Crop Planning considering Water requirements and availability of water

Introduction

Water is one of the most important inputs essential for the production of crops. Normally a crop has to be irrigated before soil moisture is depleted below 50% of its availability in the root-zone. Hence water management is plan for the use of water for better utilization in agricultural. Hence crop planning should be done considering 1. Water requirement and 2. Availability of water.

WATER REQUIREMENT

Water requirement is differ according to crops and soil type. The water requirement of crops is that quantity of water required by the crops within a given period of time for their maturity and it includes losses due to evapotranspiration plus the unavoidable losses during the application of water and water required for special operations such as land preparation, puddling and leaching. The quantity of water needed for irrigation on different soil types per meter depth of soil profile at 50% of soil moisture availability is as follows. Sandy soils (25-50 mm), Sandy-loam (45-80 mm), Loam (70-110 mm), Clay-loam (80-120 mm) and Heavy clay (100-140 mm). The water requirement of different crops is given below-

• Rice

The amount of water required for growing rice is varies widely under different conditions: - 1000-1500 mm- heavy soils high water table, short duration variety, Kharif season. 1500-2000 mm- medium soils Kharif or early spring season. 2000-2500 mm- light soils, long duration varieties during Kharif, medium duration varieties during summer. For low land rice, the practice of keeping the soil saturated of submergens of about 5 cm throughout the growing period is beneficial.

• Wheat

It requires about 4-5 irrigation. The dwarf wheat needs more wetness and the optimum moisture range is from 100-60% of availability. For tall wheat the optimum-moisture range is from the field capacity to 50% of availability.

• Barley

About 2-3 irrigation are adequate and the optimum soil moisture ranges from the field capacity to 40% of availability.

• Maize

The optimum soil moisture range is from 100-60% of availability in the maximum root-zone, which extends from 40-60 cm on different soil types. In the northern parts 2-3 irrigation are required before the onset of the monsoon. In Karnataka 2,5 irrigation are necessary during Kharif and Rabi respectively. At Rajasthan 4 irrigation (500 mm of water) are required during Kharif.

• Sorghum and Other Millets

The optimum moisture range is from the field capacity to 40% of the availability. At boot stage and grain development, the water requirement is vary important.

• Pluses or Grain Legumes

When grown alone, 1 or 2 irrigation would be beneficial. The grain legumes (gram, lentil, pea and Indian bean) are irrigated 2 or 3 times during their growth.

• Oilseeds

The crops are generally grown under rainfed conditions. Groundnut – 8 to 10 irrigation of about 50 mm each are applied at 10-15 days interval during its growth period. Safflower, Mustard and Linseeds are grown alone are mixed with cereals should receive 3 or 4 irrigation during their growth.

• Cotton

The optimum moisture range of soil moisture for the crop is from the field capacity to 20% of availability in 0-75 cm of the root-zone. Water requirements varied from 400-800 mm under different conditions and about 4-7 irrigation are required for cotton.

• Jute

The optimum moisture regime is from the field capacity to 70% of availability in the maximum root-zone of the crop which can extends to about 45 cm of soil depth.

• Sugarcane

The optimum soil moisture for sugarcane has been found to be 100-50% range of availability in the maximum root-zone, extending upto 50-75 cm in depth. In the north, the crop is planted during February-March and irrigated till the commencement of the monsoon. In Maharashtra irrigation is required throughout the year (2800-3000 mm per year).

• Tobacco

For cigar, hookah and bidi tobacco the optimum moisture regimes are from the field capacity to 70, 60 and 50% of the availability respectively. Cigar tobacco needs light and frequent irrigation during 4 months. For hookah tobacco, 12-13 irrigation of 50 mm of water is required.

• Forage Crops

The optimum moisture range is from field capacity to about 75% of availability. Berseem requires about 20 irrigation during its growth at intervals of about 20 days- December-January, 15 days-November-February-March. And 10 days-September-October-April. For Lucerne 1800 to 2000 mm of water require during the first year of growth.

• Vegetables

The soil moisture should range between 70-80% of availability in the maximum root-zone. Potato needs water at intervals of 10-12 days. Onion and Garlic need very frequent irrigation about 3 weeks before maturity the irrigation is delayed to enhance the keeping quality of the bulb. Tomato needs irrigation at intervals of 10-12 days during summer and 15-20 days during winter. The optimum moisture regime is from 100-50% of the availability in case of cabbage, cauliflower and knol-khol. Water-melon and musk-melon need water at intervals of 8-10 days. Other crop of cucurbitaceae family needs irrigation at intervals of 10-12 days during summer.

• Spices and Condiments

Important crops are turmeric, ginger, chillis, ajwan, cumin and coriander. Turmeric and ginger should be irrigated to maintain 100-60% of the available moisture in the maximum root-zone, the top 50 cm of the soil. Chillies should be irrigated to maintain 100-50% of the available moisture to about 60 cm in the soil. Coriander, cumin and ajwan need irrigation at intervals of 10-12 days on light soil and 15-20 days on heavy soils.

• Fruit-trees

For fruit trees soil moisture should be maintain in the range of 100-75% of availability. On the full development of the root-zone down to 75-90 cm, the crops may be irrigated when 2/3 of the available moisture is depleted during blossoming, fruit settings are fruit enlargement. Papaya and banana needs irrigation at intervals of 8-10 days in a tropical climate. The date palm needs regular irrigation during flowering and fruiting to produce good yields.

• Coffee

To irrigate coffee after the cessation of the monsoon rains during flowering to avoid flower shedding is of profitable.

AVAILABILITY OF WATER

When the land does not receive any irrigation, the cultivator takes a single crop in Kharif season on the available moisture in the soil. If the soil is heavy, a second crop in Rabi season after a short duration crop in Kharif season, but two seasonal or perennial crops is not beneficial. When irrigation becomes available the cropping plan can include heavy perennials like sugarcane and banana, light perennials like guava or orange, two seasonal crops like long staple cotton, chillies, turmeric etc. besides Kharif and Rabi seasonal crops and also follow double cropping such as groundnut green gram, black gram etc. followed by wheat or rabbi jowar, kharif jowar or cotton followed by wheat, gram or some vegetable to seasonal crop followed by summer groundnut or some vegetable crop. The cropping plan in irrigated area is more intensive.

Green manuring can also be followed maintain the fertility of the soil and to reduce the expenditure on organic manures and fertilizers. With the possibilities of double cropping its should see that it does not become lopsided.