Performance of Cover Crop-Based No-till Planted Soybean in Rolled-Crimped Cereal Rye and Barley Mixtures.

Maximizing biomass of cereal rye has been recommended for effective weed suppression in cover crop-based organic rotational no-till soybean. However, very little research has been done on other overwintering cereal cover crops or mixtures of cereal cover crops in this system.

We conducted an experiment in 2013 in central New York to compare the weed suppression effects of cereal rye and barley in herbicide-free no-till planted soybean. Our first hypothesis was that a mixture of the two cover crops would result in greater weed suppression than a monoculture of either cover crop. Barley and cereal rye were seeded in a factorial arrangement, allowing us to assess the weed-suppressive ability of each cover crop in monoculture, as well as in several bicultures. A split-block design with four replications was used with cover crop seeding ratio and management treatments as main plots. Management treatments included high-residue cultivation (HRC) and standard no-till (SNT) management without high-residue cultivation. Our second hypothesis was that HRC would result in lower weed biomass and higher soybean yield relative to SNT management.

Photosynthetically active radiation (PAR) transmittance through the cover crop canopy decreased and total cover crop biomass increased as the proportion of cereal rye seed increased. Average weed biomass ranged from 43 to 127 g m^-2 across treatments and tended to decrease as the proportion of cereal rye increased. However, we observed disproportionately lower weed biomass than expected based on cover crop biomass in some mixtures. Soybean yield averaged 3,000 kg ha^-1 and was not affected by cover crop or management treatment. Preliminary results illustrate the weed suppression benefits of combining cultural and mechanical tactics, and they suggest that mixtures of cereal rye and barley could enhance weed suppression relative to cereal rye monocultures.