Softening and Loss of Subterranean Clover Hard Seed under Sod and Bare Ground Environments
- T. E. Fairbrother
Natural reseeding of subterranean clover (Trifolium subterraneum L.) grown with a warm-season grass in the southern USA depends on the proper softening rate of hard seed. Three experiments were each conducted over 2 yr to determine (i) the rate of seed softening, (ii) the cause of reduction in seed softening over time, and (iii) the effect of clipping management on seed softening. In all experiments, subterranean clover hard seed were placed in dacron bags and buried 1 cm deep in field plots. In Exp. 1, bags were placed in bermudagrass [(Cynodon dactylon (L.) Pers.] sod and in bare ground in July and sampled over the summer and fall. In Exp. 2, bags were placed in soil and bare ground and replaced with separate samples at intervals of 28 d throughout the summer and fall. In Exp. 3, bags were buried in bare ground or sod that was clipped monthly to 7.5 cm or biweekly to 2 cm starting in August, September, or October. Hard seed softened more rapidly in bare ground than in sod, reaching a minimum of 15.6 and 49.0%, respectively. The softening of hard seed over 28-d intervals decreased from 75.5 and 67.1% in July to 92.6 and 93.2% in November for sod and bare ground, respectively. Fall clipping management had no effect on hard seed softening rate of subterranean clover, reaching a minimum of 64.0% hard seed averaged over all sod clipping treatments compared to 47.0% hard seed for bare ground. Results indicated that subterranean clover reseeding ability should be evaluated under the same environment as the clover is used.
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