The effect of timing of post-harvest foliar urea sprays on nitrogen absorption and partitioning in peach and nectarine trees

Summary

The effects of timing of autumn foliar urea-N sprays on nitrogen absorption and partitioning were studied in mature peach and nectarine trees. A 10% ¹⁵N enriched urea solution was applied by either dipping individual shoots in 1995 or spraying whole tree canopies in 1996. Trees whose canopies were sprayed during the post-harvest period with a 10% w:v urea solution in 1996 were excavated in the dormant season, and ¹⁵N contents and distribution were determined. Peach leaves rapidly absorbed urea-N irrespective of application date, and transport of urea-N to perennial tree parts occurred primarily within 4–7 d after application. Between 48 and 58% of the urea-N applied was recovered in abscinded leaves and perennial organs. Leaves exported ≥60% of the foliar-applied urea-N following application in early autumn (September or October), but <50% export occurred when applied shortly before leaf fall (November). Of the urea-N translocated, most was recovered in roots (≥38%) following application in September or October. Urea-N applied in November, however, remained largely in the current year wood (ca. 45%). Thus, export and translocation of foliar applied urea-N diminished during the final stages of leaf senescence. Foliar application of urea in September or October supplied the equivalent of about 20% of crop nitrogen content, but only 14% (i.e. ca. 30% lower) when applied shortly before leaf senescence in November.     

Isotopically-labelled nitrogen uptake and partitioning in sweet cherry as influenced by timing of fertilizer application

Sweet cherry (Prunus avium L.) is a fruit of increasing economic importance though it is less significant than other stone fruit species such as peach. Cherry has received little attention concerning nitrogen (N) uptake and dynamics in mature trees. The aim of this work was to determine N uptake and partitioning as influenced by the timing of fertilizer application in 7-year-old sweet cherry trees cultivated in a cold region (Los Antiguos, Santa Cruz, Argentina; 71°38′ W, 46°32′ S). Nitrogen (95 kg ha⁻¹) was applied as ammonium nitrate to a soil with ‘Bing’ sweet cherry trees grafted onto Prunusmahaleb rootstocks. Fertilization was split into two equal applications per treatment, involving either the commercial fertilizer ammonium nitrate or the same fertilizer labelled with ¹⁵N isotope (10% atom.). Treatments consisted of one early spring (full bloom, October 2005) or one summer (late January 2006, 15 days after harvest) application of ¹⁵N ammonium nitrate to three replicate trees. Fruit were harvested in early January and leaves were collected at both full canopy and leaf fall. All trees were excavated in winter (August, 2006). Trees were partitioned into their components: trunk, branches (current-season shoots, 1-year-old and over-1-year-old branches), buds of the same age, small roots (less than 1 mm thick), large roots, leaves (sampled in February and April), and fruit (collected at harvest). Those components were dried and analysed for total N and ¹⁵N content. Total N per tree and N content derived from the fertilizer did not differ between treatments. Summer postharvest ¹⁵N application partitioned not only to structural components (trunk and roots) but also to buds and leaves. Uptake efficiency was significantly (p = 0.0113) higher in the spring than in the summer application (65.7% vs. 37.44%). Nevertheless, 52.5% of N applied in spring was lost due to harvest and summer pruning. This emphasizes the importance of the postharvest N fertilization which increases N accumulation in both reserve organs and buds though, according to our data, it is less efficiently used. The extent of nitrogen uptake, efficiency of use and partitioning in the following growing seasons are still open questions that deserve further research.     

Spring growth of almond nursery trees depends upon nitrogen from both plant reserves and spring fertilizer application

