At present, in some major cucumber production areas, the upper leaves of the cucumber plants have yellow leaves with gold edges, but the leaf tissues are not necrotic. It was misunderstood by vegetable farmers as a phytotoxicity. In fact, the cucumber leaf "inlaid with gold edge" is a physiological obstacle caused by improper nitrogen fertilizer.
In the nitrogen fertilizer applied 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. Of these three nitrogen fertilizers, cucumbers have a special preference for nitrate-nitrogen. According to experiments, when the nitrate content in the culture solution accounts for 90%, the stems and leaves of the cucumber are bright green, and the growth is also large. The absorption of calcium and magnesium is high; when the nitrate nitrogen in the culture solution only accounts for 10%, the cucumber The growth rate decreased by 80%, the absorption of calcium decreased by 69%, and the absorption of magnesium decreased by 52%. Cucumber leaves "inlaid gold edge" because too much ammonium in the soil, hindering the absorption of calcium in cucumber.
The application of too much ammonium will also cause a series of other pathological states. The color of a leaf changes from dark green to dark green, and the leaves appear to have wax and shine. 2 The leaves are raised and the veins are relatively concave; 3 The middle part of the leaf is uplifted and it is parachute-like; 4 the growing point is atrophic, the heart is bent downward, and it is not yet developed. Once it is unfolded, it is obviously smaller than other leaves, making the top blade sharply and sharply shrink; 5 colors rust, root tip blunt Qi was truncated, with severe rot and dead seedlings. This phenomenon is actually caused by the application of ammonium nitrogen into soil, which is easily adsorbed by the soil and increases the concentration of soil solution. However, after the nitrate nitrogen is applied, it is not easily adsorbed by the soil, and thus the concentration of the soil solution does not increase much. Therefore, applying nitrate nitrogen fertilizer to cucumber is an important measure to prevent physiological diseases and ensure good growth.
In the case of leaf "gold edge", spraying 0.5% calcium superphosphate solution or 0.4% calcium chloride solution 2-3 times can effectively enhance the plant's viability.
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