Principles of Irrigation Management for Vegetables

*Selda Ors, Ustun Sahin, Melek Ekinci, Metin Turan and Ertan Yildirim*

#### **Abstract**

Vegetables have a very high percentage of water content. Some of the vegetables, such as cucumber, tomato, lettuce, zucchini, and celery contain over ninetyfive percent of water. As a result of the high-water content in the cells, they are extremely vulnerable plants to water stress and drought conditions. Their yield and quality are affected rapidly when subjected to drought. Therefore, irrigation is essential to the production of most vegetables in order to have an adequate yield with high quality. However, over-irrigating can inhibit germination and root development, decrease the vegetable quality and post-harvest life of the crop. Determination of suitable irrigation systems and scheduling to apply proper amount of water at the correct time is crucial for achieving the optimum benefits from irrigation. This determination requires understanding of the water demand of the vegetable, soil characteristics, and climate factors. All these factors have major impact for the success and sustainability of any vegetable irrigation. This section contains fundamentals of water requirements on different vegetables and summarizes important issues related to soil, water, and vegetable growth relations together with irrigation management concept by evaluating the challenging issues on the selection of proper irrigation system, suitable irrigation timing, and other parameters to increase vegetable yield in an irrigated agriculture.

**Keywords:** vegetable, irrigation, water, quality, yield

#### **1. Introduction**

Water is one of the important inorganic resources for all living things to maintain their vital events. Therefore, it plays a major role when it comes to consumption of nutrition in human body directly and indirectly. According to the World Health Organization, 100 liters of water per day is needed to optimally meet an individual's basic needs [1]. However, 4 billion people in the world already live in water-scarce areas. By 2050 global demand for water will increase by 20–30% and water scarcity, exacerbated by climate change, could cost some regions up to 6% of gross domestic product [2]. Besides human use, water is also very important due to the fact that its deficiency significantly restricts plant production. Water in agriculture is central to feeding the planet, providing livelihoods, and building resilience to climate shocks and extremes.

Irrigation, which is the largest usage? of water, covers the functions related to the production of cultivated plants. One of the most important conditions for the regular development of plants is to have sufficient water in the root zone during the growing season. Irrigation is the delivery of the water, to the plant root zone where the required water amount cannot be met with any precipitation. The history of irrigation begins with the history of humanity. It is known that even before the birth of civilizations, primitive irrigation techniques were used for crop production. Many civilizations have developed in areas where water is available, and irrigation can be implemented. Today, just 20% of the world's croplands are irrigated but they produce 40% of the global harvest which means that irrigation more than doubles land productivity [3].

Most of the cultivated crops needs irrigation during their growing period. Some of the field crops such as grain, wheat, rye etc. can survive under rainfed agriculture. But when it comes to vegetables, the requirement of irrigation turns into a requirement. Vegetables comprise very high percentages of water. Some of them, such as cucumber, tomato, lettuce, zucchini, and celery contain even over ninety-five percent of water [4]. Due to high levels of water content in the cells, they are critically vulnerable plants to water stress and drought conditions. Their yield and quality are affected rapidly when subjected to drought. Therefore, irrigation is essential to the production of most vegetables for having a good yield with high quality. However, over-irrigation can inhibit germination and root development, and decrease vegetable quality and post-harvest life of the crop. This can be concluded as vegetable crops may experience water stress in two different ways: firstly, when there is insufficient amount of water (drought stress), or secondly, when there is excess amount of water (waterlogging or soil water saturation). Under these circumstances the amount of irrigation water, when to irrigate and how to irrigate are the questions that have to be considered carefully. The selection of proper irrigation management is vital to maximize vegetable quality, yield, and water use efficiency while minimizing environmental impacts. Deciding suitable/ efficient type of irrigation system for vegetables is quite challenging as there are so many variables such as water amount and quality, soil type, vegetable grown, and economic limitations. Once all the parameters are optimized, the highest yield could be obtained with most favorable water amount and energy.
