Sources of nutrients
- Urea, ammonium nitrate and ammonium sulphate nitrogenous fertilizers are suggested for fertigation. The content of nutrients in solid form and under saturated liquid form is given in the Table 1.
- Generally the application of phosphatic fertilizers through the drip irrigation system is not recommended because in majority of the cases basal application of phosphorus satisfies the plant P needs. Applied phosphorus creates chemical and physical precipitation leading to clogging problems.
- Phosphoric acid being soluble with low pH, no clogging occurs with orthophosphate. Inorganic phosphorus like Mono Ammonium phosphate and Di ammonium phosphate are the other sources of phosphorus for fertigation.
- Potassium is easily soluble in water, easily leached in sandy soils and can be fed through drip irrigation to maintain a proper N: K ratio for crop production. Potassium as potassium sulphate, potassium chloride, potassium nitrate and mono potassium phosphate may be through drip irrigation since these are soluble in water and do not cause any precipitation problem.
- Among the different fertilizers, sulphate containing fertilizers can cause problems if irrigation water contains lot of calcium by forming insoluble calcium sulphate. Chloride containing fertilizers should not be used on certain crops like strawberry and tobacco. Phosphatic fertilizers can also become insoluble at high pH, by forming relatively insoluble calcium and magnesium phosphate.
Table 1.Nutrient (N, P2O5, K2O) content of common fertilizers suitable for fertigation in their solid and saturated liquid forms
4. Liquid fertilizers
||N:P2O5:K2O under solid form
||N:P2O5:K2O Under saturated liquid form
Mono Ammonium Phosphate
Di Ammonium Phosphate
5. Chloride free fertilizers
- Liquid fertilizers contain one or more plant nutrients including micronutrients. The raw materials used in liquid fertilizer production are mainly bulk fertilizers such as ammonium sulphate, ammonium nitrate, Urea, ammonium phosphate, phosphoric acid, potassium nitrate, potassium chloride, potassium sulphate etc. The liquid fertilizers are pure and do not precipitate. Normally the liquid fertilizers are acidic (pH 5.5-6.5) and help in correcting the soil pH to some extent and also help in the prevention of clogging of emitters. For acidic soils, liquid fertilizers with neutral pH or even higher pH could be used.
6. Normal fertilizers
- These fertilizers are produced by using Urea, ammonium nitrate phosphate and potassium nitrate as basic ingredients and are useful for high value crops and crops which are more sensitive to the chloride injury. Ex: Tobacco, grapes, citrus, arecanut and vegetables.
7. Micro nutrients
- These are produced by using ammonium nitrate, urea, ammonium phosphate, ammonium sulphate, phosphoric acid, potassium chloride etc.
8. Fertilizers unsuitable for fertigation
- Micronutrients are generally applied separately to plants in most soils as their application through fertigation would react with salts in the irrigation water and cause precipitation and clogging. Chelated micronutrients are highly water soluble and can be applied through fertigation since they cause very little clogging or precipitation.
- Aqueous ammonia
- Calcium nitrate
- Calcium ammonium nitrate
- Potassium sulphate
- Zinc nitrate and
- Ferric sulphate are not suitable for using in fertigation due to precipitation and clogging problems
Last modified: Saturday, 23 June 2012, 4:33 AM