When to use subsoiler and scarifier

Equipment is extremely important for crops and it is necessary to know when and how to correctly use each of these implements.

22.05.2020 | 20:59 (UTC -3)

Despite being two simple implements, subsoiler and scarifier are extremely important for crops where the producer wants to maintain productivity without giving up care for preserving the land and coverage, so it is necessary to know when to use each of these implements and how to use them. correct to operate.

The subsoiler and the scarifier have a minimum surface (vertical) mobilization, as they operate on the sub-surface, in the soil fracture zone in a three-dimensional cut, that is, they harm the soil less, with no elevation of the same, unlike the plow that cuts, elevates and inverts the till and the harrow that levels and destroys, moving the soil laterally. The scarifier and subsoiler leave residue on the surface, which brings all the benefits of organic matter in the soil which, in addition to improving infiltration, maintains part of the soil's structure, as it does not promote excessive disintegration. Due to the greater contribution of organic matter and the non-destructuring of the soil, there is better water retention and a reduction in erosion processes in the soil.

SCARIFIER

The scarifier used in the minimum cultivation system replaces the function of the plow as primary soil preparation. It disintegrates the soil less, as it reaches the soil's fracture zones and does not invert the hill and also has the advantage of uncompacting deeper layers than the plow.

The scarifier working at the same depth as a disc plow has a 60% lower energy requirement than the plow (Martuchi, 1985) When compared to other agricultural soil preparation equipment, it has the lowest energy requirement for operation (Salvador et al.

In a well-managed scarification there are economic benefits (less time with equipment in the area, savings on fuel, savings on labor time and less equipment to be purchased) and soil conservation benefits (less soil disruption, less erosion, maintenance of organic matter on the surface, among others).

LIMITATIONS

Despite the advantages, there is no total replacement of the functions of the harrow and the plow, as the last two have better destructuring and, consequently, better contact between the soil and the seed. As the scarifier was developed to work in soil conservation systems, it was not designed to work in conditions of rocks and stumps, situations that could damage the equipment if working in these conditions.

In the evolution of an area, there is initial preparation (deforestation, deforestation, uprooting, removal of stones and windrowing), conventional preparation (primary and secondary preparation) and minimum cultivation. If the activities preceding minimum cultivation were carried out correctly, the soil should be practically free of stumps or stones.

As the scarifier was designed to work in the minimum cultivation system and in this system one of the premises is to maintain at least 30% of organic matter on the surface, there is a high chance of plant material “embedding” in the equipment if it is not equipped with a disc. cut.

Metal rings to limit depth in the hydraulic piston.
Metal rings to limit depth in the hydraulic piston.
Metal rings to limit depth in the hydraulic piston.
Metal rings to limit depth in the hydraulic piston.

SUBSOLADOR

Subsoiling is a practice of sub-surface soil mobilization to correct it, destroying compacted layers in the sub-surface. Like the scarifier, the subsoiler also does not revolve the soil, it reaches the soil fracture zones in three dimensions. Despite the similarity with the scarifier, the subsoiler reaches deeper layers, therefore, there is a greater need for tractor power and if not handled well, it can compact the sub-surface. Therefore, its use is only recommended when other equipment cannot reach the compacted layer.

As the subsoiler reaches deeper layers, there is a need for greater tractor power, which is why this equipment requires the greatest power and fuel consumption among all agricultural soil preparation equipment.

Subsoiler with automatic rod disarming system.
Subsoiler with automatic rod disarming system.

LIMITATIONS

The subsoiler has a greater power requirement per rod and, consequently, greater fuel consumption. It should not be used in very humid soil conditions and, if its use is poorly planned, it destroys the soil structure at greater depths, which makes correction more difficult than in more superficial layers, and thus increases losses. of water and nutrients.

Among the main advantages and benefits of using a subsoiler and scarifier are: greater water infiltration, better root penetration, better soil aeration, better drainage and reduced erosion.

OPERATIONS AND ADJUSTMENTS

Basically, the factors to be taken into consideration when operating and adjusting are: depth of scarification or subsoiling, number of rods, type of tip, spacing between rods and travel speed.

