Shortage of water in arid and semiarid areas throughout the world makes utilization of marginal water for agricultural irrigation a necessity. The marginal water most used for irrigation in Israel is secondary-treated urban effluents. In spite of the water treatment process, these waters often contain higher levels of bacterial human pathogens than the potable water from which they were derived. Utilization of the treated effluents for irrigation in Israel is strictly regulated according to the water quality and the irrigated crop. Due to health concerns, and a lack of experimental data, the treated effluents are not yet used for irrigation of vegetables. In the present study we have evaluated safety and agronomic issues involved in irrigation of summer melon with secondary-treated urban effluents, administered to the production field by surface and sub-surface drip irrigation according to the national regulations. Two water qualities were compared, secondary-treated wastewater and potable water. The effluents contained higher levels of EC, pH, Na and Cl, N, P, K, microelements, and heavy metals than the potable water. Potable water was applied by surface drip irrigation, and three irrigation regimes were compared for the treated effluents. These included surface irrigation, and subsurface irrigation at 20 or 40 cm below the soil surface. No differences in yield quantity and quality were found between treatments. Na concentrations and SAR levels of the soil were higher under irrigation with the effluent. Contamination by E. coli, fecal coliforms, and total coliform bacteria were found on the melon peel of all treatments, and the quantity and quality of the contamination did not vary significantly between treatments. E. coli and fecal coliforms were found in the surface 0-2 cm soil samples of treatments irrigated with both water qualities by surface drippers, but no contamination was found in the treatments irrigated by subsurface irrigation. The fact that the microbial contamination of the fruit was not prevented by subsurface drip irrigation or by irrigation with fresh water suggests that environmental factors, rather than an irrigation treatment affect, were the cause for the microbial spread. Further analysis is required concerning effects of environmental factors, such as the interaction between weather conditions and distance from the effluent oxidation ponds on temporal geospatial distribution of the bacterial human pathogens and the potential for subsequent contamination of fresh produce in the field.
Ca deficiencies induce a range of physiological disorders in plants. The disorders typically appear in young growing tissues that are characterized by high demand for Ca and restricted Ca supply due to low transpiration. In this study, we examined the effect of supplementing Ca by foliar spray and through the irrigation solution to Anemone coronaria plants, in order to evaluate if flower abortions and leaf damages that appear in the production fields are related to Ca deficiencies. With the goal to develop a preventive nutritional regime, four Ca treatments were evaluated. The supplemented Ca was applied with the fertigation solution in the concentrations of 60 or 110 ppm Ca; with the 60 ppm application an additional application of Ca by foliar application was tested in concentrations of 3 g/l Ca or 6 g/l Ca, as Ca(NO3)2. The plants were cultivated in a net-house, in soilless culture (Tuff) beds. Application of 110 ppm Ca compared to 60 ppm with the fertilizing solution increased the concentration of Ca in the leaf tissue, resulting in an increase in the quantity and quality of the flowers. Calcium supply by foliar spray, at both 3 g/l or 6 g/l Ca(NO3)2 caused leaf necrosis and did not improve yield production. Application of 110 ppm Ca reduced the concentrations of Mn, Cl and Na in the leaves. Application of Ca in the irrigation solution, or by foliar spray, did not reduce the percentage of non-marketable flowers. The identified lower concentrations of Ca in damaged compared to non-damaged leaves on the flower stem suggests that the damages to the flowers and the leaves is related to local deficiencies of Ca.
The irrigation and fertilization regime of different varieties of Grevillea in Israel are based on existing knowledge for growing various varieties of the Proteaceae family for production of cut flowering branches. However, growers face problems in cultivating Grevillea “Spiderman,” such as leaf chlorosis, prolonged growth until flowering, and reduced quality of cut flowering branches. The present study aimed to examine whether these problems stem from deficiency or excess of Fe, Mn, Zn, P, and Mg, focusing on the effect of these nutrients on growth, flowering, and appearance of visual leaf symptoms and on yield, quality, and vase life longevity of cut flowering branches. The nutrient treatments significantly affected plant development and flowering. Increasing the Fe concentration from 1 to 2 or 3 mg l–1 resulted in improved leaf color, from slightly yellow to dark green. The combination of 2 mg l–1 Fe + 1.8 mg l–1 Mn resulted in early flowering, highest yield, and development of long lateral branches. Low levels of P caused in the first year of treatment leaf chlorosis, which was intensified during the third year, resulting in severe yellowing of the flowering branches. Leaf necrosis and tip burn appeared in treatments with high concentrations of Zn, Mn, and Mg. Deficiency of Fe and Mn and high concentration of P and Mg led to the development of a large number of branches without flowers. The optimal fertilization treatment that yielded the highest quality of flowering branches after harvest was 2 mg l–1 Fe. Branches of this treatment had green foliage at harvest and the longest vase life (10 days) following the recommended postharvest treatment and air transport simulation. Based on the findings of the present research, it can be concluded that the problems in the cultivation of G. “Spiderman,” such as leaf chlorosis, delayed flowering, and reduced quality of flowering branches, result from improper fertilization.
Eucalyptus silver dollar (Eucalyptus cinerea) is cultivated under intensive agronomic practices for production of cut foliage branches for the floriculture industry. A range of damage symptoms, suspected to be related to unoptimized mineral nutrition, routinely occur in the leaves at the production plantations and reduce yield quality. No information is available about the nutritional requirements of Eucalyptus silver dollar, or of any other Eucalyptus species under intense cultivation for cut foliage branches production. In this study we evaluated the hypotheses that: (1) leaf damage symptoms in the Eucalyptus silver dollar plantations might be related to the nutritional status of the leaves; and (2) they are affected by environmental and growing conditions, and will therefore differ between seasons and location of the plantations. To test these hypotheses we studied the seasonal and location variations in the ionomics of damaged and healthy leaves, physiological parameters, and postharvest attributes of cut foliage branches during vase life in four plantations of Eucalyptus silver dollar in Israel. The observed leaf symptoms were also characterized anatomically. The range of concentrations for individual macronutrients in the leaves was (in g kg–1): N (18–40); P (1.2–3.0); K (5.5–17.0); Ca (3.5–14.0); Mg (1.1–2.8); S (1.3–2.6). The concentrations range for micronutrients was (in mg kg–1): B (10–100); Fe (30–170); Zn (14–27); Mn (38–190); Cu (3.5–5.9). None of the identified leaf symptoms correlated with a consistent increase or decrease of the content of a specific mineral nutrient or heavy metal compared to the healthy leaves, suggesting that they were not caused by mineral deficiency or toxicity. The leaf ionomics was affected by season and varied between locations. The main damage symptoms observed in the four examined plantations during the four harvests were red and purple spots, and oil stains. Postharvest experiments showed that the quality of branches was reduced during 7–15 days of vase life following transport simulation to the local market. The degree of reduced quality during vase life was also dependent on the location of the plantation and the season of harvest. The oil stains appeared in the two most southern locations during summer, suggesting that this symptom might be derived from the summer conditions such as the high temperatures and high light intensities occurring in the southern part of Israel.