Does winter cereal rye seeding rate, termination time, and N rate impact no-till soybean?

Abstract

Some farmers who use cover crops (CCs) have moved from CC preplant kill (PK) to delayed CC termination, called planting green (PG). We conducted a study to explore if soil conditions and crop production can be optimized by manipulating winter cereal rye (Secale cereal L.) seeding rate and spring N topdress rate for these two termination times. Treatments were arranged in a split-split plot, randomized complete block design with four replications for three years at two Pennsylvania locations. Main plots were seeding rate (34, 67, and 134 kg ha⁻¹, or 1x, 2x, and 4x, respectively), subplots were termination timing (PK and PG), and sub-subplots were N rate (34 and 67 kg ha⁻¹, or low and high, respectively). Planting green nearly doubled rye biomass at both sites, and at Landisville the high N rate accumulated 17% more biomass than the low N rate, while there was no biomass N rate effect in PK. Soil in PG was 7–15% drier at planting, up to 7% wetter later, and up to 0.9–1.3 °C cooler compared with PK at both sites. Soybean (Glycine max L.) yield was reduced by 3–4% when PG was paired with the high N rate across seeding rates at Rock Springs and with the 1x seeding rate at Landisville compared with other treatment combinations. Soybean population was not impacted by treatments. We conclude rye seeding and N topdress rates of 34 kg ha⁻¹ in PG can maintain similar conditions and soybean yield equivalent to PK, thereby reducing seed and N costs.