Summary

June-budded ‘Nonpareil’/‘Nemaguard’ almond (Prunus dulcis (Mill) D. A. Webb) trees were fertigated with one of five nitrogen (N) concentrations (0, 5, 10, 15, or 20 mM) from July to September. The trees were sprayed with either water or 3% urea in October, then harvested bareroot after natural leaf fall, and stored at 2°C. One set of trees was destructively sampled for total N content; the remaining trees were transplanted into N-free media in the spring after cold storage. After budbreak, these trees were supplied for 70.d with either N-free Hoagland’s solution or Hoagland’s solution containing ¹⁵N-NH₄NO₃. Nitrogen concentrations in both stem and root tissues were positively correlated with the N-fertigation concentration. Fall foliar urea applications increased levels of stem and root N regardless of the N-fertigation concentration. During the first 70 d of spring growth, the trees utilized nitrogen from both their reserves and spring fertilizer applications. The amount of N reserves used for growth of new shoots and leaves was proportional to the total amount of reserves. Trees with low N reserves relied primarily on the spring fertilizer as their source of nitrogen. We conclude, therefore, that both reserve N and spring-applied N fertilizers are important for enhancing the regrowth of bareroot almond nursery trees during establishment after transplanting. Nitrogen fertilization in the spring can especially improve the performance of trees with low N reserves.     

Evaluating foliar nitrogen compounds as indicators of nitrogen status in Prunus persica trees

Mobile nitrogen (N) forms may be better N indicators of the N status of trees than total nitrogen (TN) due to their higher sensitivity to increasing N supply. A field experiment was carried out over a 3-year period to compare foliar concentrations of total N (TN), soluble N (SN), chlorophyll (Minolta SPAD readings), NH₄–N and NO₃–N as indicators of soil N availability in nectarine, Prunus persica L. Batsch, cv. ‘Fantasia’ (grafted on ‘Nemaguard’ peach, P. persica × P. davidiana) trees. Young trees were exposed to a range of fertilizer-N application rates. Based on correlation analysis, the best association between leaf N compounds with soil N supply and trunk diameter and/or fruit yield was obtained with TN and chlorophyll SPAD readings. Leaf concentrations of mobile N compounds (NH₄–N and NO₃–N) increased more than any other N compound under high N supply; however, their inconsistency among years and low leaf concentration difficult their use as N indicators. The optimum foliar TN for growth decreased with tree age, 4.4%, 3.6% and 3.3% in non-bearing 1-year-old trees, non-bearing 2-year-old trees and 3.3 fruit-bearing 3-year-old trees. The optimum SPAD readings were 40 in 2-year-old trees and 42 in 3-year-old trees. Stable N compounds (TN and chlorophyll SPAD) could be used to N diagnosis in the zone of N deficiency, and soluble N compounds (NH₄–N and NO₃–N) to diagnoses N excess.     

Rate of nitrogen application during the growing season alters the response of container-grown rhododendron and azalea to foliar application of urea in the Autumn

Summary

One-year-old rhododendron (Rhododendron ‘H-1 P.J.M’) and azalea (Rhododendron ‘Cannon’s Double’) plants grown at different nitrogen (N) fertilisation rates were used to assess the influence of soil N applications during the growing season, and foliar applications of urea in the Autumn, on N uptake and accumulation, and plant growth in the following Spring. N uptake efficiency declined linearly during the first growing season with an increasing rate of N fertilisation. For both cultivars, foliar urea application in the Autumn significantly increased plant N content without affecting plant size, regardless of plant N status. Leaves of rhododendron accumulated more N than other plant structures. Plants sprayed with foliar urea in the Autumn had more new growth the following Spring than plants receiving no urea, regardless of whether the plants received fertiliser in the Spring. For azalea, N uptake in the Spring was, in general, not affected by applications of urea during the previous year. For rhododendron, urea application in the Autumn decreased N uptake the following Spring. For both cultivars, increasing N availability during the growing season increased the ratio of above-ground to below-ground dry weight. Our results suggest that combining optimum N applications during the growing season with foliar application of urea in the Autumn can improve N uptake efficiency, increase N storage, and optimise growth in Rhododendron.     

