Drip and Sprinkler Irrigation Method | Agriculture Optional Notes for UPSC PDF Download

Sprinkler Irrigation Method

In this agricultural water application technique, water is delivered to the soil in the form of a spray using a network of pipes and pumps. It essentially simulates artificial rainfall, yielding highly effective results. Although it is an expensive process, it is extensively used in the United States. It is adaptable for a wide range of soil types and different terrains and slopes. This method is advantageous for various crops because it meets the essential requirement of uniformly distributing water. It holds great potential for irrigating regions in Rajasthan, India, where other surface irrigation methods face significant challenges.

Despite the numerous advantages it offers over alternative methods, this technique has not gained popularity in India, primarily due to the economic constraints of being a developing nation. It not only involves high costs but also demands a substantial level of technical expertise. Proper design and efficient operation are crucial for the success of this method. Special measures must be taken to prevent the entry of sediment and debris, which can be highly detrimental to the sprinkler equipment. Debris can clog the nozzles, disrupting the water application on the land, while silt's abrasive action can cause excessive wear on pump impellers, sprinkler nozzles, and bearings. The system's design should ensure that all the sprayed water is absorbed into the soil, with no runoff from the irrigated area.

Conditions that encourage the adoption of this method include the following:

• When the land has irregular topography that is unsuitable for surface irrigation.
• When the land has steep gradients and easily erodible soil.
• When the soil is either excessively permeable, making surface irrigation ineffective, or highly impermeable.
• When the water table is high.
• When the area has low seasonal water requirements, such as coastal regions.
• When specific crops are to be grown, including those that require humidity control (e.g., tobacco), crops with shallow root systems, or crops needing frequent and substantial irrigation.
• When water is scarce and challenging to obtain.

Sprinkler systems can be categorized into three types:

• Permanent system: In this system, pipes are permanently buried to avoid interference with farming activities.
• Semi-permanent system: Main lines are buried, while the lateral pipes are portable.
• Portable system: Both the main and lateral pipes are portable, allowing for flexibility and movement from one farm to another.

Within a sprinkler irrigation network, there are mains and sub-mains that carry pressurized water. Revolving sprinkler heads are typically mounted on rising pipes connected to the lateral pipes. These sprinkler heads release water in a forceful spray. In cases where sprinkler heads are not used, pipes have perforations and nozzles to release water, which falls onto the ground. Perforated pipe systems generally operate at low pressure, while revolving head sprinklers can function effectively at both high and low pressure, depending on the type of rotary head used.

Here are the advantages of sprinkler irrigation:

• It eliminates seepage losses that occur in earthen channels used in surface irrigation methods and ensures that only the required amount of water is used.
• Land leveling is unnecessary, avoiding the removal of the top fertile soil, a common practice in other surface irrigation methods.
• No cultivation area is lost for creating ditches, as is often the case in surface irrigation methods. This can lead to an increase of approximately 16% in the cultivable land.
• The sprinkler system applies water at a rate lower than the soil's infiltration capacity, thus preventing surface runoff and its associated problems, such as water loss and topsoil erosion.
• Fertilizers can be evenly distributed because they are mixed with the irrigation water itself.
• Sprinkler irrigation helps leach salts from the soil and prevents issues like water-logging and salinity.
• It requires less labor, making it practical in areas where labor is both costly and scarce.
• This method can achieve efficiency of up to 80%, meaning that up to 80% of the applied water can be stored in the root zone of plants.

Here are some of the limitations associated with sprinkler irrigation:

• Strong winds can distort the sprinkler pattern, leading to uneven distribution of water across the crops.
• In regions with high temperatures and strong winds, there can be significant water losses due to evaporation.
• Sprinkler systems are not well-suited for crops that require frequent and substantial amounts of irrigation, such as paddy rice.
• The initial cost of installing the system is quite high, and its operation demands a high level of technical expertise.
• Only water that is free of sand and silt can be used, as water with these impurities can damage the pump impellers used in the system.
• The system requires a significant amount of electrical power to operate effectively.
• Soils with poor water intake, particularly heavy soils, cannot be efficiently irrigated using this method.
• Commercial use of the equipment necessitates a constant and reliable water supply.

Note: A well-known Indian company that specializes in the installation of sprinkler irrigation systems is "Premier Irrigation Equipments (Pvt. Ltd.), based in Calcutta, with an office in Delhi as well. For specialized information in this field of irrigation, you can refer to this company and its publications.

Drip Irrigation Method

Drip irrigation, often referred to as trickle irrigation, is a modern technique used in areas with severe water shortages and salinity issues. This method involves the slow and direct application of water to the root zone of plants, minimizing losses due to evaporation and percolation.

The system comprises various components, including head, mains, sub-mains, laterals, and drip nozzles. Water is released uniformly and at a very slow rate from these small drip nozzles directly into the root area of the plants.

The head includes a pump to elevate the water, creating the necessary pressure of around 2.5 atmospheres to ensure the proper water flow through the system. The irrigation water is passed through a fertilizer tank to mix the fertilizer directly with the irrigation water and then through a filter to remove suspended particles and prevent clogging of the drip nozzles.

The mains and sub-mains are small-sized pipes, usually made of flexible materials like black PVC. They are typically buried or laid on the ground and should be appropriately sized to accommodate the system's design discharge.

The laterals are even smaller-sized pipes, typically 1 to 1.25 cm in diameter, made from materials like black PVC. They extend from the mains or sub-mains and can be up to 50 meters long, with one lateral line for each crop row. Specialized dual-chambered micro tubing, such as Hardie Biwall, made from linear low-density polyethylene, is used for laterals.

Drip nozzles, also known as emitters or valves, are fixed on the laterals at regular intervals, releasing water at very low rates, typically ranging from 2 to 10 liters per hour.

Similar to sprinkler systems, drip irrigation requires specialized knowledge and is not commonly adopted by traditional farmers. However, it is used in small nurseries, orchards, and gardens. "Jain Irrigation Systems Ltd., Jalgaon" is a well-known Indian company that specializes in this method of irrigation and can be contacted for assistance with designing such systems.