In order to realize the fast growth and high yield of poplar, it is necessary to choose excellent varieties and strong seedlings for afforestation. The improved tree species are artificially selected. After strict tests and identification, it is proved that its main characters such as yield and quality are obviously superior to the local main tree species or cultivated varieties in suitable areas, and it has production value. At present, in the practice of forestry production, improved varieties of forest trees include approved and recognized excellent varieties, excellent families and excellent clones, as well as seeds produced by normal stands, seed orchards and parent forests of excellent provenances. The use of improved varieties of forest trees should choose the approved improved varieties of forest trees. After half a rotation period of introduction test, it is proved that truly excellent forest species can be popularized and used in a large area.
For specific afforestation plots, suitable varieties should be selected according to site conditions such as climate, topography, soil and moisture, and the principle of suitable land and trees should be followed. Choose good varieties, but also choose strong seedlings. General selection of poplar afforestation: seedling height is more than 4m, ground diameter is more than 3cm, trunk is straight, terminal buds are full, lignification degree is high, there are no pests and diseases, no mechanical damage, and the root system is relatively complete. When planting, the long lateral roots should be cut off to avoid the nest roots affecting the growth. At the same time, the roots with serious injuries, broken roots and mechanical injuries should be removed to avoid rot and infection. Selecting excellent varieties and planting strong seedlings is one of the main measures for fast growth and high yield of poplar. Poplar rotation usually takes more than ten years, and improper seedling selection affects wood output for more than ten years, causing huge losses. We should attach great importance to the selection of improved varieties and strong seedlings.
Second, apply base fertilizer.
In order to promote the growth of trees, increase the output of wood or improve its quality, all organic or inorganic substances that are directly or indirectly supplied to trees for absorption and utilization are called fertilizers. Fertilization is the process of transporting fertilizer containing one or more nutrient elements to soil, soil or plants. Poplar needs to absorb various nutrient elements, such as carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, iron, shed, copper, zinc and so on. Among them, carbon, hydrogen and oxygen are provided by the atmosphere, which is easy for trees to obtain, and the rest elements are generally provided by soil. Among these elements, nitrogen, phosphorus and potassium are the most needed, but these three elements are low in content in soil and need to be supplemented in time.
(A) the role of fertilization
Fertilization is the main measure to improve soil fertility and improve the nutritional status of plantation in the process of afforestation and stand growth. In order to realize the fast growth and high yield of poplar, we must pay attention to fertilization. This is because: 1, most of the forest land suitable for afforestation is barren and the fertility is not high, so it is difficult to meet the needs of forest growth for a long time; 2. The continuous cultivation of poplar pure forest from generation to generation makes various nutrients, including trace elements, extremely scarce, soil fertility declines and soil physical and chemical properties deteriorate; 3. Affected by natural or human factors, the amount of forest litter returned to the soil is limited or very small, and some nutrients are seriously lost; 4. The main cutting of forest (especially clear cutting) has caused a lot of loss of organic matter.
The main functions of fertilization are: 1, which directly provides nutrients for forest growth; 2. Improve the physical properties of soil. After fertilization, the soil structure is loose, and the conditions of water, fertilizer, gas and heat are improved, which is beneficial to soil microbial activities, accelerates the decomposition of organic matter and improves soil fertility. 3. Improve the chemical properties of soil. Fertilization can adjust the chemical properties of soil, such as pH value and salinity, reduce the leaching and loss of nutrients, promote the dissolution of some insoluble substances and increase the content of effective nutrients in soil.
(II) Application method of base fertilizer
Base fertilizer is fertilizer applied during or before planting. The purpose is to provide nutrients for trees and improve the soil for a long time. The fertilizer used as base fertilizer is mainly organic fertilizer, which has a long validity period. Organic fertilizer, also known as farmyard manure, is a fertilizer made of plant residues or organic matter such as human and livestock manure and urine by microbial decomposition and decomposition. Organic fertilizer has dual functions of improving soil and providing nutrients. Woodland commonly used are: compost, manure, green manure, human manure, cake fertilizer and humic acid fertilizer.
Organic fertilizer is characterized by containing various nutrient elements such as nitrogen, phosphorus, potassium, etc., and its fertilizer efficiency is long, which can meet the demand for nutrients in the growth cycle of trees, improve soil permeability, water, gas and heat conditions and soil structure, and provide favorable conditions for the activities of microorganisms in soil and the growth of forest roots, but organic fertilizer is usually slow in fertilizer efficiency.
