EFFECTS OF LATE-AUTUMN NITROGEN APPLICATION ON HILL COUNTRY PASTURES AND SHEEP PRODUCTION

Abstract

Effects of late-May/early June application of fertiliser nitrogen (N) on pasture and animal performance from hill pastures, were measured durmg 1982.1984 on four 10 ha farmlets at Ballantrae Research Area near Woodville. Two farmlets had a history of high superphosphate (375 kg/ha/year) application and were stocked at 16.1 ewes/ha and two farmlets that received less superphosphate (125 kg/ha/year) were stocked at 12 ewes/ha. Urea was applied at rates equivalent to 3kg N/ewe, or 50 and 37kg N/ha/year respectively on one high fertiliser and one low fertiliser farmlet. Pasture production responses were large and reliable (range of 17 to 34, average of 28kg DM/kg N), and extended through winter into spring. Average legume content of pastures was depressed from 12 to 8% by N applicahon. Ewes were heavier in winter and spring where N was applied, but not at mating in April/May. Lambing performance was similar across farmlets, but weaned lamb liveweight was 14% higher where N was applied. Nitrogen use resulted in 6% greater ewe wool production and 12% greater lamb wool production. Profitability of N use would have been enhanced if utilisatlon of N-boosted pasture had been greater, more responsive stock classes used, or application of superphosphate reduced temporarily. Keywords: Hill country, North Island, hill pastures, urea, fertiliser nitrogen, sheep production. wool production, lamb produchon, profItabIlity.