Abstract:

[Significance] Orchard fertilization is an important field management practice affecting nutrient supply, yield formation, and fruit quality. Ditching combined with fertilization can place fertilizer within 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 spacing, 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. This review systematically summarizes the research progress of orchard ditching and fertilization equipment from four aspects: agronomic requirements, key components, whole-machine equipment, and intelligent technologies, to identify existing technical bottlenecks and development directions and to provide 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 for furrow depth, fertilizer placement, fertilizer application rate, and equipment configuration imposed by inter-row spacing, root distribution, and terrain conditions are discussed. Second, the structural characteristics and applicable conditions 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 requirements and maintenance demands. 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 differing adaptability to different fertilizer forms. Granular fertilizers require greater 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 implements are suitable for orchards with flat terrain and wide row spacing; crawler-type 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 sensing, ultrasonic sensing, laser ranging, and 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 purely 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 non-visible 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 are expected to promote the upgrading of orchard ditching and fertilization equipment from single mechanical implements to an intelligent, precision-oriented equipment system for smart orchards.

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