To measure a farmer’s ability to produce “more crop per drop”, agricultural scientists now use the term “water productivity”. Farm water productivity can be as high as 20kg/cubic metre water with cereals, or about 10kg/cubic metre with oilseeds and legumes, but such high efficiencies are obtained only in the best managed crops. Almost any factor that can influence crop yield or vigour will influence water efficiency.
Over the coming decades, rises in global demand for food, fibre, feed and fuel are predicted to cause large increases in the amount of water used by agriculture. Currently, agriculture world-wide uses 6,800 cubic kilometre of water annually (km3/y), but by 2050 global water use in farming will need to rise to dramatically to 12,600km3/y unless substantial improvements occur in the water-use efficiency of farming.