Fertilizer Requirements of Chestnut in China and High-Yield Fertilization Techniques and Timing

Chestnut has long been known as the “king of dried fruits,” and abroad it is also called “ginseng fruit.” So what are the requirements for the fertilizer requirements of chestnut in China and high-yield fertilization techniques and timing? Chestnut requires a relatively large amount of fertilizer, especially more nitrogen and potassium, and during the flowering and fruiting stage, chestnut also requires relatively high boron.

Fertilizer Requirements of Chestnut

Throughout its life, the absorption of nitrogen, phosphorus, and potassium by chestnut changes with the growth period. Nitrogen begins to be absorbed from root activity until before bud break, continuously increases during new shoot growth and the flowering and fruiting stage, is absorbed the most during the fruit swelling stage (about July to September), and declines rapidly after harvest. Phosphorus absorption is relatively balanced throughout the year, slightly higher from flowering to harvest, and almost stops before leaf fall. Potassium absorption is relatively low before flowering (before about June), increases sharply after flowering (July), and is absorbed the most from the fruit swelling stage to the harvest stage, which is the period most prone to potassium deficiency; potassium absorption drops rapidly after harvest. In recent years, it has been found that chestnut is sensitive to magnesium and has a high demand for it, especially during fruit development, and magnesium deficiency is quite common, so attention should be paid to magnesium fertilizer application.

Chestnut Fertilization Techniques

Chestnut has a well-developed root system, and the new roots generally have ectomycorrhizae. When the soil pH is 5.5 to 7.0 and the site conditions are good, there are many mycorrhizae, which can improve chestnut's absorption of water and phosphorus and calcium nutrients. This characteristic should be taken into account when fertilizing. Chestnut fertilization is mainly based on base fertilizer, with topdressing applied in stages, combined with foliar fertilizer application.

According to research, for a mountain chestnut orchard with a yield of 400 to 500 kg of chestnuts, each 667 sq m requires 22 kg of nitrogen, 26 kg of phosphorus, and 29 kg of potassium. Of this, base fertilizer accounts for 2/3 and topdressing accounts for 1/3. Base fertilizer is applied in late autumn in combination with deep plowing, by opening circular trenches under the canopy. Topdressing can be applied twice, before bud break and during the fruit swelling stage, with the fruit swelling stage being the main one. Combining topdressing with watering can improve the effect. According to practices in some high-yield chestnut orchards, applying magnesium fertilizer during the growing season and spraying foliar fertilizer have good effects. Magnesium fertilizer is applied during the fruit swelling stage, with 0.1 to 0.5 kg of magnesium sulfate per tree, applied in trenches with water. During the new shoot growth stage, fruit swelling stage, and after harvest, spraying 0.5% urea and 0.25% monopotassium phosphate has a good effect on promoting new shoot growth, fruit swelling, and post-harvest tree vigor recovery. Spraying a 0.2% borax solution during the flowering stage can increase the fruit-setting rate of chestnut, reduce the rate of empty burs, and can significantly improve yield and quality.

Variety Classification

China has a vast territory and greatly differing ecological conditions, forming a large number of chestnut variety resources. More than 300 chestnut varieties in the country have been named, but they can generally be divided into two major variety types, namely northern chestnut and southern chestnut.

1. Northern Chestnut

It is mainly distributed in the Yanshan and Taihang Mountain areas of North China and adjacent areas. This includes Hebei, Beijing, northern Henan, Shandong, Shaanxi, parts of Gansu, and northern Jiangsu. Its characteristics are few fruit shapes, with an average single nut weight of about 10 grams; waxy flesh, with a sugar content as high as about 20%; low starch content in the flesh and high protein content; darker skin color with luster; strong aroma, and the astringent skin is easy to peel off. It is suitable for roasting and is called sugar-roasted chestnut.

2. Southern Chestnut

It is mainly distributed in Jiangsu, Zhejiang, Anhui, Hubei, Hunan, and southern Henan. In this region, with high temperature and abundant rain, chestnut nuts are large, with an average single nut weight of about 15 grams and a maximum of up to 25 grams, but the sugar content is low, the starch content is relatively high, and the flesh tends to be japonica-like, so it is mostly used as vegetable chestnut. There are many chestnut varieties in northern and southern China, and there are differences in the characteristics and traits of the southern and northern variety groups. Generally, the quality of the southern variety group is not as good as that of the northern varieties, and the flesh tends to be japonica-like, suitable for stir-frying, also known as vegetable chestnut.