Why is cucumber "inlaid with gold"?

At present, a common phenomenon is found in the main cucumber producing areas. The leaf margin of the upper part of the cucumber plant is yellow, like the gold edge, but the leaf tissue is not necrotic. Vegetable farmers often mistakenly believe that this is caused by excessive pesticide spraying. According to the author's many years of practical experience, the phenomenon of cucumber leaves with gold edges is caused by physiological obstacles caused by improper application of nitrogen fertilizer.

In the nitrogen fertilizer applied in production, the form of nitrogen is different, such as ammonium nitrate as nitrate nitrogen, ammonium ammonium as ammonium nitrogen, and urea as ammonium amide. Among these three nitrogen fertilizers, cucumber has the most special liking for nitrate nitrogen. Someone has done a nutrient solution culture test for cucumber. When the nitrate nitrogen in the culture solution accounts for 90%, the stems and leaves of the cucumber are fresh green, the growth amount is also large, and the absorption amount of calcium and magnesium is high. When the nitrate nitrogen in the culture liquid only accounts for 10%, the growth of cucumber decreases. 80%, the amount of absorbed calcium decreased by 69%, and the amount of magnesium absorbed decreased by 52%. Cucumber leaves are inlaid with gold, because the ammonium in the soil is too much, which hinders the pathological state caused by the absorption of calcium by cucumber.

Excessive application of ammonium nitrogen can also lead to a range of other pathologies. 1. The leaf color changes from dark green to dark green, the leaf surface looks like wax and the oil shines brightly; 2. The leaf flesh protrudes, the veins are relatively concave; 3. The leaf edge is rolled down, the middle part of the leaf is raised, and it is parachute-like; 4. Growth The point is atrophy, the heart leaves are bent down, and it is delayed. Once it is unfolded, it is obviously smaller than other leaves, so that the top leaves are sharply and sharply reduced. 5. The root color is rusted, the apex is blunt and truncated, and the roots are bad. Dead seedlings. The occurrence of this phenomenon is actually the application of ammonium nitrogen into the soil, which is easily adsorbed by the soil and increases the concentration of the soil solution; while the nitrate nitrogen is not easily adsorbed by the soil after the application of the nitrate nitrogen, the concentration of the soil solution does not increase much. Therefore, the application of nitrate nitrogen in cucumber is an important measure to prevent physiological diseases and ensure good growth.

In the case of "inlaid rim", foliar application of 0.5% superphosphate solution or 0.4% calcium chloride solution 2 to 3 times can effectively enhance the viability of the plant.