AUTUMN SAVED PASTURE IN A HIGH FROST ENVIRONMENT

Abstract

Herbage mass, moisture content and in vitro OMD of autumn saved ryegrasslwhite clover pasture grown on irrigated flats in the Upper Waitaki Basin were monitored over four winters from 1979-82. During the winter of 1981 and 1982 the effect of closing date and nitrogen application was examined. In addition Merino ewes were all-grasswintered from mid June to mid September without supplements on a feed allowance of 1.2 kg DMlhd.day to determine effect on liveweight. Mean herbage mass and OMD loss from mid May to early September were 25 and 13% respectively and the moisture content of the pasture decreased from 73 to 45%. Herbage mass by mid May was less for March and April than for February closing, although for March closing this deficit was offset through use of nitrogen. Approximately 50% of the sward was frosted by mid September with OMD of the f-m_.c-.tAcd rnwn,rti.nIVn.I IC,*"O"/. ,v, .-vrvrmlllnv-~-r~C~.ul-l~ +L-U k0-1.a.y. Ewe liVeWeightS initialiy ieii but recovered during the latter half of the winter despite the constant fall in herbage OMD. Sward desiccation exceeded loss in digestible herbage mass over the winter, suggesting increasing rather than decreasing food value. Keywords: High country, herbage losses, frosting, in-vitro OMD, irrigated pasture, autumn-saved-pasture, nitrogen, feed value, all-grass-wintering, Merino ewes