Fertilization during poplar planting should be based on organic fertilizer, supplemented by chemical fertilizer, so as to combine soil improvement with support, and the late effect and quick-acting complement each other. Pay attention to the ratio of nitrogen, phosphorus and potassium fertilizer. It is not advisable to apply too much available nitrogen fertilizer, otherwise it will affect the survival rate of seedlings. At the same time, it is necessary to apply trace elements in a targeted manner. Fertilization amount should be determined according to soil conditions, seedling size and cultivation methods. Generally, 20-30 kg of organic fertilizer, 0.5- 1 kg of phosphate fertilizer and 0. 1-0.2 kg of potash fertilizer are applied to each seedling. When determining the variety and quantity of base fertilizer, special attention should be paid to the following points:
1. The obstacle of fertilizer concentration must be prevented. If excessive chemical fertilizer is used as base fertilizer, it will cause local high concentration fertilizer obstacles. However, organic fertilizer is slow-acting and buffering, and even if it is applied in large quantities, there is little concentration imbalance. Therefore, when the total amount of base fertilizer applied to poplar seedlings is insufficient, it is generally met by increasing the amount of organic fertilizer. When watering afforestation, generally only organic fertilizer is applied, but no quick-acting fertilizer is applied, otherwise the quick-acting fertilizer will dissolve, and the fertilizer concentration in the planting hole is too high, which will easily lead to seedling burning and affect the survival rate of afforestation.
2. Use less nitrate and ammonium nitrogen fertilizer. Nitrate nitrogen fertilizer is not easily adsorbed by soil, but easily leached by rain or irrigation, so it is not suitable to be used as base fertilizer in large quantities. Excessive application of ammonium nitrogen fertilizer will affect the absorption of calcium and magnesium fertilizer by poplar, so it is not suitable to use it as base fertilizer in large quantities. Therefore, if it is really necessary to apply nitrogen fertilizer, it is best to apply amide nitrogen fertilizer (urea), and the amount of fertilizer should not be too much.
3. Phosphate fertilizer should be used as an important base fertilizer. Phosphorus fertilizer has a significant effect on forest growth. When the soil is short of phosphorus, the leaves will turn dark green purple or purple, which will affect the forest growth.
(3) inoculating mycorrhizal fungi
While applying base fertilizer, mycorrhizal fungi can be inoculated. Mycorrhiza is a common plant symbiosis phenomenon in nature. It is a combination of mycorrhizal fungi hyphae in soil and vegetative roots of seedlings, which can strengthen the absorption of water and nutrients by seedlings, especially phosphorus and nitrogen.
The methods of inoculating trees with mycorrhizal fungi include forest mycorrhizal soil inoculation, pure culture inoculation, fruiting body inoculation and mycorrhizal inoculum inoculation.
Inoculation of forest mycorrhizal soil: in the same old forest as the seedlings, select the place where mycorrhizal fungi develop well, dig the root layer soil, then mix the dug soil with appropriate amount of organic fertilizer and phosphate fertilizer, furrow it and apply it to the root layer of the seedlings, and water it after inoculation. This method is simple, the inoculation effect is very obvious, and the mycorrhiza degree is high, but it needs a lot and is inconvenient to transport, and may also bring new pathogenic bacteria, nematodes and weed seeds.
Pure culture inoculation of mycorrhizal fungi: scrape mycelium from mycorrhizal fungi culture medium, or filter mycelium from liquid fermentation culture solution and directly inoculate it into soil or lateral roots of seedlings. This method has not been widely used in production.
Inoculation of fruiting bodies: The fruiting bodies and spores of various ectomycorrhizal fungi can be used as inoculants for seedlings and soil. In particular, basidiospores produced by Pleurotus, Pleurotus ostreatus, Pleurotus ostreatus and other fungi are easier to collect in large quantities for large-scale inoculation. Generally, the collected fruiting bodies are mashed and mixed with soil, or spores are directly applied to planting holes, or made into suspension for watering, or the roots of seedlings are soaked with suspension, or fruiting bodies are buried near rhizosphere. Mixed inoculation of two or more kinds of fruiting bodies has better effect.
Inoculation with mycorrhizal agent: soak the roots with artificially cultivated mycorrhizal agent or spray it on the leaves.
Third, deep planting
Roots are important vegetative organs of trees, and trees can't live without roots. One of the functions of roots is to fix the whole tree in the soil and keep the whole tree in gravity balance; The second function is to absorb water in the soil and mineral nutrients dissolved in water; The third function is that the roots of some trees can form adventitious buds, which have reproductive effects. The sum of all the roots of a single tree is called the root system. According to the distribution of root system in soil, it can be divided into deep-rooted tree species and shallow-rooted tree species. Deep-rooted tree species have developed straight roots, which go deep into the soil layer and grow vertically downward. The main roots of shallow-rooted tree species are underdeveloped, and the lateral roots or adventitious roots grow by radiation, which is much longer than the main roots, and most of the roots are distributed in the soil surface. Poplar is a deep-rooted tree species, the vertical distribution of roots can reach 4 meters, mainly concentrated in the soil layer 0-90 cm deep, accounting for 80.2% of the total root system. Poplar is planted in deep pond, and the depth of pond is generally not less than 1m, and the planting depth of seedlings reaches 80cm. Deep planting in Datang can promote the rooting of seedlings, absorb water and inorganic salts deeper underground, enhance drought resistance, and be beneficial to the survival and growth of seedlings. However, it is not suitable for deep planting in places where the groundwater level is too high or water often accumulates in summer.
