Nitrogen fertilization mainly promotes the new growth of branches and is closely related to fruit yield. The uptake of nitrogen fertilizer by grapes starts during the budding period when the soil temperature rises to 12-13°C. The fertilizer uptake is greatest during the flowering period and decreases during fruit coloring. It is greatest from flowering to young fruit expansion and decreases during fruit coloring. The uptake is minimal during fruit ripening, and is high during secondary rooting after harvesting. Under normal cultivation conditions, there is no shortage of nitrogen. Excessive nitrogen fertilization from flowering to fruit harvesting will result in undesirable consequences such as branch and leaf growth, poor fruit coloring, and multiple disease damage.
B. Excessive nitrogen fertilization of grapes showed
(1) late sprouting
A sprout on the rapid growth, mostly 1-2 buds at the apex of the stout, the lower end of more dead buds.
(2) many long internodes of secondary tips
Leaves are thick, rich green, lateral than the apical lobe developed. The leaves are wider, the new tips mature late, the branches are flat, and the internodes are long and straight.
(3) Large pith
The fruit has poor coloring and low sugar content. Therefore, to master the nitrogen benefit, fertilized land less, thin land more.
C. Fertilizing effect of grapes
① Phosphorus fertilizer
It can also reduce the acidity of grapes and increase the sugar content. The absorption period starts from the wounding period, reaches a peak during the vigorous growth period of the new shoot and the fruit expansion period, then decreases and is absorbed again after harvesting. The phosphorus in the fruit is mainly supplied from the leaves and other organs transport. Phosphorus fertilizer is easily fixed by the soil, available outside the root fertilizer or base fertilizer mixed with phosphorus.
② Potassium fertilizer
is an essential element for fruit growth and ripening. When the fruit matures, potassium is transferred from the leaves and branches to the fruit, and the potassium content of the leaves and branches decreases, while the potassium content of the fruit is two times more than that of nitrogen. Grapes have a long potassium uptake period, from budding to fruit ripening. However, too much potassium will prevent the absorption of magnesium and nitrogen fertilizers, often resulting in magnesium deficiency, i.e. leaf yellowing. In order to avoid magnesium deficiency, the application of potassium fertilizers such as grass ash and potassium sulfate should be moderate.
Calcium is one of the most absorbed elements in grapes absorbed throughout the reproductive period. Calcium neutralizes the acids in acidic soils.
It is one of the components that make up chlorophyll. Magnesium deficiency causes leaf receding and yellowing, and the symptoms appear mostly in the middle of fruit development. Acidic soils are prone to magnesium deficiency, causing early leaf drop and quality loss. The magnesium uptake of grapes is 1/5 of that of nitrogen.
D. Grape uptake and fertilizer application
The amount of fertilizer absorbed by grapes in a year is closely related to its various reproductive stages. For example, rose dew, a European-American hybrid, absorbs three times as much potassium as nitrogen in its fruit. However, N and K uptake is about the same for the whole tree. The uptake of nitrogen and potassium is twice as much as that of phosphorus.
E. Fertilization techniques for grapes
Fertilization of grapes should adhered to: “three fertilizers” (base fertilizer, follow-up fertilizer and supplemental fertilizer). “Three looks” (look at the seedlings to apply, look at the ground to apply, look at the sky to apply). “three appropriate” (the right time to apply, the right amount of application, appropriate application). “Three preventions” (prevention of excessive nitrogen, prevention of phosphorus fixation by the soil, and prevention of deficiency disease).
F. Main fertilization techniques for grapes
1. Base fertilizer is mainly organic fertilizer
It is applied during the dormant period of the grapes, i.e. from late November to the beginning of January. This is so that the fertilizer is fully effective in June during the fruit growing period. It is a good idea to apply it in a ditch, generally 40-50cm deep, and to expand the pond, replacing it every other year and expanding it year by year, in order to improve the soil. After the application of soil and watering, to accelerate the fertilizer decay and fertilizer penetration. The ratio of base fertilizer components is generally 30%-40% of nitrogen, 80%-100% of phosphorus, and 40%-50% of potassium applied throughout the year.
The fertilizer is usually applied after the grapes have blossomed, with a mixture of fast-acting nitrogen and potassium fertilizers (e.g. Colifax, Uconitin). The amount of potassium applied should be 50%-60% of the whole year, and it is necessary and safe to apply this nitrogen and potassium fertilizer after flowering. If the base fertilizer is not enough, sandy soil or too much fruit, you can force to apply nitrogen and phosphorus fertilizer once in the budding period. Before the fruit is colored, it can chased again with nitrogen and potassium fertilizer.Its phosphorus is easily fixed by the soil and can be sprayed with a high phosphorus foliar fertilizer.
3. Supplementary fertilizer
In order to restore tree strength, the fruit should be immediately after harvesting a nitrogen fertilizer. The amount of fertilizer should be moderate, too much will cause late growth, unfavorable overwintering.