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Abstract
Foliar spray applications of ammonium phosphate were more effective than potassium nitrate sprays in reducing creasing of ‘Valencia’ oranges (Citrus sinensis (L.) Osbeck). Ammonium phosphate decreased fruit size and increased its soluble solid content. Potassium nitrate applied before or after ammonium phosphate prevented smaller fruit and increased the effectiveness of ammonium phosphate in preventing creasing.
Abstract
Foliar spray of ammonium phosphate in combination with potassium nitrate during the June drop season, on trees of ‘Wilking’ mandarin (Citrus reticulata Blanco) was effective in thinning and brought about an increase of fruit diameter, reduced fruit acidity, and improved total soluble solids to total acid ratio.
Abstract
Mature Marsh seedless grapefruit trees on Sour orange stock planted in a loamy soil were subjected to three levels of nitrogen fertilization with and without phosphate or chicken manure added. The details of the experimental plan and tree responses during the five-year experimental period will be described elsewhere. Briefly, the phosphate and manure treatments resulted in a significant increase in yield and in improved fruit quality. As far as the leaf composition is concerned, the phosphate and manure treatments caused an increase in the P and a decrease in the N content of the leaves, thus producing a completely inverse relationship between leaf N concentration and the yield of the corresponding trees. This situation served as an opportunity to test—under orchard. conditions—the validity of NaR (nitrate reductase) assay in leaves as a measure for some “active fraction” of leaf nitrogen and as a parameter for tree productivity. The use of the NaR assay has been suggested for the determination of N requirements of citrus trees (1).
Abstract
Peroxidase activity measured on leaf disks of vegetable plants is suggested as a rapid tissue test for diagnosing iron deficiency. The reaction is rapid, may be executed under field conditions and apparently corresponds with the metabolically active part of the iron in the leaf tissue.
Abstract
Band application of MgCl2·6H2O under the tree canopy of ‘Shamouti’ orange [Citrus sinensis (L.) Osbeck] trees significantly increased leaf Mg and Cl concentration. MgSO4 and MgO were not effective. Fertigation with MgCl2·6H2O was less efficient than band application and was not superior to foliar application of Mg(NO3)2·6H2O for increasing leaf Mg concentrations. In spite of high Cl concentration of the leaves, no visible toxicity symptoms were observed.
Abstract
Summer water stress in grapefruit (Citrus paradisi Macf.) trees caused high titratable acidity levels during the winter. The after effect of water stress lasted up to 6 months. Brief sudden rises in acidity during the winter were correlated with short durations of relatively high day temperatures. Such episodes did not affect the percentage total soluble solids.