After the red soil hilly land is reclaimed as an orchard, before planting dragons, sufficient base fertilizer should be applied under the planting holes to improve the local soil. However, the overall orchard soil still shows a series of basic characteristics of natural soil, such as acidic, dry, sticky and barren red soil, and the soil fertility of longan orchard does not have the potential of stable yield increase. Longan, especially in China, is located in the hilly and mountainous areas of southeast China, with high availability of soil nutrients and organic matter content below 1%. Therefore, for the completed longan orchard, soil management cannot be relaxed, and the practice of "opening seeds and ending" cannot be adopted. It is necessary to invest more labor and funds, improve soil fertility management, create water, fertilizer, gas and heat conditions conducive to the growth and development of longan, and ensure the sustained and stable development of longan production.

Green manure is an important source of organic fertilizer. On average, each ton of green manure and fresh grass can provide 200 kilograms of organic matter, 5 kilograms of nitrogen, 2 kilograms of phosphorus and 4 kilograms of potassium for the soil. According to the evaluation results of Dai (199 1) on the economic benefits of developing and utilizing green manure in longan orchard, it is considered that the application of green manure has great potential to increase production and obvious effect. The application of green manure in longan orchard increased the yield by 32.4%, the sugar content of fruit increased by 0.9%, the soluble solids increased by 65,438 0.2%, and the vitamin C increased by 7.7 mg (per 100 g pulp). The application of green manure can improve the nutritional level of the tree, and the contents of nitrogen, phosphorus and potassium in the longan tree are increased by 0.2 16%, 0.028% and 0. 132% respectively compared with the control. After intercropping green manure in longan orchard, soil organic matter content increased by 0.43%, nitrogen content increased by 0.052%, available phosphorus increased by 17.7 ppm and available potassium increased by 26.3 ppm. Green manure can adjust the water and heat conditions of orchard. According to the observation of high temperature season in July, the soil temperature decreased by 65438 06.3℃, the soil temperature decreased by 9.65438 0℃ in 5cm, decreased by 9.3℃ in 65438±00cm, and the soil water content increased by 8.5%. Therefore, taking advantage of the characteristics of small crown and rhizosphere of young trees and many gaps in the garden, we should vigorously advocate and popularize grass cultivation based on green manure before entering the fruiting period after planting. It is the core of soil management measures in young longan orchards and a major reform of the old cultivation system. In this way, we can not only cover the ground with green manure to reduce soil erosion, but also develop herbivores with green manure, provide domestic fuel and biogas residue with a large amount of feces as raw materials, cultivate gardens, increase soil nutrient accumulation, adjust the proportion of organic and inorganic nutrients, improve the ecological conditions of orchards, and create a good soil management system for multi-level and three-dimensional utilization of orchards. Therefore, the method of planting grass in longan orchard is not only the most basic measure to adjust and improve soil conditions, but also the link to closely combine fruit industry and animal husbandry.

The most ideal varieties of winter sowing green manure in south subtropical fruit areas of China are early-maturing vetch, Vicia faba, 6625 Vicia faba and pea, and summer sowing green manure includes Indian cowpea, August white, mung bean and black mung bean. When interplanting green manure crops in orchards, we must pay attention to raising fertilizer with small fertilizer, and at the same time, we must be outside the crown to prevent competition with longan for fertilizer and water and excessive damage to the roots. At present, in view of the shortage of green manure seeds, mowing and ploughing consume labor, which limits the interplanting area of green manure in orchards, and it is difficult to coordinate the contradiction between the stubble pressing period of green manure and the fertilizer demand period of longan. Therefore, the technology of interplanting green manure in orchard has not been able to form a scale in longan production, nor has it been well popularized and applied as a conventional cultivation measure. Therefore, in the future, we should first expand the planting proportion of perennial green manure such as Cassia rotundifolia, Phyllanthus urinaria, butterflies, mimosa, Bahia grass, Pinto peanuts and Stylosanthes, and vigorously promote the green manure mulching technology in orchards. Secondly, appropriately increase the planting of green manure crops rich in crude fiber, such as stinky chrysanthemum, Amorpha fruticosa, crabgrass and barnyard grass, expand the source of fertilizer and accelerate the improvement of orchard soil. It also advocates the technology of direct tillage and utilization of green manure, reduces the labor of digging holes and mowing grass, and promotes the fertilization of orchard topsoil, so as to raise the utilization of green manure interplanting in longan orchard in China to a new level. In addition to green manure crops, some longan producing areas in China also use the gap between young orchards to plant fast-growing fruit trees such as vegetables, medicinal materials, peaches, plums and pineapples to increase their income. Longan will be eliminated after it grows and bears fruit.