Corn (Zea mays L.) and cover crop response to corn density in an interseeding system and subsequent dry bean (Phaseolus vulgaris L.) yield

Reliable cropping strategies are needed to enhance legume cover crop utilization as a nitrogen (N) source for corn (Zea mays L.) and dry edible beans (Phaseolus vulgaris L.). Nitrogen can be applied as a fertilizer or provided by leguminous cover crops. Planting corn with interseeded legume cover crops into a killed leguminous stand and planting dry bean the subsequent year can reduce N input costs for corn and dry bean. It is important to know how leguminous cover crops affect corn yield when used as the sole N source, the effect of interseeding, and the maximum plant density at which this approach is feasible. This study evaluated (1) the effect of four corn densities (37 500 to 75 000 plants ha-1) in an interseeding system on corn yield and on red clover (Trifolium pratense L.) or Chickling vetch (Lathyrus sativus var. AC Greenfix,) dry matter; (2) the effect of mineral N fertilizer versus organic N provided by plowed red clover on corn yield and N status at various corn densities; (3) the effect of corn density and interseeding on N status in plant tissues of corn and cover crops; and (4) the effect of these management practices on soil mineral N (NO-3 and NH+4), subsequent dry bean yield, and N status of dry bean. Results suggest that interseeded cover crops did not affect corn yield at any plant density. Across years, yield of corn planted into plowed red clover was similar to that of corn fertilized with mineral N. During optimum growing conditions, corn fertilized with mineral N outyielded corn planted into plowed red clover, however the reverse was seen in dry years. Interseeded cover crop biomass decreased as corn density increased. However the subsequent spring, red clover biomass was similar regardless of previous corn density.; Across years, corn grain N concentration decreased as corn density increased and was highest in corn fertilized with mineral N. Interseeding cover crops did not reduce corn grain N concentration. Overall, grain N content of corn planted into plowed red clover was lower compared with fertilized corn. By fall, interseeded cover crops accumulated more N at low corn density compared with higher plant densities. The subsequent spring, red clover accumulated significant N ranging from 58 to 162.3 kg ha-1.; Interseeding cover crops did not influence soil mineral N. During optimum growing conditions, dry bean yield following corn interseeded with red clover was similar to yield of dry bean fertilized with 45 kg ha-1 of mineral N. Similar trends were seen for bean seed N accumulation. Red clover can be interseeded at high corn densities (up to 75000 plants ha-1 ) and accumulate sufficient N the subsequent spring to meet the N demand of the following dry bean crop. These results are valuable to conventional, organic and low-input or low-resource farmers as they seek to maximize production while reducing the cost of N fertilizer.