Management of Nitrogen Fertilization for High Yield and Quality of Grapefruit (Citrus paradise) in Sandy Soils
Nitrogen (N) fertilization and irrigation management have considerable influences on citrus growth, fruit yield and quality. This study was designed to develop N management recommendations for grapefruit production on flatwoods soils under optimal irrigation scheduling to support high yield and quality fruit with minimal N leaching losses. A field study was conducted from 1997 to 2000 to evaluate the effects of N sources as either dry soluble granular (DSG) , fertigation (FRT) , or controlled-release fertilizer (CRF), and rates 0 336 kg/(ha ? yr) with optimum irrigation management on fruit yield and quality and leaf N concentrations of 30 + year-old white Marsh grapefruit (C. paradisi M.)trees on sour orange rootstock (C. Aurantium L.)grown on a Riviera fine sand (loamy, siliceous, hyperthermic, Arenic Glossaqualf). There was no significant difference in leaf N concentration, fruit yield, and fruit quality between the two irrigation treatments (irrigation was scheduled when the 15 cm soil depth tensiometer reading attained - 150 kpa and -300 kpa, respectively). Nitrogen source had no significant influence on fruit yield. The effects of N sources on leaf N concentration and fruit quality properties were variable. In one out of the three years, leaf N concentration was higher with DSG or CRF than with FRT. The DSG provided higher solids content than the CRF or FRT. A significant yield increase was obtained at N rates up to 168 kg/(ha ? yr) , and the yield leveled off at N rates from 168 to 224 kg/(ha ? yr). A yield response was again observed from 224 to 336 kg/(ha ? yr), but the mechanism behind this high rate response is unknown. Concentrations of juice, Brix, and acid generally increased with increasing N rates. Fruit weight was the greatest at the N rates of 56 to 168kg/(ha ? yr) and reduced at lower or higher N rates. Brix/acid ratio was higher at N rates of 0 to 56 kg/(ha ? yr) , decreased at higher N rates, but was not significantly different at N rates higher than 112 kg/(ha ? yr). The annual average concentrations of nitrate (NO3-N) in the soil solution at either the 120 or 180 cm depths were below 10 mg/L, the maximum contaminant level for drinking water established by the US Environmental Protection Agency, even at the highest N rates regardless of the N sources. There were no differences in NO3-N concentrations between the two irrigation treatments or among the three different N sources.
Leaf nitrogen Fruit quality
Z. He B. J. Boman Alva X. Yang
University of Florida, Institute of Food and Agricultural Sciences, Indian River Research and Educat USDA-ARS-PWA Irrigated Agriculture Research and Extension Center, Prosser, WA 99350 M0E Key Laboratory of Environmental Remediation and Ecological Health, College of Natural Resources
国际会议
11th International Citrus Congress(第11届国际柑橘大会)
武汉
英文
639-645
2008-10-01（万方平台首次上网日期，不代表论文的发表时间）