Authors: BOLLAVENI SATHISH KUMAR1*, J. RAVINDER2, AKHILESH KUMAR GUPTA1, BAVAJIGUDI SHOBHA RATHOD3
1Department of Agronomy, Sardar Vallabhbhai Patel University of Agriculture & Technology, Meerut, Uttar Pradesh, India.
2 Department of Soil Science and Agricultural Chemistry, Dr.Panjab Rao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra, India.
3 Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India.
*Corresponding author's email: sathishbollaveni44@gmail.com
Paddy crop is strongly influenced by water supply. Water should be kept standing in the field throughout the growth period. In water scarcity areas, saturated soil in a chemical reduced stage is desirable. The characteristics of flooded soil which are conducive to high yields are: (i) greater availability of nutrients such as phosphorus, iron and manganese, (ii) suppression of weed competition, (iii) elimination of moisture stress as a limiting factor, (iv) micro-climate favourable to crop production.
- Excess / limited / no water leads to reduction in yield.
- Rice a semi - aquatic plant requires near submergence
- Submergence helps in - suppressing weed growth and more availability of certain nutrients
- Daily consumptive use of rice is 6 - 10mm
- Total water requirement of rice is 1200 - 1400 mm
- 2000 - 3000 litres of water required to produced 1kg of rice
- Highly saline and brakish water not good for irrigation
- Application of FYM or incorporation of green manures reduce adverse effects of excess salts
- Application of FYM or compost or green manures increases water holding capacity of light textured soils and thus saving of water
- Thorough puddling creates impermeable layer which reduces deep percolation losses
- Perfect leveling maintains uniform depth of water throughout field
- Maintenance of water depths in field as recommended for high water use efficiency and yield
Water requirement of rice crop at different growth stages
| Stages of growth | Avg. water requirement (mm) | % of total water requirement (approx.) |
| Nursery | 50-60 | 5 |
| Main field preparation | 200-250 | 20 |
| Planting to Panicle initiation (PI) | 400-550 | 40 |
| P.I to flowering | 400-450 | 30 |
| flowering to maturity | 100-150 | 5 |
| Total | 1200-1460 | 100.0 |
Critical stage refers to a stage when water scarcity or deficit of water causes comparatively greater reduction in yields which cannot be made by favourable water supply at earlier or later stages. Hence, water deficit during these stages should be avoided. Following are the important critical crop growth stages for water stress.
(a) Tillering
(b) Panicle initiation
(c) Boot leaf stage
(d) Heading/ panicle emergence
(f) Flowering/anthesis (Reproductive phase)
During these stages, soil moisture level should be maintained at saturation level
- Moisture stress at active tillering phase - 30% yield reduction
- Moisture stress at reproductive phase - 50 - 60% yield reduction
Water requirement and losses of water in rice fields
| Particular | Clay Loam | Silty Clay | Loam | Sandy Loam |
| Water requirement | 1583 | 1602 | 1995 | 2261 |
| Irrigation | 1125 | 1200 | 1500 | 1775 |
| Runoff | 207 | 191 | 193 | 161 |
| Percolation | 893 (56%) | 870 (54%) | 1187(60%) | 1515 (67%) |
| Evapotranspiration | 690 (44%) | 732 (46%) | 808 (40%) | 745 (33%) |
- Summer ploughing minimises water requirement for land preparation
- Seepage and percolation reduced to considerable extent by puddling and perfect leveling
- Application of FYM or compost or green manures reduce evaporation, percolation and seepage
- Evaporation losses can be minimized by 50% when the soil is kept at saturation under levelled field conditions
- Addition of clay or tank silt (to light textured soils only) @ 150m 3/ha reduce the percolation loss by 20 -25%
- Higher the transpiration higher the yield (a normal crop of 4.5t/ha with an irrigation period of 100 days consumes 6mm/day by transpiration. When figure declines to 1.4mm/day the yield decreases to 1t/ha when it increases 10.5mm the crop yield will increase to 7.5t/ha )
- Maintain thin film of water at the time of planting (2cm)
- Life irrigation should be given on 3rd day and up to 7 days, 2cm water level should be maintained Gradually raise water level to a depth of 5 cm up to maturity
- Moisture stress during rooting and tillering stage cause poor root growth leading to poor crop establishment and low yield.
- Spray Cycogel @ 1000ppm (1ml of commercial product in one litre of water) under water deficit situations to mitigate ill effects moisture stress.
