Measures to improve fruit setting rate of walnut

  Because of the site conditions and biological characteristics of walnut, low nutrition level of tree, improper pollinating varieties, lack of pollinating trees, extensive management, poor flower bud differentiation, serious diseases and insect pests, etc., fruit setting rate can be reduced.

  1. Select varieties with strong adaptability

  There are many excellent varieties of walnut, but their adaptability to environmental temperature has certain differences. Therefore, variety planning should be carried out at the beginning of walnut garden construction, and varieties with good adaptability to local climate conditions should be selected. Fine varieties with poor adaptability shall be planted in areas with mild climatic conditions. Large trees with poor adaptability and quality that have been put into production shall be grafted with high grades and replaced with excellent ones, inferior varieties shall be eliminated and improved varieties shall be developed.

  2. Reasonable allocation of pollination trees and artificial pollination

  The importance of pollinating trees in walnut cultivation is determined by dioecious maturity. New walnut orchards are basically equipped with female and male pro-type pollinating trees, which can ensure normal pollination. However, pollinating varieties are often neglected in walnut orchards under extensive management, or high-grafting for high-quality orchards, so special pollinating trees should be grafted in the orchards to improve pollination conditions.

  In order to improve the fruit setting rate and increase the yield of walnut, artificial pollination must be carried out. According to research, artificial pollination at the peak of female flowers can increase the fruit setting rate by 17. 3% ~ 19. 1%,twice artificial pollination, fruit setting rate can be increased by 26%.

  III. Tree spraying fertilizer

  Spraying water on flowering trees can increase air humidity, reduce the rate of pollen and stigma dehydration due to dryness, so it can increase fruit setting rate. Spraying 0. 1%~0. 2% boron fertilizer can promote pollen tube elongation. Spraying 0. 3% ~ 0. 5% urea or potassium dihydrogen phosphate can also promote fruit setting and reduce the occurrence of flower and fruit drop.

  The results showed that the application of growth regulators and rare-earth solution could improve the fruit setting rate to some extent. It is reported that the fruit setting rate of 40-year-old mountain bearing walnut trees was increased by 22. The average yield per plant increased by 10% ~ 64.9% compared with that of the control plants, and the duration of effect could reach more than two years. The NL- 1 rare earth was sprayed at 300~800 mg/L at the early stage of female flower, and the yield increased by 48%. 6%~66. 5%。

  IV. Strengthening the comprehensive management of trees

  On the basis of rational fertilization and deep ploughing of soil, strengthen pest control, protect leaves and enhance tree vigor. In addition, spraying 0.3%~0.5% urea or potassium dihydrogen phosphate once every 15 days after stigma withering for 2~3 times can promote rapid fruit expansion and effectively improve fruit quality.

  V. Other techniques to improve fruit set

  Girdling the base of auxiliary branch or trunk of vigorous tree in the middle and last ten days of May, the width of which is not more than 0.6 cm, can relax tree vigor, improve fruit setting rate and promote new branch germination under peeling mouth. These are consistent with the saying of Shangluo Mountain in Shaanxi Province that "cut a sickle, bear a lot; cut an axe, press a broken stock".

  The reason of serious fruit dropping and low fruit setting rate of walnut is wind damage and excessive nutrient growth, which is not direct mechanical damage, but large leaf area of walnut, serious transpiration and water loss, excessive nutrient consumption, resulting in a large number of flowers and fruits dropping. Therefore, removing walnut leaves at flowering stage, leaving only 3 leaves at the top of each compound leaf, can increase fruit setting rate and yield.