**5. Soil compaction management in agriculture**

Although the chassis and undercarriage design of tractors, combines, and harvesters is of obvious concern to engineers when trying to decrease soil compaction, agriculturalists have developed a variety of other methods and practices that contribute to the alleviation of soil compaction impact. These conservation tillage practices and alternative process design considerations are an important element in overall soil compaction reduction, as they can be applied to any and all farming operations, even those that do not have the most up-to-date equipment. Farm management practices can have a profound impact on reducing soil compaction, as well as maintaining soil organic content, reducing nutrient suppression, and decreasing time and energy spent in the field. From a sustainability standpoint, these conservation practices may even be more impactful for farm and field management at reducing soil compaction than any specific tractor or undercarriage design.

### **5.1 Tillage equipment and practices**

The design of tillage equipment is an important and fruitful area of research for reducing soil compaction during the necessary ground-working operations. Tillage equipment design affects the ways in which tillage equipment interacts with the soil to help to alleviate long-term effects of disturbance in heavily-worked ground. Some of the core ideas within tillage implement design are load distribution, working point and shank design, working depth, the different types of soil disturbance, and the soil pulverization level. Most modern research is targeted at collecting specific information about the impacts of these conditions on soil health, compaction levels, and seed bed preparation, as well as energy use and the time spent in the field. The implications of tool design, structural loading, the types of conservation and reclamation

equipment, and the impacts of soil compaction management on the energy consumption and overall performance of an agricultural venture will be examined in this section.

#### *5.1.1 Tool design*

In early agricultural practices, the moldboard plow dominated tillage as the most effective tool for turning the soil to create a seedbed. Its design was maintained in many forms of tillage equipment for years before its harmful impact on soil health, organic material, and erosion was realized. In contrast to the simplistic design of the moldboard plow, modern tillage equipment tool designs come in many shapes and sizes. The effects of tool geometry, orientation, depth, field speed, and other factors impact the level of soil disturbance and compaction. Various tool types can create a multitude of different outcomes in the upper soil layers in terms of soil aggregate size, topsoil density, porosity, and organic matter distribution. Other tools act predominately at the sub-surface level. In particular, deep cutting tines have the greatest impact on sub-soil compaction. Their shape, working depth, and spacing all affect the resulting soil compaction differently.

The effects of specific tine geometry and individual tine orientation were explored by researchers using finite element analysis (FEA) modeling [45]. **Figure 24** depicts the range of geometric variation explored, including the alteration of tine width, rake angle, and tilt angle. The primary results from this study concluded that at comparable field speeds, the increase in tine width linearly increased the resulting downward vertical force, while increasing rake or tilt angle linearly decreased the downward vertical force [45]. The implications of this study affect tractor power sizing, the uniformity of transmitted force along a vertical soil profile, the soil pulverization level, and the subsoil compaction. Most certainly, the results also present a variety of design trade-offs, depending on the immediate and long-term priorities of the specific farm manager. However, from the standpoint of reducing compaction whilst maximizing surface soil pulverization, minimizing the tine width and maximizing the tilt and rake angles create the least amount of sub-surface compaction.

It is important to note that the tilt angles can be non-uniform both on individual tines and on the overall tine set-up for an entire tillage unit. Many times, a compromise between minimizing draft forces, decreasing compaction, and managing soil upheaval can be achieved by applying a diverse range of different geometric and orientation values throughout a single tillage implement [46]. This becomes even more applicable the larger the implement is, due to the increased number of rows and columns of working points. Besides the considerations outlined above, two other vital components of tillage implement design are tool spacing and working depth in relation to the "critical depth". Critical depth is generally considered to be the point below which soil disturbances are concentrated near the working point and not distributed throughout the soil. **Figure 25** shows both the effects from operating below a critical depth and the dramatic increase in soil compaction as a result of tillage below this level [46].

Unfortunately, critical depth is not uniform by any means. It varies significantly with multiple variables, and it can be heavily impacted by moisture level, soil type, and the presence of a cover crop. This makes determining an operational depth a challenging task, particularly for inexperienced operators. Often initial passes are needed to estimate ideal working depths. There has been some research done regarding the use of strain gauges on subsoiler tines in conjunction with depth sensors,

#### **Figure 24.**

*(A) Six single sideway-share subsurface tillage implements with the same rake and tilt angles of 10° and 15° with different cutting widths; (B) dual sideways-share subsurface tillage implements with rake angle of 15° with different tilt angles; and (C) five dual sideways-share subsurface tillage implements with share tilt and rake angles of 10° and 15° with different shank rake angles (Hoseinian et al., 2022) – [42].*

which can utilize a closed loop response system automatically adjusting height to maintain the desired draft and vertical forces [47]. These systems still require a degree of experience and skill to determine the expected shank loading at, above, and below the critical depth, in order to set the necessary system limits prior to operation. Although the practical difficulties with feedback-based systems are numerous, increased implementation of the above described depth adjustment mechanisms will provide a wealth of data regarding forces at and around critical depth. This information will only make these systems more effective in the future [48]. **Figure 26** illustrates the effects of tine spacing on overall soil disturbance. When tine spacing exceeds 1.5 to 2.0 times the working depth, an interesting phenomenon takes place, where the soil disturbance only occurs locally and results in a non-uniform subsoil profile and soil surface [46].

