Generally, after the grapes are harvested, farmers feel that the busy year of farming has ended, and they do not pay attention to the rapid shedding of grape leaves. This is wrong.
After the grapes are harvested, the leaves are still undergoing assimilation, and the nutrients produced by photosynthesis are used for mature branches, root growth, and root nutrient accumulation. If the leaves turn yellow and fall off prematurely, it will seriously affect the maturity and lignification of the branches. The branches that have not reached lignification cannot bear fruit in the following year, resulting in a decrease in the yield of the following year. Therefore, this period is particularly important for leaf protection.
Only by grasping the cause of yellow leaves can we take correct measures to effectively prevent yellow leaves. The reasons for the yellowing of grape leaves are discussed below, hoping to bring some help to your actual production.
1. Leaf senescence
After fruit picking, some vineyards showed symptoms of leaf scorch, which led to the premature loss of photosynthetic efficiency of grape leaves in autumn, which affected the ripening and lignification of branches, and led to splintering in winter.
In addition, immature branches and branches that have not achieved lignification cannot bear the heavy responsibility of flowering and fruiting, resulting in a decrease in yield in the following year.
Cause Analysis
●Dry weather leads to premature yellowing, scorching and shedding of leaves, especially Kyoho varieties are sensitive.
●Disease control is not effective, and fungal diseases such as downy mildew remain after the fruit is harvested, which can cause symptoms such as scorch of leaves in severe cases.
● It is a normal phenomenon that the amount of occurrence is small, the branches are partly mature and the new leaves are normal, and generally it is not a big problem.
2. Leaf macula
After the grapes are harvested, the obvious yellow spots (or plaques) appear on the grape leaves, which are mostly caused by nutritional problems, such as magnesium deficiency, manganese deficiency, zinc deficiency, etc. Magnesium deficiency is mainly due to yellowing of the mesophyll of old leaves and zinc deficiency. The leaves are chlorotic between the veins, the leaf margins are poorly developed, and the manganese deficiency produces dense punctate chlorotic patches.
Cause Analysis
●The grape yield is too large and the fruit is too much, but the application and supply of organic fertilizer and medium and trace element fertilizer matching the high yield are insufficient.
●The excessive application of potassium fertilizer in the later period inhibits the absorption of magnesium by the grape root system and the transport of magnesium ions to the aerial parts, resulting in magnesium deficiency.
●The damage of the root system leads to a decrease in the absorption capacity of fertilizer and water, resulting in a comprehensive lack of nutrients.
3. Leaf brown spots
Brown spots on grape leaves may be caused by a variety of reasons, among which disease is the most common.
Cause Analysis
●When there is more rain in the later period, downy mildew and brown spot disease occur in a large area, and brown spots appear, resulting in early defoliation.
●The unreasonable application of grape fertilizer will cause fertilizer damage and brown spots will appear on the leaves.
Comprehensive solution
For fruit trees that have yellow leaves, effective remedial measures must be taken immediately to minimize the damage.
●Supplementary tree nutrition
For root treatment, choose products that promote root and support roots, such as Shi Dezan No. 4 (containing magnesium). Grapes are typical potassium-loving fruit trees, which require a lot of potassium during the growth period, and they absorb potassium throughout the growth period. Potassium fertilizer mainly makes straw and stalk thick. And because of the reason of "mother and big son fertilizer", as far as grape production is concerned, as long as the plant grows vigorously and robustly, the fruit volume will be large and the fruit grains will be large. As the root system resumes growth and vitality increases, the symptoms of yellowing will be significantly improved.
Dosage of Shi Dezan No. 4: flushing 5-10KG/mu, with an interval of 7-10 days; drip irrigation: 2-5 KG/mu, diluted 500-800 times, with an interval of 7-15 days; foliar spray: diluted 750- 1000 times, every 7-10 days. According to the actual situation of the soil, climate and fertilization habits in various places, the dosage should be appropriately increased or decreased.
●Irrigation in time
In order to promote the normal growth of grape vines and roots, and promote the transformation and absorption of nutrients by grape plants, it is necessary to combine irrigation with water once during fertilization. However, if autumn flooding occurs, ditches should be opened for drainage in time to reduce the air and soil moisture in the vineyard, and to control the infection of fungi.
● Deep digging and loosening
Deep plowing in this period greatly deepened the soil layer thickness of the garden, improved the soil micro-domain environment, was conducive to the germination of new roots of the vines, and accelerated the rapid growth of the root system.
●Autumn scissors
After the fruit is harvested, it is necessary to carry out autumn pruning without losing time. When pruning in autumn, mainly cut off dry ears, diseased branches, insect branches, tendrils, and residual leaves to reduce the number of branches and leaves without photosynthetic efficiency.
