Causes of annual fruit of Carya cathayensis and measures to overcome it

Causes of annual fruit of Carya cathayensis and measures to overcome it

1 causes of annual fruit of Carya cathayensis and its overcoming technical measures

1.1 present situation of annual fruit of Carya cathayensis and its harm

The annual fruiting phenomenon of Carya cathayensis is the incoordination of tree growth and fruit, nutrient accumulation and consumption, which shows the difference in fruit yield between years. The annual fruit phenomenon of Carya cathayensis often occurs alternately, which is a physiological response that the tree automatically adjusts the balance of vegetative growth and reproductive growth under the same climate and low cultivation level in the producing area. Some trees are particularly weak, or they suffer from natural disasters such as diseases and insect pests, droughts and floods for several years in a row, and there will be several small years in a row, and then another big year, while others will have another small year after several consecutive years of favorable weather and good management. Although the output is high in the big year, but in the small year, the output is very low, or even no harvest, and the annual average output in the big year plus the small year is far lower than the stable yield every year. The phenomenon of big and small years not only directly causes economic losses to forest farmers, but also can not make full use of production tools, storage and packaging equipment; for consumers, it can not guarantee the normal and stable supply of market fruits and affect the normal development of the food industry.

1.2 reasons for the annual fruit of Carya cathayensis

1.2.1 malnutrition

In a year, the branches and long leaves of the Zhongshan walnut tree are usually carried out at the same time as flowering and fruiting. The carbohydrates produced by the leaves and the nutrients absorbed by the roots can not only meet the growth of branches and leaves and fruit development in the current year, but also accumulate nutrients for flower bud differentiation in the current year and flowering and fruiting in the next spring. If there are too many fruits in that year, too much nutrient consumption, not enough nutrients for flower bud differentiation or incomplete flower bud differentiation, next year will become a small year. When flowers and fruits decrease in a small year, and have the ability to produce a large number of branches and form a large number of flower buds, it becomes a big year again in the third year, thus forming a vicious circle of big and small year results.

1.2.2 hormone imbalance

The flowering and fruiting of fruit trees is not only controlled by nutrition, but also regulated by the type and content of hormones in the receptor. In the big year, flowering, fertilization and fruit development can produce more gibberellin to stay in the tree, and if there are few flower buds, the following year will become a small year. On the contrary, the number of flowers and fruits decreased, the formation and content of gibberellin were less, and the content of hormones promoting flower bud formation was relatively increased, then the flower bud formation also increased, and the third year became the big year.

1.2.3 Natural disasters and pest hazards

Typhoons, freezing injuries, droughts, waterlogging and serious diseases and insect pests can all cause early defoliation in autumn, reduce nutrient synthesis and nutrient accumulation in trees, and make trees weak and unable to form flower buds, resulting in a small year in the following year.

In addition, the soil erosion is serious, the content of organic matter is low, and there are many results in the big year, which is also one of the main reasons for the big and small years.

1.3 Technical measures to overcome the annual fruit of Carya cathayensis

1.3.1 Grass planting green manure to improve soil

Like the fruit orchard, Carya cathayensis forest should carry out green manure planting every year to increase the content of soil organic matter, improve soil structure and cultivate deep, broad and micronutrient groups, which is the fundamental measure to overcome the annual fruit phenomenon caused by nutritional imbalance. When conditions permit, natural grass or artificial recommendation can be promoted.

The advantages of natural grass growth: first, it can prevent typhoon rainstorm from scouring the soil and leaching nutrients; second, it can stabilize the temperature and humidity of the soil root distribution layer, which is conducive to root growth; third, it can increase the content of soil organic matter; fourth, it can save labor. However, the disadvantage of natural grass growing is that it is easy to appear the contradiction between grass growing and trees competing for fertilizer and water. The solution is to mow the grass with a lawn mower during the peak period of hickory growth, especially during the peak period of root growth.

