Abstract:

[Significance] Orchard fertilization is an important field management practice affecting nutrient supply, yield formation, and quality improvement of fruit trees. Ditching and fertilization can place fertilizer in the main root distribution zone and is more conducive to improving nutrient use efficiency than surface broadcasting. However, its operational performance is jointly constrained by orchard inter-row space, tree structure, terrain conditions, root distribution, and fertilizer properties. With the development of orchard production toward high-density planting, standardized tree forms, mechanization in hilly and mountainous areas, and intelligent management, the limitations of conventional ditching and fertilization equipment have become increasingly prominent in terms of furrow-depth stability, fertilizer placement consistency, fertilizer discharge uniformity, adaptability to complex terrain, and intelligent control capability. The aim is to systematically summarize the research progress of orchard ditching and fertilization equipment from four aspects: agronomic requirements, key components, whole-machine equipment, and intelligent technologies, with the objective of identifying the existing technical bottlenecks and development directions and providing a reference for the optimized design and intelligent upgrading of precision orchard fertilization equipment. [Progress] First, the main fertilization methods, including ring-furrow fertilization, strip-furrow fertilization, radial-furrow fertilization, hole fertilization, fertigation, and surface broadcasting, are summarized, and their differences in fertilizer use efficiency, root injury risk, and adaptability to mechanized operation are analyzed. Combined with typical orchard patterns, including dwarf high-density orchards, traditional large-canopy orchards, hilly orchards, and standardized orchards, the requirements of inter-row space, root distribution, and terrain conditions for furrow depth, fertilizer placement, fertilizer application rate, and equipment configuration are discussed. Second, the structural characteristics and application scopes of ditching mechanisms, including disc-type, auger-type, chain-type, and rotary-blade-type mechanisms, are summarized. Disc-type mechanisms are suitable for shallow-to-medium furrows and narrow-row operations. Auger-type and chain-type mechanisms have stronger deep-ditching capability, but require higher power consumption and maintenance. Rotary-blade-type mechanisms have good soil crushing and mixing performance, but soil disturbance and root injury risks should be controlled. In terms of fertilizer metering and conveying mechanisms, star-wheel, screw, centrifugal, scraper-conveyor, and combined fertilizer discharge systems show differentiated adaptability to different fertilizer forms. Granular fertilizers require higher metering stability, whereas high-moisture organic fertilizers and organic-inorganic mixed fertilizers rely more on anti-blocking, anti-bridging, and forced-conveying capacity. Third, at the whole-machine level, orchard ditching and fertilization machinery has gradually developed from conventional trailed and mounted implements to crawler self-propelled machines, remote-controlled machines, multifunctional combined-operation machines, and variable-rate fertilization equipment. Among them, trailed and mounted equipment is suitable for orchards with flat terrain and wide row spacing; crawler self-propelled and remote-controlled equipment is more suitable for hilly, mountainous, and complex field plots; and multifunctional combined-operation and variable-rate fertilization equipment can help improve operational integration and fertilization accuracy. Finally, in terms of intelligent technologies, existing studies have gradually introduced information acquisition methods, such as mechanical displacement measurement, attitude sensors, ultrasonic sensing, laser ranging, light detection and ranging (LiDAR). When combined with hydraulic or electric actuators, these methods have been used for furrow-depth adjustment, fertilizer-rate control, and operation-state monitoring, promoting the transformation of equipment from simple mechanical execution to closed-loop control involving sensing, decision-making, actuation, and feedback. [Conclusions and Prospects] Overall, orchard ditching and fertilization equipment still faces several challenges, including difficulty in controlling furrow depth under complex terrain conditions, difficulty in determining fertilizer placement due to hidden root distribution, strong coupling among parameters such as furrow depth and fertilizer application rate, and pronounced trade-offs between the cost and reliability of intelligent systems. Future research should focus on multi-source information fusion-based perception, coordinated multi-parameter control, modular and standardized design, and green and efficient operation technologies. These developments will promote the upgrading of orchard ditching and fertilization equipment from single mechanical operation equipment to a precision and intelligent equipment system oriented toward smart orchards.

Key words: orchard trenching and fertilization machinery, fertilizer discharge mechanism, trenching depth control, intelligent control, variable-rate fertilization