The Effect of Cool Season Grass Cover Crops on Nitrogen Cycling in Soil.

Winter rye (Secale cereale) is commonly used in the upper Midwest as a cover crop to prevent soil erosion, and can be planted in the fall after early harvested crops such as corn silage. Alternative cool season grasses, including including triticale (x Triticosecale), annual ryegrass (Lolium multiflorum) and barley (Hordeum vulgare), may provide alternative benefits while increasing on farm diversity. Fall manure, when applied in conjunction with fall cover crop seeding, may be more beneficial to the following years crop, though nitrogen (N) immobilization can detract from benefits of cover cropping. In this study, first year effects across several soil types typical of the upper Midwest are quantified, including N uptake and release with and without manure with fall planted grass cover crops, potentially mineralizable N, and yield. With increasing N application rate treatments in the subsequent corn crop, optimum N rates were also determined, as affected by cover crops. Plant-available N decreased at late fall, preplant and presidedress timings with cover crops compared to the control. Optimum N rate varied depending on cover crop and location. Potentially mineralizable N increased with a cover crop, indicating that immobilization was not limiting corn yield. Study results indicate that alternative cover crops are viable for use by Wisconsin growers seeking ecosystem and production benefits.