Zhaotong City regional walnut fine seed harvesting nursery construction technology

Zhaotong City regional walnut fine seed harvesting nursery construction technology

Li Zhengyin and others

Zhaotong is located in the transition zone from the Sichuan Basin to the Yunnan-Guizhou Plateau, with complex geological structure, significant geomorphological characteristics, deep mountains and valleys, large altitude difference, the highest altitude of 4 040 m, the lowest altitude of 267 m, belongs to the subtropical, warm temperate coexistence of the plateau monsoon three-dimensional climate, the average annual temperature of 12.6 °C, the average annual sunshine hours of 1 900 h, the average annual rainfall of 760 mm, precipitation is relatively abundant, but the distribution of north and south is uneven, the south is dry and wet, floods and droughts occur from time to time. The average annual temperature is 11-21 °C, with the coldest temperature occurring in January, with an average monthly temperature of 1-12 °C, and the hottest temperature occurring in July, with an average monthly temperature of 20-27 °C. Unique geography, climate determines the regional particularity of walnut cultivation, the city's 11 counties (cities) have walnut distribution, Zeng Qingxian and others put forward the southern region of Zhaotong mainly cannabis walnuts, the northern region of wuren walnut-based varieties selection principle, for zhaotong city walnut main planting varieties laid the foundation. In recent years, with the strong support of the Forestry and Grassland Bureau of Yunnan Province and the Forestry and Grassland Bureau of various counties and districts, the forestry department of Zhaotong City has carried out the selection of walnut germplasm resources for many years, and finally selected a number of regional walnut excellent single plants with unique local characteristics, excellent quality and high promotion value, in order to support the improvement, quality and efficiency of low-yield and inferior walnut varieties in the city. In order to further accelerate the process of fine walnut breeding in the city, improve the overall yield and quality of walnuts, and provide sufficient scion sources for suitable areas, the current two ways to expand the excellent tree spikes are mainly adopted: new harvesting nurseries and reconstructed ear picking gardens. Through years of technical exploration and experimental demonstration, the author summarizes the construction technology of regional walnut fine seed harvesting garden as follows.

1 Construction of the ear picking garden

1.1 New harvesting nursery

1.1.1 Garden selection. Choose gentle slopes or flat lands of neutral and slightly alkaline sandy loam soils with convenient transportation, flat terrain, easy irrigation, good drainage, deep soil layer, fertile soil, leeward sunshine, sufficient light, and no long-term water accumulation. It is not advisable to choose saline, heavy clay or sandy soil sections.

1.1.2 Garden planning. According to the planting scale, the area of the harvesting nursery is determined. Bounded by obvious markers, the nursery land is divided into several communities, each of which is the same clone (variety), and a planting configuration map is drawn, indicating the location, asexual lineage number (variety name) and quantity.

1.1.3 Preparation of the garden. Generally in late autumn, early winter or spring, the land is prepared to achieve deep ploughing and fine cleaning, remove debris, and the depth is 25 to 30 cm. After the land preparation, the pond was planted in advance, the specifications were 60 cm× 60 cm×60 cm, and the excavated topsoil was stacked separately from the raw soil. After the pond is laid, the topsoil is mixed with the cooked farm manure 15.0~20.0 kg + compound fertilizer 0.25~0.50 kg to fill the pond, and the pond mouth is "steamed" after returning to the soil.

1.1.4 Selection of clones (varieties). Through the examination (recognition) and adaptation to the growth of the local area of the excellent clones (varieties); after the introduction of cultivation tests, suitable for the development of the local region of the excellent clones (varieties); based on the "Zhaotong City Quality Walnut Evaluation" project selected excellent single walnut plants, comprehensive consideration of the regional forestry department leaders and the people to recognize the willingness to accept, can meet the local development, unique local characteristics, excellent quality, high promotion value of the excellent single walnut plant.

