Present situation and development trend of green manure mechanization in fruit orchards

Abstract: Green manure is made up of green plants, which can promote the growth of crops and improve the soil structure by turning all or part of the fresh body into fertilizer, or by intercropping with crops. Green manure is a traditional source of organic fertilizer in China. It is one of the three main sources of agricultural fertilizers (chemical fertilizer, organic fertilizer and green manure) in China’s fertilizer industry. It is an important link between man and nature, consumption and protection, and an important link of low-carbon agriculture. Planting green manure in orchards can not only save energy and reduce consumption, meliorate soil physical and chemical properties, increase soil organic matter,and improve crop yield and quality, but also resist drought disaster and preserve soil moisture, prevent wind damage and dune movement, prevent soil from erosion and improve ecological environment. Since the founding of the People’s Republic of China, the development of green manure has experi-enced rapid development period, peak period, declining period and recovery period. The duration of 1960’s—1970’s was the best and fastest development period of China’s green manure. In the 1980s, due to the rural system reform, the rapid development of chemical fertilizer industry and other reasons, the green manure industry in China entered a recession period. In recent years, due to the call of nation-al policies and the demand of ecological civilization development, China’s green manure industry has entered the recovery period. Green manure is of great significance to environmental protection, energy  conservation and consumption reduction, food safety and food health, and is widely used in paddy field, dry land and orchards. Different green manure crops have different effects on soil chemical properties,such as legume green manure, vetch, alfalfa, etc., which can increase the nitrogen content in the soil through nitrogen fixation by rhizobia, while the green manure rape of Cruciferae can promote the accu-mulation of P and increase the content of organic matter in the soil. Under the production mode, the va-rieties of green manure are different. In the aspect of fertilizer efficiency, the speed of green manure is not as obvious as that of chemical fertilizer, but the effective time of green manure is longer than that of chemical fertilizer. The main planting mode of green manure in an orchard is intercropping with fruit trees, where green manures are planted between rows of fruit trees. Orchard green manure mainly in-clude Leguminosae, Gramineae and Cruciferae. Generally, single planting or mixed sowing is carried out between rows of fruit trees as a means of drought resistance, moisture conservation, fertilizer sav-ing, fruit improvement and environmental protection. In orchards, the green manure of annual and pe-rennial Leguminosae, Gramineae and Cruciferae is selected to single seeding or mix sowing between rows, as a means of drought resistance, soil moisture conservation, chemical fertilizer saving, fruit im-provement and environmental protection. According to the relevant research, planting green manure can reduce 1/3 of chemical fertilizer application. In addition, planting green manure between orchard rows  can produce a lot of fresh grass, which can be used as a source of high-quality feed. The typical green manure in orchards includes Vicia villosa Roth, Melilotus suaveolens Ledeb., Trifolium repens L., Sesbania cannabina (Retz.) Poir., Medicago sativa Linn., Festuca myuros L., Brassica campestris L., Orycho-phragmus violaceus (Linnaeus) O. E. Schulz, Astragalus sinicus Linn., Lolium perenne Linn., Rapha-nus sativus Linn., Astragalus adsurgens Pall. and so on. Among them, legume green manure includes sweet potato, sweet clover, white clover, alfalfa, astragalus, Astragalus adsurgens, etc., which are char-acterized by strong drought resistance, nitrogen fixation through nodules, providing fertilizer elements (mainly N element) for fruit tree growth, covering moisture preservation, and improving soil structure and fertility. Lolium perenne Linn. and Festuca myuros L. belong to gramineous green manure, which are characterized by strong ability to cover the ground surface and preserve moisture. They can improve the soil micro ecological environment, increase the content of soil organic matter, and produce a large number of high-quality fresh grasses. Brassica campestris L., Raphanus sativus Linn. and Orychophrag-mus violaceus (Linnaeus) O. E. Schulz belong to Cruciferae green manure, which can improve the avail-ability of phosphate and some trace elements. According to production practice and field experiment, the yield of green manure in these typical orchards can reach more than 10 t·hm-2, which can not only provide organic matter and fertilizer for fruit trees, but also be used as high-quality forage for livestock raising or as a source of silage feed. The production of green manure in orchards mainly includes sow-ing, plant protection, crushing, rolling and other links. Due to the low efficiency of manual operation and high labor intensity, the mechanized production and management of orchard green manure is in ur-gent need. However, the stagnation of relevant research in the early stage of green manure and the lack of relevant machinery in orchard green manure have restricted the further development of green manure in orchards. Orchard sowing machinery mainly includes sowing, drilling and hole sowing machineries. The specific sowing methods and machines can be selected according to the growth characteristics of green manure and different agronomic requirements. Plant protection operation is generally carried out at the same time as the fruit tree plant protection operation. At present, the general plant protection ma-chinery in orchards is mainly used. The main problem is that most of the plant protection equipment is designed for fruit tree plant protection, but the green manure crops growing on ground is not targeted. There are two types of green manure crushing and rolling machinery: general-purpose machinery and  special- purpose machinery. General machinery, such as field straw crushing machine, shared plough and grass crusher, have poor adaptability to the growth characteristics of green manure and agronomic requirements, and are prone to failure due to blockage and winding of working parts during operation.Green fertilizer special grinding and turning machine has good adaptability to green fertilizer growth characteristics and agronomy, but there is no series of products that can be quickly applied and popular-ized, and there is a common problem of high cost. The mechanized management of orchard green ma-nure requires the integration of agricultural machinery and agronomy. This paper introduces the typical green manure, green manure varieties and their planting patterns, as well as summarizes the technologi-cal process of orchard mechanized management. Based on the analysis of the existing special and gener-al machinery for green manure and their working principles, the countermeasures and suggestions are put forward based on the perspective of agricultural machinery and agronomy integration. This paper can be used for reference for the mechanized production technology of green manure in orchards and the reasonable selection of relevant machinery, which has positive significance for promoting the devel-opment of green manure in orchards.