Tensiometers for Rice Water Footprints

Abstract

Water footprints (WFs) of rice are quite higher viz. 992 billion cubic metres per year (Gm3 yr−1) than from the other cereals which further responsible for the lower water productivity. Out of global WFs for crop production viz. 7404 Gm3 yr−1 corresponds to 78 % green, 12 % blue, and 10 % grey water, respectively. Around 3000-4000 litres of water required for one kg of rice grains and conventional puddle transplanted flood irrigations responsible for this. Therefore, there is an urgent need to cut down rice WFs share. Over irrigated pounded water under conventional puddle transplanted rice responsible for the emissions of the green house gases in atmosphere, which further has its own complications. With time, due to excessive withdrawals of the underground water, the water table is declining at a faster rate and seems to be beyond the reach of the middle class rice farmers. Rice water productivity declining day by day due to huge water demand of rice crop followed by reduced yields. A major share of the applied irrigation water lost/evaporate in the atmosphere. Soil water tension controls the soil moisture dynamics and directly linked to the plant need based approach. Being a kharif crop, rice season faces harsh summers and where evaporative demands of atmosphere intensified to many folds and thus, irrigation water has to be applied frequently. Annually additional water of worth US $ 39 million is withdrawn in NW Indian Punjab state for feeding crops, particularly rice. Tensiometer is the only instrument provided to the rice farmers for applying irrigation water judiciously based on the plant need which further cut down WFs from 18 to 22%. This practise where on one side saves irrigation water, improves declining land as well as water productivity of rice, also controlled the emissions of GHGs from the soil.