Date of this Version
In India, about 70% of the cultivable land is rainfed. This includes areas where crops are rarely affected by drought and areas where crops experience moisture stress and often fail. The regions with the latter characteristics are often called dryland areas and the agriculture so practiced there is known as dryland agriculture. About 35% of the total cultivable land belongs in this category. To determine the magnitude of water deficiency in these regions, the moisture deficit index (MDI) has been evaluated for dryland stations in India. The MDI is usually determined on the basis of annual precipitation and annual potential evapotranspiration, as adapted by Thornthwaite and Mather in 1955. This does not reflect the true nature of MDI for the purpose of crop production, although it does give information regarding the degree of aridity. Since this index sometimes is used as a criterion for crop planning, it would appear more appropriate for it to be based on precipitation and PET during the crop growth period. In this article, the monthly MDI for dryland stations in India based on normal data has been worked out. We have also discussed its implications for crop production in relation to other meteorological factors.