The aboveground management of fruit trees has attracted people's attention, but the underground management is easily ignored. In the long-term growth and development process, fruit trees and natural conditions have formed a unity of mutual connection and mutual restriction. Fruit trees have irreplaceable requirements for natural conditions such as soil, light, moisture, temperature and air. It is also impossible to try to make fruit trees yield high and stable by pruning alone. Strengthening underground management of fruit trees is as important as aboveground management.
Rooting, leaf growth, germination, flowering and fruiting of fruit trees, and the structure of all organs. Nutrients are mainly produced by leaves, and photosynthesis of leaves is the material basis for fruit tree growth and yield formation. However, the size of leaf area, working ability and working time are always affected by roots. Roots ensure the normal work of leaves by absorbing water, fertilizer and synthesizing other substances. Leaves are rooted, and leaves must also be rooted. Practice also feels that all trees with deep underground organic fertilizer application and good management have good resistance, high yield and good fruit quality.
Roots live in soil environment, and the management of soil, fertilizer and water is to create an optimal environment for the growth and absorption of roots. Therefore, understanding the internal and external factors of root growth and activity is the basis of good soil, fertilizer and water management.
1. Factors affecting root growth and absorption activity
(1) Internal cause: Too many fruits in the new year make the growth of new roots weak, which hinders the growth of roots in autumn after early defoliation; After girdling the trunk, the root system becomes smaller and weaker. It can be seen from these phenomena that the growth of roots is restricted by the growth results of aboveground parts. Further analysis shows that there are many fruits in the new year, and the nutrients made by leaves basically enter the fruits, and the rest are left to the roots for transportation, which affects the growth and absorption capacity of the roots. Through experimental research, the absorption activity of fruit tree roots decreased rapidly when some leaves were removed or most leaves were covered by crown. Therefore, the return of nutrients produced by leaf photosynthesis to the root system is the internal cause that affects the root growth activities. The main reasons are as follows:
① Growth of new roots: The construction of root system needs raw materials, which come from two aspects, one is nutrients in the soil, and the other is carbohydrates made by leaves through photosynthesis. Raw materials from two aspects make the root system swell under the action of tree metabolism mechanism, which increases the ability of absorption and self-construction.
② Root growth and absorption: energy is needed, which is produced by root respiration, which is a process of oxidative decomposition of carbohydrates. Therefore, the energy required for root growth needs aerobic supply (increasing the air permeability of soil). Second, there must be carbohydrates as respiratory substrates. Therefore, the photosynthetic products produced by leaves and transported to the root system have a decisive influence on the growth and absorption of the root system. Why do trees die when they are stripped of bark?
(3) The growth of new roots, the thickening of old roots, meristem and elongation of all cells need certain hormones to start. These hormones mainly come from the young leaves at the tip of the stem, so the growth of aboveground stems and leaves is also indispensable to the growth of underground roots. These are the reasons why roots depend on leaves. Rooting not only focuses on improving soil, but also attaches great importance to leaves, so management should be as unified as possible with aboveground parts.
(2) External factors: There are many external factors that affect the growth and absorption of roots, and there are also complex interactions among these factors.
(1) Oxygen in the soil: The aboveground part of the fruit tree is in a free space, where air circulation, oxygen and breathing are not restricted, but the roots of the fruit tree are in the soil, and the soil is composed of solid, liquid and gas. The gaps in the soil are limited, and these gaps are often occupied by moisture, which drives the air out. The air remaining in the limited soil pores is consumed by the respiration of roots and soil microorganisms, and the carbon dioxide discharged by respiration is in a stagnant state. Therefore, in most cases, oxygen in soil often becomes a factor limiting the growth and absorption of roots. Fruit farmers have also recognized this factor in years of planting, and summed up the truth that breathing comes first in the middle of the root soil. Improving the oxygen status in soil is the most important content of orchard soil management. It is also seen from the actual production that most orchards with high yield and high quality are distributed in soil with good air permeability.
