Delaying cover crop termination reduced corn yields in a dry spring

Abstract

The hypothesis of this research was that in a semiarid frigid environment, cover crop termination can be delayed beyond 2 weeks prior to planting without sacrificing corn (Zea mays) yield. To test this hypothesis, the impact of cover crop termination timing (2 weeks prior to, at corn planting, V2, and V4 corn) on cover crop biomass, soil water, inorganic N, and corn yields was quantified. Rye (Secale cereal) was dormant seeded in autumn (2018 and 2019), with corn planted the following May. In 2019 and 2020 growing seasons, precipitation was 607 and 324 mm, respectively, and corn growing degree days (base 10°C and maximum value of 30°C) were 1266 and 1436, respectively. Rye biomass increased when termination was delayed and averaged 25 kg ha⁻¹ when terminated 2 weeks prior to corn planting and 911 kg ha⁻¹ when terminated at V4. In both years, terminating the cover crop about 2 weeks prior to planting did not increase yields, but delaying termination from V2 to V4 reduced yields. In the dry year, when rainfall totaled 324 mm, delaying termination beyond corn planting (V0) reduced yields, whereas in the wet year (607 mm of rainfall) terminating rye at V2 did not reduce corn yields. These data suggest that in a semiarid environment, climatic conditions, especially early spring rainfall, must be carefully monitored when considering the cover crop termination date.