Response of vulpia [Vulpia bromoides (L.) S. F. Gray and V. myuros (L.) C. C. Gmelin] and subterranean clover to rate and time of application of simazine

Abstract

The responses of vulpia [Vulpia bromoides (L.) S. F. Gray and V. myuros (L.) C. C. Gmelin] and subterranean clover (Trifolium subterraneum L.) to rate and time of application of simazine were compared on a red loam soil containing 1.8% organic matter and on sands containing 0.4 and 0.8% organic matter. In 1988 and 1989, applications of 0.50, 0.75 and 1.00 kg a.i./ha of simazine in late May-early June resulted in 96.4, 99.8 and 99.6% control of vulpia, respectively. Later applications in July-August, or earlier applications in April, were less effective. There were no differences in the levels of control obtained on the 2 soils, nor were there any differences in the susceptibility of V. bromoides or V. myuros to simazine. On the red loam soil simazine did not reduce subterranean clover plant density or dry matter production; however, severe reductions of both were recorded on the sandy soils. Reasons for the different responses, along with the potential for the use of simazine to control vulpia in subterranean clover pastures, are discussed in detail.