According to scientific research, when the oxygen content in the soil reaches more than 15%, new roots grow most vigorously. 10%, the root system grows normally, about 5%, the root system grows slowly, below 3%, the root system stops growing. The wound of the broken root heals and new roots are produced, which requires more oxygen. Different tree species have different demand for oxygen in soil because of different root respiration intensity. The results showed that the roots of peach and cherry breathed vigorously and had high oxygen demand. Apricot and apple take the second place, while pear, jujube and grape have lower requirements, which is consistent with their performance in actual production. Pears, grapes and dates can grow normally in heavy soil, while apples, apricots, especially peaches and cherries grow abnormally. There are two kinds of cherry rootstocks and plum rootstocks in li miao in the northern market, so you should pay attention to them when choosing them. The respiration of roots and soil microorganisms consumes oxygen in the soil, releases carbon dioxide, then discharges it into the atmosphere from the soil, and fresh air enters the soil again. This process is the exchange of gas between soil. The larger the soil gap, the greater the air holding capacity. If the soil is not hardened, the gas exchange will be smooth and there will be no lack of oxygen in the soil. It is an important goal of soil improvement and cultivation to deeply loosen the clay layer and prevent the surface layer from hardening.
② Soil moisture: The most suitable soil moisture for root growth is 60-80% of the maximum water content in the field (the maximum water content is saturated). The closer the soil moisture is to the upper limit of this range (80%), the more white extended roots will grow on fruit trees. The closer to or slightly below the lower limit of this range (60%), the more branches the roots are, and the more reticular roots are absorbed. Branches with more white extended roots have vigorous leaves, and trees with more reticular absorbing roots are easy to blossom and bear fruit. Irrigation should be suitable for trees. When the trees are weak or bear more fruits, the soil water holding capacity is close to the upper limit, and when the trees are flourishing, it is less, so that the soil water holding capacity is close to the lower limit. When the soil water content is reduced to about 40%, the root growth stops completely and the fine root senescence accelerates. In drought, roots are damaged earlier than withered leaves on the ground. When there is serious water shortage, the leaves can absorb the original water in the roots, so the roots lose water first and die of drought. In the process of root dying from water loss, the branches and leaves on the ground not only show the symptoms of water shortage, but also show the symptoms of various nutrient elements deficiency, that is, comprehensive element deficiency caused by drought. Drought will cause short branches, few leaves, weak photosynthetic capacity, few buds and flowers, falling flowers and fruits, even falling leaves, low or no yield and poor fruit quality. Maintaining suitable soil moisture is very important for raising roots, strengthening trees and achieving high quality and high yield. However, too much water is not enough. First, there is too much water, and the branches on the ground are easy to grow in white, which consumes a lot of nutrients and is difficult to form flower buds. Second, soluble nutrients in water-rich soil are easily lost with water leakage, making the soil barren. Thirdly, excessive water fills the gaps in the soil, which deteriorates the air permeability of the soil and affects the normal respiration of the roots, thus limiting the growth and absorption of the roots. This is the reason why the branches and leaves on the ground are short of water when the accumulated water becomes waterlogged. Long-term water accumulation causes soil hypoxia, and the chemical changes in the soil tend to be mainly reduction, producing many reduction products (such as methane and hydrogen sulfide). ), directly poisoning fruit trees.
(3) Soil temperature: The temperature required for the growth and absorption of water and fertilizer for new roots of various fruit trees is different. The most suitable soil temperature for root growth and absorption of deciduous fruit trees in the north is between 15-25℃, and the new roots of apple grow at 7℃ in spring, and the whole growth is 18-2 1℃. When the temperature exceeds 30℃, the growth will stop. Pear is close to apple. Grape new roots grow at 12- 13℃ and stop at 26-28℃. Regulating ground temperature is also an important task of orchard soil management.