Fourth, irrigation.
In the main distribution areas of poplar in China, the key to improve the survival rate of poplar afforestation is to promote water balance at seedling stage and ensure water supply. Therefore, the success of poplar afforestation mainly depends on whether it can be watered enough. In order to ensure sufficient water for poplar planting, it is generally said that three levels should be guaranteed: First, the bottom water. Before planting, bottom water should be poured in the tree pool to make the soil around and at the bottom of the tree pool fully absorb water and create a moist soil environment for the seedlings. The second is to solidify the root water. When the seedlings are cultivated to two thirds, water the feet. In order to reduce soil porosity, make the root system closely combined with the soil, and ensure that the rhizosphere soil has enough water to meet the needs of root system to absorb water. The third is water permeability. When the soil cultivation is basically completed, water should be poured once to supplement the water needed by the seedlings and reduce the water loss caused by natural evaporation.
Fifth, cultivate the soil.
Soil is the foundation of seedling growth, one is to fix seedlings, the other is to provide water and nutrients, so we should grasp the link of soil cultivation when planting. When cultivating soil, cultivate topsoil first. The topsoil is loose in structure and rich in nutrition, which is beneficial to seedling growth. After cultivating the core soil, the core soil is hardened, the aggregate structure is poor and the nutrient content is low. The subsoil placed on the upper layer can be improved by natural differentiation, farming and fertilization. Fine soil and molten soil should be placed around the root system of seedlings, and blocky soil should be as far away from the root system as possible to promote the wound healing of root system of seedlings, restore physiological functions and the germination and growth of adventitious roots. In the process of soil cultivation, it is necessary to ensure that the roots of seedlings are not nested, but also to fill the soil while stepping, so that the roots and soil are closely combined.
The height of soil cultivation depends on different situations. In dry areas in spring, the cultivation height of soil is lower than the ground, so cup-shaped watering holes are made around the seedlings to facilitate regular watering. In other areas, the height of soil can be higher than the ground, which is conducive to fixing seedlings, increasing the thickness of soil layer and eliminating rainwater. After ridging and watering, the top surface should be covered with a layer of dry soil, which is beneficial to reduce water evaporation, keep the soil moist and improve the survival rate.
Six, pruning and whitewashing
1, pruning
In areas with low air relative humidity in spring, when transplanting large seedlings, all the side branches should be pruned to reduce water loss. In order to prevent new shoots from sprouting, some large lateral branches can also be cut short, leaving short piles with a length of 5- 10cm, and cut off from the base after 1-2 years.
After the seedlings are planted, the redundant lateral branches, damaged branches and pest branches should be trimmed appropriately to reduce the transpiration of seedlings. In some places, paintings are still carried out after planting, and the main function is to mark the seedlings, so that they can be found after being stolen or destroyed.
Step 2 paint it white
In some places, newly planted trees and even mature trees have the habit of whitewashing. White paint is generally applied to trees on both sides of the road. Its main functions are as follows: First, it is used as a traffic sign. The trees on both sides of the road are painted white, so it is easy to distinguish the road surface, curve and intersection when driving at night, which is conducive to driving safety; The second is to beautify the environment. Trees painted white are neat, bright and pleasing to the eye, giving people beautiful enjoyment. The third is to eliminate pests. White paint combined with pesticides and fungicides can kill pathogenic bacteria and pests and play a role in preventing diseases and insects.
Whitening method: take a small amount of quicklime, dissolve it in water, and dilute it with water to make limewater (some pesticides and fungicides should be added to the limewater according to the situation of pests and diseases), and apply the limewater on the trunk with a brush, with the drying height from the root of the trunk to the height of the chest at1-1.5m. Precautions for painting: First, the painting height must be consistent, including all trees and trees. Second, the application must be fine, and the bark cracks should be carefully applied; The third is to work for a week, not half a face, to one side of the road, not to the back.
Seven, the application of new technologies
In recent years, with the continuous progress of science and technology, many new technologies have been applied to afforestation. It mainly includes the application of new materials such as water-retaining agent, mycorrhizal agent, rooting powder and poplar special fertilizer.
1, water-retaining agent
Water-retaining agent is a non-toxic, non-flammable, non-explosive and non-corrosive functional polymer, which can absorb 100-250 times its own weight of natural water and is easy to degrade. The degradation products are beneficial to soil. Absorbed water can not be squeezed out by simple physical methods. It has strong water retention, just like a micro-reservoir, which can be slowly absorbed by the roots of plants and can release and absorb water repeatedly. If the water-retaining agent is combined with pesticides, trace elements, rooting powder and chemical fertilizer, it can also be released slowly and improve the utilization rate.
