The amount of nitrogen fertilizer in vegetables was too high for each application, which was the most prone to damage. It was the most harmful to the vegetable seedlings. The lightest seeds inhibited the germination, the seedling leaves showed necrotic spots, and the severe plants died of wilting.
(1) The type of vegetable damage.
1 ammonia hazard. Excessive application of ammonia, ammonium bicarbonate, urea, and other chemical nitrogen fertilizers will increase ammonia concentrations in the microclimate of shallow soil and vegetable fields, especially in protected areas. When the ammonia in the surrounding space hits 5ppm, the leaves will appear to be harmed, and water-soaked spots begin to appear, followed by water loss as a dead-spot. When the ammonia gas reaches 40 ppm, the chloroplast decomposes and black spots appear between the veins.
2 The concentration of soil solution is poisonous. Excessive amount of nitrogen fertilizer, resulting in excessive concentration of salt ions in the soil solution, making the roots difficult to absorb water, when the water in the roots will be seriously infiltrated into the soil, so that the vegetable plants die into pieces.
3 foliar fertilizer poisoning. Under normal circumstances, the young shoots and leaves of vegetable seedlings are young, and the resistance is poor. The concentration of urea aqueous solution that seedlings can adapt to is only 0.3%-0.4%, and the growth period is only 0.7%-0.8%. Fertilizer concentration is too large and the leaves will burn when the leaves are sprayed.
(2) Measures to prevent fertilizer damage.
1Add organic fertilizer. Manure, compost, and earth miscellaneous fertilizers contain humus colloids. These colloids have a strong ability to adsorb ions and increase soil buffering performance. That is, excessive application of one fertilizer will not cause a sharp rise in soil solution concentration. Therefore, it will reduce the fertilizer damage caused by excessive fertilization.
2 Fertilizer should be mixed after basal application. After applying the basal fertilizer, use a planer to do it again and then level it and sow it. Mix the fertilizer with the plough layer soil to prevent the fertilizer from spreading and cause localized fertilizer damage.
3 Apply fertilizer deeper and reduce volatilization. Ammonium bicarbonate, urea, etc. should be ditched, fertilized, then covered with soil to reduce evaporation.
4 Do not overdo fertilize once. In particular, for the cucumber-like fertilizer crops that are not fertilizer-resistant, it is beneficial to adhere to a small number of times when top dressing.
5 Strictly control the concentration of foliar spray fertilizer. The seedling concentration is low and the growth period can be slightly higher.
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