Introduction to irrigation period and water quantity of walnut trees

   walnut tree has tall body, broad leaves, large transpiration and high water demand. Water deficiency will seriously affect tree growth and development, flower bud differentiation and nut yield. Walnut can tolerate dry air, but is sensitive to soil moisture. Too dry or too wet soil is not conducive to the growth and development of walnut. Soil drought hinders root absorption and transpiration of branches and leaves, and affects the process of physiological metabolism. Severe drought can cause fruit drop or even early leaf drop. In the case of drought in the early stage and rainy climate in the later stage, young trees are easy to grow and lead to dry shoots after overwintering. Excessive soil moisture and poor ventilation will weaken the physiological function of the root system and grow poorly. The groundwater level of the walnut orchard should be below 2 meters. Soil and water conservation projects such as terraced fields must be built to plant walnuts on sloping land. The problem of drainage must be solved in places where water is easy to accumulate.

   the area with annual rainfall of 600mm to 800mm and uniform distribution in China can basically meet the requirements of walnut growth and development. The annual precipitation of most walnut producing areas in southern China is more than 1 000 mm, which generally does not need watering except in dry years. The annual precipitation in the northern region is mostly about 500 mm, and the distribution is uneven, which is characterized by drought and less rain in spring, so it should be irrigated timely. Studies have shown that timely irrigation is needed when the maximum soil water holding capacity in the field is less than 60% (the absolute soil water content is less than 8%).

There are mainly three irrigation periods determined by    according to the critical period of water demand of walnut.

   was first irrigated before and after the sprouting of walnut trees in spring. From late March to early April in the northern region, walnut needs adequate water supply to complete the life processes such as sprouting, branching, leaf spreading and flowering. At this time coincides with the northern spring drought season, if the soil moisture is poor, irrigation should be carried out in time. The aim is to reduce spring drought, promote autumn fertilization to continue to play a fertilizer effect, and promote tree growth and fruiting.

The second irrigation of    was before flower bud differentiation after the Beginning of Summer. The northern region from May to June is the dry season of water shortage before the onset of the rainy season. At this time, when the fruit is expanding and the tree is growing rapidly, its growth can reach more than 80% of the annual growth, and the female flower bud has begun to differentiate, and the physiological metabolism in the tree is very exuberant. If there is not enough water, it will not only lead to a large number of fruit drop, but also affect flower bud differentiation. During this period, drought and little rain should be irrigated in time.

The third irrigation of    was from fruit harvest to defoliation. From late October to before defoliation, irrigation can be carried out combined with the application of base fertilizer in autumn, which requires adequate irrigation, which is beneficial to the decay and decomposition of base fertilizer, the recovery of injured roots, the promotion of new roots and tree storage nutrition, and provides an indefinite nutritional basis for germination, flowering and fruiting in the coming year.

   can also irrigate the soil again before freezing where there is plenty of water, commonly known as "frozen water", which can improve the cold resistance of trees and is very beneficial for walnut trees to survive the winter.

The most suitable irrigation amount of    should be in the primary irrigation to make the soil moisture in the root distribution range to the most beneficial to the growth and development of walnut. Generally speaking, it is necessary to infiltrate more than 1 meter of soil at one time. The determination of irrigation amount can be calculated according to soil water holding capacity, soil moisture before irrigation, soil bulk density, required soil infiltration humidity, etc., namely:

   irrigation quantity-irrigation area × required soil infiltration degree × soil bulk density × (field capacity-soil moisture before irrigation)

What    should pay attention to is that the water management of walnut orchard should be promoted before and after control, that is, more watering in spring and drainage in rainy season. Its purpose is to control the late growth of new shoots, promote the tree body to be strong, and improve the rate of flowering and fruit setting.