Irrigation is pouring water to the soil using proper methods and in proper times as required by the plant growth as a result of insufficient rain. The success of irrigation depends on the selection of the most proper irrigation method as per the conditions and planning, projecting, establishing and operating the irrigation system necessary for that method.
Irrigation methods are divided into two groups according to the features related with deliver and application of water on soil. These are surface irrigation and pressure irrigation methods. The first method, surface irrigation methods such as flow irrigation, basin irrigation, border irrigation and furrow irrigation.
The water bought to the fron of field generally through open channels is delivered to furrows through irrigation siphons or orifices. The furrows are reopened every year. Very little inclinations are demanded for flow.
In basin irrigation method, water is delivered to borders whose corners have been heightened by soil barriers through this method.
The use of border irrigation method resembles with basin irrigation method. However, width of the basin is shorter, the lenght of the basin is longer and basin ends are wider. A certain inclination is required for flow in the border irrigation method.
In flow irrigation technique, the water angled from front field channel is randomly spread onto field to cover soil surface.
In the second method, pressure irrigation method, the water is given to soil by using closed pipe systems with an additional energy or a drawing effect. In sprinkler irrigation, the water is given to the soil surface under a little pressure and through laterally located sprinkler heads spraying thin drops.
In drip irrigation system, irrigation water necessary for plant growth is applied around the root of plant in the form of drops through specially designed tools named droppers located on or inside the lateral pipe.
Irrigation method should be selected in accordance with the position of water source; flow, quality and economy of irrigation water; soil structure; condition of ground water; salinity, drainage and stone content conditions of the land; slope level and erosion risk of the land; climatic conditions such as wind, heat and frostiness; variety of plants; and socio cultural levels of farmers.
Sprinkler or drip irrigation methods are among pressure irrigation methods should be preferred if the pumps are used for bringing water to the land.
While bringing water to the field, one of the pressure irrigation methods can be used with the selection of a proper pump. Moreover, if the water source is placed close enough to land level and if the necessary pressure is sufficient enough, pressure systems should be preferred.
If the water is obtained through angling way from river or pond, it is proper to use surface irrigation methods.
If the water carries unfamiliar materials such as sand, gravel or moss, pressure systems should not be used because pipes and nozzles may clog or these systems should be used by adding a good filtration system.
Moreover, the water should be analyzed for its salt content. If the saltcontent is not at an acceptable level, drip irrigation or surface irrigation methods with good running underground drainage system should be preferred.
Because heavy soils keeps water in a long time, surface irrigation is applied in such condition. Pressure irrigation methods should be used on sandy soil because water can easily get into deep of this kind of soil. For that reason, the water should often be given in little amounts. And also pressure irrigation methods having low soil depth and not requiring landscape grading should be preferred.
If ground water level is high on the land that irrigation is made, irrigation water should be given in a controlled way not increasing the ground water level. If the ground water level increases to the root of the plant, the roots can not take the necessary oxygen from soil for their growth. Pressure irrigation methods can be applied successfully on this kind of soil.
Beside salt content of irrigation water, salt content of soil also carries importance. If both irrigation water and soil include salt above acceptable level, drainage systems should be established in order to remove the salt accumulated with more water application through basin irrigation method on the lands having such drainage system. If such establishment does not exists, drip irrigation methods will give successful results in these conditions.
If land contains more stones, landscape grading may not be economic because landscape grading costs for such lands will increase. For that reason, pressure irrigation methods not requiring landscape grading should be preferred for such lands.
If the land has many slopes or a weaving structure, surface irrigation methods will create erosion problem on sloping lands and giving water equally to field will not be possible on fields with weaving structure. Surface irrigation can be applied on lands with weaving structure after landscape grading. Especially in sprinkler irrigation method used on sloping lands, erosion can be prevented by the application of high irrigation pressure and minimizing the drip size.
Surface irrigation methods can be applied through opening channels in parallel to inclination on land with little slope.
In production areas where the wind speed is high and always toward the same direction and the weather heat is high and relative humidity is low, the water can be used in a most cost-efficient way by choosing drip irrigation method instead of sprinkler irrigation method among pressure irrigation methods.
However, sprinkler irrigation method should be preferred on lands where late spring frost is seen frequently, rainfall is sufficient and land requires irrigation in certain periods.
For the plants such as sunflower or cotton planted in rows, furrow irrigation method among surface irrigation methods can be applied successfully. Sprinkler irrigation method is not offered for the irrigation of long plants such as corn, sunflower or for lands where epidemic diseases can be seen often.
If the plants are planted densely or scattered as grains, they should be irrigated by basin irrigation methods.
Because drip irrigation method enables more controlled irrigation for greenhouse crops, it can be applied successfully. Because the contact of water and flower will create negative effect on fruit bearing period of some plants such as tomato, sprinkler irrigation method should not be preferred.
Surface irrigation methods draining the water to the depth give more successful results for plants with long roots.
Pressure irrigation methods require less first investment cost than surface irrigation methods on the lands in need of landscape grading, terrace or drainage establishment.
However, first establishment costs of pressure irrigation systems are higher on coditions not requiring cost of grading and terrace. Continuous operation and maintenance costs should be taken into consideration beside establishment costs. Such costs will be less for surface irrigation methods on the lands where labor costs are cheap and energy costs are high.
However, surface irrigation methods are not economic for enterprises in which intensive agriculture is done and land is valuable because a part of the land, in such enterprises, is occupied by irrigation and thus whole land cannot be used.
After the selection of irrigation method, another point to be considered is a misconception of “the more irrigation, the more yield”. The excessive irrigation will result in fewer yields than expected. It will also bring together many problems such as erosion, aridity and environmental pollution as well as increase in operation costs. During transition to irrigated agriculture from non-irrigated agriculture, agricultural technique should be changed as per new conditions. Best wishes from Istanbul / Turkey
An irrigation method video included at the top right side of this page !
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