1.1.5 Specifications of colonized seedlings. Select annual or biennial grafted seedlings of walnut clones (varieties). Annual seedlings are more than 50 cm tall and have a diameter of more than 0.8 cm, and second-year seedlings are more than 80 cm tall and have a diameter of more than 1.0 cm, which requires strong seedlings, developed roots, and no pests and diseases and mechanical damage.

1.1.6 Colonization density. It is advisable to plant seedlings in late autumn after they have gone dormant or before the seedlings have germinated in late winter and early spring, that is, from the end of september of the lunar calendar to the first month of the following year. The row spacing is 2.0 m×2.0 m or 2.0 m×3.0 m, i.e. 1 665 to 1 740 plants /hm 2; the row spacing of high-density plants is 1.0 m×1.0 m or 1.0 m×2.0 m, that is, 4 995 to 9 990 plants /hm 2. Plant in accordance with the technical requirements of "three burials, two steps and one seedling" [1] to ensure that the seedlings are positive, root-soothing, soil compacted, watered and covered with film.

1.2 Renovation of the ear picking garden

1.2.1 Stand selection. Choose a five- to ten-year-old walnut young forest or forest belt with convenient transportation, flat terrain, good three-dimensional conditions, good growth, and neat gardening, and clean up trees, shrubs, weeds and other debris in the woodland that hinder the growth of seedlings.

1.2.2 Spike selection and treatment. Select the branches of the excellent clones (varieties) described in 1.1.4 as the scion, and select the annual growth branches that are robust, free of diseases, full of buds and small in the heart of the marrow, and the thickness is preferably 1.5 to 2.5 cm [2]. The collected spikes are scattered in a ventilated place, naturally dehydrated until the buds are deeply asleep, then heated and melted with 95% paraffin + 5% yellow wax, and then quickly dipped in wax in the range of 70 to 90 °C. After the treatment, the spike strips are sorted and loaded with labels, and stored in cold storage and cellars for backup.

1.2.3 Grafting. Take the method of "slotting waterproofing, delayed grafting" [2], at the rootstock trunk 1.3 to 1.5 m from the ground, grafted with the skin connection or skin tongue connection method, partial grafting is not alive, and then in the summer on the newly issued branches using square buds for supplementation.

1.2.4 Post-grafting management. According to the walnut high pile exchange excellent grafting technology, followed by post-management and implementation, including the process of removing germination and picking flowers, fertilizer water management, windproof folding of new shoots, picking and fixing branches, untying, etc., to achieve timely and fine management of 2 years [3].

2 Ear picking nursery management

One is plastic trimming. After planting the seedlings in the newly built ear garden, they are shortened at 40.0 to 60.0 cm from the ground, and 3 branches are selected as backbone branches for cultivation, and the buds other than the backbone branches are removed in time. In the 2nd and 3rd years, the side branches are re-pruned in the spring, retaining 2 to 3 buds per branch, and the side branches are re-sprouted to allow them to grow. The tree body of the redevelopment of the ear garden should maintain the original tree shape and the shape of the backbone branches, and remove dry and dead branches, over-dense branches, weak branches, internal wrong branches, etc. [4]. The second is to suppress flowers and promote shoots. The flower bud differentiation stage and the young fruit stage erased flower buds and young fruits to promote the germination of branches. The third is irrigation and drainage. Each year during the dry season, water should be irrigated 1 to 2 times a month, depending on the soil moisture of each construction area; pay attention to timely drainage during the rainy season. The fourth is fertilization. In the later stage of the construction of the nursery, it is reclaimed once in autumn and winter, with a depth of 20 to 25 cm, and an appropriate amount of farm manure is applied, and the fertilizer is topdressed 1 to 2 times a year in the growth season, and the amount of fertilizer depends on the soil fertility and plant size. The reconstruction of the ear picking garden can adopt the "mowing and fertilization" technology [5], raising grass and accumulating fertilizer in the forest, mowing the grass to cover the woodland in a timely manner, turning the ground into the dormant period, and turning the covered grass into the soil for slow-release fertilizer. Fifth, weeding in middle cultivation. The new ear collection garden weeding is carried out at the same time with loose soil, and the weeding is cultivated 2 to 3 times a year, and the depth is 10 to 15 cm. Sixth, disease and pest control. Common diseases in the ear garden are brown spot disease, powdery mildew, anthrax disease, dry rot disease, insect pests include wood folly moth, flat leaf beetle, scarab beetle, shell worm, cloud spot tianniu, thorn moth (foreign pepper) and so on. It is easy to use winter trunk whitening, early spring spraying 1 to 5 °Bé stone sulfur compound 1 to 2 times, June to July spraying equal amount of Bordeaux liquid 3 times, the use of artificial trapping of adult insects, medicine plug worm holes and other methods to control insect pests [6]. The introduced seedlings and scion are subject to strict quarantine before they can be transferred.

