What is the effect of mulching in walnut orchards?

  Orchard mulching is an important technical measure for achieving high quality and high yield in dryland walnut orchards. Orchard mulching improves soil fertility, changes the underground water, air and heat environment, suppresses weed growth, reduces the occurrence of pests and diseases and reduces the labor used for hoeing, and can create a good growth and development environment for the walnut tree roots and even the whole tree, promote tree growth and development and improve walnut yield and quality.

  Walnut orchards can be mulched in all four seasons, with spring, after the wheat harvest or after the autumn harvest being suitable, and it is best done in the season when grass sources are abundant. Generally, in sandy land and dry poor land, mulching is mostly done in spring after the soil temperature rises, when the soil temperature at a depth of 20 cm reaches 20°C; on clay land and plots with good fertility, mulching when the soil temperature at a depth of 20 cm reaches 22°C is more suitable.

  Dense mature walnut orchards that are not intercropped should use whole-orchard mulching, while young walnut orchards should use partial mulching, mainly covering the tree disk or tree row, with dry grass in spring and green grass pressed in summer. Weeds, leaves, crop straw and chopped firewood and grass can all be used for mulching; after chopping, spread them evenly between the rows and under the tree disk, and the grass should cover the main root distribution area, that is, within the outer edge of the tree canopy. The mulching thickness is generally 15-20 cm; after mulching in spring, a small amount of soil must be pressed on top to prevent wind blowing and fire. For partial mulching, use 1000-1500 kg of dry grass per mu, or generally 2000-3000 kg of fresh grass. For whole-orchard mulching, use 2000-2500 kg of dry grass or 4000 kg of fresh grass respectively.

  Before mulching, water thoroughly in combination with deep plowing or deep hoeing, and according to tree age, apply 0.2-0.5 kg of nitrogen fertilizer per tree to meet the nitrogen fertilizer needs of microorganisms decomposing organic matter. After mulching, when applying base fertilizer in autumn, do not turn the grass into the ground; the grass should be added again each year. When topdressing, the mulch can be pushed aside, using the method of applying in multiple holes, and irrigate with the fertilizer. Orchards with thin soil layers and poor fertility can use the method of combining trenching and deep burial with mulching, mulching continuously for 3-4 years and then plowing once, applying sufficient base fertilizer, and mulching again the next year.

  It should be noted that the mulch used in orchard mulching is straw and grass with relatively high carbon content, and mulching will cause temporary immobilization of soil nitrogen. Therefore, when mulching, an appropriate amount of more nitrogen fertilizer should be applied to prevent the tree from lacking nitrogen nutrition. At the same time, when using weeds as mulch, the grass seeds should be removed completely, and weeds with strong vegetative propagation ability must not be used, to prevent weeds from growing in clusters and increasing the difficulty of weeding. For disease prevention, fungicides such as carbendazim can be sprayed before leaf fall to reduce the pathogen base; before Awakening of Insects the next year, spray 600-800 times phoxim under the trees to eliminate overwintering pests and overwintering eggs in the grass. In addition, clean up the mulch once each year. Furthermore, mulching will also make the root distribution of fruit trees relatively shallower, with more roots in the upper soil layer, which should be overcome in combination with other technical measures.