Rational Intercropping Cultivation Models and Key Technical Points for Walnut Trees
Intercropping is an important cultivation model. Rational intercropping can make full use of space, land and light energy, and improve economic returns, especially the early returns of young walnut orchards.
The types and methods of intercropping should follow the principle of not affecting the growth and development of walnut trees. According to the different types of intercrops, it can be divided into different models such as fruit-grain intercropping, fruit-vegetable intercropping, fruit-medicinal herb intercropping and fruit-green manure intercropping. Suitable intercrops should be selected according to the local site conditions, management level, and planting and marketing habits.
Fruit-grain intercropping is a traditional intercropping model. Grain and oil crops have the characteristics of a short growing season, early maturity and easy cultivation, so fruit-grain (oil) intercropping can be carried out on plots with good site conditions and high fertility. Commonly used crop types include soybean, various miscellaneous beans, potato, rapeseed, peanut, etc. When the planting spacing of walnut trees is relatively large, tall crops such as corn and sorghum can also be intercropped. Fruit-grain intercropping can effectively promote flower formation in walnut trees and increase the yield per tree, because measures such as deep plowing, loosening the soil, weeding and fertilizing promote flower formation and fruit setting in walnut trees. At the same time, due to the nitrogen fixation of leguminous plants, the soil nitrogen content can be effectively increased, promoting the vegetative growth and reproductive growth of walnut trees.
Fruit-medicinal herb intercropping is an important way to increase the economic income of walnut orchards. Because Chinese medicinal herbs have high economic value and considerable income, and conform to the current national industrial policy, they have become one of the preferred items for current walnut orchard intercropping. Medicinal herb types commonly used for intercropping include Salvia miltiorrhiza, Platycodon grandiflorus, Bupleurum chinense, Isatis indigotica, Scutellaria baicalensis, Atractylodes macrocephala, Rehmannia glutinosa, honeysuckle, etc.
Fruit-vegetable (melon) intercropping is generally carried out in walnut orchards adjacent to towns and with irrigation conditions. Commonly used vegetable types include white radish, Chinese cabbage, cabbage, various melons, strawberry, etc.
Fruit-green manure intercropping. Intercropping green manure is an effective measure to fertilize and make full use of the soil in walnut orchards. Green manure crops are easy to cultivate, high-yielding and effective as fertilizer, and are a high-quality fertilizer source. In walnut orchards with poor site conditions, insufficient fertilizer sources and weak tree vigor, green manure crops can be intercropped in the orchard in alternate years, and during the flowering and budding stage, they can be buried into the soil through intertillage, so as to increase soil organic matter and improve the physical and chemical properties of the soil. Green manure crops such as melilotus, alfalfa and mung bean are all suitable for intercropping in walnut orchards. Reasonable selection can be made according to environmental characteristics such as soil and the adaptability of the green manure. For example, Amorpha fruticosa has strong adaptability and can grow in all types of soil, and can be even more productive in walnut orchards with better soil conditions; Astragalus adsurgens is tolerant of barren soil and can be planted in sandy land; sesbania and others are tolerant of saline-alkali soil and prefer moisture, and can also be planted in orchards with a relatively high groundwater level. Perennial root green manure crops can grow continuously for 3~4 years, and are cut 3~4 times each year. The cut grass is spread over the tree disk or buried and pressed in the orchard to increase soil organic matter.
When intercropping, strip intercropping or whole-orchard intercropping should be used. Regardless of which form is used, a tree disk with a diameter of more than 1 m should be left under the trees, and attention should be paid to crop rotation. As the tree canopy expands, the intercropping area should be reduced year by year. After 5~6 years of planting, when the tree canopy is basically closed, the intercrops should be withdrawn. The intercrops should be given loosening of the soil, weeding, fertilizing and irrigation every year to prevent the land from becoming overgrown or competing with the trees for water and fertilizer.