DEPTH CONTROL

Depth control will vary according to the type of equipment (coupling method) and its depth limiting wheel. If the subsoiler is mounted, it will have a metal wheel that only has this purpose, whereas if the equipment is for dragging, it will have a wheel for transportation that will also be used to limit the operating depth.

When the equipment is dragged, to obtain the necessary depth, it is necessary to use metal rings on the equipment's hydraulic piston. These rings prevent the piston from reaching the end of its stroke, limiting the depth of the operation. The more rings, the shallower the equipment will work; Without the rings, the equipment will work at its maximum capacity.

Subsoiling in soils with different moisture percentages.
Subsoiling in soils with different moisture percentages.
Subsoiling in soils with different moisture percentages.
Subsoiling in soils with different moisture percentages.

WORKING DEPTH

The working depth is the actual depth that will be worked, it is the depth that must be reached to exterminate the compacted layer. The working depth is 5cm to 10cm from the compacted layer, therefore, if there is a compacted layer at a depth of 60cm, the working depth will be between 65cm and 70cm, that is, the tip of the tip must reach this depth to make sure that you will be breaking the compacted layer.

Figure 1 - Working depth.
Figure 1 - Working depth.

 

SPACING BETWEEN RODS

The spacing between rods is of fundamental importance so that no part of the area remains unworked or compacted, or that the rods are not too close together, causing the work of one to cancel out the effect of the other. If this occurs, there will be a need for a greater number of passes and, consequently, greater fuel consumption.

 

Figure 2 - Difference between well-spaced and wrongly spaced rods
Figure 2 - Difference between well-spaced and wrongly spaced rods

What influences the spacing between the rods is the width of the tip. If the tip is narrow (between 4cm and 8cm), the spacing between rods must be 1 to 1,5 times the working depth, whereas if the tip is winged (8cm <), the spacing between rods will be 1,5 at 2 times the working depth.

Taking as an example a layer compacted at 30cm and equipment with a narrow nozzle 8cm wide, the working depth should be 35cm to 40cm. If the adopted depth is 35cm, the spacing between rods will vary between 35cm and 42,5cm. If the working depth is 40cm, the distance between the rods should vary between 40cm and 60cm.

Assuming that the tip was exchanged for a 15cm, winged one, now the spacing between rods will be between 42,5cm and 70cm, if 35cm is used as the working depth. If the depth adopted is 40cm, the spacing between the rods should be 60cm to 80cm.

If the equipment has rods in the front and back (Figure 3), the spacing between rods must be the same between them all, that is, if a piece of equipment has five rods (two in the front and three in the back), the spacing of the first rod that is behind for the first one from the front it must be equal to the spacing of the first one from the front and the second one from the back and so on.

Figure 3 - Correct spacing between rods in two-row situations with four rods
Figure 3 - Correct spacing between rods in two-row situations with four rods

CRITICAL DEPTH

Critical depth is the maximum depth to which there is benefit from scarification or subsoiling, below this depth the operation only causes harm. It is different from the working depth, as it is conditioned by the depth at which the compacted layer is located, while what determines the critical depth is the width of the tip. In other words, a situation may occur where equipment reaches below the compacted layer, but if the critical depth is less than the working depth, the equipment will not perform the operation. In this case, the equipment has reached the working depth, but there is no decompression of these layers at that depth, but rather a contribution to increased compaction in them.

Figure 4 - Difference between depth and critical depth
Figure 4 - Difference between depth and critical depth

Below the critical depth there is no increase in the worked area, what occurs is an increase in the traction force at that point, which helps to compact the soil at points below the critical depth. From there, the equipment is only scratching the ground. What determines the critical depth is the width of the tip, which is determined by multiplying the width of the tip by 5 and 7.

Assuming that you are working with a 6cm wide tip and want to reach a working depth of 60cm, the critical depth for this tip is between 30cm and 42cm, that is, under these conditions, even if the rod reaches the working depth, it will not There will be benefits to the operation, and it may even be worsening the current condition of the soil. In this case, you must exchange for a wider tip. If the critical depth is between 60cm and 84cm, it is recommended to use a 12cm tip, for example, to solve the problem.

