Mixing calcium chloride with commercial fungicide formulations results in very slow penetration of calcium into apple fruits

Foliar applications of calcium salts are usually combined with fungicides. In the years 2002 and 2003, it was tested if this practice assures high rates of penetration of calcium. Amounts that penetrated in 24 h were measured at 20 °C using ⁴⁵CaCl₂. To ensure maximum penetration rates, humidity was maintained at 100 %. Sample size was 40 to 50 fruits, and data were presented as box plots because distribution of data was not normal. Median rates of penetration of CaCl₂, measured with mixtures of fungicides and CaCl₂ at 5 or 10 g l^–1, respectively, were very slow, and amounted to only a few percent of the dose applied. Rates were a little higher with very young fruits (55 days after full bloom, DAFB). Adding alkyl polyglycoside surfactants at 0.2 g l^–1 significantly decreased surface tensions, and increased rates of penetration by up to 15‐fold. Still, total penetration of CaCl₂ rarely exceeded 20 % of the dose applied (median penetration), even in the presence of an additional surfactant. In all treatments, outliers with 60 to 100 % penetration in 24 h occurred, and this was attributed to penetration into lenticels. This is expected to result in unequal concentrations of calcium in fruits, especially in the sub‐epidermal layers. Addition of a suitable surfactant to mixtures of fungicides with CaCl₂ is strongly recommended as it enhances wetting and greatly increases penetration rates of CaCl₂.     

Cuticular penetration of calcium salts: effects of humidity,anions, and adjuvants

Physical laws of cuticular penetration of calcium salts have been studied using astomatous isolated pear (Pyrus communis L.) leaf cuticular membranes (CM). Penetration followed first order kinetics and was greatly affected by humidity, hygroscopicity, solubility of salts, and nature of adjuvants. Penetration required dissolution of the salts and this is determined by their point of deliquescence (POD). POD corresponds to the humidity over a saturated salt solution containing undissolved salt. When humidity was above POD the salt residue on the cuticle dissolved, while below a solid residue was formed and penetration ceased. CaCl₂ and Ca(NO₃)₂ have POD's of 32 and 55%, respectively, while POD's of organic calcium salts (acetate, lactate, propionate) were between 95 and 100%. Furthermore, aqueous solubility of the inorganic calcium salts is one to two orders of magnitude higher than that of the organic salts. Thus, organic calcium salts are not well suited for foliar nutrition since POD's are very high and driving forces of penetration are low due to low solubility even at 100% humidity. CaCl₂ and Ca(NO₃)₂ penetrate even at low humidity and solubility is much higher. When humidity was above the POD, rate constants of penetration increased with increasing humidity by about a factor of three and maximum rates were measured at 100%. Temperature did not affect rate constants of penetration from which it can be concluded that penetration is most rapid during the night when humidity is high. All salts should be used with an effective wetter as with an alkyl polyglucoside half time of penetration was decreased from 204 to 17 h. All other adjuvants tested (protein hydrolysates, EDTA, gum guar) decreased rate constants of penetration by factors of 3 to 9. This finding is discussed in relation to mixing foliar nutrients with fungizides.     

Post-harvest disorders and mineral composition of apple fruits as affected by pre-harvest calcium treatments

Abstract

The effect of pre-harvest calcium sprays, CaCl₂ and Ca (NO₃)_2, on apple (Malus domestica) N, P, K, Ca and Mg content, storability and incidence of physiological disorders (superficial scald, bitter pit, physiological spot) was studied using two cultivars, ‘Krameri Tuviõun’ and ‘Talvenauding’. In the first year calcium treatment did not reduce any physiological disorders or loss of marketable yield. In the second year calcium treatment reduced storage losses until four months after storage. Bitter pit in ‘Krameri Tuviõun’ was unaffected by calcium treatment, but physiological spot of ‘Krameri Tuviõun’ and superficial scald of ‘Talvenauding’ were reduced by calcium treatment in the second year. Both physiological disorders of 'Krameri Tuviõun’ correlated negatively with Mg and P content and Mg/Ca ratio in apples. Superficial scald of ‘Talvenauding’ correlated negatively with Ca content and positively with K/Ca ratio, N/Ca ratio and Mg/Ca ratio in fruits. The conclusion can be made that content of Ca and its ratios with other nutrients plays an important role in the development of superficial scald on ‘Talvenauding’ fruits, and increasing Ca content in fruit can therefore be recommended for improving post-harvest quality of this cultivar. Since bitter pit in 'Krameri Tuviõun’ was not reduced by calcium treatment, it would be worth trying other measures for this cultivar.     

