Phosphorus nutrition of high rainfall pastures - Peel Harvey estuarine system study (phase II) and related phosphorus work

A. Sources, rates, time of application of phosphorus on high rainfall pastures. 80AL2, 80AL5, 81AL5, 81AL6, 81KE2, 81MA4, 82AL10, 82HA31, 82HA32, 83HA26, 83HA27. B. Soil test calibration curve trials on Bassendean sands. 82HA20, 82HA21, 82HA22, 82HA23, 82HA24, 82HA25, 82HA26, 82HA27, 82HA28, 82HA29, 82HA30. C. Soil test calibration curve trials on Coolup sands. 83HA20, 83HA21, 83HA22, 83HA23, 83HA24, 83HA25. D. Phosphorus rundown. 82HA14, 82HA15, 82HA16, 82HA18. NOTE: Summary is in two parts. 1. Peel Harvey catchment program (Deeley, Barker). 2. General program on high rainfall sandy soils (Yeates, Clarke). Summary of Experimental Work. General Aims. The work summarized here was commenced with the following aims: 1. To improve the efficiency of agricultural utilization of phosphorus applied to pastures on the deep leaching sands of the high rainfall areas. 2. To minimize phosphorus loss to drainage from the deep sand, and thus reduce eutrophication problems in adjacent waterways. Five potential ways of reducing the phosphorus losses from fertilizer sources while still maintaining optimum level of agricultural productivity were considered possible. These were: 1. The use of accurate soil tests for predicting phosphorus requirements and thus ensuring that only phosphorus actually required is applied. 2. Modification of times of application of soluble phosphorus fertilizer to maximise the plant utilisation.of applied P, and to minimise losses. 3. Development of phosphorus fertilizers of lower water solubility than ordinary superphosphate (and hence with reduced leaching losses). 4. Use of deep rooted and/or perennial plant species which are better able to utilize applied soluble P. 5. Modification of the sandy soils to increase phosphorus adsorption capacity and hence reduce or eliminate leaching losses. To date research has been chiefly concerned with the first three of these possibilities