Today, given the increasing global scarcity of water resources, and particularly in Iran, proper water management in agriculture is considered one of the most critical areas of food production. As the largest consumer of fresh water in the country, agriculture requires a more precise, scientific, and intelligent approach. Many farmers, despite their significant efforts, do not achieve the expected efficiency from their irrigation systems; the root cause of this problem is often a lack of familiarity with the basic principles of plant physiology and local climatic conditions. In this article, we aim to explore the various layers of irrigation management from the soil level to the plant canopy and present practical solutions in simple yet specialized language.

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To better understand how water resources affect various crops, it is recommended to refer to the following:

One of the most significant challenges farmers face is determining the precise water requirement of the plant at each growth stage. Every plant has a critical period during which water stress results in minimal damage. Using soil moisture sensors and calculating crop evapotranspiration (ETc) is a powerful tool for reducing personal guesswork. When we know exactly how much water must reach the roots, we not only prevent waste and extra irrigation costs but also prevent root rot caused by over-wetting or severe stress caused by excessive drought.

The impact of soil type on the irrigation schedule

آفات و بیماری‌های تره با آبیاری قطره‌ای - تصویر 1 — crop pests diseases drip irrigation leaf

Sun orientation (background) and soil texture are factors we sometimes overlook. In soils with high clay content, permeability is low, so irrigation should be applied in smaller volumes at shorter intervals to prevent surface crusting. Conversely, in sandy, light soils, water infiltrates quickly, causing the leaching of water-soluble nutrients; therefore, under these conditions, intermittent irrigation with larger volumes and the use of fertigation (applying fertilizer solution with irrigation water) are essential. Identifying your farm’s soil type through simple laboratory tests or even by observing water flow behavior is the first step in designing a customized irrigation plan.

One popular method that has been growing in recent years in semi-arid regions is drip irrigation. This system places water droplets directly in the active root zone, optimizing soil moisture while keeping the seedbed surface dry, which reduces weed growth and the occurrence of surface fungal diseases. However, drip irrigation has higher initial costs and requires ongoing maintenance to prevent nozzle clogging and sedimentation. Washing with mild acids at the beginning of the season and proper filtration of inlet water are two main requirements for the long lifespan of these systems.

Determining the correct irrigation scheduling

Irrigation at inappropriate times can destroy up to 40% of crop profitability. The best time for irrigation is early morning or dusk, as air temperatures are lower and evaporation rates from soil surfaces and leaves are reduced. Irrigating at midday heat, in addition to water loss, can cause localized scalding due to thermal shock and water droplets dripping onto leaves. Furthermore, frequent, short-duration irrigation stresses the roots, causing them to remain shallow in the soil surface and reducing soil permeability. After several years of improper management, topsoil becomes compacted and its water-holding capacity drops significantly.

For farms still using surface irrigation (furrow), proper channel construction and precise land levelling can increase irrigation efficiency by up to 30% without changing the system. Uneven land levels cause some areas to be waterlogged while others remain dry. Using a laser level or laser grading to correct field surface is an investment that pays off in the long term. Additionally, reducing water flow velocity in channels by creating gentle slopes prevents the washout of the capillary layer and the transport of nutrients to downstream areas.

آفات و بیماری‌های تره با آبیاری قطره‌ای - تصویر 2 — crop pests diseases drip irrigation herbs

Root and fungal diseases are directly linked to soil moisture management. When soil moisture remains above 80 percent of field capacity for an extended period, air in the soil pore spaces is displaced by water, causing root respiration to become impaired due to oxygen deficiency. This condition promotes the growth of phytopathogenic fungi, such as Pythium. Therefore, the Irrigation-Drainage cycle can function as a mechanical-biological method for disease control without increasing the need for chemical pesticides.

In addition to physical water management, fertilizer management is closely linked to irrigation. Many nutrients, such as calcium, magnesium, and boron, can become toxic at very high concentrations; therefore, they should not be injected with heavy irrigation water unless diluted in a specific solution. Potassium fertilizers are generally best injected with the final irrigation water so they can be translocated to the leaves before harvest to enhance grain quality. The use of liquid fertilizers in drip systems requires more precise filtration to prevent nozzle clogging.

Consideration of rainfall patterns and weather forecasts also plays a role in irrigation planning. If mild rainfall is forecast, delay irrigation by 24 to 48 hours to allow rainwater to penetrate deep soil layers and to prevent the loss of irrigation water. However, if heavy rain with thunder and lightning is forecast, irrigation should be suspended because surface runoff can cause soil erosion and root rot. Smart farmers utilize free natural water resources and implement flexible plans based on these conditions.

After the harvest, inspecting and auditing the irrigation system is of paramount importance. Leaks, broken connections, and clogged nozzles must be identified and repaired. Allowing the system to rest during the dormant period and properly maintaining pressure vessels prevents premature equipment wear. Maintaining transducers and electromechanical switches is also part of this cycle, which is often overlooked by farmers.

آفات و بیماری‌های تره با آبیاری قطره‌ای - تصویر 3 — crop pests diseases drip irrigation lettuce

Ultimately, educating the next generation of farmers about modern irrigation technologies is the key to safeguarding water resources for the future. By utilizing data from IoT sensors and mobile applications, farm management can become significantly more precise and automated. We must move from guesswork farming to data-driven farming to produce the highest quality with minimal water consumption. This is a continuous process that requires ongoing monitoring, learning, and correction.

The figure below illustrates the water cycle on the farm and points of loss, which must be reduced through engineering-driven approaches.

The chart below shows a comparison of water consumption across different irrigation methods.

In summary, agricultural irrigation is not merely sprinkling water on plants; it is a complex engineering and management process involving a wide range of variables. Given resource constraints, every drop of water must be carefully planned. We hope this guide offers a fresh perspective on this critical issue and contributes to the development of sustainable agriculture in the country.