Two trials in the Nelson province with 6 alternative phosphate(P) fertilisers and 4 sulphur (S) fertilisers measured initial and residual responses ovar 3 seasons and used the results to determine appropriate topdressing frequencies, from which economic implications could be determined. P and S treatments were applied at 50 kg total element/ha for all alternatives in a randomised block design with 4 replicate.s Appropriate basal fertillsers were applied, and plots were mown at intervals for 2% years. Superphosphate was an effective P fertiliser at both sites, but at the lower rainfall yellow brown earth site at Dovedale the intermediate solubility P fertiliser Longlife Super and Phospate PARPR and the low solubility P fertilisers Sechura and North Carolina RPR caught up with Superphosphate by years 2 and 3. At the high rainfall Collingwood site on a pakihi soil Superphosphate and Longlife super responded significantly in year 1 only while there were no significant responses to the other 4 P fertilisers at any stage. Gypsum S was an effective source of S at both sites, but tended to be exceeded by elemental S forms at Collingwood. There were however, no significant differences between the four S ferfilisers at either site. The economic analysis of all products, assuming a PS requirement of 1 : l and appropriate spreading frequencies, shows Superphosphate to be the most cost effective at the time of analysis. Keywords: yellow-brown earth, pakihi. cost effectiveness, phosphorus, sulphur, fertilisers, economics
