Detailed Explanation of Labor-Saving Cultivation Techniques for Qingxiang Walnut

Labor-Saving Cultivation Techniques for Qingxiang Walnut

Labor-saving cultivation of fruit trees is based on intensive cultivation, through the use of orchard grass cover, water-saving irrigation, mechanized operations, integrated pest and disease control, bag-free cultivation and other series of techniques to reduce orchard labor intensity, save labor time, lower production costs and improve efficiency. Forestry workers in Pingshan County, relying on national science and technology projects, took labor-saving walnut cultivation as a research focus, starting with Qingxiang walnut, and carried out multiple experimental studies on tree shape selection, branch bending and pruning, artificial pollination, scientific fertilization, grass management, pest and disease control, etc., and explored a set of efficient labor-saving cultivation techniques for Qingxiang walnut on dry slope land, which reduced costs, improved efficiency, and achieved a bumper harvest of walnuts on dry slope land in the Taihang Mountain area.

1 Labor-Saving Land Preparation

Labor-saving land preparation means changing the previous manual land preparation to mechanical land preparation. According to local conditions, promote mechanical land preparation of terraced fields in hilly areas, mechanical land preparation of horizontal ditches in low mountains, and horizontal terraces in medium and high mountains, to ensure normal growth of young trees. For orchard establishment, excavators are used for land leveling of large terraced fields, digging large pits of 1m x 1m x 1m. According to investigation and comparison, mechanized large-pit land preparation has low cost and high efficiency. One excavator can dig 480 pits per day, and its work efficiency is equivalent to 22 laborers. The cost of an excavator is 2.2 yuan per pit, saving 3.3 yuan compared with manual labor. Digging 56 pits per 666.7 sq m can save 184.8 yuan in land preparation costs. Pingshan County has many hills and mountains, and the land is barren. Using machinery to open ditches and prepare land can deep-plow the soil layer, speed up afforestation progress, reduce afforestation costs, and lay a good foundation for the growth of young walnut trees.

2 Labor-Saving Soil, Fertilizer and Water Management

2.1 Natural Grass Cover

Natural grass cover means retaining natural 1- to 2-year-old weeds between fruit tree rows and removing perennial weeds as well as weeds within 60cm around the tree trunk. When weeds are 50cm tall, mow them with a mower. In addition, low-stalk crops such as peanuts and potatoes can be intercropped between rows, reducing fertilizer input in the orchard, saving the cost of cultivating and weeding, improving soil structure, increasing organic matter content and water content, reducing surface evaporation, and lowering the incidence of freezing injury. Natural grass cover uses 1.14 labor units per 666.7 sq m per year, costing 114 yuan, while manual weeding under clean cultivation requires 4.29 labor units, costing 429 yuan. Natural grass cover can save 315 yuan (Table 1). For walnut orchards on arid mountain land without irrigation conditions, a large funnel-shaped tree basin is used, and plant straw or weeds are mulched in the tree basin to store water and preserve soil moisture.

Table 1 Comparison of costs between natural grass cover and manual weeding

2.2 Integrated Water and Fertilizer Management

Labor-saving water and fertilizer management means changing traditional trench fertilization to simple integrated water and fertilizer fertilization. Simple integrated fertilizer and water fertilization is a fertilization method that uses mechanical devices such as the pesticide storage tank, pressure pump, high-pressure hose and tricycle used for orchard spraying, changes the spray gun into a topdressing gun, dissolves fertilizer in water, pressurizes it with a pesticide pump, and then applies it with the topdressing gun into the concentrated distribution area of fruit tree roots. After repeated experiments, compound fertilizers that are easily soluble in water and have fewer impurities were finally selected, such as Leili seaweed organic fertilizer and Baiquan urea sulfate water-soluble compound fertilizer. Apply base fertilizer after the autumn shoot stops growing, apply pre-flowering fertilizer from late March to early April, and apply fruit-setting fertilizer after the spring shoot stops growing from late May to June. Each time, mix with 2000kg of water and apply with a topdressing gun (Figure 1). Fertilization depth is 25-35cm. According to tree size, make 4-16 topdressing holes per tree, fertilize each hole for 10-15 seconds, and apply 20-25kg of fertilizer water per tree. Investigation found that the total cost of using this technique in a 17.3hm2 walnut demonstration orchard was 441,000 yuan per year, 95,250 yuan lower than trench fertilization, and the average fertilization cost per 666.7 sq m was reduced by 158.7 yuan.

Figure 1 Integrated water and fertilizer fertilization method

3 Labor-Saving Shaping and Pruning Techniques

Labor-saving shaping and pruning techniques mean cultivating a spindle-shaped tree form and promoting pruning techniques throughout the four seasons, mainly through branch bending.

