Grower-scale strip trials evaluating strategies for P & K nutrition

Abstract

Grower-scale strip trials are being used to assess subsurface (deep) placement of phosphorous (P) and potassium (K) across multiple collaborative projects. Grain yield responses to deep P across southern Queensland (SQ) ranged from 0 up to 10% across 31 site years. We hypothesis that this variability may be related to fertiliser band direction as we have observed biomass responses more often when P was applied at 90 degrees to the crop rows compared with the same direction as the rows (0 degrees). Grain yield responses to deep K across SQ were observed at one site with an exchangeable K value of 0.18 cmol/kg in the 10-30 cm soil layer. No yield responses to deep K have been observed with exchangeable K>0.35 cmol/kg in the 10-30 cm soil layer. A national K project will implement further strip trials to better define critical K values and crop responses.