Fertilizer strip tests for the identification of superphosphate responsive pastures

Abstract

The ability of superphosphate strip tests to identify responsive pastures was evaluated at eight sites on the Southern Tablelands of New South Wales. Five rates of superphosphate (0, 100,200, 300 and 600 kg/ha) were applied in 100 x 7 m strips in early spring and the pasture dry matter responses measured every three months with a capacitance probe. Herbage responses, ranging from 12 to 232% occurred in the following three months on seven of the eight pastures. The spring and autumn periods gave the largest quarterly responses. The variation in growth within strips observed was small enough to establish differences in dry matter between strips. On deficient sites all fertilizer rates produced measurable responses, however the 300 kg/ha rate was sufficient to give clear-cut responses at all the deficient sites. As the pasture responses observed in the strip tests were consistent with predicted responses by plant and soil analyses, it was concluded that they offer a practical alternative for use by farmers. Suggestions are made on the layout of fertilizer strips, and the interpretation of results.