DEVELOPMENT OF A METHODOLOGY FOR THE VARIABLE-RATE APPLICATION OF FERTILISER IN IRRIGATED COTTON FIELDS

摘要

The technology to apply different rates of fertiliser within a single field has existed for some time, however methods for determining fertiliser rates at this scale are still problematic, especially for irrigated cotton in Australia. A majority of the research in variable-rate fertiliser application has focused on either developing 'nutrient budgets' for a crop based on pre-sowing soil nutrient levels and crop nutrient uptake or by identifying similar regions within a field termed 'management zones'from both spatial and temporal data sources. This study has examined the suitability of both these methods for determining site-specific nitrogen fertiliser recommendations for cotton in Australia. Measurement of pre-sowing soil nitrogen levels from directed soil sampling of each field based on yield maps and soil electrical conductivity data enabled a nitrogen fertiliser requirement map to be developed using response curves for yield versus fertiliser generated for the local area. Secondly, multivariate clustering of a number of data layers was used to determine homogeneous zones within the field which then received fertiliser based on the yield potential of each zone. Both methods were implemented simultaneously within a field as well as the traditional fertiliser approach used by the grower as a means of comparison. No benefit in terms of yield was achieved with either variable-rate approach compared to the uniform approach, however the results indicated there is potential for variable-rate fertiliser application when more appropriate fertiliser recommendations for site-specific application exist.