- Split application of potassium 50% at basal and 25% each at tillering and panicle initiation stage along with Azospirillum (seed inoculation, seedling dipping or soil application) alleviates harmful effects of the soil moisture stress
Water quality and critical values Major considerations of water quality:
1. Salinity
2. Water infiltration rates
3. Specific ion toxicity
Types of problems and critical values to be considered for irrigation
| Potential problem | Units | No problem | Slight to moderate problem | Severe problem |
| pH | No units | 6.5-8.5 | <6.5: > 8.5 | <6.5: > 8.5 |
| Salinity ECw | Ds/m=m mol/cm | <2.0 | 2.0-2.6 | >2.6 |
| Salinity ECe | Ds/m | <3.0 | 3.0-3.8 | >3.8 |
| TDS* | Mg/l | <450 | 450-2000 | >2000 |
| Specific ion toxicity | No units | <3 | 3-9 | >9 |
| Chloride | me/l | <4 | 4-10 | >10 |
| Boron ** | me/l | <0.7 | 0.7-3.0 | >3 |
| Bicarbonate | me/l | <4 | >4 | >>4 |
** B toxicity is encountered on highly sodic soils or under use of brackish water.
- For each 1ppm element in the water, the input is 1000mm equivalent to 10kg/ha
- If pH is out of range (6.5 - 8.4) but with low salinity (<0.2 Ds/m) then there is likely no problem as the water has very low buffering. However, additional checks should be pursued for possible nutrient imbalance
- High bicarbonate levels in irrigation water can cause Zn deficiency
- High sodium water cause deflocculation of soil particles leading to increase stickiness and compactness and decrease permeability
- Specific conductivity of ideal water : (K x 106) < 7500
- Boron < 1ppm
- S.A.R. Index < 10
- Ecw = Irrigation water salinity
- Ece = Soil salinity a measure on a saturation extract SAR = Na/ (Square root (Ca + Mg/2)); Na, Ca and Mg in me
Measures of efficient water management in rice
- One ploughing by mould-board plough and puddling twice by disc harrow gave the best result in terms of crop establishment, water use efficiency and yield.
- Studies conducted for evolving design criteria for different methods of irrigation for efficient use of water indicated that maximum water-use efficiency for rice can be obtained with check basins with size in between 250-300 m2 area.
- Recycling run-off water in flood-irrigated rice can irrigate 10% additional area
- In command areas where field to field irrigation is common cost effective recycling structures may be constructed for reusing drainage water.
- A mixture of fly ash and clay with 50% cement was found to be a suitable lining material for field channels.
- Pre-cast structures for water management work under different land situations will improve water-use efficiency by about 50%.
- Perpendicular orientation of field channel to main supply found superior to parallel orientation. The interval between outlets should be 425-450 meters rotation areas for parallel orientation and 650-700 m for perpendicular orientation.
Scheduling of irrigation to rice
| 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) | |
| 1-25 | 5-7 | 2-3 | 1-30 | 5-7 | 2-3 | 1-35 | 6-8 | 2-3 | |
| 25 | - | Thin film of water | 30 | - | Thin film of water | 35 | - | Thin film of water | |
| 28 | - | Life irrigation | 33 | - | Life irrigation | 38 | - | Life irrigation | |
| 29-50 | 6 | 2-5 | 34-65 | 6-8 | 2-5 | 39-90 or 95 | 12-15 | 2-5 | |
| 51-70 | 5-6 | 2-5 | 66-95 | 8-10 | 2-5 | 96-125 | 7-9 | 2-5 | |
| 71-105 | 5-6 | 2-5 | 96-125 | 6-8 | 2-5 | 126-150 | 5-6 | 2-5 | |
Precautions for irrigation
- Withhold water for few days till the seedlings have established.
- Field to field irrigation should be avoided.
- Drain-off water for about 2 days prior to the application of fertilizers.
- Small bund may be formed parallel to the main bund of the field at a distance of 30 to 45cm within the field to avoid leakages of water through main bund crevices.
- To minimize percolation loss, the depth of stagnated water should be 5cm or less.
- In water logged conditions provide open drains about 60cm in depth and 45cm width across the field. Care should be taken not to allow development of cracks.
- In canal command area, conjunctive use of surface and ground water may be resorted to for judicious use of water.
- Where irrigation facilities are not available, store all the rain water in paddy fields by making 25 to 30 cm raised bunds.
- Maintain about 8-10 cm of water level in the fields at puddling time and subsequently depth of ponded water may be maintained throughout the growing period
- Drain-off water completely for 5 to 7 days following tillering and flowering stages. This helps to remove the toxic substances like sulphides and regulates oxygen supply to root
About Author / Additional Info:
I am currently pursuing Ph.D in Agronomy from University of Assam agricultural university.