Fertigation is related to Chemigation—the injection of chemicals— the two terms are sometimes used interchangeably. However, Chemigation is generally a more controlled and regulated process due to the potentially harmful nature of the chemicals used. Chemigation often involves pesticides, herbicides and fungicides, many of which pose health dangers to humans, animals, and the environment.
- Fertigation is used to add additional nutrients or to correct nutrient deficiencies detected in plant tissue analysis. It is usually practiced on high-value crops such as vegetables, turf, fruit trees, and ornamentals.
Commonly Used Nutrients
Most plant nutrients can be applied through irrigation systems.
Nitrogen is the most commonly used plant nutrient. Naturally occurring nitrogen (N2) is a diatomic molecule which makes up approximately 80% of the earth’s atmosphere. Most plants cannot directly consume diatomic nitrogen. Therefore, the nitrogen must be contained as a component of other chemical substances which plants can consume. Commonly, anhydrous ammonia, ammonium nitrate and urea are used as bioavailable sources of nitrogen.
Other nutrients needed by plants include phosphorus and potassium. Like nitrogen, plants require these substances to live, but they must be contained in other chemical substances such as monoammonium phosphate or diammonium phosphate to serve as a bioavailable nutrient. A common source of potassium is muriate of potash, which chemically, is potassium chloride.
Determining Which Nutrient is Used
- A soil fertility analysis is used to determine which of the more stable nutrients should be used.
The benefits of fertigation methods over conventional or drop-fertilizing methods include:
- Increased nutrient absorption by plants
- Reduction in fertilizer, chemicals, and water needed
- Reduced leaching of chemicals into the water supply
- Reduction in water consumption due to the plant's increased root mass's ability to trap and hold water
- Application of nutrients can be controlled at the precise time as they are needed and at the rate they are utilized
- Minimized risk of the roots contracting soil borne diseases through the contaminated soil
- Elimination of soil erosion issues as the nutrients are pumped through the water drip
- The concentration of the solution decreases as the fertilizer dissolves. This may lead to poor nutrient placement.
- The water supply for fertigation is to be kept separate from the domestic water supply to avoid contamination.
- There may be pressure loss in the main irrigation line.
- The process has a limited capacity.
- The use of chemical fertilizers of low-sustainability, instead of organic fertilizers.
- The process is dependent on the water supply's non-restriction by drought rationing.
Methods Used in Fertigation
- Drip Irrigation
- Less wasteful than sprinklers.
- Sprinkler Systems.
- Increases leaf and fruit quality.
- Continuous Application
- Fertilizer is supplied at a constant rate.
- Three-stage Application
- Irrigation starts without fertilizers. Fertilizers are applied later in the process.
- Proportional Application
- Injection rate is proportional to water discharge rate.
- Quantitative Application
- Nutrient solution is applied in a calculated amount to each irrigation block.
- Other methods of Application
- Lateral Move
- Traveler Gun
- Solid Set Systems.
Possible Strategies to be Used
- Modifications to fertilizer content throughout the growing season is important in order to adjust for fruit, flower, and root development.
- Injection during the middle one-third or the middle one-half of the irrigation is recommended for fertigation using micropropagation.
- Injecting for short time-periods at the beginning, middle, and end of the irrigation cycle
- Injection during middle 50% of the irrigation cycle
Fertigation assists distribution of fertilizers for farmers. The simplest type of fertigation system consists of a tank with a pump, distribution pipes, capillaries, and a dripper pen.
All systems should be placed on a raised and/or sealed platform, not in direct contact with the earth. Each system should also be fitted with chemical spill trays.
This formula determines the injection rate for the particular fertilizer being used:
Maximum injection rate = (5 x Q x L) / (f X 60)
where Q = irrigation pump discharge in liters per second, L = fertilizer tank volume in liters, F = amount of fertilizer in grams.
Because of the potential risk of contamination in the potable (drinking) water supply, a backflow prevention device is required for most fertigation systems. Backflow requirements may vary greatly. Therefore, it is very important to understand the proper level of backflow prevention required by law. In the United States, the minimum backflow protection is usually determined by state regulation. Each city or town may set the level of protection required.
What Should be Considered:
- Water quality.
- Soil type.
- Nutrient consumption (daily).
- Appropriate nutrient materials.
- Fertigation tank or injector.
- Correct irrigation setup to distribute the nutrient evenly.
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2. Asadi, M.E., Clemente, R.S.2000.Impact of nitrogen fertilizer use on the environment. Proceedings of the 6th International Agricultural Engineering Conference, December 4–7, Bangkok, Thailand. PP.413–423.
3. Asadi, M.E., Clemente, R.S., Gupta, A.D., Loof, R., and Hansen, G.K. 2002. Impacts of fertigation Via sprinkler irrigation on nitrate leaching and corn yield on an acid - sulphate soil in Thailand. Agricultural Water Management 52(3): 197-213.
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