What is the reason for the defoliation of fast growing poplar now, and when is it more appropriate t

The other is physiological potassium deficiency. Brown necrotic lesions of 1-2 mm size are evenly distributed on the leaves, the edges of the lesions and healthy tissues are clear, the larger lesions** are grayish-white, the edge tissues of the leaves grow normally, and the leaves fall off. Tree leaf litter develops from bottom to top, and it is initially thought to be pathogenic spot blight.

2. Characteristics of field distribution. There are three types of fast-growing poplars in our nursery: spring cuttings in 2001, transplanting in spring 2002 and spring cuttings in 2002; The varieties are mainly poplars, which contain other unknown varieties. In general, the fallen leaves are unevenly distributed.

However, among the above three types of seedlings, there were obvious differences in the severity of defoliation. In 2001, the cuttings were the heaviest in situ, followed by the transplanting in 2002, and the cuttings in 2002 were lighter. In the field transplanted in 2002, we found that the leaves of two adjacent plants with almost the same height and diameter specifications were almost the same, one with almost all the leaves and the other with thick and lush leaves.

The two varieties are only different, and the name of the variety needs to be verified The difference in the degree of defoliation between the two varieties is not significant.

3. Analysis of the causes of defoliation. Salt damage induces scorched leaf margins and defoliation caused by potassium deficiency, such as the non-necrotic spot part of the leaf described in the symptoms; The early defoliation of poplar trees has occurred sporadically in 2002, and the degree of occurrence this year is heavier than last year, because the root system of the tree grows underground with the growth of tree age, the nursery is located in the saline-alkali soil area of Tianjin Binhai, the underground saline water level is higher, generally speaking, there is salt water 2-3 meters below the tillage layer, and the salt content of these water is more than three thousandths of the irrigation water standard. The height of the tree is directly proportional to the depth of the root system, and the longer the age of the tree, the deeper the root system, the more severe the salt damage performance, which is completely consistent with the performance of the degree of defoliation in the field at different ages.

Pathogen spot blight, which is contagious. The severity of its occurrence is closely related to tree potential, rainfall, and bacterial accumulation. The high accumulation of fungus sources in the long-aged nursery, coupled with the early precipitation in 2003, the large precipitation and high air humidity were very conducive to the occurrence of this disease.

Summary. Hello: Fast-growing poplar is one of the fast-growing tree species, so it has high requirements for the growth environment, and the plant itself is relatively fragile.

Hello: Fast-growing poplar is one of the fast-growing tree species, so it has high requirements for the growth environment, and the plant itself is relatively fragile.

It is now autumn and the temperature is gradually getting lower, so if you want to plant fast-growing poplar now, you may be affected by some unfavorable conditions.

For example, the growth period is shortened, the seedlings have poor drought resistance and cold resistance, and are easy to be attacked by pests and diseases.

Therefore, it is recommended to wait until next spring before planting.

If it has been planted, Lianhuanshan should pay attention to maintaining the soil suitable for the humidity, nutrients and other conditions in the shed, and strengthen the management and intimate care of the fast-growing poplar to help it better overwinter and grow.

Pruning of fast-growing poplar.

The purpose of fast-growing poplar pruning is high yield and high quality. The principle of pruning fast-growing poplar seedlings is light pruning, heavy crown preservation, branch competition, auxiliary surplus and staring branches.

Pruning time of fast-growing poplar.

Under normal circumstances, fast-growing poplars should not be pruned within 1-3 years, so as not to weaken the tree and inhibit its growth. When the fast-growing poplar dbh reaches 10 cm, prune the side branches. According to the growth of the canopy masking ring, prune appropriately.

Fast-growing poplar pruning propagation.

Fast-growing poplars can be cut from November to spring of the following year after the leaves have fallen. At this time, the temperature and humidity are suitable for rooting, and the survival rate is high.

Pruning method of fast-growing poplar.

Pruning and drying: Pruning of fast-growing poplar is the cultivation of material for processing. When the diameter of the lateral branches on the trunk of fast-growing erectors and poplars below 8 m grows to 10 cm, the side branches should be pruned to ensure that there are no knots 10 cm beyond the core of the dry timber.

Pruning is decided based on the diameter of the trunk. Generally, 1-3 year old trees can be pruned in small amounts, and 4-5 year old trees can be pruned by one-third. Prune the sprouts:

After pruning fast-growing poplars, new shoots on the lower trunk should be removed in time. Prune close to the trunk and leave no stubble. When pruning thick branches, a pruning saw should be used.

