Paris, France: A new technology, using sensors on satellites, could help to establish standards for the amount of water that farmers need to irrigate their crops and help to optimise the use of that water, an increasingly scarce resource.
The technology measures water productivity in agriculture, or the amount of a crop produced by a given volume of water, drawing on remote sensing data and satellite images to measure evaporation and yield.
Calculations are made to take into account the minimum and maximum temperatures of an area, the amount of available solar energy, and maps of the Normalized Difference Vegetation index, or N.D.V.I., and the surface albedo. The N.D.V.I. assesses the amount of live green vegetation, using data from the vegetation instrument system on the French-developed SPOT 4 earth observation satellite. The surface albedo is a measurement of how strongly an area reflects sunlight, in this case using data from NASA.
The results can help to identify where water is used productively and where it is squandered. Reasons for wasted water can be analysed, allowing farmers and agricultural policy makers, to establish best practice for irrigation in specific locations, with the aim of cutting down on water use without compromising the harvest.
Developer of the technology, Dr Zwart also highlighted alternative water-saving methods, which could be applied to some small-scale farms. He suggested that farmers store rainwater or apply deficit irrigation, which involves reducing the water supply during specific stages of the season — a technique that he said “hardly affects” crop yield.
Dr Zwart said other factors affecting production, like overall water availability and soil fertility, should be taken into account alongside water productivity. In a report this year, he said this would “assist policy and decision makers to define priority areas, to set goals for improvement, and to define and justify the type of investment or measures that are made to make agriculture more productive.” This could be done using a global database of fertiliser use and a global map of main soil types held by the F.A.O., he said.