• Relative yield increased with greater pH for most crops except potatoes and oats. • The different yield-pH relationships of crops have implications for arable rotations. • Soil type significantly effects the nature of the relative yield-pH relationship. • Long-term liming increases pH, but effects on soil extractable P were inconsistent. • P fertiliser significantly reduces the critical pH value of selected crops.

Nitrogen fertilization is the most critical agronomic input affecting barley production and farm profitability. The strict quality requirements for malting barley are challenging to achieve for farmers. In addition, soil variability and weather conditions can affect barley yield and quality. Thus, the objectives of this study are to (a) quantify the variability of soil properties, and (b) use spatial data in a crop simulation model, quantifying the impacts of climate−soil interactions on the barley crop yield and grain quality. Based on historical yield maps, a commercial field was divided into different yield stability zone levels. The Decision Support System for Agrotechnology Transfer model was used to evaluate soil and crop spatial data. The bulk density affected the soil water content and soil mineral N and hence the crop-growing conditions in each yield stability zone. Our observed and simulated results showed that 120 kg N ha⁻¹ is the optimal rate to increase grain yield while still keeping within the grain N% requirements for malting quality. This study shows the great value of integrating crop modeling with on−farm experimental data for improving understanding of the factors which affect site−specific N fertilization of barley.

The effect of increasing rates of potassium (K) fertiliser was studied on a soil with base exchangeable K values ≤ 0.1 cmol(+)/ kg by assessing biomass, feed quality, mineral concentration and grain yield for wheat, triticale and canola. The crops showed variable biomass response to K rates at early plant growth stages, however at anthesis there were significant positive biomass responses to increasing rates of K. A positive K rate effect was detected on feed quality with significant increases in metabolisable energy. Irrespective of sampling time, increasing K rate resulted in significant increases in crop K concentration and mineral ratios, such as the Tetany index, but significant decreases in Ca and Mg concentrations. Final grain yield was significantly increased by K rate and there were beneficial effects on grain quality (thousand grain weight). Overall, this study highlights the importance of K to production responses and implications for the health and productivity of grazing livestock.