Fertigation

Fertigation is the application of fertilizers, soil amendments, or other water-soluble products through an irrigation system.

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 in general more regulated than fertigation.

Usage

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

• Usually practiced with high-value crops such as vegetables, turf, fruit trees, and ornamentals

• Injection during middle one-third or the middle one-half of the irrigation recommended for fertigation using micropropagation

• Water supply for fertigation kept separate from domestic water supply to avoid contamination

• Change of fertilizer program during the growing season in order to adjust for fruit, flower, and root development.

Commonly used nutrients

• most plant nutrients can be applied through irrigation systems

• Nitrogen is most commonly used nutrient

• Other nutrients include nitrate, ammonium, urea, phosphate, and potassium.

Determining which nutrient is used

• A soil fertility analysis is used to determine which of the more stable nutrients should be used

Advantages

Benefits of fertigation over traditional broadcast or drop-fertilizing methods include:

• Increased nutrient absorption by plants
• Reduction in fertilizer and chemicals needed
• Reduced leaching to the water table
• Reduction in water usage due to the plant's resulting increased root mass's ability to trap and hold water
• Application of nutrients at the precise time they are needed and at the rate they are utilized

Disadvantages

• Concentration of solution decreases as fertilizer dissolves, leading to poor nutrient placement

• Results in pressure loss in main irrigation line

• Limited capacity

• Use of chemical fertilizers of low-sustainability, instead of organic fertilizers.

• Dependent on water supply's nonrestriction by drought rationing.

Controls

Because of the potential risk in contaminating the potable (drinking) water supply, a backflow prevention device is required for most fertigation systems. Backflow requirements 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, but each city or town may increase the level of protection required.

Methods used in fertigation

• Drip irrigation, which reduces per water and nutrient application rates relative to sprinklers

• Sprinkler systems, which 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 the later in process fertilizers are applied

• Proportional application - injection rate is proportional to water discharge rate

• Quantitative application - 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.

System design

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

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

References

Department of Natural Resources, Environment, "Fertigation systems." Web.4 May 2009. <www.nt.gov.au/nreta/publications/natres/pdf/FertigationSystems.pdf>.

Hanson, Blaine R., Hopmans, Jan, Simunek, Jirka Effect of Fertigation Strategy on Nitrogen Availability and Nitrate Leaching using Microirrigation HortScience 2005 40: 1096 http://hortsci.ashspublications.org.ezproxy.lib.vt.edu:8080/cgi/content/abstract/40/4/1096

North Carolina Department of Agriculture and Consumer Services, "Chemigation & Fertigation." (2003) Web.4 May 2009. <www.ncagr.com/fooddrug/pesticid/chemigation2003.pdf>.

Neilsen, Gerry, Kappel, Frank, Neilsen, Denise Fertigation Method Affects Performance of `Lapins' Sweet Cherry on Gisela 5 Rootstock HortScience 2004 39: 1716-1721 http://hortsci.ashspublications.org.ezproxy.lib.vt.edu:8080/cgi/content/abstract/39/7/1716?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=Fertigation&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT

NSW department of primary industries, "Horticultural fertigation."2000. Print. http://www.dpi.nsw.gov.au/agriculture/resources/water/irrigation/crops/publications/fertigation

See also

• Sustainable agriculture
• Water conservation
• Drip irrigation

Notes

Bibliography

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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