Chemigation, a related and sometimes interchangeable term, is the application of chemicals through an irrigation system. Chemigation is considered to be a more restrictive and controlled process due to the potential nature of the products being delivered - pesticides, herbicides, fungicides - to cause harm to humans, animals, and the environment. Therefore chemigation is generally more regulated than fertigation.
Fertigation is used extensively in commercial agriculture and horticulture and is starting to be used in general landscape applications as dispenser units become more reliable and easy to use.
- Fertigation is used to spoon-feed additional nutrients or correct nutrient deficiencies detected in plant tissue analysis. It is usually practiced on high-value crops such as vegetables, turf, fruit trees, and ornamentals.
- Injection during the middle one-third or the middle one-half of the irrigation is recommended for fertigation using micropropagation.
- The water supply for fertigation is to be kept separate from the domestic water supply to avoid contamination.
- The change of fertilizer during the growing season is important in order to adjust for fruit, flower, and root development.
Commonly used nutrients
Most plant nutrients can be applied through irrigation systems.
Nitrogen is the most commonly used nutrient; however, naturally occurring nitrogen (N2) is a diatomic molecule which makes up about 80% of the earth’s atmosphere. Most plants cannot directly consume N2, so 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 element to live, but they must be contained in other chemical substances such as monoammonium phosphate or diammonium phosphate to serve as an appropriate nutrient. The 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 chemicals to 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
- Minimizes the risks of the roots contracting soil borne diseases through the contaminated soil
- Eliminate the 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.
- There may be pressure loss in the main irrigation line.
- It has a Limited capacity.
- The use of chemical fertilizers of low-sustainability, instead of organic fertilizers.
- It is dependent on the water supply's non-restriction by drought rationing.
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. So 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 increase the level of protection required.
Methods used in fertigation
- Drip irrigation is less wasteful than sprinklers.
- Sprinkler systems increase leaf and fruit quality.
- Other methods of application include lateral move, traveler gun, and solid set systems.
- Continuous application fertilizer is supplied at a constant rate.
- Three-stage application irrigation starts without fertilizers and then later in process fertilizers are applied.
- Proportional application where injection rate is proportional to water discharge rate.
- Quantitative application where nutrient solution is applied in a calculated amount to each irrigation block
All systems should be placed on a raised and/or sealed platform, not in direct contact with the earth, and fitted with chemical spill trays.
In order to determine the injection rate for the particular fertilizer being used, one should use the formula:
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, and F = amount of fertilizer in grams.
Fertigation assists distribution of fertilizers for farmers. The simplest type of fertigation system consists of a tank with a pump, distribution pipes, capillaries, and dripper pen.
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.
Possible strategies to be used
- Injecting for short time-periods at the beginning, middle, and end of irrigation cycle
- Injecting during middle 50% of the irrigation cycle
- Continuous irrigation
- Postering index Imex
1. Asadi, M.E., 1998. Water and nitrogen management to reduce impact of nitrates. Proceedings of the 5th International Agricultural Engineering conference, December 7–10, Bangkok, Thailand, PP.602–616.
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.
4. Asadi, M.E., 2004. Optimum utilization of water and nitrogen fertilizers in sustainable agriculture. Programme and Abstracts N2004. The Third International Nitrogen Conference. October 12–16, Nanjing, China. PP.68.
5. Asadi, M.E., 2005. Fertigation as an engineering system to enhance nitrogen fertilizer efficiency. Proceedings of the Second International Congress: Information Technology in Agriculture, Food and Environment, (ITAFE), October 12–14, Adana, Turkey, pp. 525–532.
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