In‐season calcium‐spray formulations improve calcium balance and fruit quality traits of peach

Experiments to evaluate the effect of in‐season calcium (Ca) sprays on late‐season peach (Prunus persica L. Batsch cv. Calrico) were carried out for a 2‐year period. Calcium formulations (0.5% and 1.0% in 2008 and only 0.5% tested in 2009) supplied either as CaCl₂ or Ca propionate in combination with two or three adjuvants (0.05% of the nonionic surfactants Tween 20 and Break Thru, and 0.5% carboxymethylcellulose, CMC) were sprayed four to five times over the growing season. Peach mesocarp and endocarp Ca concentrations were determined on a 15‐day basis from the beginning of May until the end of June. Further tissue analyses were performed at harvest. A decreasing trend in fruit Ca concentrations over the growing season was always observed regardless of the Ca treatments. Both in 2008 and 2009, significant tissue Ca increments associated with the application of Ca‐containing sprays in combination with adjuvants were only observed in June, which may be coincident with the period of pit hardening. In 2008, both at harvest and after cold storage, the total soluble‐solids concentration (° Brix) of fruits supplied with Ca propionate (0.5% and 1.0% Ca) was always lower as compared to the rest of treatments. The application of multiple Ca‐containing sprays increased firmness at harvest and after cold storage, especially when CaCl₂ was the active ingredient used. Supplying the adjuvants Tween 20 and CMC increased fruit acidity both at harvest and after cold storage. Evaluation of the development of physiological disorders after cold storage (2 weeks at 0°C) indicated a lower susceptibility of Ca‐treated fruits to internal browning. Fruits treated with multiple CaCl₂‐, CMC‐, and Break Thru®‐containing sprays during the growing season were significantly less prone to the development of chilling injuries as compared to untreated peaches.     

Enhancing biological efficacy and rainfastness of foliar applied calcium chloride solutions by addition of rapeseedoil surfactants

The efficacy of a homologous series of biodegradable rapeseedoil derivatives (triglyceride ethoxylates; Agnique RSO® series, Cognis, Düsseldorf, Germany) with an average of 5, 10, 30, and 60 units of ethylene oxide (EO) as adjuvants for foliar‐applied calcium chloride (CaCl₂) was evaluated in Malus domestica L. Borkh. Previous experiments revealed that the surfactants used are not phytotoxic. All the surfactants applied decreased contact angles of spray solutions. The lipophilic surfactants RSO 5 and RSO 10 reduced contact angles more than the hydrophilic ones. Drying time of spray droplets was most prolonged when RSO 5 was added. Our data provide evidence that the most lipophilic surfactant RSO 5 can enhance Ca penetration, which was shown in isolated cuticles of tomato fruits (Lycopersicon esculentum cv. Panovy) as a model system. The surfactant effect was most pronounced during the first 4 h and reached a plateau after 24 h. Rainfastness of Ca on surfaces of Malus domestica leaves was improved when RSO 5 was added to CaCl₂ spray solutions. All surfactants applied improved rainfastness of Ca on ’︁Braeburn’ fruit surfaces compared to the treatment with CaCl₂ alone. Under field conditions, leaf/fruit application of CaCl₂/RSO 5 led to an increased Ca content in ’︁Braeburn’ apple fruits and a reduced bitter pit incidence.     

苯嗪草酮疏果剂对苹果边果营养与激素含量的影响

为明确苯嗪草酮疏果剂对苹果边果的疏除作用,以9年生天红2号/SH38/八棱海棠为试材,在最大边果直径6 mm左右时喷300 mg/kg苯嗪草酮2次,清水为对照,生理落果后调查坐果率及坐果比例;喷药后7、9、11、17、29 d采集处理和对照边果,测定氮磷钾矿质营养,淀粉、葡萄糖、果糖、蔗糖和山梨醇碳水化合物,可溶性蛋白...     

幼果期富士苹果树体各器官钙定量分析

对幼果期矮化富士苹果树体各器官及其皮层、木质部的生物量、钙含量和钙累积量进行了研究。结果表明，单株干重为10．21kg，皮层和木质部干重分别为2．14和7．07kg，骨干枝干重为各器官之首；各器官钙含量差异显著，根系平均钙含量高于地上部多数器官，中央干皮层钙含量最高；单株钙累积量为76．67g，皮层和木质部钙累积量分别为52．44和13．83g，直径1．0-5．0cm根的钙累积量最高。     

钙对苹果果实发育及果肉细胞超微结构的影响

以"红富士"苹果果实为试材,从盛花后10d开始,分3次向果实中引入CaCl2及EGTA,研究了钙对果实细胞超微结构和果实生长的影响。结果表明,钙处理使果实细胞细胞壁、质体等区域的电子密度增大,质体上的嗜锇颗粒大而清晰;钙的缺乏造成细胞壁扭曲、断裂等现象,使质体结构异常。钙处理抑制了果实生长。花后10～20d钙缺乏,促使果实横径发育,之后缺乏,对果实横径生长起到抑制作用。     

Effect of Pre-Harvest Calcium Sprays on Calcium Concentrations in the Skin and Flesh of Apples

During 2004 and 2006, experiments were conducted that measured the absorption of calcium (Ca) by the fruit and assessed the effects of Ca sprays on the skin and flesh of apples. Frequent (1 spray/month for 2 or 4 months) Ca treatments increased the concentration of Ca in the skin, but not in the flesh of fruit, and several sprays were needed to promote a prolonged increase in the concentration of Ca in the skin. Calcium sprays did not influence the concentrations of magnesium (Mg) and potassium (K). Foliar analyses confirmed the absorption of topical Ca by the apple tree following the Ca sprays as the concentration of Ca in leaves increased.