# Applications of Water Jet Cutting Technology in Agricultural Engineering: A Review
## 3 Applications of Water Jet Cutting Technology on Different Agricultural Materials
### Stems
#### 3.5.2 Jet Weeding  
Long-term use of chemical weeding will increase herbicide-resistant weeds, and herbicides may cause water pollution and affect the farmland environment. Therefore, thermal or mechanical methods are put forward, and water jet weeding is one of the mechanical weeding methods [79, 80].  
[PERSON] et al. [81] found that small oilseed rape could be cut off by water jet at 100-300 MPa of pressure and a 1-5 m/s traverse speed, which indicated that as a new physical weeding method, water jet weeding could be used along roadsides or railway embarments. [PERSON] et al. [82] conducted water jet cutting single seedlings experiments using rice seedlings instead of weeds. The results showed that seedlings could be completely cut off at 30 MPa of pressure (the highest pressure tested), a 100 mm target distance, and a 0.4 mm nozzle parameter, and the cutting ability was stronger near the beginning of water  
Figure 8: Simulation of jet cutting process: (**a**) breaking; (**b**) deepening; (**c**) crossing; (**d**) cutting off ([75], reproduced from the Ph.D. thesis “Study on anti-blocking device for no-till seeder with non-connect stalk cutting by ultra-high-pressure waterjet” with permission from the Author, 2022).  
Figure 6: Bench tests of cutting wheat straw internode stem by water jet ([73], reproduced from “A laboratory evaluation of waterjet cutting of crop residue using the Aqua-Till® liquid coulter” with permission from Elsevier, 2022).  
Figure 7: Field experiments for disparate types of furrow openers coordinate with a water jet: (**a**) Double-disc opener; (**b**) Hoe opener ([22], adopted from “Anti-blocking performance of ultrahigh-pressure waterjet assisted furrow opener for no-till seeder” with permission from IJABE Editing and Publishing Office, 2022).  
jet diffusion. Meanwhile, the appropriate angle between the water jet and the seedling was approximately 45\({}^{\circ}\). Through experiments on water jet cutting weeds, [PERSON] [83] concluded that the nozzle diameter less than 1.5 mm was suitable for weeding. That was because a larger nozzle diameter would lead to a jet impact force exceeding the bending capacity of weeds, making weeds bend rather than be cut off. Nevertheless, water jet weeding has some limitations. The growing points of some grass species are protected at or below the soil, making them more difficult to control with water jets [84].  
In general, there has been some success with water jet cutting stems, including anti-blocking and jet weeding, but there are still some problems in the design of mobile machines. Due to the limitation of pressurization equipment and water tanks, mobile water jet cutting devices are heavy with large sizes (taking anti-blocking devices as an example, as shown in Table 1) that may cause soil compaction. Hence, soil compaction needs to be dealt with in different ways. For example, adjusting the cutting parameters in real-time according to the amounts of stems on the soil surface is of great significance to reduce water consumption. In addition, equipping the jet nozzle in front of the furrow opener can complete operations of anti-blocking and opening furrow at one time, reducing the number of machines entering the field.