Study on Top Grafting Technology of Bare Scions of Walnut Trees in Eastern Hebei

[Objective] To accelerate the improvement of walnut varieties and change the cultivation status of low yield and poor quality. [Method] Through experimenting on the optimization technology of walnut trees, this paper studied the suitable top grafting period and scientific top grafting protection measures of walnut trees in Eastern Hebei, and established the top grafting technology system of walnut. Moreover, this paper explored the impact of different time and scientific management and protection measures on the survival rate and growth of bare scion top grafting of walnut trees. [Results] The grafting time had a great impact on the growth of new shoots, and there were significant differences in the survival rate among different grafting periods. The highest grafting survival rate was 96.97% on April 27 and the lowest grafting survival rate was 66.67% on May 4; the average survival rate was 78.10%. Among them, the survival rate of top grafting was the highest on April 20 and April 27. The growth of new shoots grafted in the early stage was greater than that in the late stage. The growth of new shoots and branches on April 8 and April 20 were the largest, with lengths of 160.3 and 143.7 cm respectively; the thickness was 1.72 and 1.43 cm respectively; the branch lengths were 79.8 and 63.4 cm respectively; the branch thickness was 0.98 and 0.82cm; the growth index was also the highest on April 8 and April 20 at 10 , 20 and 30 d, which was significantly different from other time periods. [Conclusion] Walnut trees with early grafting in Eastern Hebei can quickly restore their crown growth and had higher yield, thus this technology can be widely applied in Eastern Hebei or Yanshan area.