The key to the greening of artificial grass is to select the right grass species. At present, the grass species suitable for planting in hickory forest are: Amorpha frutescens, clover, ryegrass and Bahia grass and so on. Amorpha fruticosa is called "iron green manure". It contains 6.6 kg of nitrogen, 1.5 kg of phosphorus, 3.9 kg of potassium and more rhizobium per 500 kg of Amorpha fruticosa, which can be used to improve soil quickly and well. It is appropriate to take belt planting along the contour lines, the forest glades can also be planted in small blocks, and the planting density on steep slopes can be appropriately increased. It is appropriate to increase the application of nitrogen and phosphorus fertilizer within 1-2 years of planting to promote its growth. After planting, it is not cut in the same year, and can be cut in the following winter with a height of less than 10 cm. Starting from the third year, it is cut once every year in late May and late July, which is directly covered or shallowly buried in the forest as green manure, and can also be planted along the edge of the forest operating path and horizontal steps. Red clover, white clover and ground clover in clover are suitable for planting in Jiangnan mountainous area. in the mountain area without irrigation, clover often dies in the aboveground after dry season and rain, and its persistent roots and seeds germinate again in autumn and rain season. In the first year of planting clover, if it can inhibit the growth of other weeds, the persistent roots and seeds of clover will grow vigorously after 10 months, and become the main grass species covering the ground in winter. Ryegrass is most suitable for growing at pH 6.0-6.5. It is moisture-resistant and cold-resistant. It grows rapidly and luxuriantly in spring. It can cover the whole garden quickly. The stem is thin and soft, and the root is shallow and developed. It began to wither in late June, withered completely in the middle of July, and propagated on its own in the following year. The stems and leaves of Bahia grass are rich in various nutrient elements, which are very suitable for planting in mountainous red and yellow soil.

On the basis of artificial green grass, it is appropriate to plant local green manure such as rape, radish, Ziyunying, cauliflower and so on. Except for the mountain fields with high gravel content and shallow soil layer, it is appropriate to plant rape under the Carya cathayensis forest, but do not harvest. The seeds were sown from the end of August to the beginning of September, and cut before the full flowering stage in early April of the following year, falling directly in the forest or covering around the rhizosphere. Radish can be sown in drought-intolerant mountain fields such as high gravel content and shallow soil layer. Where the soil moisture is good, the soil layer is deep and relatively fertile, you can choose to plant Ziyunying, cauliflower and so on.

1.3.2 Scientific fertilization to coordinate the imbalance between vegetative growth and reproductive growth

According to the growth of branches and leaves and the development of fruit, the lack of nutrients should be replenished in time, and the excess nutrients of trees or soil should not be applied, so as to promote the healthy growth of trees and ensure the nutrient needs of fruit and flower bud formation in the same year. It is best to apply base fertilizer when Carya cathayensis is planted. 0.5 kg organic fertilizer can be mixed with 0.25 kg superphosphate and planted with soil cover. From the current year to the third year, block grass was cut to cover the rhizosphere. From the fourth year to the seventh year, organic fertilizer or organic-inorganic compound fertilizer can be applied at the beginning of March, pure organic fertilizer 0.5 kg (cake fertilizer, etc.) or organic-inorganic compound fertilizer 0.25 kg can be used per plant, and the amount of application can be increased year by year. After the seventh year, the organic-inorganic compound fertilizer was applied 0.5 kg per plant, and the potassium fertilizer was increased by 0.05-0.1 kg year by year.

1.3.3 thinning flowers and fruits and protecting flowers and fruits

In the Lunar New year, according to the size and growth of the crown, keep the right amount of fruit and remove too much and too dense fruit, so as to prevent the overburden in the current year and the appearance of the following year. In young years, while reducing nitrogen application, the overgrowing branches of Carya cathayensis can be coring or wiping, so as to increase the fruit setting rate and yield.

1.3.4 reasonable pruning

In the Lunar New year, cutting off too many flower branches, reducing the amount of fruit hanging in the current year, promoting vegetative branches, increasing the rate of flower bud formation and the yield of the following year, its effect is the same as that of thinning flowers and fruits and protecting flowers and fruits.

