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  • Author or Editor: K. Uriu x
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Boron(B) deficiency in almond (Prunus dulcis Mill.) is characterized by leaf tip scorch, leaf drop, twig dieback, brown gummy areas in the endocarp, and embryo abortion followed by nut drop in May. Additional symptoms revealed by our work include failure of flowers to set nuts and lateral bud drop. Lack of production in part or in all of the free canopy causes spurs to elongate leading to a “willow twig” symptom on the small fruitwood. This can be confused with the nonproductive “bull” syndrome or with virus bud failure (ABFV or PRSV). Comparative leaf, pericarp, or kernel analysis in May gave a better indication of low B than did leaf analysis in August. In August, analyzing the hulls (mesocarp and exocarp) gave better separation between deficient and adequate trees than did leaf, kernel, or shell analysis. B critical levels for almond leaves should be re-evaluated since deficiency symptoms occur at currently accepted “adequate” levels.

Free access

Abstract

The water balance of both irrigated and unirrigated olive (Olea europaea L. cv. Manzanillo) trees was improved by spraying a film-forming antitranspirant (AT). This was evidenced by increased resistance to water vapor diffusion from the leaves, reduced daytime shrinkage of limbs, and increased leaf and fruit water potential. The improvement in plant water potential by AT was equivalent to the effect of an irrigation. Transpiration at night through incompletely closed stomates, especially when night humidity was low, retarded normal nocturnal rehydration of the olive limbs and fruit. The improved water balance of AT-treated olive trees indicated a potential for increasing fruit growth.

Open Access

Abstract

An antitranspirant (AT) applied 2 3 weeks before harvest accelerated olive (Olea europaea L., cv. Manzanillo) fruit growth and led to larger fruit at harvest. The fruit-enlarging effect was detected within 1 day of application. A simulated rain also increased fruit size, but much of the gain in size was lost as soon as the “rain” was terminated. Daytime fruit shrinkage was reduced significantly with the AT. At harvest, fruit moisture was higher in AT-treated fruits, and after harvest the water lost from fruits was lower. When AT was substituted for the last pre-harvest irrigation, fruit size was increased.

Open Access

Abstract

Radial trunk growth of mature almond trees under 4 irrigation treatments was measured with Verner dendrometers for 4 consecutive years. Trunk growth rates and total seasonal growth were affected primarily by soil water and secondarily by crop density conditions. In early spring, when soil water was abundant (near field capacity in entire root zone), the rate of trunk growth was inversely correlated with crop density. Later on, trunk growth was influenced more by soil moisture conditions. Irrigation early in the season increased trunk growth rates even though 30 to 40% available water remained throughout the root zone at time of irrigation. Irrigations after mid-season merely maintained the prevailing trunk growth rates.

Open Access

Abstract

Split-pit of ‘Dixon’ cling peaches was correlated with all 3 variables in a multivariable cultural system study involving differential N applications, irrigations, and crop loads. Any factor that enhanced fruit size contributed to increased split-pit. Fruit size at reference date was more important than fruit size at harvest. In different years fruits of the same size at reference date or at harvest did not necessarily have the same amount of split-pit. Fruit set was more important than other factors in determining fruit size at thinning. Crop load after thinning influenced split-pit where fruit set was moderate; however, where fruit set was light split-pit was severe regardless of thinning and where fruit set was heavy split-pit was of minor concern regardless of thinning. Early thinning accomplished about reference date (10 days after beginning of pit hardening in 80% of fruit) increased split-pit over thinning 2 weeks later. Maintenance of high soil moisture (< 40% used) after reference date increased split-pit over that of less frequently irrigated plots. Manipulation of cultural factors cannot satisfactorily control split-pit, but may considerably influence its occurrence.

Open Access

Abstract

Ground application of urea increased yields of ‘Nonpareil’ almond (Prunus amygdalus Batsch) by increasing the number of flowers per tree rather than by increasing blossom receptivity and percentage fruit-set. Hand pollination of flowers on caged limbs indicated that blossom receptivity declined between 3 and 6 days after anthesis.

Open Access

Abstract

Fertilization with K2SO4 resulted in good uptake of K by trees of French prune (Prunus domestica L. cv. Agen) whether K was applied in drip water or dry K2SO4 was placed on the soil under the emitter and then drip irrigated. These methods were much more effective than applying K2SO4 in trenches alongside the trees and then sprinkler-irrigating. K fertilization with a drip system resulted in K movement to depths of 60 to 75 cm, where the soil is wet from drip irrigation and roots are abundant, enhancing K uptake.

Open Access

A study was undertaken to determine the seasonal dynamics of leaf and fruit K content and the influence of tree K status and fruit growth on leaf and fruit K accumulation rates in French prune (Prunus domestics L. cv. d'Agen). Mature trees in a commercial orchard were treated with various rates of K2 SO4. (O to ≈20 kg/tree) in the fall. Fruit dry weight yield per tree at harvest and fruit K content were higher for high-K trees, but fruit percent K (by dry weight) was ≈1.0% for all trees. Leaf scorch and subsequent abscission severely reduced the canopy of K-deficient trees. Significant positive linear relationships between leaf and fruit K accumulation rates existed for the periods of 28 Apr.-28 May (May) and 28 May-7 July (June). A significant negative linear relationship existed between these two criteria from 7 July-3 Aug. (July). May (0.237 mg K per fruit-day) and July (0.267 mg K per fruit-day) mean fruit K accumulation rates were similar, but both were significantly higher (P = 0.001) than those for June (0.140 mg K per fruit-day). Mean leaf K accumulation rates for May (- 0.007 mg K per leaf-day) and July (-0.010 mg K per leaf-day) were similar, but both were significantly (P = 0.001) less than for June (0.005 mg K per leaf-day). Potassium per fruit accumulation was highest in trees with highest K status. Periods of net leaf K efflux and influx did not precisely correlate with fruit growth stages measured by fruit dry weight. The period of lowest fruit K accumulation (28 May-7 July) coincided with the period of maximum dry matter accumulation by the kernel. After 7 July, all increases in fruit dry weight and K content were due to mesocarp growth.

Free access

Abstract

The correction of K deficiency in fruit trees frequently has not been obtained due to failure of surface applications of fertilizer K to penetrate into root zones. The effectiveness of gypsum, as a displacing agent, to move K downward was studied using soil columns. Postassium applied at the surface accumulated in a shallow zone of K-rich soil. Increasing amounts of gypsum resulted in displacing the K to both a greater depth and a broader zone in the soil.

Open Access