Detailed Explanation of Plastic Mulch Soil Management Techniques in Walnut Orchards

  Plastic mulch, as a form of orchard soil management, has been applied over an increasingly large area in recent years, showing broad application prospects. Adopting plastic mulch cultivation in young walnut orchards can affect the phenological phases of walnut development, prolong the growth period of walnut trees, and promote flower formation and fruit set in young walnut trees. Through plastic mulch, the physical and chemical properties of the soil can be effectively improved, soil temperature can be raised and soil heat accumulation increased, thereby promoting vegetative growth and flower bud differentiation of walnut trees; plastic mulch can reduce water leaching and increase soil permeability, which is favorable for microbial activity, and can therefore increase the content of available nutrients; plastic mulch can reduce wind and rain erosion and artificial trampling, keeping the soil in a relatively loose state; plastic mulch can enhance reflected light, especially increasing scattered light in the morning and evening, which is conducive to improving walnut photosynthesis, increasing dry matter accumulation, and favoring flower formation and fruit set.

Pictured: walnut

  Plastic mulch involves covering the soil between and within the rows of walnut trees with plastic film and punching holes in the film to allow rainwater to infiltrate. The best time for plastic mulching is in autumn. Mulching in early spring has more disadvantages than advantages. Plastic applied in early spring can remain basically intact until late summer, but summer has high temperatures and heavy rain, and mulching causes excessively high soil temperature and excessive humidity, which is unfavorable for fruit tree growth. By late autumn, when plastic mulch is needed to raise temperature and conserve moisture, the plastic applied in early spring is mostly severely damaged and can hardly play its proper role. In autumn, however, soil moisture is abundant, and mulching with sufficient soil moisture can reduce drought in late autumn, winter and spring, prolong the period of root growth activity, increase the number of new roots and total root volume of fruit trees, promote the return flow of organic assimilates from the aboveground part and the synthesis of amino acids, etc. in the root system, and increase the storage of nutrients in the root system. If mulching is combined with the application of base fertilizer, it can enhance the effect of autumn base fertilizer application, while effectively prolonging the activity time of soil organisms, promoting the dispersion and release of nutrients, improving tree nutrition, and providing good conditions for the safe overwintering of fruit trees and their growth the following year. Autumn mulching can also play a role in heat preservation and freeze prevention in winter, and its mulching effect can still be exerted into spring; by summer the plastic has already deteriorated, which can eliminate adverse effects.

  It is worth noting, however, that experiments have shown that in arid and cold regions, plastic mulching of young walnut trees in autumn and winter actually aggravates overwintering freeze damage to young trees. Because mulched soil has a relatively high temperature, the root system of young trees is vigorous in activity and shallow in dormancy, making it prone to freeze damage; other measures should be taken to prevent winter soil drying in order to conserve water and moisture.