Irrigation Methods for Horticultural Crops
Methods of Irrigation:
The amount of water to be applied to crops depends on different factors. Different systems of irrigation are practiced for garden crops.
1. Flood System:
When the land is flat, the entire area is flooded by letting in water. This system is commonly practiced in canal or tankard areas, in wet lands for banana, and other crops. This is a water method as the water is supplied in excessive quantity. The entire area is allowed_to_saturate with water and the interval between two irrigations is kept fairly long. It also causes stagnation is shallow and ill drained soils.
2. Basin System:
This system is widely practiced on large scale all over the/world. A basin is a small patch or land bounded around a tree. It is usually a square with the tree in the centre. The soil gradually slopes down from, the base of the tree to the edge of tile basin, resulting in a trough. Circular basins are also made sometimes. Water let In from the main water channel first reaches the periphery, soaks the outer area and "gradually spreads towards the trunk, and thus is prevented from coming in contact with the tree trunk. This system is useful for loamy soils.
The basins, initially four feet square; are increased in size as the trees grow, and are gradually extended to even 40 feet square, roughly corresponding to the periphery of the trees. Roots or plants as a rule spread much further than the above ground portion./It is, therefore, necessary to irrigate a wide area to supply adequate moisture to the entire root zone. In very old plantation basins may not be suitable as the root system would have gone far beyond his size of the trees and irrigation of the entire orchard may be necessary. Basin system minimizes loss of water, and is economical.
3. Furrow System:
Furrow system of irrigation is commonly practiced in orchards in Western countries. The entire orchard is ploughed up and divided into furrows. The number of furrows between the rows of trees legends on the age of the plantation. When trees are young, a single furrow is sufficient A furrow is ordinarily about 200 to 300 feet long about 18 inches wide at the top and 6 inches deep, with sloping sides. The size of the furrow varies with the type of soil and slope of the land. Furrow run at right angles to the slope or gradient of the land. When the land is highly slopy the length of the furrow is reduced. Normally, for every. 100 feet of the length of the furrow a six inch gradient of fall is adequate. Furrows are kept hallow so that water may spread quickly all over the area. When furrows are deep the water is likely to be absorbed by deeper layers or the soil and water intake becomes high. Thus by adjusting the depth of furrows, the quantity of water to be applied to crops can be controlled.
4. Ring System:
In this system the water is applied in a ring around the tree. The method is recommended for citrus trees, is in this system the water is not allowed to touch the bark of the tree thereby reducing the chances or coller rot to which the trees are susceptible. The size of thering will increase as the trees grow.
In applying water to crops, care should be taken to see that the optimum quantity is applied at proper interval. The water applied should reach the entire root zone of the tree. For this it is necessary to study the relationship between the spread of trees and root penetration.
Cultivators usually guide the entire quantity of water from their well into main (one) channel and take it round each tree or sub – plot. Due to a large quantity of water rushing in a small channel, there is severe, erosion. Frequently, the sides of the channel break away and the rushing water erodes the soil. The water travels at a much faster rate horizontally than vertically. As a result of the quick flow of water, its penetration into the sub soil is poor. The water remains only on the surface and dries of quickly due to insufficient penetration into the soil. When the flow of water is fast, much vigilance and labour is necessary in guiding the water. This system is therefore, uneconomical and harmful.
Water has; therefore, to be applied to crops with a gentle flow so that it percolates deep into the soil rather than flow off superfluously. This will minimize loss or water and allow penetration to the root zone of plants. This is possible by using the furrow system of irrigation.
5. Border Strip or Modified Furrow System:
A better system of irrigation is the modified furrow system. Water is applied from one main channel simultaneously into several furrows. It is let out first in a main feeder channel where it rises up and flows uniformly into all the furrows at the same aped A good initial preparation of land is necessary. The land should be perfectly leveled with a gently slope.
In this system, water penetrates quickly into the deeper layers the horizontal movement is slow. There is thus deep penetration of water into the entire root zone of the crop. Erosion is almost eliminated due to slow flow of water supervision is easy, the main feeder or head channel alone has to be regulated and this saves considerable amount of labour.
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