In this essay we will discuss about the irrigation practices used for growing oilseeds.
Essay Contents:
- Essay on the Irrigation Practices Used for Growing Groundnut
- Essay on the Irrigation Practices Used for Growing Rapeseed and Mustard
- Essay on the Irrigation Practices Used for Growing Sunflower
- Essay on the Irrigation Practices Used for Growing Soybean
- Essay on the Irrigation Practices Used for Growing Castor
Essay # 1. Irrigation Practices Used for Growing Groundnut:
Groundnut, largely a rainfed crop during kharif is not irrigated in major groundnut producing states. In recent years, however, there is emphasis for rabi and summer irrigated groundnut crops, which accounts for about 20 per cent of total production. Water management for groundnut crop is complicated due to prolonged flowering period with two to three flushes of flowering.
It is not uncommon to observe the crop with flowers, pegs, developing pods and mature pods at a time, especially when the crop is subjected to soil moisture stress at first or second flush of flowering. Water requirement varies from 500 to 700 mm.
Flowering, pegging and pod developmental stages (flowering to pod development) are considered sensitive to soil moisture stress. Results of experiments indicated necessity for scheduling irrigations at 25 per cent DASM throughout the crop period for high pod yield of groundnut on sandy loam soils.
Irrigating the crop at 25 per cent DASM from pegging to early pod development and at 50 per cent DASM at other stages appears to be ideal for high water use efficiency without significant reduction in pod yield. An IW/CPE ratio of 1.0 at moisture sensitive stages and at 0.6 during other stages leads to high water use efficiency.
At several situations, 10 to 12 irrigations at 10 days interval resulted in highest pod yield. On sandy loam soils, seven irrigations- presowing, 25, 35, 45, 55, 70 and 90 DAS appears to be optimum for high yield.
Groundnut may require a minimum of 7-10 days of irrigation depending upon on the soil type. As compared to heavy soils, light textured soils require more frequent irrigation.
General irrigation schedule for bunch type groundnut with duration of 105 days is as follows:
1. I irrigation: Immediately after sowing (not necessary if the soil contains optimum soil moisture at sowing)
2. II irrigation: 5-7 DAS, if needs (early growth stage)
3. III irrigation: 25 DAS (flower initiation)
4. IV irrigation: 32 DAS (flowering stage)
5. V irrigation: 39 DAS
6. VI irrigation: 46 DAS (pegging)
7. VII irrigation – 56 DAS
8. VIII irrigation – 66 DAS (pod filling)
9. IX irrigation – 78 DAS (pod maturity stage)
10. X irrigation – 88 DAS
11. The crop needs no irrigation thereafter till harvest.
From the results of experiments at several situations, irrigation practices for groundnut can be summarised as indicated below:
Critical stages approach:
1. Presowing irrigation (stand establishment) and no irrigation up to three weeks after sowing
2. Starting from three weeks after sowing (flowering to pod formation), five irrigations at 10 days interval.
3. Last two irrigations (pod development) at 15 days interval.
DASM approach:
1. Irrigation at 25 per cent DASM, especially for a crop on sandy loam soils, throughout the crop period if irrigation water is not a limiting factor
2. No irrigation up to three weeks after sowing. From three weeks after sowing up to pod development, irrigation at 50 per cent DASM followed by irrigation schedules at 75 per cent DASM up to pod maturity.
IW/CPE approach:
1. Irrigation at IW/CPE ratio of 1.0, especially for a crop on sandy loam soils, throughout the crop period if irrigation water is not a limiting factor
2. No irrigation up to three weeks after sowing. From three weeks after sowing up to pod development, irrigation at IW/CPE ratio of 0.75 followed by IW/CPE ratio of 0.6 up to pod maturity.
Essay # 2. Irrigation Practices Used for Growing Rapeseed and Mustard:
Brassicas are responsive to irrigation due to scanty winter rainfall. About 60 per cent of the total area under the crop is irrigated. Among the brassicas, raya is most responsive to irrigation.
Flowering and pod formation stages of mustard are most sensitive to soil moisture stress. Irrigation at these stages increases the seed yield by 30 per cent. Additional irrigation at 30 DAS may be given, if irrigation water is not a limiting factor. Scheduling irrigation at 75 per cent DASM was adequate on sandy loam soils of Punjab. However, scheduling irrigation at 40 per cent DASM was beneficial.
Scheduling irrigations at IW/CPE ratio of 0.6 at Kharagpur and at 0.8 at Pusa resulted in higher mustard yield. As per phenological stages, mustard needed one irrigation 30 DAS at Morena and Ludhiana, one during flowering at Pantnagar and two at flowering and pod development at Navsari.
Based on the available information, the following irrigation management practices can be recommended for rapeseed and mustard:
1. Mustard crop needs only three irrigations, one each at 30 DAS, flowering and pod formation, for high yield even if irrigation water is not a limiting factor
2. If irrigation water is a limiting factor, only two irrigations at flowering and pod development can optimise the mustard yield
3. Scheduling irrigation at 50 per cent DASM at the above three stages is ideal. If irrigations are scheduled based on IW/CPE ratio, 0.75 ratio could be optimum at most situations
4. Under the conditions of limited irrigation water, scheduling irrigations at 75 per cent DASM or at IW/CPE ratio of 0.6 increases the water use efficiency.
