Preplant herbicides don`t increase forage production of cereal rye interseeded into bermudagrass
Interseeding cereal rye (Secale cereale L.) into a bermudagrass sod [Cynodon dactylon (L.) Pers.] can increase season-long forage production and land use efficiency. However, previous research has shown that competition from the bermudagrass sod can significantly reduce autumn forage production from cereal rye. Our objective was to determine if the application of a preplant herbicide to a bermudagrass sod before interseeding cereal rye influenced seasonal or total annual forage dry matter (DM) yields in the southern temperate-humid zone. In mid-September, cereal rye was interseeded into bermudagrass after treating with (i) no herbicide, (ii) 1.37 kg a.i. ha–1 of paraquat dichloride (Gramoxone), or (iii) 0.56 kg a.i. ha–1 of clethodim (Select). The control treatment was bermudagrass sod that was neither treated with herbicide nor interseeded with cereal rye. Treating with Select reduced forage DM yield in the subsequent summer by as much as 35% compared with unseeded bermudagrass. Treating with Gramoxone did not improve forage DM yield in autumn. Forage DM yield was approximately 3300 to 4500 kg ha–1 greater in autumn and spring when cereal rye was interseeded into bermudagrass, but the net increase in forage DM yield for the cereal rye–bermudagrass system was only 1100 to 3300 kg ha–1 yr–1 greater than the unseeded control, which yielded 10,000 kg ha–1. Producers who stock growing or lactating animals in autumn or spring would benefit most from this practice because the cereal rye would be available for grazing at a time when many forage–livestock systems must use more expensive stored feedstuffs.