# Current Status and Future Directions for Combined Tillage and Sowing Technology and Equipment
## 2 Status of Development of Combined Tillage and Sowing Machines
### Subsoiling Technology and Equipment  
Subsoiling is a mechanized farming method that involves loosening the deep soil using machine tools without disrupting the original tillage structure. This process helps to loosen the soil, break the subsoil layer, and improve the soil structure. It is an essential technology for increasing crop yield, as it enhances the soil's capacity to store water, retain moisture, and resist drought and flooding. Subsoiling is commonly used in combined tillage and sowing machines [47; 48]. The research on subsoiling technology mainly focuses on drag reduction and energy reduction to improve the effect of subsoiling operation by means of structural optimization. Figure 5: Biomimetic rotary filler blade. Figure 6: Schematic diagram of the operation. Based on the physical characteristics of brick red loam soil in Hainan banana land, [PERSON] et al. designed a slanting shank folding subsoiling shovel that can effectively reduce the operating resistance. It solves the problems of high operating resistance, a small loosening area, and poor surface flatness, and can better adapt to the operating environments of banana land in tropical agricultural areas, and the optimization effect is shown in Figure 7[49]. [PERSON], JP has designed a subsoiling machine with a plate-like scale structure based on bionics, which mimics shark skin. It can effectively reduce the adhesion of soil on the subsoiling shovel while reducing the operating resistance [50]. In the interest of innovation, [PERSON] designed a pneumatic subsoiling mechanism, through using different air pressures to disturb the soil, to build a subsoiling pneumatic model, and to realize the purpose of pneumatic subsoiling. It has less resistance and a lower energy consumption than traditional subsoiling. The existing drag reduction is carried out around the structural improvement, bionic principle, material optimization, etc., all of which have achieved a better drag reduction effect [51]. [PERSON] et al. designed an anti-vibration and anti-entanglement rotary component, which was installed on a subsoiling rotary tillage combine to reduce soil backfill and excessive vibration, prevent stubble entanglement, and enhance the operating effect of the machine [52]. For the application of a multi-link operation, [PERSON] et al. designed a subsoiling full-layer fertilizer shovel that is suitable for a banded no-till planter by obtaining theoretical values of key parameters and working optimal parameter combinations through theoretical analysis and EDEM simulation in terms of improving the efficiency of the machine tools, reducing the number of operations and optimizing the use effect. It realizes that a single application of fertilizer meets the nutrient demand of crops in different fertility periods, and promotes the application of subsoiling technology in multi-link operations [53]. [PERSON] et al. developed the 1 MXQ-4 stubble rotary tillage and ridge for the drought problem of having low amounts of precipitation and high amounts of evaporation throughout the year in the brown soil area of western Liaoning, which further promoted the development and maturity of subsoiling technology in compound operation [54]. The research on subsoiling technology focuses on improving operation performance and enhancing stability. Through means such as structural optimization and form innovation, it aims to solve problems such as soil adhesion, stubble entanglement, and high operation resistance.