Survival of endophyte-free perennial ryegrass after autumn spray/ drilling in the Waikato

Abstract

The persistence of an endophyte-free ryegrass (Lolium perenne L.) pasture established by autumn spray/drilling was studied over two years at the Dairying Research Corporation, Hamilton. Main plots were sprayed with glyphosate at 1.44 kg a.i./ ha (4 l/ha of Roundup G2) in mid March 1996 (S), or mid March and again in mid April (D). White clover (Trifolium repens L.) was removed from half the area of each main plot using herbicide and the remainder was drilled with white clover. All plots were direct drilled with endophyte-free peren-nial ryegrass in late April. Plots were rotationally grazed by dairy cows. Double spraying killed germinating volunteer ryegrass, Poa species and weeds, almost doubling the ryegrass content of D compared with S plots in the first winter/spring, and maintaining an advantage over the first year from drilling. Plants were larger in D than S over the first winter/spring, contributing to about a 10% improvement in their survival, reducing to about 5% by March 1998. Sown-plant densities were 200-250/m2 by April 1998, similar to those found in high-endophyte pastures. Double spraying reduced the clover content of +Cl plots to similar levels as those in -Cl plots, lowering the potential herbage accumulation for D. Double spraying before drilling had a transitory effect on seasonal herbage accumulation, and no effect on overall herbage accumulation. Keywords: dairy pastures, endophyte, persistence, plant competition, ryegrass, tillering, white clover