Rainfed rice - IRRI books - International Rice Research Institute

RAINFED RICE A SOURCEBOOK OF BEST PRACTICES AND STRATEGIES IN EASTERN INDIA
Schematic diagram of water availability periods
200
Rainfall probabilities
Stable rainfall periods
In eastern India, both the daily ET and percolation losses are around 3-4
mm/day. Thus, the water requirement of rice without stress is about 50
mm/week.
A stable rainfall period is a period when the weekly rainfall is 50 mm or
more in a given place. Based on this, the stable rainfall periods at 30%, 40%,
50%, 60% and 70%) probability levels of all meteorological stations of the
states in eastern India were worked out. It was found that the stable rainfall
period at 60% probability level exceeds 60 days in most places in eastern
Madhya Pradesh. The implication of this finding is that, with 30 days for
the seedling stage and 30 days for the maturity stage in eastern Madhya
Pradesh, rice varieties of 120-125 days duration can be used successfully in
two out of three years.
The stable rainfall periods at different probability levels in different states
are shown in the table.
Stable rainfall period duration (days) at different probability levels in different
states of eastern India
States/probabilities 30% 40% 50% 60% 70%
Eastern Madhya Pradesh
Eastern Uttar Pradesh
Bihar
Orissa
West Bengal
83-1 13
74-98
92-1 16
84-1 37
111-124
73-95
60-83
73-89
0-101
92-1 00
68-88
17-47
0-53
0-81
39-68
8-83
0-8
0-54
0-65
16-37
In most of the states, the stable rainfall period at 70% probability is either zero or negligible.
Even at 50% probability level, the stable rainfall period is zero in some stations in Bihar and Orissa.
0-45
0
0
0-51
0-6