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Abstract
Drip irrigation of peach [Prunus persica (L.) Batsch cv. Hermosa] and grape [Vitis vinifera (L.) cv. Perlette] was scheduled according to soil matric potential and water applied was expressed as a coefficient of class A pan evaporation. Water consumption by grape increased progressively from planting until the 4th year. A sigmoidal pattern of water consumption from budbreak through harvest was evident in both crops. The gradual rise of water consumption after budbreak was correlated with development of the full canopy, while a 2nd rise coincided with the final fruit-swelling stage and harvest. An intermediate period of steady water consumption was evident in the late-maturing crop (peach) while absent in early maturing crop (grape). Volume of water, as well as frequency of applications, had to be increased to maintain soil water potential within predetermined limits. At the period of peak requirement, tensiometers indicated rapid withdrawal of soil water and the necessity for daily irrigation. Estimates show a 12% to 23% conservation in water use by programming irrigation according to soil water potential rather than by pan evaporation.
Abstract
Export of urea N was quantified after 15N-enriched urea was applied to ‘Manzanillo’ olive leaves (Olea europaea L.). Labeled N derived from foliar urea applications to mature trees in October 1982 and March 1983 constituted 4.3% and 23.0%, respectively, of the nitrogen composition of olive flowers at anthesis (May 1983). Labeled N applied to leaves following anthesis was translocated to fruit within 3 days. Export of N from treated leaves was greatly reduced when developing fruit and shoot tips were removed. Preloading of leaves with standard urea (before foliar application of labeled urea) increased leaf N by 30% and increased slightly the translocation of labeled urea N to the fruit 2 to 4 weeks later. The nitrogen status of small, potted ‘Manzanillo’ plants did not influence subsequent absorption of foliage-applied urea; however, nitrogen deficiency reduced translocation of labeled urea N from the treated leaves to new shoots and, to a lesser extent, roots. Olive leaves represent storage organs for N and release N in response to the metabolic demands of developing reproductive and vegetative organs.
The sensitivity of leaf (ψleaf) and stem (ψstem) water potential and stomatal conductance (gs) to soil moisture availability in apple (Malus domestics Borkh.) trees and their correlation with yield components were studied in a field experiment. Two drip irrigation treatments, 440 mm (H) and 210 mm (L), were applied to a `Golden Delicious' apple orchard during cell enlargement stage (55-173 days after full bloom). Data collected included ψstem, y leaf, gs, and soil water potential at 25 (ψsoil-25) and 50 cm (ψsoil-50). No differences in midday ψleaf's were found between irrigation treatments. Stem water potential was higher in the H treatment than in the L treatment in diurnal measurements, and at midday throughout the season. Stomatal conductance of the H treatment was higher than the L treatment throughout the day. Stomatal conductance between 0930 and 1530 hr were highly correlated with ψstem. The H treatment increased the percentage of fruit >65 mm, and increased the proportion of earlier harvested fruit reaching marketable size compared to the L treatment. Fruit size in the first harvest and the total yield were highly correlated with ψstem. The degree of correlation between plant water stress indicators and yield component decreased in the following order: ψstem>ψsoil-25,>ψsoil-50>ψleaf. The data suggest that midday ψstem may serve as a preferable plant water stress indicator with respect to fruit size.
Abstract
Translocation of 15N from foliar-applied urea to vegetative and reproductive sinks of avocado (Persea americana Mill, cvs. Fuerte and Hass) was evaluated during inflorescence development and the early stages of fruit set. Urea (2%) increased the number and the total dry weight of the lateral inflorescence per shoot. The concentration of 15N in avocado inflorescences increased proportionately to the concentration of urea applied to the old leaf surface. The amount of 15N translocated was not affected by the proximity of the source leaf to the “terminal” inflorescence. 15N translocated to developing fruit and to new sprouting leaves in similar amount. Urea N was translocated basipetally from current flush leaves to developing fruit. Removing the vegetative sink reduced N influx to the reproductive tissue and increased initial fruit set by a factor of 1.7 to 2.1 in urea-treated and -untreated shoots, respectively. These data indicate that shoot growth does not limit fruit set in avocado via competition for N.