Use of Winter Legumes As Late Summer through Spring Cover Crops.

Cover crops are an important component of sustainable agriculture. Agronomic benefits of cover crops such as soil stability, and nutrient binding are maximized with a long season of growth. Cool-season legumes offer an added advantage by fixing nitrogen from the air during the fallow season. Incorporation of cover crops into a Mississippi corn production system ideally requires planting and germination in early September and termination in March. However, most cool-season legumes are restrained by secondary dormancy which keeps seed from germinating until soils cool. Cover crop species that germinate at higher soil temperatures, can extend the cover crop growing season into late summer. Additionally, they scavenge residual nutrients from the prior field crop, preventing them from moving off site. This study compares growth of four unselected and heat-selected cool-season legume populations [crimson clover (Trifolium incarnatum L.), balansa clover (T. michelianum Savi.), berseem clover (T. alexandrinum L.), and hairy vetch (Vicia villosa Roth.)]. Statistical analysis for two trials (a lab and field test) was conducted using PROC MIXED, significance set at α=0.05. The results of laboratory and field germination indicated a difference in treatment (selection for heat tolerance) and species. Field germination indicated success for heat-selection was observed in two (berseem and crimson clover) of the test species. The results were impacted by count date, temperature, soil type, and planting date. Further selections are necessary to successfully ameliorate secondary dormancy in the recalcitrant species.