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Temperature (°C) and solar radiation (SR)705030ABCRainfall (mm)700500300100 JFMAMJ JASONDJFMAMJ JASONDMonth1000JFMAMJ JASONDMax. temp. (°C) Min. temp. (°C) SR Rainfall (mm)Fig. 2. Temporal dynamics of rainfall, maximum and minimum temperature, and solarradiation in coastal areas (Cuttack, Orissa, A), higher latitude areas (Patna, Bihar, B),and high-rainfall areas (Silchar, Assam, C).in early, causing damage from low temperature, such as high sterility in the rice crop.As all of eastern India comes under the influence of the southwest monsoon (June-October), solar radiation also becomes a limiting factor during the vegetative stageand early parts of the reproductive stage of the rice crop (mostly in July and August).Temporal dynamicsFigure 2A-C shows the temporal dynamics of rainfall, maximum and minimum temperatures,and solar radiation for three representative stations—coastal, higher latitude,and high-rainfall areas—in eastern India. In coastal areas (Fig. 2A), the maximumtemperature is always near or above 30 °C and the minimum temperature isalways above 15 °C. In higher latitudes such as in Patna, the minimum temperaturefalls sharply from October onward (Fig. 2B) and this, as stated earlier, may createproblems in grain filling, if these conditions start early. On the other hand, in highrainfallareas such as Silchar in the northeastern states, with higher rainfall from Mayto September, solar radiation is lower than in other places (Fig. 2C). The minimumtemperature falls below 15 °C only in November. As the rainfall starts early withhigher amounts and intensity, submergence or flood is the main problem in this area,especially in June and July, besides lower amounts of solar radiation.In view of the importance of these climatic factors, which limit the optimumproductivity of the rice crop, this chapter attempts to analyze three agroclimatic factors—moisture,thermal, and radiation regimes—in eastern India during different stagesof crop growth.Materials and methodsThe climatic data required for the analysis are collected from the India MeteorologicalDepartment (IMD). The rainfall probabilities are collected from the data publishedby IMD (1995). The solar radiation data required for the analysis are estimated218 Sastri and Singh