1.3.5 spraying hormones and nutrients

There are two kinds of application in the mature forest of Carya cathayensis: one is the physiologically active substance triacontanol. Spraying 0.01~4mg/kg triacontanol on the crown during flowering period can increase the fruit setting rate by more than 28% on average, among which the effect of 0.05mg/kg concentration is stable, and the effect is good when sprayed in the young fruit stage. Second, ethylene, mainly ethephon, can inhibit cell division and elongation, loosen fruit stalks, promote early ripening and facilitate harvest. The application of harvesting net combined with tall trees in hickory adult forest can minimize the occurrence of picking casualties.

1.3.6 strengthen the prevention and control of diseases, pests and natural disasters

The focus is on the control of Carya cathayensis flower bud maggot, Carya cathayensis canker, root rot, branch blight and leaf-eating pests. The control should gradually shift from chemical control to biological and physical control. Try to use low-toxic, efficient, residue-free biological pesticides and physical control represented by frequency vibrating insecticidal lamps.

2 transformation of low-yield Carya cathayensis forest

2.1 rejuvenation of weak trees of Carya cathayensis

2.1.1 causes of formation

First, the site condition is poor, the soil layer is barren, the content of organic matter is less than 1%, and the soil water and fertilizer conservation capacity is poor; second, extensive management, low fertilization level, unreasonable intercropping of long-stalk crops and potato crops with strong fertilizer absorption, as well as weeds with strong natural growth competitiveness, compete with Carya cathayensis for fertilizer and water, affecting the growth of Carya cathayensis. Third, there are many fruits, poor root development, poor absorption, weak branch growth and low photosynthetic capacity, which lead to the premature senescence of middle and young Carya cathayensis fruit trees.

2.1.2 Technical measures for rejuvenation of weak trees of Carya cathayensis

(1) turn the soil to green and improve the soil: establish a soil management system to support the land. Within 5-7 years from the planting of Carya cathayensis, green manure was interplanted in winter and spring every year. Winter green manure sowing in winter can choose purple yunying, yellow alfalfa and so on; spring green manure can choose peanut, legume (including nitrogen-fixing bacteria) and so on.

When sowing green manure, base fertilizer should be applied, proper topdressing during the growing period, and legume green manure should pay attention to increasing phosphorus fertilizer to increase fresh grass yield and achieve the purpose of "exchanging phosphorus for nitrogen". During the cutting period, it is appropriate to cut and press at the flowering stage where the fresh grass yield and nutrient content are the highest, and some green manure can also be composted or retted before application to improve fertilizer use efficiency.

Turn and press the green manure, about 2030 kg per plant, and apply appropriate amount of cake manure and barnyard manure at the same time. In the acidic mountainous area, 1 kg lime was added every 100 kg of green manure to neutralize the organic acid produced during the decomposition of green manure and reduce the acidity of mountain soil, which was beneficial to the root growth of Carya cathayensis.

The method of turning soil should be carried out separately according to the slope of woodland. For steep slopes with a slope of more than 25 °, the no-tillage method of chopping grass and laying land without loosening soil every year should be adopted to facilitate soil and water conservation. For hillsides below 25 °, fish-scale pit type can be adopted, and the depth of turning should not exceed 15 cm;10 °~ 25 °. Combined with terrace and horizontal belt, the method of digging and filling is used according to the plant spacing along the contour line, and the slope land is gradually transformed into a horizontal belt. The method of expanding holes in tree plates is usually used on slopes below 10 °. Starting from the edge of the planting hole, the hole is gradually expanded outward, digging 10-20 cm deep within the crown every year, and the crown width is 30 cm deep, which expands year by year and promotes the root system to develop deeply and widely. When turning the soil, try not to hurt the thick roots with a diameter of more than 1 cm, the topsoil and core soil should be stacked separately, and the bottom layer and root distribution layer should be filled with topsoil to promote weathering. At the same time, the effect of applying base fertilizer is better.