3 Spike collection, wax sealing and storage

3.1 Spike collection

3.1.1 Acquisition time. Hard-branched spikes can be collected during the entire dormancy period, preferably in late winter and early spring, before bud germination, and are flexibly mastered according to local climatic characteristics and actual conditions.

3.1.2 Collection Standards. Robust and straight, disease-free, axillary buds full, normal color, small pulp, full of lignification and no mechanical damage of the new branch of the year, and the effective buds should be more than 5. For the cultivation of seedling grafting seedlings, the thickness of the panicle is 0.8 to 1.5 cm, and for the improvement of high pile grafting of large tree varieties, the thickness of the panicle is 1.5 to 2.5 cm.

3.1.3 Collection Methods. Panicle harvesting is generally carried out at the same time as pruning, and the amount of panicle collection and the length of the shear should be carefully determined when harvesting, and the extension branch of the main side branch should be shortened from the fullness of the bud, and the short pile of 10 to 15 cm can be retained when shearing [7]. After the scion is cut, the useless branches, male branches and diseased insect branches are removed according to the quality requirements.

3.2 Spike treatment

3.2.1 Dehydration. The collected spikes dehydrate naturally, that is, the collected branches are placed in a cool place for 1 to 2 days (depending on the weather and temperature conditions), so that they naturally volatilize the moisture inside the branches.

3.2.2 Shearing. Collected spikes should be cut off from the top that is too long, curved or immature, and then cut into small segments containing 5 to 8 effective buds according to the situation (sealing pot or box size) to facilitate wax sealing and storage. The base mouth should be 5.0 cm below the bud and the top shear should be 2.0 cm above the bud when shearing.

3.2.3 Sealing wax. After heating and melting with 95% paraffin +5% yellow wax, in the range of 70 to 90 °C, the scion is quickly dipped in wax to seal the entire branch. Then pack 20 to 30 clones (varieties) into bundles, hang labels and pack them for later use.

3.3 Storage

It can be stored in a ventilated, shaded environment in January. It should be stored at a low temperature of 2 to 5 °C from February to March. The packing paper should indicate the variety, quantity, specifications, collection time, collection location, collection unit, handler, etc.

4 Archival records

The contents of the archives mainly include the construction project plan, contract and relevant approval documents of the harvesting nursery; all the original materials in the construction and production and operation process (the establishment time, area, colonization map, number of good seeds, the number of colonized seedlings, management measures, pest control types and control conditions, etc.) in the construction and production and operation process of the harvesting nursery; and the inspection and acceptance of the results. The technical file is assigned to a special person to record in detail the yield and destination of the spikes of each clone (variety), and shall not be omitted or interrupted [8].

Fund Project Central Financial Forestry Science and Technology Promotion Project "Promotion and Demonstration of Qingfeng Series of Fine Varieties of Walnuts with Characteristics of Northeast Yunnan" (Yun [2018] TG15), Zhaotong Municipal Finance Project "Expansion of Regional Walnut Varieties in Zhaotong City" (Yun [2017] ZT04).