Biosecurity, pests, weeds and diseases
SUMMARY The effects of lime and molybdenum applications on wheat and subterranean Clover were studied further. Wheat. In relation to lime use, my aim is to develop soil tests to be used to predict when a soil requires lime to produce maximum yield, and to predict the optimum rate of lime. Using the results from field trials commenced in 1980 and 1981 the soil parameters which may be used to predict lime responses in wheat have been narrowed down. From the relationships between soil data and lime responses it appears that soil ph (measured in 1:5 H20 or 1:5 N kcl), extractable aluminium (in 1:5 N kcl), and exchangeable aluminium expressed as a percentage of total kcl- or NH4Cl- exchangeable cations are poor predictors of the lime responsiveness of wheat on soils in the low rainfall areas of the wheatbelt. The soils are being analysed further to attempt to find an accurate predictor of lime response. Unfortunately, the Government Chemical laboratories which do our analyses, are grossly understaffed, resulting in long delays in analyses being completed. To predict the optimum rate of lime to use on a soil it is necessary to be able to predict the effect of a given rate of lime on the soil properties of interest. It was found that laboratory measurements of ph buffer capacity did not reflect the changes in soil ph induced by lime application at 13 field sites. Molybdenum responses in wheat were common in the 1981 growing season (Table 1). The biggest yield increases were on low yielding trials (80ME3 and 81M02). However, on average, molybdenum application increased yield by 130 kg/ha, or 15 per cent of the yield without molybdenum. All but one (81LG12) of these trial sites have previously received applications of molybdenum. Two long term trials (81M2 and 81LG12) were commenced to study the residual value of molybdenum on acid soils. Subterranean clover grew poorly on all sites and, although molybdenum responses were observed they were not measurable because of the low productivity and high variability of the clover. Progress towards defining a model to predict acidification rates has been made. The conceptual framework of the model has been refined through studies of the scientific literature. A trial to obtain a first approximation of the effect of acidity on the effectiveness of phosphate fertiliser was commenced east of Hyden. 79GE10, 80GE5, 80GE6, 81GL5, 81JE1, 81LG8, 80ME3, 80ME4, 81ME4, 80M29, 80M30, 80M31, 81M2, 81M5/, 81M6, 81M54, 79M027, 80M04, 80M05, 81M02, 81M03, 80NA3, 80NA4, 81N06, 81N07, 79TS1, 79TS2, 80TS6, 81TS1, 81TS2, 81TS30, 81JE2, 81LG12, 79M027,
Number of Pages
Porter, W, and Klemm, R. (1981), The effect of soil acidity on crop and pasture production.. Department of Agriculture and Food, Western Australia, Perth. Article.