Rainfed rice - IRRI books - International Rice Research Institute

INTENSE AND HIGH QUANTITY
Loss of nutrients
Mechanical damage to plants
Crop inundation
Rainfall somewhere in the catchment areas, causes flash floods in the
fields
Washing off of pesticides/fertilisers
Rainfall and Its Agronomic Interpretations
Mitigation methods
Analyse and understand the rainfall pattern.
Be knowledgeable of the rainfall pattern of the region for time of sowing,
total duration of water, availability, probability of drought, probability of
floods, probable duration and intensity of drought and floods, etc.
Based on the analysis of the rainfall patterns of eastern India, probable
sowing periods have been worked out as follows:
Probable sowing periods based on rainfall patterns in eastern India
States Sowing period
Eastern Madhya Pradesh 31 May - 21 June
Eastern Uttar Pradesh 11 June - 9 July
Bihar 5 June - 7 July
Orissa 19 May - 9 June
West Bengal 28 April - 9 June
Assam 2 February - 28 March
Duration (days)
Sowing time starts early in Assam.
Sowing duration is longest in Assam and shortest in eastern Madhya Pradesh.
Except in Assam and West Bengal, the sowing time in the other states is from early
June, but in Orissa it is from the third week of May.
Water availability periods
Water availability periods help in choosing the right kind of variety for a
given area and soil type. Water availability periods are calculated on the
basis of rainfall (input) and potential evapotranspiration (output).
The period when the rainfall exceeds potential evapotranspiration (R>PET)
is known as the humid period. This period is useful for the vegetative and
reproductive stages of crop growth.
The period when rainfall is less than potential evapotranspiration but
greater than half of it is known as the moist period (when PET>R>PET/2).
This period is useful for seedling and maturity stages of crop growth.
21
28
32
28
42
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