(2) rational fertilization: the application of fast-acting fertilizer from March to April in spring is beneficial to spring shoot growth and flowering and fruiting. The application of organic fertilizer in September could increase the assimilation ability of leaves and nutrient accumulation of trees, and lay a foundation for flower bud differentiation and shoot growth in the coming year. According to the size of the crown, the method of fertilization requires digging a ring ditch outside the crown, digging a semicircular ditch above the trunk on the slope, filling compost, barnyard manure and other organic matter into the bottom of the ditch, applying phosphorus and potassium fertilizer, acid soil, and covering soil after adding lime. The effect is better. Remember not to apply too much at once, or it will be counterproductive.

(3) stopping fruit and promoting shoots: weak hickory trees have poor root development, low absorptive capacity, weak shoot growth, small and few leaves, low photosynthetic energy and less nutrient accumulation. In the first or second year of rejuvenation of weak trees, in addition to properly cutting off some flowers and branches, fruit can be comprehensively thinned at flowering or young fruit stage, so as to reduce tree burden and promote shoot growth.

(4) cut off the diseased branches in time: cut off the dead branches from the hickory tree in time, cut off the thicker dead branches from the base, pay attention to smooth the wound, apply wound protective agent after pruning, and transport them out and burn them in time.

2.2 overcoming the non-fruiting of trees put into production

Carya cathayensis generally began to bear fruit 8 ~ 10 years after planting and entered the full fruit stage 20 years later. However, due to extensive management, there are still many pecan trees that should enter the full fruiting stage, with little or no normal fruit.

2.2.1 the reason why the trees put into production do not bear fruit

First, due to the partial application of nitrogen fertilizer or excessive nitrogen fertilizer, the vegetative growth is too abundant, and it is difficult to form flower buds. Even if a small amount of flower buds bloom and bear fruit, when the young fruit development needs more nutrient supply in early summer, it will produce fierce nutrient competition with branches and leaves. The young fruit falls off because of weak competitiveness. Second, the florescence continuous rainy weather, the lack of favorable pollination time, resulting in blossom year after year without fruit, or little fruit.

2.2.2 Technical measures to overcome the non-fruiting of trees put into production

The main results are as follows: (1) to control the excess of fertilizer and water: if there is too much fertilizer and water, especially too much nitrogen fertilizer, the branches will grow, the nutrient accumulation will be less, and it will be difficult to form flower buds. Fertilizer and water can be controlled in summer and autumn to inhibit its vegetative growth in order to accumulate nutrients and promote flower bud formation. Appropriate early application or less application of spring fertilizer in order to improve flower bud quality and fruit setting rate.

(2) the methods of root cutting, ring cutting or ring upside down peeling can significantly increase the fruit setting rate of steep long trees with good growth but poor fruit. Ring cutting is to cut or cut several times on the bark at 1m to 1.5m of the trunk, reaching to the xylem to temporarily hinder the downward transport of photocontracted products, increase the nutrient accumulation above the wound, promote flower bud differentiation, and improve fruit setting rate and yield. Ring cutting is carried out 2-4 weeks before flower bud differentiation of Carya cathayensis, which can promote flower bud differentiation, and when used in flowering or late flowering stage, it can reduce flower and fruit shedding and increase fruit setting rate and yield. Trees with few flowers should be sooner rather than later, while trees with more flowers are not easy to be cut around. Personal experience can also be applied depending on the degree of growth of the tree and the number of fruits left. If the tree is strong, you can deal with more branches, and vice versa.

(3) the treatments of coring, pulling branches and supporting branches: the growth of new shoots of prosperous trees is large, and the tree posture is upright. Coring in the prosperous period of new shoots can temporarily stop elongation growth, promote branches, and make branches form flower bud fruit. The branch is usually pulled apart by a rope or bow-shaped stretcher; the supporting branch is supported by a stick or thick branch. They all can open the branch tip angle, weaken the top advantage, ease the tree potential, in order to facilitate flower bud formation and fruit. When in use, the opening angle of the backbone branch should be more than 45 °, but the effect is not obvious if it is less than 45 °. After a growing season, the angle of the base of the branch has been fixed, and the stick and rope can be removed.

