Precision Farming of Cereal Crops: a Review of a Six Year Experiment to develop Management Guidelines Review Article

This paper summarises the results of a 6-yr study, involving five principal fields in England covering 13 soil types, which represent approximately 30% of the soils on which arable crops are grown. The aim of the project was to determine guidelines to maximise profitability and minimise environmental impact of cereal production using precision farming. The study focused on the interaction between soil/water variability and nitrogen applications. The earlier work concentrated on identifying the in-field variability and the development of a ‘real-time’ sensing technique, while the later work compared spatially controlled inputs with uniform agronomic practice. A number of techniques were used to decide upon the variable application strategy. These included yield variability from historic yield maps, variability in shoot density in the spring, and variability in the subsequent development of the canopy; the latter two enabling the development of the concept of ‘real-time’ agronomic management. In uniformly managed fields, there were considerable differences in the spatial patterns and magnitudes of yield variation between fields and seasons, which linked to soil variation and annual differences in rainfall and earlier field operations. Electromagnetic induction (EMI) was found to be a suitable surrogate for detailed soil coring and cluster analysis of EMI and yield data provided an objective method to subdivide fields into management zones for targeted sampling of soil nutrients and pH; and for estimating replenishment levels of P and K fertilisers. Considerable reductions in the cost of soil sampling were possible with this approach. Yield maps, however, were not a useful basis for determining a variable nitrogen application strategy. It was shown that the spatial variation in canopy development with a field can be effectively determined using aerial digital photography for ‘real-time’ management. This technique can improve the efficiency of cereal production through managing variations in the crop canopy and gave an average economic return of £22 ha−1 while reducing the nitrogen surplus by approximately one-third. Benefits from spatially variable application of nitrogen outweigh costs of the investment in precision farming systems for cereal farms greater than 75 ha for systems costing £4500. This area increases in size in proportion to the capital cost. Integrating the economic costs with the proportion of the farmed area that has benefit potential enables the break-even yield increase to be estimated. Typically a farm with 250 ha of cereals where 20% of the area could respond positively to spatially variable nitrogen would need to achieve a yield increase of 1·1 t ha−1 on that 20% to break even. These economic advantages linked to the environmental benefits should improve the longer term sustainability of cereal production. Common problems, such as water-logging and fertiliser application errors should be corrected prior to the spatial application of fertilisers and other inputs. From the overall results a set of practical guidelines has been incorporated in a single decision support tool to help farmers.