Legume cover crop reseeding for strategic field management

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Subterranean clover (Trifolium subterraneum) appears to be a suitable winter legume cover crop for Japan because the subterranean clover stands maintain themselves by reseeding in autumn and the large seeds facilitate establishment and enable early fall production. However, there is little information on the relationship between reseeding and tillage system for subterranean clover under Japanese climatic conditions. A simple equation model was developed to determine the effects of tillage method and timing on reseeding from year to year in subterranean clover-silage corn rotation based on data from field and pot experiments. The developed model was inserted into life-cycle models for subterranean clover growth and seed production competing with weed growth, seasonal changes of seed bank dynamics in the soil and subterranean clover seed movement within the soil by tillage treatment after seed maturation. In the simulation results, the population of reseeded subterranean clover seedlings varied according to tillage method and timing and the results agreed with the results of the experiments. Rotary tilling immediately after subterranean clover seed maturation successfully produced a good subterranean clover stand the following spring. However, rotary tillage 2 months after seed maturation withered emerging subterranean clover seedlings and the field was dominated by winter weeds. These simulation results suggest that a suitable tillage system would be able to maintain successful subterranean clover reestablishment from year to year.