Soil Requirement of Walnut
Considering the structure of the walnut and fruit development, very important values are encountered in determining the suitable climatic conditions for the cultivation of Grafted Walnut Saplings . Walnuts are cold enough to meet the cooling requirement in winter and spring (below +7.2 C); In the spring and summer, they want a warm (25-35C) temperature to ensure normal growth and maturation. Chilling in walnuts; It is the time it should spend under (+7.2) C in winter. One of the most important factors limiting walnut cultivation in a region is late spring frosts. It is frequently observed that female flowers formed on the shoots of that year are damaged by late spring frosts. It is reported that not only female flowers but also male flowers are damaged by late spring frosts.
In addition to the damage of late spring frosts, early autumn frost damage can be counted among the factors limiting walnut cultivation. It is an important fact that immature shoots are damaged by early autumn frosts, since the vegetation period is short in walnut varieties with very late leaves.
Young and vigorously developing walnut trees may be damaged during the winter months, as they will enter the resting period late. Factors such as the degree of low temperature, falling speed and duration play an important role in damage from cold.
In addition, in some years, extreme winter cold can cause significant damage to the shoots of walnut trees. Mature healthy walnut trees can withstand temperatures between -15 C and -20 C in winter.
Walnuts can withstand temperatures down to -1 C for a period of 30 minutes when the buds are closed but they are colored. It is stated that walnuts begin to be damaged after -1C in the small fruit period.
Another important climatic factor that determines the successful cultivation of walnuts in a place is meeting the need for cooling. If this cannot be met, significant delays in bud burst and low yield can be observed. A cooling period of 200 - 1800 hours (below +7.2 C) may be sufficient for walnuts.
During the walnut development period, the air temperature rises up to 38 °C, which may cause darkening and shrinkage of the walnuts. In terms of walnut cultivation, a total annual precipitation of at least 500 mm is sufficient, but it is important that this precipitation is regular.
Soil demand in walnut cultivation; What type of soil do walnuts grow in?
Walnut trees develop strongly in medium-fine textured clayey sandy soils rich in organic matter and the roots go deeper.
Clay, spindle, gravelly silt layer, water accumulation and sand deposits that limit the root depth can limit the growth power and tree size of walnut trees.
Soil depth of 250-300 cm is ideal for walnut trees obtained by grafting in Turkey. However, 100-150 cm soil depth should not be compromised, where the uptake of water and plant nutrients is approximately 75%.
High pH and Calcareous Soils; The appropriate pH value in the soil for growing walnuts is around 6. Care is taken to select acidic and basic fertilizers in order to keep the pH value at the optimum level. When the pH value is higher than 8, it can cause phosphorus, iron, zinc and boron deficiency. In walnut cultivation, 5% active lime can cause iron chlorosis.
Before creating a walnut orchard, we must have a soil analysis done in authorized laboratories.