Usage of Shoot Analyses to Assess Early-Season Nutritional Status of Apple Trees

Mid-summer leaf analyses are commonly used as the standard method worldwide to assess the nutritional status of fruit trees. However, the analyses performed at this period yield information only about current nutritional status of the trees. Several physiological processes influencing yield and quality take place early in spring. It was reported in previous studies that dormant-season shoot analyses for some nutrients may reliably be used to assess early-season nutritional status of peach trees.The present study was conducted with the shoot samples taken in dormant-season of 150 apple orchards from Isparta region during the years 2010 and 2011. Shoot samples were taken 15 days before full bloom stage and samples were subjected to nutrient analyses. Reference values for each nutrient were indicated as 25 and 75% of the resultant values. The shoot reference values for N, P, K, Ca, Mg, Fe, Mn, Zn and B were respectively observed as 0.66–0.82%, 0.12–0.15%, 0.37–0.45%, 0.84–1.24%, 0.11–0.16%, 24.55–32.24?ppm, 11.12–17.55?ppm, 12.96–21.90?ppm and 13.33–16.00?ppm. To check the reliability of shoot analyses, leaf samples were taken from the same orchards in 7 different periods until mid-vegetation season and correlations between nutrient contents of shoots and nutrient contents of leaves taken in all periods were investigated. Significant correlations were observed between N, P, K, Mg, Mn and B contents of shoots and leaves. Therefore, it was concluded that early-season shoot N, P, K, Mg, Mn and B analyses could reliably be used to assess nutritional status of apple trees.     

Foliar fertilization of peach (Prunus persica (L.) Batsch) with different iron formulations: Effects on re-greening,iron concentration and mineral composition in treated and untreated leaf surfaces

A trial to assess the effects of applying several Fe-containing formulations on Fe-deficient (chlorotic) peach leaves was carried out under field conditions. Solutions consisting of an Fe-containing compound (FeSO₄·7H₂O, Fe(III)–citrate, Fe(III)–EDTA, Fe(III)–DTPA or Fe(III)–IDHA) and one of five different surfactant treatments (no surfactant, an organo-silicon, an ethoxylated oil, a non-ionic alkyl polyglucoside and a household detergent) were applied to one half of the leaf via dipping, first at the beginning of the trial and then after 4 weeks. The re-greening of treated and untreated leaf areas was estimated with a SPAD apparatus, on a weekly basis, during 8 weeks. At the end of the experimental period, leaves were detached, and tissue Fe, N, P, K, Ca, Mg, Mn, Zn and Cu concentrations were determined in Fe-treated and untreated leaf areas. Treatment with Fe-containing solutions always resulted in leaf chlorophyll (Chl) increases, which however significantly depended on the Fe-source, the surfactant-type and the combination between both formulation components. Untreated leaf zones experienced a Chl increase only in some cases, and this depended on the type of surfactant used. Iron application significantly increased the Fe concentration of treated and untreated leaf areas, especially with some formulations. Foliar treatment with Fe-containing solutions induced significant changes in the concentration of several nutrients as compared to those found in Fe-deficient peach leaves, with changes being similar in treated and untreated leaf areas, although in some elements the extent of the changes was of a different magnitude in both materials. This indicates that some leaf mineral composition changes typical of chlorotic leaves are dependent on leaf Fe concentration rather than on leaf Chl levels. Results obtained are relevant to help understand the factors involved in the penetration and bioavailability of leaf-applied Fe, and to assess the potential of foliar Fe fertilization to control Fe deficiency in fruit trees.     

Influence of almond × peach hybrids rootstocks on flower and leaf mineral concentration,yield and vigour of two peach cultivars

Flower and foliar nutrient content of ‘Queen Giant’ and ‘Tebana’ peach [Prunus persica (L.) Batsch] on six almond × peach hybrids rootstocks (‘Adafuel’, ‘Adarcias’, ‘GF 677’, ‘Cadaman’, ‘Garnem’ and ‘Felinem’) were determined during one season. The mineral elements analysed were: N, P, K, Ca, Mg, Fe, Mn, Zn, Na and Cu. Leaf N concentration in ‘Queen Giant’ was the highest on ‘Cadaman’ and ‘GF 677’ and the lowest on ‘Adarcias’. The P, Fe and Zn concentrations in flowers and leaves were significantly correlated. The leaf chlorophyll concentration at 120 DAFB was positively correlated with Fe floral concentration and with K, Zn and Na leaf concentration, in ‘Queen Giant’, and with K and Mn leaf concentration, in ‘Tebana’. In ‘Queen Giant’, the greatest trunk cross-sectional area was exhibited with ‘Felinem’ and ‘Garnem’ and the lowest with ‘Adarcias’. In contrast, the greater yield efficiency was found on ‘Adarcias’. In ‘Queen Giant’, a negative correlation was found between yield efficiency and Ca in leaves and in flowers. A positive correlation was observed between tree vigour and flower Fe, flower Ca and leaf Ca concentration. Correlation was also found between yield efficiency and Mg in ‘Tebana’ flowers. In ‘Queen Giant’, ‘Felinem’ rootstock showed the weakest balanced nutritional values (ΣDOP index) compared with other rootstocks.     

