Development of an Australian Soil Test Calibration Database.

An on-line MySQL database of historic fertilizer response trials has been developed for cereals, pulses and oilseed crops in Australia’s diverse cropping regions. The database includes 5420 single and multi-nutrient field experiments from 5 decades of research. It consists of all available nitrogen (1709 experiments), phosphorus (2281 experiments), potassium (356 experiments) and sulfur (270 experiments) trials. Minimum trial data requirements were applied which stipulated that soil type was recorded, a recognized soil test had been undertaken, and that an estimate of crop yield with no fertilizer (Y₀) and the maximum yield (Y_max) could be obtained. Crop grain yield responses were fitted with either Mitscherlisch, quadratic or logistic functions, to estimate Y₀ and Y_max, and the percentage relative yield (RY) determined as Y₀/Y_max×100.

Using the trial data, soil test critical values can be derived online through the Better Fertiliser Decisions for Cropping Interrogator tool. A trained and registered user is able to filter the data by attributes that include crop type, soil type, soil test, yield and growing season rainfall. Fertilizer response criteria are obtained by fitting an inverted plot of the natural logarithm for the soil test value and the arcsin of the square root of RY. From these curves, critical fertilizer response values and confidence limits are determined for 80%, 90% and 95% of RY. The fertilizer response curve is presented to the user with the critical values for each of these relative yields.

The Interrogator enables users from the grains and fertilizer industries to better estimate critical soil test values for their particular situations and so improve fertilizer management. The database underpins the Australian fertilizer industry’s Fertcare program for advisors making recommendations to grain growers. It also assists direct future research to address identified knowledge gaps. The Interrogater was commissioned in March 2012, and can be found at www.bfdc.com.au.