(4) artificial pollination and vibrating branches: under normal conditions, the male flowers of Carya cathayensis fell off after 3 days, while the female flowers had the ability of fertilization and fruiting 10 days after maturity. Therefore, the natural pollination of Carya cathayensis is affected by continuous low temperature and rainy weather during flowering, so artificial pollination can be adopted to improve the fruit setting rate. Artificial pollination can be carried out by using the sequence of florescence at different elevations, that is, early flowering at low altitude, pollen can be collected and stored in advance, and when the florescence at high altitude is in bad climate, the pre-collected pollen can be pollinated by artificial pollination; on the contrary, when it rains during the florescence in the low altitude area, the female flowers can be used to wait for pollination, and pollination can be collected in the high altitude area after sunny days. If you want to operate easily, you can choose to tie the newly flowering male flower branches into bundles on the long bamboo pole in a clear and windless day, insert them into the pollinated crown, vibrate the bamboo pole to scatter the pollen, and carry out artificial pollination.

2.3 Regeneration of senile hickory trees

2.3.1 characteristics of senescent hickory trees

Some nutrient elements are extremely deficient, the content of organic matter is low, the soil layer is solid, the topsoil is hardened, the ventilation and the ability of fertilizer and water retention are weak. Therefore, the root system of the plant grew poorly, the branches were short and the leaves were small, and the photosynthetic capacity decreased. At the same time, the crown of the old tree is tall, the inner chamber is empty, and it has been affected by natural disasters such as drought and waterlogging, diseases and insect pests for a long time, many canopies are incomplete, the results are very few, and some have lost their economic cultivation value, so they have to be dug and replanted or cut off from the ground at a depth of 0.2m to 0.5m. Re-cultivate with germinating strips; some trees are still relatively healthy, and they can achieve high yield by strengthening water and fertilizer management and crown renewal.

2.3.2 Technical measures for renewal of senescent trees

(1) changing soil and adding guest soil: turn the soil of the old garden deeply and pick out it and replace it with new soil. The change of soil is carried out year by year in the form of radial or furrow, so as to avoid injuring too many roots at one time and affecting the growth. This is suitable for hickory forests with convenient transportation and small area. If the soil layer of Carya cathayensis forest is shallow and the soil erosion is serious, the guest soil method can be used to improve the soil, that is, the fertilizer soil is piled under the tree crown to thicken the soil layer, so as to facilitate root growth, restore tree potential and increase yield.

(2) increase the application of organic fertilizer: to ensure the supply of various nutrients through the application of organic fertilizers with complete nutrient elements, such as green manure, branches and leaves, mountain grass, barnyard manure and compost.

(3) shaping and pruning: at present, many hickory adult forests have high planting density, high trunk and narrow crown. If they are not pruned, it will not only affect the yield, but also increase the unsafe factors during picking. The fruiting layer of this kind of Carya cathayensis forest moves outward, and the fruiting layer is concentrated in the upper part of the crown. For the old Carya cathayensis trees with a height of more than 8m, the top branches can be cut off. The hickory is made of hard material and the wound heals slowly, so the saw must be smooth. Spread the wound with 1 ∶ 10 concentration of dioxone, cover it with tin foil and bandage it to promote healing and prevent the wound from rotting. The pruning period of Carya cathayensis can be carried out from defoliation in winter to sprouting in spring, first cutting off weak branches, overdense branches, disease and insect branches, and then cutting off spring shoots with only male inflorescences or poor female flowers in late spring to reduce the ineffective consumption of nutrients.

(4) making use of sprouting: when the crown is declining, the main branches which are dead or unable to bear fruit can be cut off by making use of the characteristic that the backbone branches are easy to sprout, and the new branches can sprout under the wound to form the crown again and bear fruit. When the crown is incomplete, sprouting can also be used for de-sprouting and re-culture to form new trunk branches, make up the crown, expand the photosynthetic area and increase the yield.