# Applications of Water Jet Cutting Technology in Agricultural Engineering: A Review
## 3 Applications of Water Jet Cutting Technology on Different Agricultural Materials
### Soils  
The purpose of cutting soil is to change soil structure and composition for jet fertilization. With the growth of fertilizer prices, the existing fertilizer application techniques have shown a trend away from the conventional spreading technique towards injection, which means that fertilizers are directly injected into the soil and deposited near the plant roots [85,86]. Compared with injection methods such as spokes, furrow openers, jet fertilization as an application of liquid jet technology can effectively avoid crop damage, fertilization holes blockage, and soil contact parts wear and tear [87]. A water depot forms inside the soil after jet injection, which may store some liquids [88]. Additionally, the higher the soil moisture content, the deeper the water jet injection depth [88].  
Jet fertilization should ensure that fertilizers are successfully injected into the soil and reduce the volatilization of ammonia and nitrogen after fertilization. [PERSON] et al. [36] compared three application techniques: a disc coulter injector, a spoke wheel injector, and a high-pressure injector using a trailing shoe technique (Figure 9). They found that in the yield test of winter wheat, spoke wheel, and high-pressure injection yields were higher than surface application yields. Both high-pressure injection and disc coulter could reach a 50-70 mm depth measured by pressing a ruler to the bottom of the soil in a laboratory  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Stem** & **Picture** & **Linkage** & **Booster Pump** \\ \hline \hline \multirow{4}{*}{Wheat} & \multirow{4}{*}{Three-point linkage} & An ultra-high pressure triplex pump is driven by PTO with a small volume and expensive cost ([73], reproduced from “A laboratory evaluation of waterjet cutting of crop residue using the Aqua-Till® liquid coulter” with the permission from Elsevier, 2022). \\  & & A piston-type pump uses additional matching diesel engine units to get power with a large volume and slightly expensive cost ([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). \\ \hline \hline \end{tabular}
\end{table}
Table 1: Water jet cutting stem devices for anti-blocking.  
environment. These results showed that the type of injection technique was not important as long as the fertilizer was injected to at least a 50 mm depth. A working pressure of more than 2.0 MPa was needed to apply water jet cutting technology in the field. [PERSON] et al. [25] designed a jet fertilization device to reduce the nitrogen loss in liquid fertilizer for rice, which belonged to the post-mixing liquid jet technology. Under the parameters of a 12 MPa constant jet pressure, a 10-30 mm target distance, and a 0.6-0.8 m/s traverse speed, liquid jets could cut paddy soil to depths of 19 to 52 mm. They also carried out computational fluid dynamics (CFD) simulations (Figure 10). Simulation results showed that the nitrogen fixation was the highest when the fertilizer inlet diameter and the nozzle diameter were 1 mm. When their diameters were 0.6 and 0.8 mm, respectively, the soil cutting capacity was the strongest.  
Therefore, as an emerging production technology, cutting soil for jet fertilization has a broad application prospect, focusing on cutting depth and fertilizer volatilization. The jet pressure required for a 19-70 mm injection depth is generally lower than 20 MPa. In contrast, other materials require jet pressures greater than 100 MPa. Optimizing cutting parameters through experiments is necessary to reduce fertilizer volatilization. However, there are still some problems when cutting soil, including a slow transverse speed or a shallow injection depth, which requires further research on agricultural machinery for good operation performance and stability.