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  • Author or Editor: Bruce Schaffer x
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Understanding plants’ response to different irrigation levels is essential for developing effective irrigation scheduling practices that conserve water without affecting plant growth and yield. The objective of this study was to evaluate the responses of three sweet corn (Zea mays var. saccharata) cultivars 1170, 8021, and Battalion under three irrigation levels (50%, 75%, and 100%). Irrigation treatments were based on soil moisture management allowable depletion. Replicated trials were conducted, in an open field using 1-gal containers, at the Tropical Research and Education Center, Homestead, FL. A drip system with microsprinklers was used for irrigation. Daily crop evapotranspiration (ETc) rates were measured using a digital scale based on differences in weights of soil containers and plants. Reference evapotranspiration (ETo) was calculated using the FAO-Penman-Monteith equation. Crop-coefficient (Kc) values for the three cultivars were calculated from measured ETc and calculated ETo. In addition, leaf area, stomatal conductance, and fresh biomass were measured. Total irrigation amounts corresponding to the 50%, 75%, and 100% treatments were 116, 162, and 216 mm, and total ETc values were 128, 157, and 170 mm, respectively. The two deficit irrigation treatments (50% and 75%) resulted in a reduction of ETc for the three cultivars compared with the 100% irrigation treatments. Results also showed that under 75% and 100% treatments, Kc values were usually greater than 1 for the three cultivars and reached as high as 1.5. Additionally, leaf area and fresh biomass weight in the 50% treatment were mostly lower than in the 75% or 100% treatments.

Open Access


The Diagnostic Recommendation and Integrated System (DRIS) approach was used to identify mineral deficiencies associated with mango decline (a disorder of unknown etiology) of ‘Tommy Atkins’ mango (Mangifera indica L.) trees in the field. Nutrient deficiencies associated with decline were related to the nutrition of entire orchards and not to the nutrient status of individual trees within an orchard. The nutrient imbalance index (NII) was higher for trees in the orchards with the largest percentage of declined trees compared with the healthy orchard. The most deficient elements in orchards with declining trees according to DRIS were Mn, Fe, or a combination of both elements. The concentration of these elements was below the critical value in two of the three declined orchards sampled. Magnesium concentration was generally higher in declined orchards than in healthy orchards. Phosphorus had the most negative DRIS index, but the concentration was still above the critical value in an orchard that contained no declined trees. DRIS determinations from potted trees showing no mineral deficiency symptoms in a previous study also showed P to have the most negative DRIS index. DRIS, when used along with sufficiency ranges, appears to be a useful approach for identifying nutritional deficiencies involved in a mango decline.

Open Access