Objective The study was carried out to explore the dynamic changes of leaf nutrients and soil nutrients of Carya cathayensis in different seasons of the year, and provide basis for fertilization, management and transformation of low yield forest of C. cathayensis economic forest and control of rocky desertification in karst area.

Method Twenty C. cathayensis were selected from 10 walnut orchards in Huanjiang County to collect leaves and soil. Leaf nutrients (total carbon, total nitrogen, total phosphorus, total potassium, calcium, iron, zinc and boron) and soil physical and chemical properties (organic matter, total nitrogen, total phosphorus, total potassium, available nitrogen, available phosphorus, rapid potassium, available boron, available iron, available zinc and available calcium) were determined, and the seasonal dynamics of leaves and soil nutrients were analyzed.

Result With the growth of C. cathayensis, the content of nitrogen in leaves gradually decreased to 13.59 g/kg, while the contents of boron and calcium gradually increased. Iron content decreased first and then increased, while phosphorus content was the opposite. The calcium content in July and October was about twice that in April (13.54 g/kg). The contents of exchangeable calcium and available boron in the forest soil increased first and then decreased, and the content of total potassium gradually increased to 8.84 g/kg. The effective zinc content in April (8.46 mg/kg) was 6.9 times that in October. There were obvious seasonal changes in leaf nutrients. Except for organic matter and available nitrogen, other nutrients in soil had obvious seasonal changes. Correlation analysis showed that there was a significant negative correlation between leaf nitrogen and soil available zinc, a very significant negative correlation between leaf phosphorus and soil available nitrogen, and a significant negative correlation between leaf iron and soil available phosphorus.

Conclusion The application of potassium fertilizer should be strengthened at the flowering stage of C. cathayensis; attention should be paid to the application of nitrogen and potassium fertilizers to improve the availability of macro elements during the fruit growth period; phosphorus fertilizer and trace element fertilizers such as calcium and boron should be supplemented during the fruit ripening period.