Explain drip irrigation method. Describe role of irrigation scheduling for maximizing irrigation efficiencies.

 In drip irrigation, also known as trickle irrigation, water is delivered at or near the root zone of plants, drop by drop under low pressure. As you can see in Fig.3.4, the system comprises of pla~tic components such as pipes and drippers in addition to filter and fertilizer applicator. This method can be the most water-efficient method of iirigation, if managed properly, since evaporation and runoff are minimized. In this method, fertilizer is applied with drip irrigation known as fertigation. If a drip system is operated for too long of a duration or if the delivery rate is too high, it may result in deep percolation. As water is applied in the vicinity of the plants, only a part of the area is wetted. As a result of this, there is considerable saving of water. The fertilizer application is also highly efficient due to its use with irrigation water. Due to optimum use of water and nutrients, not only crop productivity is high, its quality is also superior as compared with surface irrigated crops. The drip method is suited under following conditions.

· Widely spaced crops such as orchard crops

· Undulating lands with high infiltration rates

· Widely spaced crops

· Saline irrigation water

Advantages

· Considerable saving of wateras only part of area wetted.

· Less amount of fertilizer used.

· Relatively saline water usable.

· High irrigation efficiency (>90%).

· High fertilizer efficiency.

· High yields and better quality of produce.

· Less weed infestation.

Limitations

· High initial investment

Irrigation Scheduling

Irrigation scheduling helps in deciding as to when and how much water to apply to a field in order to maximize irrigation efficiencies by applying the exact amount of water needed to replenish the soil moisture to the desired level. Irrigation scheduling not only saves water and energy but enhances crop productivity as well. Irrigation scheduling criteria is based on soil moisture content and soil moisture tension.

The quantity of water to be applied depends on the irrigator's strategy. For example, \ the irrigator can replenish the soil moisture to field capacity or apply less. If no rain lis expected and the irrigator wishes to stretch the time between irrigations, it is I advantageous to refill the soil profile to field capacity. If rain is expected, it may be ,wise not to fill the soil profile to field capacity, but leave some room for rain.

Proper irrigation scheduling enables the farmer to apply the exact amount of water. to achieve higher irrigation efficiency. The accurate measurement of the volume of water applied or the depth of application is very crucial. Irrigation scheduling offers following advantages:

· Enables the farmer to schedule water rotation among the various fields to minimize crop water stress and maximize yields;

· Reduces the farmer's cost of water and labour through fewer irrigations, thereby making maximum use of soil moisture storage; Water Harvesting for Crop Production

· Reduces fertilizer costs by holding surface runoff and deep percolation (leaching) to minimum;

· Increases net returns by increasing crop yields and crop quality; and

· Results in additional returns by using the "saved" water to irrigate non-cash crops that otherwise would not be irrigated during water-short periods.

Uniform water distribution across the field isimportant to derive the maximum benefits from irrigation scheduling and management. Accurate water application prevents over or under irrigation.

The amount of water required for irrigation can be defmed in terms of Duty and Delta. Duty represents the irrigating capacity of a unit of water. It is the relation between the area irrigated and the quantity of irrigation water required during the entire period of growth of that crop. Delta is the total depth of water required by a crop during the entire peri d, the crop is in the field and is denoted by. For example, a crop requires about nine.. , ,.c[,-:15' an interval of 20 days and a water depth of 10 cm in every watering. Considering L .rop period of six months, the total water requirement i.e. delta of that crop is 9 x 10 cm = 90 cm = 0.90 meter. 

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