You can make a shallow incision under the branch and proceed slowly from top to bottom without tearing the bark.

Precautions for fast-growing poplar pruning.

When the vegetative growth of fast-growing poplar stops and the tree has no leaves, it can be pruned and shaped. Summer pruning can affect growth, and wounds are prone to pests and diseases. And summer pruning will inhibit the development of secondary branches, so in summer you can prune competing branches and hit side branches.

Its characteristics are that it requires a warm climate and sufficient rainfall, and fast-growing poplars are suitable for planting in lake areas and mountainous areas, hilly areas and alluvial flats in river valleys and "four sides", and the soil is moist, fertile, deep and well-drained. It is most suitable to grow on alluvial sand dunes and mounds with a soil thickness of more than 1 meter, a groundwater table between meters and 2 meters, an acidity and alkalinity, and a salinity content lower than that.

Fast-growing poplar is easy to reproduce and grow rapidly, according to the Yuanjiang Forestry Bureau, afforestation with annual strong seedlings, the tree height increases by 3 to 5 meters per year within two to five years, the DBH increases by 4 to 5 cm per year, and the growth amount per mu of the forest is 2 cubic meters.

Fast-growing poplar varieties identified in 2009: Populus chinensis (Populus chinensis, Populus 108, Populus 2025, Populus zhonglin 46, Populus dan, etc.).

Characteristics of fast-growing poplar after 2000: the leaf color of poplar (poplar chinensis) changes with the seasons, the male has no fly flocculent, does not pollute the environment, and can become mature in 5-6 years. It can be used for landscaping, but also for fast-growing and high-yield forests, which has been praised and affirmed by all walks of life.

The characteristics of new fast-growing poplars such as 107 poplar and 108 poplar are loved by growers for their resistance to diseases and insects, drought and flood resistance, and strong adaptability.

Fast-growing poplars can be cut down in 8-10 years, about 8 years faster than ordinary trees, and the volume of a 10-year-old single plant can reach cubic meters, and the annual pure income per mu is about 300 yuan.

<> I. Symptoms. There are two main symptoms, one is that the leaf edge tissue becomes grayish-black necrosis and gradually expands inward, the leaf healthy tissue has no necrotic spots, and the leaf falls off. The other is physiological potassium deficiency.

Brown necrotic lesions of a size of l 2 mm are evenly distributed on the leaves, the edges of the lesions and healthy tissues are clear, the larger lesions are grayish-white, the leaf edge tissue grows positively, and the leaves fall off. Tree leaf litter develops from bottom to top, and it is initially thought to be pathogenic spot blight.

2. Characteristics of field distribution. There are three types of fast-growing poplars in our nursery: spring cuttings in 2ool year, transplanting in spring in 2oo2 year, and spring cuttings in 2oo2 year. The main varieties are LO7 and L8 poplars, including other unknown varieties.

In general, the fallen leaves are unevenly distributed. However, among the above three types of seedlings, there were obvious differences in the severity of defoliation. The untouched leaves of the cuttings in situ in 2ool were the heaviest, followed by transplanting in 2oo2, and the cuttings in 2oo2 were lighter.

In the field transplanted in 2oo2, we found that the leaves of the two adjacent plants, which were almost the same in height and diameter, were basically gone, while the leaves of the other plant were thick and lush. The two strains are only different varieties, and the names of the varieties have yet to be verified.

The difference in the degree of defoliation between the two cultivars LO7 and L8 was not significant.

3. Analysis of the causes of defoliation. Salt damage induces scorched leaf margins and defoliation caused by potassium deficiency, such as the non-necrotic spot part of the leaf described in the symptoms; The early defoliation of poplar trees has occurred sporadically in 2oo2, and the degree of occurrence this year is heavier than last year, because the root system of the tree grows underground with the growth of tree age, the nursery is located in the saline-alkali soil area of Tianjin Binhai, the underground salt water level is higher, generally speaking, there is salt water 2 to 3 meters below the tillage layer, and the salt content of these waters is more than three thousandths of the irrigation water standard.

The height of the tree is directly proportional to the depth of the root system, the longer the age of the tree, the deeper the root system, the more roots distributed in the saline aquifer, the heavier the salt damage, which is completely related to the performance of the degree of leaf fall in the field between different ages.

Pathogen spot blight, which is contagious. The severity of its occurrence is closely related to tree potential, rainfall, and bacterial accumulation. The high accumulation of fungus sources in long-aged nurseries, coupled with the early precipitation in 2oo3, large precipitation and high air humidity, are very conducive to the occurrence of this disease.