Trade-offs in forage and seed parameters of annual Medicago and Trifolium species in north-central Texas as affected by harvest intensity

The trade-off between early spring harvest of cool-season annual forage legumes and summer seed production may shed light on subsequent yearly stand regeneration. Sixteen annual clover and medic cultivars or locally collected accessions were seeded in the autumn of 1999 at Stephenville, TX, on a Windthorst (fine, mixed thermic Udic Paleustalf) fine sandy loam and allowed to self-reseed in the autumn of 2000 and 2001. During the first 2 yr, three harvest treatments were imposed: harvest at 5 cm from crown whenever branches reached 10 cm from crown, harvest at 10 cm when branches attained 15 cm, and a single April harvest. Forage yields showed a year x species interaction (P = 0.001) and ranged up to 6 Mg ha(-1) yr(-1). Plants harvested in April only were consistently more productive than the 5-cm harvest and yielded nearly 4.9 Mg ha(-1) in Year 1. Forage acid detergent fiber and crude protein concentrations reflected entry x harvest x year interactions (P < 0.05). Seed yields varied considerably among entries, and all the annual clovers and most medics were able to self-reseed regardless of harvest treatment, showing promise for self-reseeding, sustainable pasture systems in the southern Great Plains.