Corn Response to Cover Crop Species, Spring Desiccation Time, and Residue Management

Cover crops are integral parts of whole farm systems that include corn (Zea mays L.), but there is a lack of synchrony between cover crop N release and corn N uptake. This synchrony may be enhanced by varying the cover crop spring desiccation time and subsequent residue management. A field study was established to determine (i) the effect of rye (Secale cereale L), hairy vetch (Vicia villosa Roth), and rye + hairy vetch spring desiccation timing on cover crop biomass, N content, and C:N ratio and (ii) the effect of the cover crop species, spring desiccation timing, and residue management on soil moisture content, soil mineral N concentration, corn tissue N concentration, and corn grain yield. Chemical desiccation times were either the boot stage of rye (approximately 3 wk prior to corn planting) or the early flowering stage of hairy vetch (several days prior to corn planting) for all three cover crop treatments. Three cover crop residue management treatments were implemented several days after each chemical desiccation: no further treatment (control), cover crop residue mowed (mow), or cover crop residue mowed and disked (mow + disk). cover crops increased in biomass accumulation, but only hairy vetch increased in N content between desiccation times. Cover crop N availability was more important for corn yield potential than cover crop soil moisture conservation. Corn yields were higher following hairy vetch than following rye and rye + hairy vetch, due to greater N availability from hairy vetch residue. Corn N concentrations and yields were not influenced by desiccation time following hairy vetch, indicating that hairy vetch should be allowed to grow until immediately prior to corn planting, to permit maximum N accumulation. However, corn N concentrations and yields were higher with early desiccation than late desiccation following rye and rye + hairy vetch, indicating that cover crops including rye should be desiccated several weeks before corn planting. Mowing may be an alternative cover crop management technique that enhances the synchrony of cover crop N release with corn N need and uptake while maintaining a moisture conserving mulch.