Additional nitrogen fertilization affects salt tolerance of lemon trees on different rootstocks

Irrigation with saline water is one of the major problems in citrus crop in arid and semi-arid regions. Because rootstock and fertilization play an important role in citrus salt tolerance, we investigated the influence of the nitrogen fertilization and rootstock on salt tolerance of 2-year-old potted Fino 49 lemon trees. For that, trees grafted on Citrus macrophylla (M) or Sour orange (SO) rootstocks were watered for 12 weeks with complete nutrient solution containing either 0 mM NaCl (control, C), 50 mM NaCl (S), 50 mM NaCl with an additional 10 mM potassium nitrate (S + N), or 50 mM NaCl with a 1% KNO₃ (S + Nf) foliar spray application. Trees on M were more vigorous than trees on SO and saline treatments reduced leaf growth similarly in trees on both rootstocks. Trees on SO had a lower leaf Cl⁻ and Na⁺ concentration than those on M. Additional soil nitrogen (S + N) decreased leaf Cl⁻ concentration and increased leaf K⁺ concentration in salinized trees on both rootstocks. However, the salinity-induced reduction leaf growth was similar in S + N and S trees. This was due to osmotic effect, beside leaf Cl⁻ and Na⁺ toxicity, played an important role in the growth response of Fino 49 lemon to the salt stress. Additional foliar nitrogen in the S + Nf treatment also reduced leaf Cl⁻ concentration relative to the S treatment but trees from S + Nf treatment had the lowest leaf growth. Net assimilation of CO₂ (ACO₂$A_{\text{C}{\text{O}}_2}$), stomatal conductance (g_s) and plant transpiration were reduced similarly in all three salt treatments, regardless rootstock. Salinity reduced leaf water and osmotic potential such that leaf turgor was increased. Thus, the salinity-induced ACO₂$A_{\text{C}{\text{O}}_2}$ reductions were not due to loss of turgor but rather due to high salt ion accumulation in leaves.     

Evaluating the effectiveness of different strategies for calcium application on the accumulation of calcium in apple (Malus × domestica Borkh. ‘Braeburn’) fruit

Summary

Orchards displaying calcium (Ca) deficiency are a common phenomenon worldwide, despite the presence of sufficient Ca in the soil and the plant. A 3-year trial was conducted between the 2007 – 2008 and 2009 – 2010 growing seasons to evaluate the contributions of soil and foliar Ca applications to Ca concentrations in ‘Braeburn’ apple (Malus × domestica Borkh.) fruit. Ca(NO₃)₂ (Calflo; Yara Africa, Fourways North, South Africa) was applied as six separate foliar sprays until run-off. Applications were made at 1-week intervals between approx. 21 – 70 d after full bloom (DAFB) at 6.75 ml l^–1. Soil applications of Ca (Tropicote^TM; International ASA, Oslo, Norway) at 300 kg ha^–1 were applied at fruit set, or after harvest, according to standard practice. Mineral analysis was conducted to assess the soluble Ca concentrations of whole fruit (without pips and stalks), to quantify the contribution of foliar sprays or soil-applied Ca. Fruit Ca concentrations were maintained at satisfactory levels (4.5 mg Ca 100 g^–1 FW) at harvest by applying a series of six foliar sprays early in the season (for all seasons) during the trial period. Fruit Ca concentrations at 80 DAFB were highest in the treatments with foliar applications of Ca. In 2009 – 2010, Ca concentrations in apple fruit were lowest (8.38 mg 100 g^–1 FW) for soil application of Ca at fruit set. Ca applications to soil after harvest in the previous season, and soil applications shortly after fruit set in the current season, did not significantly increase Ca concentrations in current-season fruit, providing soil Ca levels were above the minimum requirement for apple trees. A possible explanation is that apple trees regulate their uptake of Ca through the roots when soil Ca is available in sufficient quantities. This confirms the importance of active root growth for efficient Ca uptake by apple trees when applying Ca to the soil.     

