Effects of frequency of maintenance phosphate fertiliser application on dry matter production from permanent pastures

Abstract

In a series of 12 field uials located throughout New Zealand annual application of phosphate(P) fertiliser was compared with ttiennial application using rates which applied the same total amount of P over 6 years. Test materials were triple supetphosphate (TSP) and Sechura phosphate rock (SPR), both of which were applied annually at rates which provided 0.75 times the calculated maintenance P requirement (0.75 M) and triennially at 2.25 M.For the 12 sites combined there was a significant response to P fertiliser each year. Application frequency had no significant effect on total DM yield over the 6 year period with either TSP or SPR. A cyclic effect with triennial applications was appsrent for both fertllisers, with approximately 2-4% higher yields in the first year and 2-4% lower yields in the third year of both 3 year cycles. These results indicate that on well developed pastures a change from annual to triennial application frequency of phosphate fertillser, with either TSP or slow release SPR, will have little effect on DM production providing the same total amount of P is applied. This gives farmers the opportunity to make some adjustment to P fertiliser application frequency according to fluctuations in availability of finance. However, these conclusions do not apply to other nutrients such as sulphur, potassium and trace elements for which annual applications may he necessary. Keywords triple superphosphate, Sechura phosphate rock, phosphate fertilisers, annual application, triennial application, application frequency, reactive phosphate reck