Water management in paddy crop

Dr Laishram Kanta Singh / Dr Arati Ningombam / N Peetambari Devi / Dr S Roma Devi *

A Paddy field as seen on August 04 2019 :: Pix - TSE

Crop water requirement is the amount of water required by plants for survival, growth, and development, as well as the production of economic parts. This demand is met either naturally through precipitation or artificially through irrigation.

The daily consumption of rice ranges from 6-10 mm, and total water consumption ranges from 1100 to 1250 mm, depending on the agro-climatic environment, duration of variety, and soil characteristics.

Stage-wise water requirement for paddy

Stages of growth Water requirement (mm) Percentage of total water requirement---

Nursery Preparation 40 3.22
Paddy field preparation 200 16.12
Transplanting to panicle initial stage 458 37.00
Panicle initial stage to flowering stage 417 33.66
Flowering stage to maturity stage 125 10.00

Scheduling of irrigation for paddy

Short duration variety Medium duration variety Long duration variety Days No. of irrigation Water level (cm) Days No. of irrigation Water level(cm) Days No. of irrigation Water level (cm)
1-255-72-31-305-72-31-356-82-325-Thin film of water 30-Thin film of water 35-Thin film of water 28-Life irrigation33-Life irrigation 38-Life irrigation 29-5062-534-656-82-539-90 or 9512-152-551-705-62-566-958-102-596- 1257- 92-571-1055-62-596-1256-82-5126-1505-62-5

Critical Stages of Irrigation

The critical stage of water need is the point at which water stress produces substantial yield decrease. It is often referred to as the moisture sensitive phase. Active tillering, Panicle initiation, Booting, Heading, and Flowering are critical stages of water requirement in rice.

During these stages, the irrigation interval should not be extended beyond the time limit so that moisture is depleted below the saturation level. Continuous land submergence for rice is commonly used due to the accompanying primary benefits of increased nutrient availability and fewer weed management issues.

Throughout the crop time, shallow submergence of water up to 5 cm depth is ideal for optimal production. Standing water in lowland rice reduces irrigation requirements, resulting in high water use efficiency as compared to continuous flowing irrigation water from crop to field.

Rice Field Water Losses

Water losses from lowland rice fields can be divided into two categories: vapour losses and liquid losses. Evapotranspiration refers to the loss of vapour through transpiration from the leaf surface and evaporation at the water surface. Deep percolation plus seepage and runoff of excess water over field levees are the two types of liquid losses.

Water-saving strategies

Seepage and percolation are significantly decreased by rigorous ground puddling and flawless levelling. FYM, compost, and green manures are used to minimise evaporation, percolation, and seepage. To prevent seepage, canals and irrigation channels can be lined. When the soil is held at saturation under levelled field conditions, evaporation losses can be reduced by 50%.

The addition of clay or tank silt at 150m3/ha (to light textured soils only) reduces percolation loss by 20-25%. Grow rice in huge blocks rather than isolated tiny holdings to prevent percolation loss. During the wet season, rainwater harvesting and levee mainte- nance can significantly reduce surface runoff.

Water deficits and rice performance

When transpiration exceeds absorption, the plant experiences a water shortage. The impact of water deficits on rice growth and yield is determined by the stage of crop growth at which the deficiencies occur.

Stage of vegetative growth

Adequate ground submergence (5 cm) is required immediately after transplanting to protect establi- shing plants from high winds and to promote root development. After the early rooting stage, a shallow depth of land submergence (2 cm) promotes tiller formation and solid root attachment in the soil. Moisture stress during the active tillering phase reduces yield by 30%.

Stage of reproduction

From panicle primordial development to heading, the rice crop is particularly sensitive to water deficiency. Due to the high percentage of sterility, three days of moisture stress at 11 days and three days before heading leads in maximum yield loss. Moisture stress during the reproductive phase reduces production by 50- 60%.

Maturity level

This period of development (milk to grain maturity) is the least susceptible to soil moisture stress. There is no need for standing water after the yellowish ripening stage. To ease harvesting, water may be drained from the field 7-10 days before harvest.