Assessment of the influence of monsoon rain on rainy season rice (Oryza sativa) productivity over major rice growing states

摘要

A study was conducted to understand the influence of monsoon rainfall on rice (Oryza sativa L.) productivity and also to quantify the contribution of monthly distribution of rainfall during monsoon period on rice productivity over the important rice growing states. The main rice growing season in the country is rainy (kharif) season in which farming operations start with onset of monsoon. About 84% of the country's rice crop is grown in this season. Eventhough, south-west monsoon strikes Kerala coast normally during the first week of June, the summer /pre-monsoon showers during May also have crucial role because the farmers' of eastern, coastal and peninsular region prepare their nursery during this time, so as to start main field preparation and transplanting with onset of monsoon. Assam receives 12.2% (280.2 mm) of its annual rainfall (2291.4 mm) during May, while Gujarat receives only 1.3% (9.3 mm). The rice crop continues to show an overall steady increase in productivity in all the states. The higher percentage of increase (140%) in triennium productivity was noticed in West Bengal, followed by Uttar Pradesh (127%). However a very low 26% increase in triennium productivity was observed in Maharashtra, followed by 34% increase in Bihar. Despite 56% rice area being under irrigation over India, 67% contribution of monthly rainfall during May-October to productivity variation indicate that the multiple regression equation could be used for estimating the productivity over India. In Haryana, rainfall distribution during May-October contributes only 3% to productivity variations while in Gujarat rainfall distribution during May-October explains 72% of productivity variations.