The application method is: (1) soil mixing: 0. 1% of the weight of dry soil (bulk density 1.25- 1.35) in the cultivated layer is evenly mixed, and then watered; Or let the water-retaining agent absorb enough water to form saturated gel, and mix evenly, with the volume ratio of soil to saturated gel of 10%- 15%. Then cover at least 5 cm of topsoil to prevent the water-retaining agent from decomposing prematurely in the sun.
(2) Dipping roots: put 40-80 mesh water-retaining agent into a water container at the ratio of 0. 1%, fully stir and absorb water for about 20 minutes before use, soak bare root seedlings for 30 seconds, and then take them out, preferably wrapped in plastic film. 1 kg water retaining agent can treat 2000 seedlings. Soaking root system with water-retaining agent can prevent root system from drying, prolong wilting period, facilitate long-distance transportation and improve afforestation survival rate 15-20%.
Application effect: using water-retaining agent in soil mixing can save water by 50-70% and fertilizer by more than 30%. Water-retaining agent can also improve the permeability of soil, improve soil structure, resist hardening, and has a certain thermal insulation effect, which can effectively improve the survival rate of poplar afforestation. Water-retaining agent is not a water-making agent. Be sure to water it when using it for the first time, and replenish it regularly in areas with less rain. For general use, trees need not be watered, but used in autumn, winter and spring. In areas with high salt content, the water absorption capacity and service life of water-retaining agent will be reduced. Different areas should be used scientifically according to soil quality, plant characteristics and rainfall.
2. Mycorrhizal agents
Mycorrhizal agent is a biological agent with multiple functions, and it is a sustainable ecological technology product developed according to the principle that plants need to form mycorrhiza to help their survival and growth under natural conditions. It can induce and promote plants to form effective mycorrhiza, improve the ability of plants to absorb and utilize water and fertilizer, secrete a variety of plant physiological active substances, regulate plant physiological activities and improve the nutritional status in vivo. Secrete a variety of plant hormones and enzymes, promote plant rooting, growth and development, and improve the utilization rate of soil nutrients (especially phosphorus); Enhance plant disease resistance and stress resistance, improve soil activity, increase soil organic matter content, improve soil physical and chemical properties and improve soil fertility. Mycorrhizal afforestation greatly improves the survival rate of afforestation and the growth of young forests, promotes the rapid formation of "high-quality, high-yield, efficient and stable" stands, saves the cost of replanting and forest protection, shortens the afforestation period and reduces the afforestation cost. The implementation of this technology will change the traditional backward extensive management mode of digging forest soil and inoculation into an advanced intensive management mode of mycorrhizal afforestation, prevent soil erosion, protect forest resources, reduce or even completely avoid environmental pollution caused by the use of chemical agents such as growth regulators, fertilizers and pesticides, and promote ecological balance.
3. Rooting powder
ABT rooting powder is a broad-spectrum and efficient rooting powder with international advanced level, which was successfully developed by researcher Wang Tao from Forestry Research Institute of Chinese Academy of Forestry. The analysis of ABT rooting powder series by tracer atom and liquid chromatography shows that the treatment of plant cuttings can participate in the whole physiological process of adventitious root formation, and has the dual functions of supplementing exogenous hormones and promoting the synthesis of endogenous hormones in plants, so it can promote the formation of adventitious roots, shorten the rooting time, and promote the formation of tufted roots and explosive roots of adventitious roots. This achievement was popularized and demonstrated in 1993, and achieved remarkable economic and social benefits. ABT rooting powder series includes ABTlNo. -10, ABT3 is suitable for poplar seedling. Using it to treat the root system of seedlings can improve the survival rate of seedling transplantation, promote the development of root system, accelerate the growth of seedlings, enhance the stress resistance, and effectively improve the survival rate of afforestation and transplantation 17-3 1%. Usage: Take 1gABT rooting powder before planting, dissolve it with a small amount of alcohol, add 20kg of water, and soak the root 1.5-2 hours. 1 g rooting powder can treat 500-600 seedlings with the input-output ratio of 1:6-20.
4. Special fertilizer for poplar
Special fertilizer for poplar was selected by Professor Chen Jinlin, a poplar expert from Nanjing Forestry University, according to the characteristics of nutrients absorbed, soil physical and chemical properties, fertilizer properties and utilization rate during poplar growth, and through the comparison of different formulas and test results. It has high nutrient content, long fertilizer efficiency and even release, which can improve the growth speed of poplar, promote the root system development and lush foliage of poplar, and enhance the ability of poplar to resist pests and diseases. Poplar special fertilizer is mainly used for topdressing.