Prognosis and correction of iron chlorosis in peach trees and relationship between iron concentration and Brown Rot

This study investigates the possible correlations between bark, floral, and leaf iron (Fe) concentrations and SPAD measures to be used as early methods for prognosis of iron chlorosis in peach trees. The results showed that there were significant correlations between bark, floral and leaf Fe concentrations and SPAD measurements. This study shows for the first time the possibility of using bark analysis as an early predictive method of iron chlorosis in peach trees.Differences in mineral composition of leaves of peach trees, in relation to rootstocks were also found.This study also investigated the distribution of mineral elements in different parts of peach leaves. Tissue analysis of different leaf parts showed that the peripheral and petiole of leaves had the highest P, Ca, Mg, Zn, Fe, B and Cu concentrations. In contrast, the highest K concentration was found in the internal parts of leaves. High Mn concentration was found in the laminar of leaves, but was lower in the petioles.In other experiments, the effect of different sources of Fe application on the leaf Fe concentrations and development of Brown Rot in the year of application and one and 2 years later was also examined. No application increased significantly the leaf Fe concentrations in the year of application and 1 year later. Leaf Fe concentrations were significant higher in trees treated with FeSO₄·7H₂O + S 2 years after application.The possible effect of flesh Fe concentration to susceptibility of peach (cv. Sun Crest) to Monilinia laxa was also evaluated. The results showed no correlation between flesh Fe concentration and susceptibility of peach to M. laxa. Besides, no statistical difference was found in the susceptibility of peach to M. laxa collected from the cultivar Sun Crest grafted on different rootstocks.     

Evaluation of the effectiveness of soil-applied plant derivatives of Meliaceae species on nitrogen availability to peach trees

We assessed the effect of soil-applied derivatives of melia (Melia azedarach L.) and neem (Azadirachta indica A. Juss) on nitrogen (N) soil availability, root uptake and peach (Prunus persica L.) growth. First we evaluated the effectiveness of experimentally prepared amendments made with fresh ground melia leaves or commercial neem cake incorporated into the soil as nitrification inhibitors, then we evaluated the effect of fresh ground melia fruits and neem cake on growth and N root uptake of potted peach trees, and on soil microbial respiration. Soil-applied fresh ground melia leaves at 10 and 20 g kg⁻¹ of soil as well as commercial neem cake (10 g kg⁻¹) were ineffective in decreasing the level of mineral N after soil application of urea-N as a source of mineral N, rather they increased soil concentration of nitric N and ammonium N. The incorporation into the soil of fresh ground melia fruits (at 20 and 40 g kg⁻¹) and neem cake (at 10 and 20 g kg⁻¹) increased N concentration in leaves of GF677 peach × almond (Prunus amygdalus) hybrid rootstock alone or grafted with one-year-old variety Rome Star peach trees. An increase in microbial respiration, leaf green color and plant biomass compared to the control trees were also observed. The Meliaceae derivatives did not affect, in the short term (7 days), N root uptake efficiency, as demonstrated by the use of stable isotope ¹⁵N, rather they promoted in the long term an increase of soil N availability, N leaf concentration and plant growth.     

苹果施用硝酸钙的效果

通过对苹果树叶面喷和土施试验证明:(1)叶面喷(包括盆栽和田间试验)0.3％Ca液2次,能促进树体生长、增加叶干重、提高树体N、K、Ca等营养元素水平,并明显提高果实产量和品质。在年生育期的前期或后期喷Ca,均能进入果实中,前期进入量高于后期。(2)土施Ca(NO_3)_2,同施用筹N量的尿素相比,叶片中N、P、K、Ca、Fe、Zn等元素含量,均有明显提高,并有增产和提高品质作用。在土施方式中,以Ca(NO_3)_2与有机肥混施为佳,但土施Ca(NO_3)_2对提高果实中Ca含量未显出明显效果。(3)总体效果,土施不如叶喷。     

