Why is sprinkler irrigation practiced in arid and semi-arid regions?
Answers
Sprinkler irrigation systems apply irrigation water to the plants from above. In some greenhouse and shade structures, plumbing is mounted overhead. Overhead installation does have the advantage that the plumbing is protected from mechanical damage by vehicles and persons. Installations can also have supply lines buried in the soil below the crop or mounted to the infrastructure. Movable sprinkler systems are also in use in various parts of the world. Crops for which it is undesirable to wet the foliage (e.g. some ornamental crops) can be irrigated with micro-sprinklers to the base of the plants. One positive feature of sprinkler irrigation from above is that it supplies water to most of the top of the root zone with relatively low investment and low maintenance costs (Heemskerk et al., 1997). Each sprinkler head type has a particular circular water distribution pattern; multiple sprinkler heads with short distances between emitters can be used to create a more uniform distribution pattern, but inherently sprinkler systems have uneven water distribution. For some crops, wetting of the foliage introduces a higher risk of plant disease development.
Micro-sprinkler irrigation systems, which deliver water to the base of the plants, overcome some of the drawbacks of overhead supply of water: there is no light interception due to overhead pipes and the crop becomes only partly wet. However, the plants themselves interfere with the even distribution of the water and prevent irrigation of large surface areas so that many more sprinkler heads are required, each delivering smaller amounts of water, to provide water to all plants.
Modern sprinkler installations are typically designed for the type of cropping system and the specific demands of the grower. In outdoor nursery production, sprinkler emitters may include rotating impact sprinklers and gear-driven ones which throw a stream of water 2–20 m to ones with no moving parts which provide a circular spray pattern with a radius of 1–5 m. In greenhouse production, sprinkler systems are less common and emitters are frequently micro-sprinklers which deliver water at lower rates with greater precision to the base of the plants. Emitters have also been designed with other features that improve performance; pressure compensation assures that emitters deliver water only while the pressure is between specified minimum and maximum levels to avoid leaking of the emitters.
Due to the low expense of sprinkler systems relative to other systems, it is the most widely used system in outdoor container production. But even in these types of operations, growers typically use sprinkler irrigation only with tightly spaced plants. Plants which are spaced far apart are typically irrigated with drip or micro-sprinkler systems to reduce the amount of irrigation that misses the plants entirely. In greenhouse production, sprinkler irrigation is less commonly used due to the drawbacks mentioned above.Sprinkler irrigation systems apply irrigation water to the plants from above (Fig. 5.2). In some greenhouse and shade structures, plumbing is mounted overhead. Overhead installation does have the advantage that the plumbing is protected from mechanical damage by vehicles and persons. Installations can also have supply lines buried in the soil below the crop or mounted to the infrastructure. Movable sprinkler systems are also in use in various parts of the world. Crops for which it is undesirable to wet the foliage (e.g. some ornamental crops) can be irrigated with micro-sprinklers to the base of the plants. One positive feature of sprinkler irrigation from above is that it supplies water to most of the top of the root zone with relatively low investment and low maintenance costs (Heemskerk et al., 1997). Each sprinkler head type has a particular circular water distribution pattern; multiple sprinkler heads with short distances between emitters can be used to create a more uniform distribution pattern, but inherently sprinkler systems have uneven water distribution. For some crops, wetting of the foliage introduces a higher risk of plant disease development.
Micro-sprinkler irrigation systems, which deliver water to the base of the plants, overcome some of the drawbacks of overhead supply of water: there is no light interception due to overhead pipes and the crop becomes only partly wet. However, the plants themselves interfere with the even distribution of the water and prevent irrigation of large surface areas so that many more sprinkler heads are required, each delivering smaller amounts of water, to provide water to all plants.