Detailed Explanation of the Plastic Film Mulching and Fertilizer-Water Storage in Holes Technique

  In areas and years with high rainfall and in seasons with concentrated rainfall, ditches should be dug for drainage. Since the vast majority of China's walnut-producing areas are located in mountainous and hilly regions with good natural drainage conditions, artificial drainage is not needed. However, for walnut orchards located on flat land and in low-lying areas with poor natural drainage, attention should be paid to timely drainage during the rainy season.

  The plastic film mulching and fertilizer-water storage in holes technique is a new technique in fruit tree cultivation, widely applicable to walnut orchards on hilly land with relatively thin soil layers and no irrigation conditions, as well as in arid and water-scarce areas. The plastic film mulching and fertilizer-water storage in holes technique involves burying grass bundles in the layer where the walnut tree roots are concentrated and covering them with plastic film. Research shows that this technique can increase soil temperature and humidity in early spring, improve soil structure, promote root growth, increase fertilizer effectiveness, and enhance the roots' ability to absorb water and nutrients, thereby improving the quality of fruiting branches, promoting flower formation, and significantly improving fruit tree yield and quality.

  Many walnut orchards in northern China are established on thin hilly land and in water-scarce areas, where the soil layer is generally thin, with poor water and fertilizer retention capacity and low fertility, and organic matter content mostly around 0.3%, which seriously affects fruit yield and quality and results in low economic returns. For this reason, adopting the plastic film mulching and fertilizer-water storage in holes technique can achieve good results.

  The best time for plastic film mulching and fertilizer-water storage in holes is before fruit trees bud each spring, that is, from late March to early April. The specific technique is as follows: bundle crop straw or weeds into grass bundles with a diameter of 20-40 cm and a length of 35-45 cm, place them in water (about 10% manure, urine or biogas slurry can also be added to the water) and soak for a full day and night until thoroughly soaked, then set aside for use. The fertilizer storage holes should be located in the area where the roots are concentrated, generally 50-70 cm inward from the edge of the tree canopy projection. Dig fertilizer storage holes 40-50 cm deep with a diameter slightly larger than the grass bundles (generally 25-45 cm). The number of fertilizer storage holes should be determined according to the size of the tree canopy, generally 4-8 holes is appropriate. Place the water-soaked grass bundle upright in the center of the hole, apply 100-150 g of superphosphate around the grass bundle, then fill firmly with soil mixed with organic fertilizer (5 kg of farmyard manure or compound fertilizer per hole), apply 50-100 g of urea and water appropriately. After the water seeps in, cover with 1 cm of soil, then tidy the tree basin so that the fertilizer storage hole is 1-2 cm below the ground surface, forming a dish shape to help collect water. Water each hole with another 3-5 kg of water. If it is an orchard on saline-alkali land, add 500-1,000 g of distillers' grains to each fertilizer storage hole before burying the grass bundle.

  The plastic film selected for mulching is ordinary plastic film 0.02-0.03 mm thick. The mulching range is centered on the tree trunk until all the nutrient holes are covered. Generally, the mulching area for a single tree is as follows: for a canopy diameter of 3 m or less, a mulching film of 1-1.5 sq m is appropriate; for a canopy diameter of 3.5-4 m, a mulching film of 4 sq m; for a canopy diameter of 5 m or more, a mulching film of 6-8 sq m. Before mulching, first hoe the weeds, level the ground, pull the film tight and flat, cover it around the holes and at the junctions between two holes, then press it firmly with soil. The fertilizer storage holes should be covered under the plastic film, and a small hole should be pierced in the plastic film at the center of each fertilizer storage hole, then a small stone should be placed on it. On one hand, this can avoid water loss; on the other hand, it facilitates subsequent fertilization and watering management.

  Management of fertilizer storage holes: generally at three periods - after flowering, when new shoots stop growing, and after fruit harvest - apply 50-100 g of urea or compound fertilizer per hole as a top dressing. Place the fertilizer at the small hole at the top of the grass bundle, and water with about 3.5 kg of water along with the fertilizer. After the water seeps into the grass bundle, cover with 1 cm of soil again. When the rainy season arrives, the plastic film can be removed to allow the holes to store rainwater. In late spring and early summer, covering the plastic film with 1-2 cm of soil can prevent and control weeds. Generally, fertilizer storage holes can be maintained for 2-3 years. If the plastic film is found to be damaged, it should be replaced promptly. When setting up fertilizer storage holes again, the position should be changed, gradually achieving improvement of the entire orchard.

  The plastic film mulching and fertilizer-water storage in holes technique mainly achieves the purpose of preventing soil moisture evaporation through the use of plastic film mulching. The role of the holes is to concentrate limited fertilizer and water to increase the fertilizer and water content in local areas of the soil; the role of the grass bundles is to absorb fertilizer and water that are temporarily surplus for the fruit trees, and then slowly release them, steadily supplying fertilizer and water and reducing fertilizer and water loss. This technique can significantly improve the growth and development of fruit trees, achieving the purpose of significant yield increase and tree vigor enhancement. In application, it is simple in method, easy to obtain materials, requires little investment, has low cost, good results, and saves water (saving 70%-90% of water compared with field irrigation), and is easy to promote.