Map-sensor-based site-specific manure application in wheat

Site-specific manure application is a promising approach to optimise manure use by accounting for spatial variability of soil nutrients within the field. Traditionally, variable-rate management can be achieved by the map-based approach and the sensor-based approach, which account for the soil or manure characteristics, respectively. In this work, a new map-sensor-based methodology for variable-rate manure application (VRMA) is presented and implemented, which relies on combining a predefined soil phosphorous (P) map, and real-time measured liquid manure (pig) P2O5 using visible and near-infrared (vis-NIR) spectroscopy sensors. An on-line manure sensing device based on a retrofitted vis-NIR sensor mounted on a drag-hose liquid manure injection machine was designed and manufactured. Meanwhile, software for loading the on-line measured soil P map, parsing global positioning system (GPS) messages, controlling on-line manure sensing device, and calculating the target manure application rate was developed in the LabVIEW programming environment. Using the developed hardware and software, a phosphorus-map-sensor-based VRMA was evaluated on two commercial fields in the Flemish part of Belgium with wheat. Each field was divided into parallel strips that were divided among VRMA treatment and the uniform-rate manure application (URMA) treatment. Experimental results showed that VRMA did not reduce the amount of manure applied, while slightly increased yield, compared to URMA. Manure consumption in the VRMA treatment generally depended on the fertilisation prescription, nitrogen (N):P2O5 ratio in manure, measured P2O5 in manure, and the proportion of rich, medium, and poor P areas in a field.