1.  Greater flexibility in application of fertilizers does not depend on the climatic conditions such as rain and soil condition.  Frequent and small applications check the run-off and leaching below the root zone thus save the cost on the input and its efficient utilization.  Saves labour and energy.  Fertilizers are placed around roots uniformly in liquid form and there will be less time for leaching and run-off of the nutrients in the soil.  Rapid uptake of nutrients by the plant as they are supplied in the liquid form.

4.  Quantity applied  Duration of applications  Proportion of fertilizers  Starting and finishing time

18. Nature of nutrientsExamples 1.Basic nutrientsC, H and O 2.MacronutrientsN, P, K, Ca, Mg and S A.Primary nutrientsN, P and K B.Secondary nutrientsCa, Mg and S 3.micronutrientsFe, Zn, Cu, B, Mo and Cl Classification of essential elements

19. Basic criteria for categorizing nutrients essentiality to plant 1.A plant must be unable to complete its life-cycle in the absence of the mineral element. 2. The function of the element must not be replaceable by another mineral element. 3. The element must be directly involved in plant metabolism.

20. Fertigation through trickle irrigation requires careful planning. Important factors to be considered are uniformly of water application (uniform fertilizer application is possible only if the water application is uniform), method of injection, type of fertilizer and application scheduling. The most important requirement for effective fertilizer injection is system uniformity. Fertilizer cannot be applied uniformly to plants unless water delivery is uniform. A system uniformly of 80% and above is needed to be considered for fertilizer injection. Rate and timing of fertilizer injection depends on the plant age, root distribution as well as soil type. Fertilizer injection provides the growers greater flexibility than ground application because fertilizer is delivered to the roots of plants when they need it. Plants recover injected N most efficiently because timing is improved and fertilizer is delivered directly to the root zone.

21. It is recommended not to inject the entire annual dose rate at one time, when the fertilizer injections are coordinated with irrigation schedules and high percentage of the fertilizer will remain in the root zone. Fertilizer may leach out of the root zone and washed if injected with an excessive amount of water or if it is injected immediately before or after irrigation. Minimize leaching to improve efficiency and avoid nutrient movement into groundwater. Operate trickle irrigation system longer than the period of injection of fertilizer. Once the fertilizer injection is complete, run the system for an additional 20-30 minutes to assure that all fertilizers have been purged from the lines. This will prevent fertilizers from settling out in the supply lines when the system is switched off and thus reduce the chance of emitter clogging.

22.  High pH values in the irrigation water (>7.5) is undesirable in Fertigation as Ca and Mg carbonates precipitate readily in saline water.  High soil pH reduces the availability of Zn, Fe and P to Plants.  Ammonia use in fertigation is not recommended as it raises the pH of irrigation water.  Low pH affects root membrane and increase Al and Mn concentration in soil solution to toxic levels and can thus harm plants.

23. An impaired management of the irrigation regime may lead to an unwanted accumulation of Cl ions present in the irrigation water. If the Cl concentration in the leachate is higher than the Cl concentration in the incoming solution and surpasses 50 mg/L, it indicates a chloride accumulation in the root zone. Then it is recommended to apply an irrigation without fertilizers to leach the chlorides. A higher value of EC in the leached solution that in the applied solution indicates that the plant absorbs more nutrients than water, therefore we must apply greater amount of water to the plant. On the other hand, if the difference between the EC of the leached solution and the incoming solution is more than 0.4-0.5 dS/ m, we must apply a leaching irrigation in order to wash the excess of salts.

25. They are stable and highly soluble, dissolving rapidly and providing a balance of nutrients so only one product of handled. However they are generally more expensive per unit of nutrient when compared to standard fertilizers. FertilizerContent (N-P-K) Remarks Ammonium nitrate 20-0-0Most widely used N-source Calcium nitrate15-0-0-19 caNot to combine with phosphates and sulphates. Urea46-0-0Never combine with H 2 SO 4 Phosphoric acid0-54-0Never mix with calcium fertilizers Potassium chloride 0-0-62Desirable to use if irrigation water is highly saline Potassium nitrate13-0-46For use in area with high salinity in water. Potassium sulphate 0-0-52Alternative to KCl in high salinity area, provides ‘S’ less soluble than KCl and KNO 3

26.  Urea and ammonium nitrate are desirable as they have low clogging properties due to high solubility in water.  Anhydrous or aqua ammonia fertilizers are usually not recommended as they increase the pH of irrigation water, which in turn causes Ca, Mg and P to precipitate and block the flow of water and nutrient in the emitters.  Ammonium phosphate must be avoided where irrigation water contains high levels of Ca and Mg since they cause precipitation.  Nitrogen in irrigation water can contribute to microbial growth in soil.

27.  Ammonia is absorbed by soil colloids and metal oxides. Hence, the mobility is restricted compared to unadsorbed HO – 3.  To check rapid leaching of N, it is advisable to apply as NH + 4 - Nitrate.  Urea is highly soluble, chargeless molecule and moves easily with irrigation water.  Urea-hydrolyzed by microbial enzymes into NH + 4 increase soil pH.  Soils of pH (>7.5) reduced ‘P’ availability.  ‘P’ mobility is restricted due to strong retention by soil of oxides and clay minerals. Orthophosphate mobility through water is superior.  Avoid P-Ca and P-Mg precipitation.  Acid ‘P’ fertilizers (phosphoric acid, Mono-ammonium phosphate) are recommended.

28. From the foregoing discussion it can be concluded that fertigation provides greater flexibility and control of nutrients when applied in small quantities when required. This will check nutrients leaching by over-irrigation. Emitter clogging problems resulting from reaction of the fertilizer with irrigation water is avoid. Fertigation experiments have clearly elucidated the marked savings in fertilizers (20 to 40%) for most of the floricultural crops as compared to conventional method of fertilizer application.