- Optimal soil moisture for plant growth varies with the stage of crop growth. Certain periods during the crop growth and development are most sensitive to soil moisture stress compared with other. These periods are known as moisture sensitive periods. The term critical period is commonly used to define the stage of growth when plants are most sensitive to shortage of water. Inadequate water supply during moisture sensitive periods will irrevocably reduce the yield and provision of adequate water and other management practices at other growth stages will not help in recovering the yield lost.
- In case of vegetables, when they are young, though transpire less water, need a stress free moisture condition because of the very weak root system which is sparsely distributed and located in upper 15 to 20 cm layer of soil that gets quickly dried. Vegetable crops utilize and transpire more water in the later stages of growth during which moisture stress markedly reduces yield.
| Crop | Important moisture sensitive stages |
| Rice: | Panicle initiation, flowering |
| Wheat: | Crown-root initiation(CRI),jointing, milking |
| Sorghum: | Seedling, flowering |
| Maize: | Silking, tasseling |
| Pearl millet: | Flowering, panicle initiation |
| Finger millet: | Flowering, panicle initiation |
| Groundnut: | Rapid flowering, pegging, early pod formation |
| Redgram: | Flowering and pod formation |
| Greengram: | Flowering and pod formation |
| Blackgram: | Flowering and pod formation |
| Sugarcane: | Formative stage |
| Soybean: | Blooming and seed formation |
| Cotton: | Flowering and boll development |
| Tobacco: | Transplanting to full bloom |
| Chillies: | Flowering |
| Potato: | Tuber initiation to tuber maturity |
| Onion: | Bulb formation to maturity |
| Tomato: | From the commencement of fruit set |
| Peas: | Flowering and pod development |
| Cabbage: | Head formation until becoming firm |
| Carrot: | Root enlargement |
