- FERTIGATION: VENTURI INJECTION METHOD
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- FERTIGATION: VENTURI INJECTION METHOD book
Fertilizer plus irrigation is known as fertigation. Fertigation refers to the application of fertilizers and other chemicals along with irrigation water through drip or sprinkler irrigation to the crops on a continual basis in controlled manner so as to allow for steady uptake of nutrients by plants. Fertigation aims at uniform distribution of applied nutrients in small doses to meet the plants nutrient demand and ensures substantial saving in fertilizer usage . Besides, it is considered ecofriendly as it avoids leaching of fertilizers . Fertigation has the potential to ensure the right combination of water and nutrients to the root zone for meeting the plant’s total and temporal requirement of water and nutrients . The application of right combination of water and nutrients in optimal and proper concentration is the key for higher crop yields and the better quality of produce. Fertigation uniformity is an important consideration in design and use of micro irrigation system as nonuniform application of water and fertilizer may result in loss of valuable nutrients, considerable reduction in yield and quality, soil degradation and groundwater contamination. The uniformity of fertilizer concentration depends on injection method [1, 5]. Fertilizer uniformity could be greatly influenced by the injection method and its management during injection process . The application of small amount of fertilizer solution at frequent intervals reduces deep percolation losses . Optimum operating pressure is one of the main factors for uniform distribution of water and fertilizer through micro irrigation system. Fertigation is done using injectors such as fertilizer tank, fertigation pump and venturi. Venturi injector is the most commonly used device for fertilizer application through drip irrigation. The fertilizer application rate of the venturi depends on injection rate besides the concentration of fertilizer solution. The suction rate of venturi mainly depends on pressure gradient (difference in upstream and downstream pressure) and the density of fertilizer solution besides size of venturi. Nakayama and Buck  compared all three different methods and rated that fertilizer tank better since it had no moving parts. However, the main disadvantage of fertilizer tank lies in the difficulty to maintain a uniform concentration of fertilizer in the solution during fertigation. Sivanappan and Prasad  reported that fertigation pump and venturi can be used to inject fertilizer at constant dilution ratio. Sivanappan et al.  suggested five criteria to determine the efficiency of different fertilizer injection devices. They are (a) Dilution ratio, (b) Cost of unit, (c) Portability of the unit, (d) Method of operation and (e) Operating cost. Shani and Sapir  discussed the advantages and disadvantages of three fertilizer injection devices and described the venturi as a simple mechanism, capable of giving constant dilution ratio and cheaper in cost. They described the main limitation of venturi as the large pressure drop that occurs during its operation as compared to fertilizer tank and fertigation pump. Kranz et al.  found that venturi injectors and diaphragm pump have lower precision and repeatability than fertigation pumps. The venturi is economical and requires no electrical power to operate . Thus, it is important to select an injection device that best suits the irrigation system and the crop to be grown. Rajput et al.  reported that the injection rate of venturi directly proportional to the pressure drop across it. Kumar et al.  conducted a study and informed that injection rate of venturi varies with fertilizer solution concentration and system operating pressure.