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Allen G. Smajstrla

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ALLEN G. SMAJSTRLA

The use of microirrigation in Florida citrus production has increased rapidly in recent years. Most new groves are now being developed with microspray or drip irrigation. Many existing sprinkler and seepage (subirrigation) systems have also been converted to micro irrigation. Although water management districts have encouraged the use of micro irrigation for water conservation, research results which solved problems with the practical implementation of this technology and which demonstrated economic incentives are primarily responsible for its popularity in Florida citrus production. Research programs have (1) developed management techniques to eliminate emitter clogging, (2) demonstrated the effective use of microspray systems for freeze protection, (3) increased young tree growth with respect to conventional irrigation methods, (4) demonstrated the cost-effectiveness of microirrigation, and (5) developed management techniques for efficient use of water and nutrients in fruit production.

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ALLEN G. SMAJSTRLA

The use of microirrigation in Florida citrus production has increased rapidly in recent years. Most new groves are now being developed with microspray or drip irrigation. Many existing sprinkler and seepage (subirrigation) systems have also been converted to micro irrigation. Although water management districts have encouraged the use of micro irrigation for water conservation, research results which solved problems with the practical implementation of this technology and which demonstrated economic incentives are primarily responsible for its popularity in Florida citrus production. Research programs have (1) developed management techniques to eliminate emitter clogging, (2) demonstrated the effective use of microspray systems for freeze protection, (3) increased young tree growth with respect to conventional irrigation methods, (4) demonstrated the cost-effectiveness of microirrigation, and (5) developed management techniques for efficient use of water and nutrients in fruit production.

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Salvadore J. Locascio and Allen G. Smajstrla

Tomatoes (Lycopersicon esculentum Mill.) were grown on an Arredondo fine sandy soil to evaluate the effects of water quantity applied by drip irrigation scheduled by pan evaporation in a 3-year study. Water was applied to polyethylene-mulched tomatoes at 0, 0.25, 0.50, 0.75, and 1.0 times pan evaporation in one application per day. Irrigation was also scheduled with tensiometers to apply water to maintain soil water tension above 10 cb. The response to irrigation varied with rainfall during the three seasons. In an extremely dry season, fruit yields were doubled by irrigation. Total fruit yields were highest with irrigation quantities of 0.75 and 1.0 times pan and significantly lower with 0.25 and 0.50 times pan. In an extremely wet season, fruit yields were not influenced by water quantities from O to 1.0 times pan. In a third season that was wet from the middle to the end of the season, irrigation more than doubled the marketable fruit yield. However, with an increase in water quantity from 0.25 to 0.75 times pan, yield increased only from 65.9 to 74.1 t·ha-1. Water uses during the three seasons with 0.75 pan were 31.8, 31.1, and 29.6 cm, respectively. Fruit yields were similar with the 0.75-pan and 10-cb tensiometer treatments, but water uses with the latter treatment were 15.8, 17.0, and 18.4 cm during the three seasons, respectively. Tomato leaf N concentrations were reduced slightly with each increase in water quantity applied, even though N was applied with drip irrigation. Leaf N concentrations with the 10-cb treatment were generally equal to or higher than the concentrations with 0.75 pan.

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Gary A. Clark and Allen G. Smajstrla

The injection of chemicals into irrigation systems is discussed in terms of injection systems, concentration injections, bulk injections, quantity of chemicals to be injected, injection system calibration, and injection periods. Sufficient clean-water flush time should be scheduled to purge irrigation lines of injected chemicals unless it is desired to leave that particular chemical in the irrigation system for maintenance purposes. Chemical injection rates vary with desired chemical concentration in the irrigation water, concentration of the stock solution, volume of chemical to be injected, and duration of each injection. All injection systems should be calibrated and maintained in proper working order. This information is presented to assist irrigation system designers and operators with chemigation system design, scheduling, and management.

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Gary A. Clark and Allen G. Smajstrla

Proper design and installation are essential to provide a drip irrigation system that can be managed with minimal inputs and maximum profit. Because drip irrigation can apply precise amounts of water and chemicals, constraints associated with the plants, soil, water supply, and management must be considered in the design, installation, and management processes.