Effects of frequency of application of triple superphosphate and Sechura phosphate rock on pasture DM production, herbage P concentration, and Olsen P soil tests

Abstract

Abstract Triple superphosphate (TSP) and Sechura phosphate rock (SPR) were applied to developed pastures annually at 0.75 times the estimated annual pasture maintenance requirement (M) and triennially at 2.25 times M in small‐plot trials at 12 sites for 6 years. A control treatment receiving no phosphorus (P) fertiliser was also included. Pasture dry matter (DM) production and soil Olsen P tests were measured annually at all sites and pasture P concentration at two sites. Total DM production over 6 years did not differ significantly between annual and triennial treatments. Triennial applications resulted in higher DM production in Years 1 and 4, similar production in Years 2 and 5, and lower production in Years 3 and 6, compared with annual applications. Averaged over two 3‐year cycles of fertiliser application, the amplitude of the cyclic effect on DM production from triennial as compared to annual application was + 4% for TSP and ± 2% for SPR. Differences in annual production between triennial and annua...