Essay # 3. Irrigation Practices Used for Growing Sunflower:
Sunflower is, generally, sown during June in kharif, September – October in rabi and in January as summer crop. Sunflower will not respond to irrigation during rainy season unless prolonged dry spells occur during critical stages for water deficits. Response to irrigation during rabi and summer varies depending on the soil type and weather conditions. Response is more pronounced in summer than in rabi.
Critical stages for irrigation are, bud initiation (30 to 40 DAS), flower opening (45 to 55 DAS) and seed filling (60 to 85 DAS). Flower opening stage is the most critical stage for soil moisture stress. Three irrigations (6 cm depth) at these three critical stages resulted in highest yield of 2.5 t ha-1 at several locations during rabi. Summer crop, however, responded to another irrigation at disc formation stage (60 to70 DAS).
Irrigation at 50 to 60 per cent DASM was optimum both for rabi and summer crops at several places. During rabi, sunflower crop required only two irrigations (7.5 cm depth) at IW/CPE ratio of 0.6 on black soils as against four irrigations (6 cm depth) at 1.2 IW/CPE ratio on light soils. In general, for a summer crop IW/CPE ratio of 0.80 (6 cm depth) appears to be optimum at several locations.
From the results of experiment at different locations, the following irrigation practices can be suggested:
1. Under conditions of adequate water availability, irrigation at 12 to 15 days interval in black soils and at 10 to 12 days interval in light soils is optimum for high yield
2. If irrigations are to be scheduled based on DASM, 40 per cent level of depletion will be optimum when water supply is not a limiting factor. If the schedules are based on IW/CPE ratio, 0.75 ratio will be optimum
3. At times of deficit water supplies, three irrigations (6 cm depth) at three critical stages of bud initiation, flower opening and seed filling could be optimum during rabi. Summer crop, however, require another irrigation at disc formation stage.
4. Scheduling irrigation at 50 per cent DASM or at 0.75 IW/CPE ratio during the three critical stages and at 75 per cent DASM or at 0.5 ratio during other stages can minimise the irrigation needs at deficit water supplies.
Essay # 4. Irrigation Practices Used for Growing Soybean:
Soybean is a kharif rainfed crop in northern parts of the country. In central parts, it is largely grown as summer irrigated crop. It is grown as postrainy season crop on stored soil moisture in black cotton soils and as irrigated crop during summer in southern parts of the country.
In general, kharif crop may not receive irrigation, except at times of prolonged drought, if facility exists for irrigation. Critical stages for irrigation are flowering and pod development, when the crop needs around 8 mm per day. Soybean has extended period of flowering. The late flowers developing into mature pods can compensate early flower drop due to soil moisture stress.
Scheduling irrigation at 50 per cent DASM or at 0.6 IW/CPE ratio is optimum for soybean. At these levels, light soil needs irrigation once in 10 to 12 days and heavy soils once in 18 to 20 days. Depending on the level of management, the water use efficiency ranges from 0.4 to 0.7 kg m-3.
Recommended irrigation practices are:
1. Where irrigation water is not a limiting factor, scheduling irrigation at 50 per cent DASM or at 0.6 IW/CPE ratio is optimum for rabi and summer soybean. At these levels, light soil needs irrigation once in 10 to 12 days and heavy soils once in 18 to 20 days
2. At times of deficit water supplies, irrigation may be scheduled at 50 per cent DASM or at 0.6 IW/CPE ratio at critical stages and at 75 per cent DASM or at 0.4 ratio during other stages
3. If water is available for only one irrigation, it should be applied at late flowering when small pods begin to appear. If there is scope for two irrigations, first irrigation should be a presowing irrigation for adequate stand establishment in addition to the above. A third irrigation where possible will give best results if given at the beginning of pod filling.
Essay # 5. Irrigation Practices Used for Growing Castor:
Castor is usually a kharif rainfed crop and it responds to irrigation at times of prolonged drought spells during the crop season. One or two irrigations during the drought period can double the yield. Supplemental irrigations, if drought persists, must be given at primary spike development or secondary spike initiation. Flowering and seed developmental stages are considered critical stages for irrigation.
Improved varieties and hybrids are grown as irrigated crops during rabi, especially in Andhra Pradesh, Gujarat and Maharashtra. Castor can extract moisture from deeper soil layers due to its deep root system. As such, it is desirable to give relatively heavy irrigations than frequent light irrigations.
Suggested irrigation schedule for rabi castor is:
1. If the water supply is adequate, first irrigation must be given at 50 DAS or around full flowering of primary spike. Subsequent irrigations may be given at an interval of 20 days. A crop of 180 days duration requires around 6 irrigations for optimum yield.
2. At times of deficit water supplies, first irrigation must be given at primary spike development or secondary spike initiation followed by one or two irrigations during flowering and seed formation
3. If irrigations are to be scheduled based on DASM, 50 per cent level should be at critical stages and 75 per cent level at other stages
4. An IW/CPE ratio of 0.6 could be ideal at times of adequate water supply and a ratio of 0.4 appears to be ideal at times of deficit water supplies.