The stage at which the water stress causes severe yield reduction is also known as
critical stage of water requirement. It is also known as moisture sensitive period.
Moisture stress due to restricted supply of water during the moisture sensitive period or
critical stage will irrevocably reduce the yield. Provision of adequate water and fertilizer
at other growth stage will not even help in recovering the yield loss due to stress at
critical periods.
It general the mid season stage is most sensitive to water shortage because the
shortage during this period will be reflected significantly on yield. For most of the crops
the least sensitive stages are ripening and harvesting except for vegetables like Lettuce,
Cabbage etc., which need water upto harvesting.
Under scarce condition, in an irrigation project or in a farm, if mono cropping is
followed with staggered sowing or planting, it is better to schedule irrigation to crop
which has reached mid season stage since it is the most critical stage.
The sensitive stages vary from crop to crop as given below.
Sensitive stage of different crops cereals and millets
Crop Critical stages / Sensitive stages
Rice – Panicle initiation critical staps. heading and flowering
Sorghum – Flowering and grain formation
Maize – Just prior to tasseling and grain filling
Cumbu – Heading and flowering
Ragi – Primordial initiation and flowering
Wheat – Crown root initiation, tillering and booting
Oil seeds
Groundnut – Flowering peg initiation and penetration and pod development
Sesame – Blooming to maturity
Sunflower – Two weeks before and after flowering
Soybean – Blooming and seed formation
Safflower – From rosette to flowering
Castor – Full growing period
Cash crop
Cotton – Flowering and Boll formation
Sugarcane – Maximum vegetative stage
Tobacco – Immediately after transplanting
Vegetables
Onion – Bulb formation to maturity
Tomato – Flowering and fruit setting
Chillies – Flowering
Cabbage – Head formation to maturity
Legumes
Alfalfa – Immediately after cutting for hay crop and flowering for seed crop
Beans – Flowering and pod setting
Peas – Flowering and pod formation
Others
Coconut – Nursery stage root enlargement
Potato – Tuber initiation and maturity
Banana – Throughout the growth
Citrus – Flowering, fruit setting and enlargement
Mango – Flowering
Coffee – Flowering and fruit development
