Site requirements

CLIMATE

From a climatic perspective, the conditions for sweet chestnut cultivation are favorable throughout Hungary. The sweet chestnut’s temperature requirement is within an annual average of +5 to +15°C. Hungary’s annual mean temperature of 10°C is suitable for chestnut cultivation. The species also tolerates climatic extremes well; neither winter frosts, late spring frosts, nor early autumn frosts cause damage. Even in northern exposures within Hungary, it can find suitable conditions for growth.

In our domestic growing regions, the growing season of our chestnut varieties ranges from 176 to 183 days. The sweet chestnut varieties with the lowest heat sum requirement are those from Western Transdanubia. Their fruits reliably reach full maturity every year, even at higher-altitude sites, and the end of the growing season, autumn leaf coloring, and leaf fall proceed without disruption or frost damage.

SOIL

Among the characteristics of a growing site, soil is the most important. It is the soil that limits the possibilities for chestnut cultivation to certain areas in Hungary. In the past, the sweet chestnut was considered a typical lime-avoiding plant. This statement is only indirectly true, because for sweet chestnut, it is not the lime content of the soil but the relative availability of potassium that is decisive. Potassium uptake is hindered by the soil’s lime content and its alkaline reaction (higher pH value).

According to the growth standards for chestnut trunk circumference, the average for a 10-year-old tree is 40 cm. When soil pH values exceed 6.4, chestnut growth rapidly falls below the average. The sweet chestnut is less demanding regarding other soil properties (such as topsoil thickness or soil texture); however, the tree’s performance depends on soil fertility. On heavy, cold clay soils, shallow topsoils, and dry sites, chestnut growth is weak, the fruits are small, and cultivation is not economically viable.

The sweet chestnut tree requires over 600 mm of annual precipitation. Prolonged rainfall during flowering in late June to early July negatively affects fruit set. Droughty conditions in August and September significantly reduce fruit size.

Nutrient

We have relatively little information regarding the nutrient requirements of the chestnut. Detailed research on this topic has been conducted in Japan (Eynard I.) on varieties of the Japanese chestnut, a close relative of our chestnut.

According to these studies, the nutrient uptake of a 1-hectare chestnut orchard is as follows:

• Nitrogen (76.6 kg)
• Phosphorus (29 kg)
• Potassium (42.6 kg)
• Calcium (72.9 kg)
• Magnesium (21.2 kg)

An important relationship has been demonstrated between proper fruit size and the required nitrogen content and N–K ratio in both the fruit and the leaves. The nitrogen content should be 1.14–1.33% in the chestnut fruit and 1.98–2.34% in the leaves. The potassium-to-nitrogen ratio in the fruit should be between 0.68 and 0.97.

According to studies conducted on Italian chestnut trees (Fenaroli L.), the percentage of major nutrients detected in the leaf dry matter and its variation throughout the growing season shows a very characteristic pattern.

Chestnut has a high potassium requirement, while the absorbed calcium is an undesirable element. Unlike other nutrients, which move into the plant’s overwintering parts before leaf fall, calcium remains in the fallen leaves. The plant regularly eliminates substances that are not needed.