Calcium and Potassium Foliar Sprays Affect Fruit Skin Color,Quality Attributes,and Mineral Nutrient Concentrations of ‘Red Delicious’ Apples

This study was conducted to evaluate the influences of foliar spray of potassium (K), calcium (Ca), and their combination on the fruit red skin color and quality attributes of ‘Red Delicious’ apple under conditions of south central Iran with warm and dry summer, where low and high temperature differences are low. The trees were sprayed five times using 5 g L^–1 calcium chloride (CaCl₂) at 3-week intervals starting from 3 weeks after full bloom and three times (at 9, 12, and 15 weeks after full bloom) using 2.5 g L^–1 K sources [potassium chloride (KCl), potassium sulfate (K₂SO₄), and potassium nitrate (KNO₃)] during two growing seasons in 2013 and 2014. Anthocyanin, some physicochemical attributes, and fruit mineral concentrations were measured at harvest. Results showed that spraying with K, CaCl₂, and their combinations significantly increased fruit weight, sugar and anthocyanin concentrations, firmness, and K uptake. A combined foliar application of CaCl₂ and each of the K sources was more effective on the improvement of fruit color, firmness, fruit K and Ca uptake, and K/Ca ratio as compared to the case when either K or Ca was applied alone.     

Peach/myrobalan plum graft incompatibility in the nursery

Various peach/myrobalan graft combinations were compared in nursery trials. Two peach cultivars (Prunus persica L. Batsch) grafted on five myrobalan x myrobalan (Prunus cera- sifera L. Ehrh.) clones were observed during the first year of growth after budding. Graft combinations, comprising the same peach cultivars grafted on other myrobalan x myrobalan clones that had shown symptoms of ‘translocated’ graft incompatibility in some replicated trees during the first year, were observed during the second year of growth. The time taken for the appearance of symptoms of incompatibility was determined. The degree of incompatibility was determined from growth rates, leaf dry weight per unit area, and leaf pigment content. Root carbohydrate content was measured at leaf fall. The sanitary state of plant material was determined to explain differences in severity and/or time for symptom appearance, observed between some replicates. No relationship was found between the sanitary state of plant material and the severity or speed of expression of peach/myrobalan incompatibility. When incompatibility was expressed during the first year of growth, modifications in growth rates, leaf dry weight per unit area and leaf pigment content preceded the expression of visible symptoms on leaves by several weeks. In one peach cultivars, in which graft combinations showed symptoms of ‘translocated’ graft incompatibility in some replicates during the first year after budding, all replicates showed such symptoms during the second year. Therefore, the variation observed during the first year appeared to result from a delayed expression of incompatibility. Significant differences in speed and/or severity of incompatibility expression were shown between the two peach cultivars for any given rootstock.     

Effects of multiple applications of methyl jasmonate on fruit ripening,leaf gas exchange and vegetative growth in fruit trees

Summary

Multiple applications of methyl jasmonate (Me-J), at 10.mM, enhanced the rate of fruit ripening in peach ‘Redhaven’. The effect of Me-J on red colour development and fruit firmness was most pronounced in fruit treated six times with Me-J. Lower concentrations of Me-J had no effect of fruit colour. Me-J, at 10.mM, significantly reduced stomatal conductance, photosynthetic rate and transpiration rate of crabapple leaves, but had no effect on these parameters in peach leaves. The short-term inhibitory effects of Me-J on leaf gas exchange in crabapple persisted for up to 24 h. Fourteen applications of Me-J over a period of 28 days resulted in a 60% decrease in the concentration of chlorophyll in leaves. These Me-J applications also reduced the length of new branches, leaf number and leaf fresh weight by 65%, 31% and 47%, respectively. In peach, Me-J induced some leaf chlorosis and early leaf senescence within two weeks of the treatments which resulted in significant reductions in shoot length.     