3.1 Spindle-Shaped Tree Form

The spindle shape has a relatively strong central leader, with 10-13 main branches growing on the central leader. No lateral branches are retained on the main branches; fruiting branch groups grow directly on them. The spindle-shaped tree form has few levels of skeletal branches and a small pruning amount, is well ventilated and lit, bears fruit early, and is suitable for dense planting cultivation (Figure 2).

Figure 2 Spindle-shaped tree form of walnut

3.2 Pruning Techniques Throughout the Four Seasons

Adopt pruning techniques throughout the four seasons, with branch bending as an important measure to control vigor and promote fruiting. Bend branches flat or downward to moderate branch growth vigor, promote the sprouting of branches and buds, increase the number of medium and short branches, and promote early formation of flower buds. The central leader maintains absolute dominance, and main branches whose thickness exceeds 1/2 of the central leader thickness are removed. After years of experiments, bending branches to 90 degrees can significantly increase the sprouting rate, flowering rate and yield per tree, achieving the effect of 3% flowering tree rate in the second year after grafting, 35% in the third year, and 100% in the fifth year (Table 2).

4 Labor-Saving and Efficient Flower and Fruit Management Techniques

Labor-saving and efficient flower and fruit management techniques are artificial male flower thinning and artificial pollination to improve fruit set rate.

4.1 Artificial Male Flower Thinning

"Thinning male walnut flowers is better than applying fertilizer." Thinning male flowers can reduce nutrient consumption of the tree and allow more nutrients to be used for female flower development and flowering and fruiting. After thinning male flowers of Qingxiang walnut for 4 consecutive years from 2012 to 2015, the results showed that a male flower thinning amount of 80%-90% had an obvious yield-increasing effect, and compared with the control, male flower thinning increased yield by 15.91%-19.16%. The time for male flower thinning is from March to early April, after flower buds sprout and during the elongation period of male inflorescences; when male inflorescences are 1-2cm long is the most suitable. When thinning male flowers, use a 1-1.5m long wooden pole with a hook to pull down branches, manually break off male inflorescences, retain 5%-10% of male inflorescences in different parts of the canopy, and remove all the rest to save tree nutrients.

Table 2 Flowering effect 3-5 years after branch bending treatment of Qingxiang walnut

4.2 Artificial Pollination

Use the nylon stocking shaking pollination method. Mix pollen and corn flour at a ratio of 1:5, put the mixture into a nylon stocking (1-2 layers), tie the opening tightly, tie it to a bamboo pole, and then gently shake it above the canopy. Artificial pollination can increase the yield of each walnut tree by an average of 0.4kg, increase yield by 22kg per 666.7 sq m, and increase yield by 8.2% compared with the control.

4.3 Spraying Foliar Fertilizer

Spray Fuman Tianxia foliar fertilizer during the flowering and fruit-setting period and fruit expansion period, and spray 0.4% potassium dihydrogen phosphate during the hard kernel period, increasing yield by 25% compared with the control treatment, with large fruit size and very few diseased and rotten fruits.

5 Labor-Saving Pest and Disease Management Techniques

Labor-saving pest and disease management techniques mean strengthening forecasting, implementing biological, physical and manual control, reducing the number of pesticide applications, and effectively controlling the occurrence of pests and diseases. Pest and disease control should mainly rely on biological and physical control, with chemical control as a supplement, strengthen pest forecasting, and reduce the number of pesticide applications. The walnut fruit moth is a common pest of walnut, and conventional control of the walnut fruit moth requires 3 pesticide applications. Research has confirmed that spraying 1000-1500 times diluted Mieyouniao No. 3 once during the peak adult occurrence period and early larval hatching period (late early July to early mid-July) can achieve the control purpose, with a good fruit rate of 86%, reducing control costs and pesticide pollution. Installing black light lamps in walnut orchards and raising chickens in the orchard can effectively control scarab beetles.

6 Labor-Saving Postharvest Handling Techniques

Peeling, cleaning and drying after walnut harvest are all mechanized.

From late August to early-to-mid September (around White Dew), when walnut green peel turns yellow-green or light yellow, some fruit tops crack, or individual fruits fall naturally, is the best harvest period for walnut. After harvest, fully soak green-peel fruits in 3000-5000mg/kg ethephon solution for half a minute, remove and drain the water, pile them indoors to a height of 30-50cm, cover with about 10cm of dry grass, and peeling can be completed in 2 days. The peeling rate can reach 94%, and the shell surface is clean. Using a peeling machine can greatly improve efficiency. A green walnut peeling machine can peel and clean about 250kg per hour. Mechanical peeling, cleaning and drying per 666.7 sq m uses 1.04 labor units, 3.13 labor units less than manual peeling, cleaning and sun-drying, saving 313 yuan. Establish a drying room and purchase a walnut grading machine to facilitate walnut drying, storage and grading. Save labor, improve efficiency, and increase returns.