|E. Jovicich, D. J. Cantliffe, E. H. Simonne, P. J. Stoffella
|Cucumis sativus, irrigation, fertilization, greenhouse, field, nitrogen, potassium, hydroponics
Potential future restrictions of amounts of water and fertilizer to be used by farmers lead to the need for evaluation of production systems that are highly efficient in the use of these resources.
Water, nitrogen (N) and potassium (K) use efficiencies were estimated from data derived from Beit Alpha type of cucumbers produced in a greenhouse and from data reported for field-grown slicing cucumbers in central Florida.
Beit Alpha fruits were produced in a high-roof passively ventilated green¬house, with a plant density of 3 plants/m2, 1-plant/11-L-container filled with pine bark, and plants pruned and trellised to a single vertical stem.
Total yield was 270 t/ha after 27 harvests in a 105 day crop.
With a drain-to-waste irrigation system in the greenhouse, a total of 8,190 m3/ha of nutrient solution were applied to keep drainage between 20% to 30% of the daily irrigation volume.
Field cucumbers were designated as being planted on polyethylene mulched beds (5.4 plants/m2) on a sandy soil treated with methyl bromide.
Field drip irrigation would deliver 1,406 m3/ha of water, 160 kg/ha of N, and 243 kg/ha of K. Yield after 9 harvests was calculated as 31.2 t/ha.
Water use in 1 ha of greenhouse was 5.8 times greater than field water use but water volume per gram of fruit was 1.5 times greater in the field than the greenhouse.
Nitrogen and K used per kg of fruit was 28% less and 23% less, respectively, in the greenhouse than in the field (6.5 g N/kg fruit, and 7.8 g K/kg fruit). Greater fruit yields, fruit quality, and crop water and nutrient use efficiencies resulted with green¬house than with field production system.
With a closed irrigation system in the green¬house, water needs per unit of produce could be further reduced, potentially 50% to 60%, as compared to field production systems under drip irrigation.
When developing best management practices for greenhouse production systems, crop water and nutrient use efficiency, the capability of water and nutrient reuse, and off-farm water and nutrient discharge, should be added to consideration when determining amounts of water and fertilizers to be used per unit of area.
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