Relationship of leaf necrosis and defoliation to phosphorus and potassium concentrations in selected tissue and to certain fruit quality parameters of pecan

Pecan [Carya illinoinensis (Wangenh.) K. Koch] trees developed necrotic areas in the leaves late in the growing season. July samples indicated that leaf P (0.114% DW) and K (0.62% DW) were low, but other elements were within accepted sufficiency ranges. Relationships between leaf P and K concentrations with nut quality and return bloom were determined. Trees were rated for leaf necrosis 1 October using a 1 (none)–5 (severe) scale. Fruit were harvested and analyzed for weight/nut, kernel weight, and kernel grade. Leaflet pairs collected 1 October from fruit bearing shoots were analyzed for N, P and K. Return bloom was determined on branches that bore fruit the previous year. Necrosis ratings were positively related to leaf N and negatively correlated with weight/nut; kernel, shuck and leaf P concentrations; and kernel and leaf K concentrations. Leaf, kernel and shuck P concentrations were positively correlated with weight/nut and percentage number 1 kernels. Leaf K was positively correlated with return bloom and weakly negatively correlated to weight/nut. Phosphorus was the primary element limiting fruit development and K shortage substantially reduced return bloom. Data support minimum pecan leaf standards in July for fertility recommendations of 1.0% K and 0.14% P.     

半根交替干旱对‘大久保’桃叶片中几种有机渗透调节物质的影响

 和良好水分条件的对照相比较, 半根交替干旱处理(ARS) 对‘大久保’桃叶片日出前水势无显著影响, 但显著高于全根干旱(WRS) 处理。WRS导致叶片中游离氨基酸、脯氨酸和可溶性糖含量显著增加和淀粉含量显著降低, 而ARS和对照之间叶片中游离氨基酸、脯氨酸、可溶性糖和淀粉含量均不存在显著性差别。此外, 叶片中游离氨基酸、脯氨酸和可溶性糖含量与日出前叶片水势呈显著或极显著负相关, 而淀粉含量与日出前叶片水势呈极显著正相关。上述结果表明, ARS条件下植株具有良好的水分供应能力, 并不存在积累上述有机物质进行渗透调节的现象。     

Antagonism of micronutrient cations on sweet orange leaves

The effect of combined applications of micronutrient cations in spray solutions, usually used to correct simultaneously nutritional disorders and fungal diseases, was investigated, especially regarding absorption of Zn at the surface of sweet orange leaves. Foliar application of 0.0, 0.4, 0.8, and 1.2% CuSO₄ solutions, neutralized with Ca(OH)₂, in combination with 0.15 and 0.45% ⁶⁵ZnSO₄ solutions caused a significant and marked decrease in the absorption of ⁶⁵Zn. Application of unneutralized solutions of 0-0.8% CuSO₄ in combination with 0-0.6% of ZnSO₄· 7 H₂O showed mutual antagonism between Cu and Zn for their absorption at the leaf surfaces. Similarly, the absorption of ⁶⁵Zn in leaves decreased from 53 to 26% with simultaneous application of 0–2% MnSO₄ solutions and 0.45% ⁶⁵ZnSO₄ solutions neutralized with Ca(OH)₂. This emanated from the mutual antagonism between the two for their absorption at the surface of leaves. The absorption of ⁶⁵Zn decreased from 53 to 31% with foliar application of 0–2% FeSO₄ in combination with 0.45% ⁶⁵ZnSO₄ solution neutralized with lime. Again, Fe and Zn each inhibited the absorption of the other at the leaf surface.     

多效唑对桃树生长和结果的影响

应用多效唑对桃树进行土施和叶面喷布等不同方法,不同剂量的试验。土施0.125～1.0g/m~2,叶面喷布500ppm×2以上的浓度都可有效地抑制植株营养生长。它降低了新梢生长长度,抑制了副梢的发生和生长,以及干周的增长。多效唑在抑制营养生长的同时也促进了生殖生长,有效地促进花芽形成,降低了始花节位,增加了成花节位数和复花芽节位数。对果实大小也有促进作用。成倍地提高了早期产量。施用同等剂量,土施的效果优于叶面喷布。在我国中部地带,陇海沿线沙壤土上以0.25/m~2的剂量为好,第二年以后用量减半。在土施情况下它的“呆滞期”只1.0～1.5个月。土施应在旺盛生长前1.5～2.0个月以前施入。