Effect of oversown ryegrass(Lolium perenne)and white clover(Trifolium repens)on the genetic structure of New Zealand hill pastures

Abstract

Abstract The botanical composition and genetic structure of North Island hill pastures were studied after oversowing. Three pre‐sowing treatments were applied: (a) no herbicide; (b) herbicide to suppress existing pasture; and (c) herbicide to kill existing pasture. Four oversowing treatments were imposed: (1) no oversowing; (2) hill country ryegrass and ‘Prop’ white clover; (3) ‘Yatsyn’ ryegrass and ‘Prop’ white clover; and (4) a mixture of hill country grass species. Five times as many ryegrass seeds were oversown than emerged from buried seed, giving the introduced material an advantage. The ryegrass content was greater at the high‐fertility sites than at the low‐fertility sites, both before and after oversowing. Killing the original pasture tended to increase ryegrass content for 16 months at the low‐fertility sites but increased the ryegrass content for less than 9 months at the high‐fertility sites. The ryegrass content was not significantly different on any of the sown and unsown plots, 16 months af...