Within-field spatial variability and potential for profitability of variable rate applications

Since literature is not unanimous about profitability of variable rate application (VRA), a systematic analysis is essential to determine when, where and how to increase the production profits. This paper examines the relationship between the within-field spatial variability of soil fertility and profitability of variable rate fertilisation (VRF) and VR seeding (VRS). Within-field spatial variability was determined using high resolution data of key soil attributes, subjected to a modified Cambardella Index (CI). Profitability was determined as the net revenue over the VRA input, which is an adjusted form of the contribution margin. Results showed that the contribution margin of VRAs ranged from 847 to 6624 EUR per ha. Variations in the adjusted contribution margin were positively correlated with the adjusted Cambardella index, confirming the assumption that VRA is more profitable in fields with a higher spatial variability. Findings are interpreted in a production-theoretical framework, which discussed whether, when and under which circumstances, the observed potential for profit will effectively lead to profitability increases.