Fertilizer requirement characteristics, high yield fertilization technology and time of walnut in China

Walnut has long fruiting years, high tree body, large crown and deep root system, which requires good site conditions, and insufficient fertilizer supply has a great effect on yield and quality. So what is the fertilizer requirement characteristics, high-yield fertilization technology and time of walnut in China?

Walnut has a higher demand for nitrogen and potassium, followed by calcium, magnesium and phosphorus. 1.4 kg of nitrogen is needed for every 50 kg of walnut harvested. The nitrogen supply is insufficient, the branches are short and thin, the leaves are yellow and easy to fall, the flowering is less, the fruit drop is more, and the size is serious. There are some differences in nutrient uptake in different growth stages. The period of more nitrogen absorption is in the long leaf stage, flowering and fruiting stage and hard core stage of fruit; the absorption of potassium is similar, but the absorption of potassium is the most after flowering to the hard core stage of fruit; the absorption of phosphorus is relatively stable; calcium is absorbed more after falling flower, it is easy to produce calcium deficiency; magnesium is also needed more in the period of fruit formation.

For adult trees, walnut fertilization should ensure the nutrient balance of tree growth and flowering and fruiting, usually with equal emphasis on base fertilizer and topdressing, and the proportion of base fertilizer is about 60%. After autumn harvest, people are given according to the size of the tree. Each tree was applied about 200 kg of organic fertilizer, 2 kg of superphosphate and 3 kg of potassium sulfate, combined with deep ploughing and soil improvement.

The manuring of walnut was carried out in three stages. Before sprouting and flowering for the first time, this fertilization mainly provides nutrients for the rapid growth of new shoots and flowering stage. Insufficient nutrients hinder the growth of new shoots, and the flowering and fruit setting is poor. Therefore, each plant can apply about 1.0 kg of urea and 0.3-0.5 kg borax to increase the fruit setting rate and promote fruit development. The second time after falling flowers, the fruit began to form and expand, accompanied by flower bud differentiation, which was the period of the most nutrient needs, insufficient fertilizer supply, slow fruit development, serious fruit drop, and flower bud differentiation was affected. Therefore, each plant should be applied urea 0.5-1.0 kg, calcium superphosphate 1 kg, potassium sulfate 1 kg, magnesium sulfate 0.5-1.0 kg, ditching combined with irrigation. The third time was carried out in the fruit hard-core stage, and each plant was re-applied 0.5-1.5 kg of urea and 0.5-1.0 kg of magnesium sulfate. It is beneficial to the development of kernel and improve the yield and quality. The tree potential is poor after harvest, so 0.5% urea can be sprayed to restore the tree potential.