Forecasting fertiliser requirements of forage brassica crops

Abstract

Fertiliser management is an important aspect of growing good forage brassica crops. Every crop has a different requirement, depending on soil fertility and the expected yield response. Systems were developed for forecasting how much fertiliser, and what types, to apply to individual kale and Pasja crops. First, yield responses to fertiliser application were measured in trials in diverse climates and soil fertility conditions. Yield responded strongly to N and P availability, there were few responses to K fertiliser application, and there were no responses to S application. Second, overall responses to the nutrient supply from soil and fertiliser sources were determined in a comprehensive across-trials analysis using the PARJIB model. R-squared values for correlations between actual yields and yields simulated with the PARJIB calibrations were 0.65 and 0.64 for Pasja and kale respectively. Finally, the results were programmed into new software systems (The Kale Calculator and The Pasja Calculator) that deliver a forecast for each crop of the types and amounts of fertiliser that will give the best economic return on the investment in fertiliser. Keywords: The Kale Calculator, The Pasja Calculator, fertiliser application, yield response, PARJIB analysis