*Reducing Soil Compaction from Equipment to Enhance Agricultural Sustainability DOI: http://dx.doi.org/10.5772/intechopen.104489*

**Figure 25.**

*Varying level of soil disturbance with narrow tine: (a) above critical depth; (b) below critical depth (Spoor, 2006) – [43].*

**Figure 26.**

*Influence of tine spacing on the soil disturbance profile: (a) wide spacing; (b) narrow spacing (Spoor, 2006) – [43].*

This outcome is likely to be troublesome for planting, as different row unit depth wheels will be penetrating the surface soil to different depths. The lack of consistency in seed depth, because of this poorly prepared seedbed, will result in emergence and

germination issues. Although not initially obvious, the lack of uniform soil disturbance also affects compaction levels. Firstly, the lack of a uniform soil disturbance cross-section that occurs when using widely-spaced tines, illustrated in **Figure 19**-a, results in some subsoil being undisturbed. This soil remains compacted over time. When using a tillage implement with a wider tine set-up, it is easy for an operator to exceed the critical depth in order to achieve a cleaner surface profile, but in doing so, the subsoil compaction has been increased throughout the field. Using a narrow tine design dramatically decreases the chances that an operator will need to exceed critical depth in order to achieve the desired seed bed quality.

#### *5.1.2 Structural loading*

While magnitude of downward vertical force for tillage equipment simply does not compare to tractor units, it is still important to consider how the soil reacts with the implement loading as it moves through the field and what factors play into determining the optimal number of tines and the structure of tillage equipment. There are three primary ways in which soil reacts to the loads and forces placed on it by cultivation implement: brittle loosening disturbance, compressive disturbance, and tensile disturbance [43]. Brittle loosening occurs when the implement load compresses the soil and causes a sliding or slipping during the operation. The effects of the sliding and slipping are such that the soil aggregates, clumps, and masses move relative to one another. The overall volume of soil masses is increased, cracked, and spread-out. Contrary to compressive disturbances, a large quantity of the soil is actually decompressed or loosened as a result of brittle loosening. This is the kind of soil response that occurs primarily under ideal loading and working depth conditions.

Compressive disturbance also occurs under compressive loading, but without the exposure to masses sliding relative to one another. In this case, without sliding, the soil is more likely to experience high degrees of compression and increases in density. This process is more common using heavier implements, when there is a low draft force. Tensile disturbance is virtually the same as brittle loosening and has similar results, such as decreased density and alleviated compaction. The difference lies in the fact that tensile disturbance occurs when soil aggregates are pulled-away from one another and forced to spread-out. This kind of disturbance is more likely to occur under high moisture conditions, where the load is cushioned and absorbed to a greater extent, thus negating the compressive impact of the load.

Each of the three kinds of soil matrix disturbances can be modified and impacted by the working depth, operation speed, and the weight of the implement. **Table 1** provides the basic tendencies for determining the design of the implement, based on the power of the tractor unit, and for potentially determining necessary engine power or anticipated working depth, based on the tine and structural design of the tillage implement and its working points. **Table 1** can be used for reclamation projects in which the soil has experienced long-term compaction and where aggressive subsoiler action is needed to prepare the soil for further tillage and planting preparation [46].

#### *5.1.3 Soil loosening equipment*

There is a big difference between common tillage equipment used for routine crop cultivation, associated with planting and harvest, and machinery used to rejuvenate the soil from excess compaction. Robust subsoilers are utilized when efforts are made to restore long-term compacted soil. These subsoilers must be capable of decreasing soil


*Reducing Soil Compaction from Equipment to Enhance Agricultural Sustainability DOI: http://dx.doi.org/10.5772/intechopen.104489*

**Table 1.**

*Wheeled tractor capability for operating loosening tines in compacted soil (Spoor, 2006) – [46].*

density and effectively disturbing the mid-subsoil level to make the land workable under normal cultivation protocols. As seen in **Figure 27**, these reclamation subsoilers typically utilize a three-point hitch attachment for depth adjustment, rather than a drawbar attachment and trailing configuration [46]. One issue with these subsoilers is the need to operate below the critical depth to create an adequate soil disturbance to restore the soil profile. Unfortunately, this process can cause further, deeper subsurface soil compaction, despite alleviating the compaction in the upper subsurface soil levels.
