showed no difference in cereal rye grain yields across seeding rates ranging from 1.0 to 1.7 million seeds/ac.While utilizing seeding rates based on pounds per acre gets you in the ballpark, consider taking additional steps to understand seeding rates based on germinable seeds per acre and fine-tune cereal rye management, particularly when sowing it as a forage or grain crop.Lower seeding rates will work for fall weed suppression. When targeting specific cover cropping management goals, cereal rye seeding rate is less likely to be a primary driver. Fall sowing dates, spring termination timing, and fertility management will have a greater effect given that many cover cropping goals are positively associated with cover crop biomass production.It is generally thought that increasing cereal seeding rates improves suppression of winter annual weeds that emerge with or soon after sowing fall cover crops. This is based on the idea that higher initial plant densities will create quicker ground cover and outcompete emerging weeds for light. We tested this idea for three years at Rock Springs and Landisville, Pennsylvania in the context of horseweed management. Our research found significant horseweed suppression (> 70%) when sowing rye in mid-October but no differences between seeding rates of 45 to 120 lb/ac were observed (Ficks et al. 2022).When targeting cover crop goals such as weed suppression and soil erosion protection, consider seeding rates in the 45 to 90 lb/ac range.Lower seeding rates will work for planting green. Management goals for planting green differ among growers. Some growers manage for moderate levels of cover crop biomass while others focus on maximizing biomass production. Penn State research suggests that increasing rye seeding rates from 30 to 120 lb/ac will have minimal effects on total biomass production when delaying termination until the late-heading stage. In some cases, using higher seeding rates for later planting dates may contribute to increased suppression of early emerging summer annuals like common ragweed due to greater spring ground cover. But our research suggests that there is little benefit to increasing seeding rates for summer annual grasses and small-seeded broadleaf species like pigweeds.When planting green, consider using seeding rates in the 30 to 60 lb/ac range to target soil health, soil conservation, and weed management goals.
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