Drip Irrigation: The Silver Bullet? Eric H. Simonne Horticultural Sciences Department University of Florida AfrICANDO Conference Miami, FL Sept. 16, 2004 Plants need Water (plants = 80% to 90% water) Mineral salts (13 essential elements) Oxygen (O 2 ; final electron acceptor in respiration) Carbon dioxide (CO 2 ; source of C) Light (for photosynthesis) Time (everything takes time!) Seepage irrigation Furrow irrigation Center pivot 1
Drip irrigation Emitter = controlled leak Drip irrigation + Plastic mulch + Raised beds = Plasticulture Drip irrigation The slow application of water directly to the plant s root zone Allows for simultaneous management of irrigation and fertilization Full benefit when used with plasticulture May require transplants 2
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Back flow prevention Drip Irrigation System Overview Venturi injector Irrigation systems differ in Efficiency of delivery water saving Application uniformity enhanced production Dosatron Di 16 Irrigation System Efficiency Definition: the ratio of the amount of water available for plant use to the total amount of water pumped. Efficiencies: - drip: 85-95% - overhead: 65-75% - seepage: 50% Irrigation Uniformity Uniformity (Us) can be estimated from the statistical distribution of emitter flow rates as: Us = 100 x (1-Vqs) where Vqs is the coefficient of variation of emitter discharge rate 4
Classification of Uniformity Class Uniformity (Us, %) Excellent >90 drip Good 90-80 overhead Fair 80-70 gravity Poor 70-60 Unacceptable <60 The ideal drip system is the one in which all emitters deliver the same volume of water in a given time so that each plant will receive the same quantity of water. Advantages of Drip Irrigation Uses less water than other systems Wets a small part of the field: - improved aeration - less weed growth Easy to automate Scalable and adaptable Low operating pressure (14 to 140 kpa) High efficiency (85%) Increased yields and earliness Advantages of Plasticulture Increased soil temperature (2 to 4 C) Reduced soil compaction Reduced risk of flooding Reduced evaporation Cleaner product Reduced weeds problems (in theory ) Reflective mulches reduce primary infection by virus vectors Disadvantages of Drip Irrigation Technically involved method and unforgiving Requires quality water Requires maintenance Disposal 5
Disadvantages of Plasticulture Specialized equipment needed for application Need for soil fumigation May need to irrigate even when it rains Cost (up to $1,000/acre) Disposal What you don t want with drip irrigation: Root intrusion Rodents and/or insects eating or damaging parts Cross precipitation Clogging Loss of performance after modification of a welldesigned, existing system Keys to success with drip irrigation How to avoid disasters with drip irrigation? Use proper design Know and monitor water source and quality Develop a schedule for fertilizer injection Use 100% soluble fertilizer sources Develop and follow a maintenance program Develop a schedule for irrigation What for? Do you have a maintenance plan? Maintenance-is-best-medicine program Filtration Chlorination and acidification Flushing Observation 6
Water Quality Parameters ph Iron Hydrogen sulfide Total dissolved solids (TDS) Chlorine testing with a pool kit Conclusions Ag engineers are good designers, horticulturists should be good managers Drip advantages: - low volume - low pressure - adaptable - double cropping Drip disadvantages: - cost - high management - unforgiving When should we use drip irrigation? Drip irrigation is best suited for the production of high-water content, high-value food crops when water is scarce and when irrigation supplies are available. 7