The upper leaves of the cucumber plants have yellowish leaves, like gold rims, but the leaf tissue is not necrotic. The vegetable growers often mistakenly believe that this is caused by excessive spraying of pesticides. However, in fact, the phenomenon that cucumber leaves are inlaid with gold is due to a physiological disorder caused by improper application of nitrogen fertilizers.
In the nitrogen fertilizer used in production, the form of nitrogen is different. For example, ammonium nitrate is nitrate nitrogen, ammonium bicarbonate is ammonium nitrogen, and urea is ammonium ammonium. Among these three nitrogen fertilizers, cucumbers have the most preference for nitrate nitrogen. Some people have done cucumber nutrient solution culture experiments. When nitrate nitrogen accounted for 90% of the culture solution, the stems and leaves of the cucumber were bright green, and the growth was also large. The absorption of calcium and magnesium was high. When the nitrate nitrogen accounted for only 10%, the growth of cucumber decreased. 80%, absorption of calcium decreased by 69%, magnesium absorption decreased by 52%. Cucumber leaves are inlaid with Phnom Penh because of too much ammonium in the soil, which hinders the absorption of calcium by cucumber.
Excessive application of ammonium nitrogen can also lead to a series of other pathological conditions. 1 Leaf color changed from dark green to dark green, leaf surface appeared waxy and shiny; 2 leafy meat raised, leaf veins were relatively concave; 3 leaf margins rolled down, middle leaf uplifted, parachute-like; 4 growth point atrophy, heart When the leaves are bent, they are not developed. Once they are unfolded, they are obviously smaller than other leaves. The leaves of the head are significantly reduced. Five colored rusts and apical bluntness are truncated. In severe cases, rot and dead seedlings appear. This kind of phenomenon is actually applied to the soil according to nitrogen. It is easy to be adsorbed by the soil and increase the concentration of the soil solution. After the nitrate nitrogen is applied, it is not easy to be adsorbed by the soil, so the concentration of the soil solution does not increase much. Therefore, the application of nitrate nitrogen in cucumber is an important measure to prevent and control physiological diseases and ensure good growth.
In the case of "gold-rimmed", spraying 0.5% calcium superphosphate solution or 0.4% calcium chloride solution 2 or 3 times on the foliage can effectively enhance the plant's viability.
In addition, the application of ammonium nitrate as the base fertilizer, the amount should not be large. Topdressing should also be used multiple times to avoid excessive use of an excessive amount of soil solution and affect absorption.
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