How Effective Are Drip Irrigation Systems

The article evaluates the efficiency, effectiveness, social, economic and environmental impacts of the drip irrigation system. The drip irrigation system has the potential to increase the agricultural productivity and also to reduce water usage required for irrigation. It is a system of pipes and tubing located under the soil. Water is passed through these pipes which end at near the roots of the plants. This makes the water loss minimal. Initial stage is designing the system and its installation follows it. The article states the advantages and disadvantages of the system and also cites evidence with regard to the social, economic and environmental aspects.

Poverty is one of the primary concerns the world faces in its road to development. Eradication of poverty tends to be the prime aims of governments worldwide. Lack of proper nutrition is a major cause contributing to poverty. Improving agricultural standards can help in producing more food and thus counter the lack of food factor. One way to improve agricultural standards is to develop the irrigation methods used. Irrigation is closely related to poverty. Irrigation benefits the poor through higher production, higher yields, low risk of crop failure and higher and year round farm and non-farm employment. Irrigation leads to high value market oriented agricultural production [1]. However, in developing countries like India, the agricultural sector is heavily dependent on the south-west monsoons. In view of the rising temperatures worldwide due to global warming and changes of weather patterns associated with it, dependence on rains is not always a possible solution. Failure of proper rains can cripple the agricultural sector which can lead to an overall rise in poverty. Thus efficient methods of irrigation need to be developed. The drip irrigation system is one such method of irrigation that is being utilised. Drip irrigation is water saving, efficient and effective watering system .The article focuses on the different aspects of the drip irrigation system, its contribution in poverty alleviation and the social economic and environmental impacts of this technology.

Subsurface drip irrigation or SDI is another way of terming a drip irrigation system. As stated by C. Shock, drip irrigation is the slow even application of low-pressure water to soil and plants using plastic tubing placed near the plants’ root zone [8]. Water is supplied to the soil at very low rates from the system of the plastic tubing pipes which are fitted with emitters at the ends. Therefore loss of water through evaporation, water run-off and percolation is minimized to a great extent. Also water contact with the stems, leaves and fruits of the plant is reduced which helps in prevention of formation of disease on the plant. Since the tubing is buried under the soil, it is less at risk of damage due to weeding and cultivation activities.

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Designing a subsurface drip system requires an experienced qualified designer. As G. Harris has stated, proper hydraulic design is the initial step in installing a successful SDI system [5]. This will ensure that the system effectively deals with the constraints imposed by the crop and soil characteristics, field size, topography, water supply and shape. The system must be capable of meeting the crop water need during the peak water demand times. A block or zone, which is the portion of the field that can be watered at the same time, is determined by the characteristics of the drip tubing selected. The optimal tube spacing is determined by the soil characteristics and the depth of tube placement. If the installations are too deep it will restrict the availability of surface applied nutrients limits the effectiveness of the system for crop germination. Adequate flushing velocities must be allowed for in the design to remove sediments from the emitters. This helps to prevent the SDI system from getting clogged and increases the system’s life.

Following the designing comes the installation part of the SDI system. Proper installation ensures that the system performs optimally and it also determines the life of the system. Installation is done in sites which have not been cropped recently as insect activity or weedy areas could destroy the pipes within days of installation [6].Initially location of the tubing is marked out. A subsoiler can be used or if more accurate positioning is needed, GPS can also be used. Specialized injectors are available for installation of the SDI pipes. The power and water source limitations are to be considered during the installation of the system. Filters are also used which helps in removing particles and keeps the emitters from getting clogged.

The major feature of this system that makes it highly desirable is that the water use efficiency will be better compared to other systems or methods of irrigation. Evidence put forward by C.R. Camp show that drip irrigation systems implemented in Virginia require 30% less water compared to sprinkler irrigation for cultivating corn [3]. For cotton, the water usage was reduced significantly by 40%. Implementation of the system in Hawaii helped the farmers to get a greater yield than when using sprinkler irrigation system [4]. Additional advantages include:

Drip irrigation systems are suited to farms having uneven topography or soil texture.

Precise application of nutrients is possible. Timely application of herbicides, insecticides and fungicides is possible.

The drip irrigation system can be automated.

Irrigation can be carried out day and night regardless of the wind, daylight availability or other cultivation activities [7].

The SDI system can be used for fertilizing. Nutrients can be supplied in a sustained way, and regulated in rate and composition, according to the crop requirements [7].

The hydraulics help in easy water control the number of points provides excellent uniformity of supply.

There are a number of disadvantages for the drip irrigation system.

Initial investment is quite high for this system.

Root development is limited and hence resulting in root rot and dust problems [7].

The emitters can get clogged frequently and cleaning it is a costly and time consuming process.

Accumulation of salts might occur at the interface between the wet and dry zones of the soil.

It is generally accepted that irrigation can transform society as well as land and landscapes. Drip irrigation has brought about a number of positive and negative social impacts. It helps in alleviating poverty in irrigated areas, minimizes the differential distribution of benefits across farmers and increases the social benefits [7]. The positive effect it has brought on the demographics of the Waitaki valley has helped arrest the population decline [9]. The additional population would not only strengthen the social structure and networks but also increase economic growth. Thus services such as health and education would become more viable. On the other hand, automated drip irrigation systems tend to require less labour and in low wage economies, where job opportunities lag behind growth in labour force owing to rise in population, reducing hired labour can be socially problematic [10]. This leads to further unemployment.

Considering the economic aspects, drip irrigation systems have helped farmers to attain better profits due to higher yield. Farmers can conserve water more and also increase the productivity of their farms. The yield of cotton increased by 21% in Dalby and Moree while in Lucerne, yield improvement was between 13-34% [5]. The profits obtained in tomato cultivation in California were about 867 to 1493 dollars more [12]. Water usage was reduced by 45% for corn cultivation in the Great Plains in USA [13]. In spite of all these a major hindrance in the implementation of the system is the high initial cost. Designing and installation requires qualified people and moreover the cost and time for maintenance of the system is also on the higher side. However in the long run farmers can make up for the high initial costs with the higher amount of yield they obtain.

The drip irrigation helps in improving the soil surface and the environment. It allows pre treated coalbed methane waters to flow into the root zone of an agricultural field which minimized environmental impacts by storing detrimental salts in the vadose zone [11]. It reduces off-farm movements of fertilizers and pollutants and improves the water use efficiency of irrigated agriculture [3]. It offers potential for increased water and nitrate fertilizer efficiency and decreases ground water contamination by NO3 [14]. The certain negative traits that the system has on the environment are that root rot may occur and levels of salinity rises. Root development is affected leading to insufficient protection against lack of water and poor root anchorage [7].

Overall, the drip irrigation system is an effective way of irrigation. It saves on water usage and allows farmers to increase their farm output. The increased outputs helps counter the rise in food demand and helps the poorer sections of the society with more food at cheaper prices. Evidence presented in the article show the increased crop yield. Even thought the technology comes at a higher price, the effects of implementing it will be long lasting and positive.