Showing papers by "Indian Agricultural Statistics Research Institute published in 1984"

A statistical study on incidence of drought in relation to agricultural production

Abstract: In India about 75 percent of the cultivated area is rainfed and since about 42 per cent of- our food comes from such areas, there is considerable variation in food production depending upon the amount and distribution of rainfall Semi-arid areas where the annual potential evapotranspiration exceeds-the mean—annual rainfall exist in several of our States. In such areas crop fortune depends very much on vagaries of weather: The annual rainfall in these areas is usually less than 75 cm and there occurs sometimes prolonged dry spells within the rainy season. It is then the distribution of rainfall during a season more important than its amount. While the rainfall, coupled with the moisture storage property of soils-ensurethe--moisture supply, the Water loss taking place in the form of evapotranspiration, runoff and deep drainage places an evapotranspirative demand during the growing season. It is, therefore, the- progressive balance. between the receipt and expenditure of the moisture in the soil which creates favourable or unfavourable conditions for successful crop production. One can, thus, with the help of rainfall distribution and potential evapotranspiration values determine conditions for drought for a specific period in relation to a given variety of crop in the region. Several research workers have attempted to study the various aspects of drought on this basis. Their studies mostly relate to occurrence of dry spells, water availability periods, drought mapping, Palmer indexing and spectrum analysis for assessing and forecasting of drought. These studies have not taken into account the crop yields in determining the agricultural drought. In the present paper, therefore, data on rainfall and yield of a crop like jowar have been analysed for certain, semi-arid areas of western India for characterising the agricultural drought and its intensity. The recurrence of drought in relation of jowar has also been studied.

Assessment of atmospheric drought during monsoon cropping season

Abstract: During break periods in the southwest monsoon season in the semi-arid environment of India, crops under rainfed as well as irrigated conditions are prone to the effect of "atmospheric drought" as distinguished from 'soil' or "agricultural drought". This situation occurring at different stages of crop growth for a week or two is not reflected in the soil water balance, but is revealed in the crop growth rates and yields. Evidence exists of energy gain through advection by evaporating surfaces of the order of 4 to 5 mm/day resulting in an increase in potential evapotranspiration rates by 2-3 mm/day. This situation can be traced on a macroscale to the westerlies during the 'break periods' and on a local scale to the post monsoon warming of surroundings with a reduces intensity. As yet, apart from the soil budgeting approach with the limitation mentioned above, there appears to be no method by which years with widely varying amounts of total seasonal rainfall but with different distribution patterns in the different growth stages resulting in atmospheric drought could be distinguished from one another or grouped together. This paper while focussing the attention to this aspect illustrates an empirical technique based on sequential dry days for assessment of atmospheric drought.

πPS Sampling Scheme Through Grouping

Abstract: A πPS sampling scheme is developed by combining Stevens and Midzuno-Sen Sampling schemes. The restriction on original probabilities is less severe in the proposed scheme than that in Stevens and Midzuno-Sen schemes. The performance of the scheme is satisfactory.