RATIONALISING TOPDRESSING OF HILL COUNTRY

Abstract

Measuremgnts of Pasture production were made on both Easy (1 O-20' slope) and Steep (30-40 slope) strata of a yellow brown earth-brown granular loam hill soil complex of medium P retention status. Results showed that whereas maximum growth required 50 kg P/ha/year on Easy slopes (14,900 kg DM/ha) only 30 kg P/ha/year were needed on Steep slopes (7700 kg DM/ha). Efficiency of production IEP) in kg DM/kg P from Easy and Steep slopes was similar at the same relative production level but much higher from Easy slopes at any one fertiliser rate. There was a poor relationship between soil Olsen P status and relative yield. However maximum production was obtained with mean Olsen P levels (O-7 cm depth) of 15, on Easy Slopes, and 10 on the Steep slopes. A procedure is described to assist in setting fertiliser rates for topdressing hill country. Keywords: hill country, phosphate fertiliser, pasture production, efficiency of production