The long-term use of nitrogen fertiliser in intensive hill country farming

Abstract

In 1969 the initial objective in using a nitrogen compound fertiliser was to bridge a feed deficit in late winter-early spring. Further advantages were observed, including an improvement in pastures from browntop to ryegrass dominance, better growth into dry summer, and faster recovery from droughts. Diammonium phosphate (DAP) was also incorporated into land development out of manuka, resulting in much faster establishment of dense pasture. Cost comparisons with superphosphate encouraged the use of DAP as an annual maintenance fertiliser from 1975, usually at a rate of 125 kg/ha. Details are given of sulphur additives, molybdenum, lime and copper for animal health. The lift in productivity from 1969 to 1992 is shown. The conclusion is that a DAP/ sulphur fertiliser applied from late autumn to early spring is a cost-effective and balanced input. It allows a high stocking rate (12/ha) on poorer hill country, without supplementary feed, plus high per head performance. Feed generated has been sufficient to shear 2100 ram hoggets in early August, culminating in ram sales of 1400 per year. Lambing percentages are above 130% survival to sale in good years, and wool weights have averaged 7.7 kg/year, including wool sold on sheeps' back. Ewe hoggets are mated, averaging 30% survival to sale. Keywords: diammonium phosphate, feed cover, fertiliser, hill country, land development