WHAT IS THE MAXIMUM PRODUCTION ON OTAGO HILL COUNTRY ABOVE 700 METRES ALTITUDE?

Abstract

To ascertain the maximum production of grass/clover pastures over a range of altitudes on OtagO hill country, and the increase obtainable by applying nitrogen (N). 4 trials were set up at intervals from 730 m to 1190 m altitude, on yellow-brown earth soils of the Dunstan set on Loch Linhe station overlooking Lake Wakatlpu. The trials were oversown with a grass/clover mixture. The effects of fertilizing with adequate phosphate(P) and sulphur (S), with and without lime. and with and without N. was investigated. Yields were compared with those at other sites in Otago at similar altitudes Responses to P and S only were noted in year 1 and no altitude-related trend was evident Production in years 2 and 3 however showed a clear altitude-related trend. Without N maximum production ranged from 6390 kg/ha at 730 m to 1690 kg/ha at 1190 m. Yields with N were 8130 kg/ha at 730 m and 4150 kg/ha at 1190 m, i.e N increased yields by 27% to 146%; the greatest percentage increase was at highest altitude. Maximum production decreased by about 865 kg/ha per 100 m of altitude increase Lime depressed yields at the lower altitude sites and raised yields at the higher altitude sites, but only at the most acid site (topsoil pH 4.9) with N was the yield difference due to lime statistically significant. Yields of clover/grass pastures obtainable with adequate P and S fertiliser without added lime, are greater than at sites of comparable attitude in east and north Otago. Soil temperature measurements indicate that higher temperatures are the likely cause of the higher production Areas of favourable climate and soils, such as the one studied, will probably give the greatest return on investment in fertitiser. Climatic maps of hill country are needed to help predict production potential. Keywords: hill country, Otago, fertiliser, pasture yields, yellow-brown earths