LEVELING

Finally, after all adjustments, the equipment must be leveled on the ground. In mounted equipment, this is done in the third point, while trawling equipment has its own system. The operator must lower the equipment to the ground as much as possible and operate a few meters until he realizes that the rods have completely entered the ground; Once this is done, he must get off the tractor and level the equipment so that it is straight at ground level.

SOIL MOISTURE

In most operations with agricultural equipment, the moisture content in the soil must be at any point of friability, however, for the scarifier and the subsoiler the ideal point is the lower limit of friability, that is, close to tenacity, where the strength cohesion is a little higher than adhesion.

At this point, less energy will be needed by the tractor to prepare the area, resulting in a greater spread of compression stress, that is, the activity will be better developed, obtaining better results with an increase in the area worked compared to working in other humidity conditions. .

When working in conditions of excess humidity, the water acts as a lubricant, preventing the tip from reaching fracture zones in the soil, resulting in a smaller area worked. The predefined spacing of the rods will not have a beneficial effect, in addition to the harmful effects of possible compaction of the area. A simple analogy would be like passing a knife (rod) through margarine (very moist soil), after the knife is passed, the margarine tends to return to its previous position.

Figure 5 - On the left, condition of high humidity, and on the right, the difference between the equipment's pass on a soil in ideal condition and with excess humidity
Figure 5 - On the left, condition of high humidity, and on the right, the difference between the equipment's pass on a soil in ideal condition and with excess humidity

Working in conditions of low humidity will leave many clods of large size, therefore, greater tractor power will be required, consequently, greater energy, in addition to being able to damage the scarifier or subsoiler due to the greater power demand and the numerous times in which that the rods will trip.

IRREGULAR OPERATION

Great care must be taken when operating with the scarifier or subsoiler, inexperienced operators tend to raise and lower the equipment too much, making it an inefficient activity, as in some points the rod goes below the depth to be worked and, in others , above, leaving points in the area still compacted.

To check whether the operation is being carried out correctly, it is recommended that you use a measuring rod of considerable size and follow the tractor, sinking the rod as far as the ground offers resistance. If, after a few checks, it is found that the rod is always sinking to the same depth, it is because the activity is being carried out correctly. If it is found that there are different depths, it is necessary to go through the area again and this time be more careful in adjusting the depth.

Rod safety system

The safety system for scarifier or subsoiler rods is the fuse pin and the automatic disarming system.

When passing through terrain with rocks, stumps or very dry soils, which would require greater power from the tractor and consequently the rods, the fuse pin breaks, leaving the rod loose and removing the pressure previously exerted on it. When noticing that the rod is raised and is not working, the operator must replace the fuse pin with a new pin. It is worth noting that you should never, at any time, place other parts other than the pin, as other material can be very resistant and, instead of breaking like the fuse, to preserve the rod, it ends up transferring the effort to the rod and breaking.

The automatic disarming system is more modern than the fuse pin, while the pin breaks and needs to be replaced, the automatic disarming system raises the rod, removing it from contact with the resistant part. When observing this, the operator must raise the equipment, either using the three-point hydraulic lifting system (mounted) or using the remote control (drag), so that the rod can return to the correct location and continue the operation.

MAINTENANCE OF THE SUBSOILER AND SCARIFIER

After the end of each working day, all screws and nuts on equipment that are loosening must be tightened, this prevents premature wear. After retightening, the equipment must be washed and stored in a protected place.

Another factor to be frequently analyzed is tip wear. As it has two tips that can be used, it is important to monitor and invert the tip when one side is worn. When both ends are worn, the part must be replaced to prevent wear on the equipment rod, which is the most expensive and difficult to replace component.

Two important implements

Scarifier and subsoiler are implements used under the soil surface to break up compacted layers. They were developed due to the need for equipment that worked on periodic soil preparation with plant material on the surface. At the end of the 70s and beginning of the 80s, farmers who used conventional tillage, soil preparation with plows and harrows, realized that they were losing a lot of soil through erosion, losing in a cycle what was previously lost. within ten years, problems related to erosion were very serious. To try to reduce these losses, conservation systems were born, which today are the minimum cultivation and the direct planting system, however, it was observed that the equipment present at the time was not suitable for the systems, as they, after preparation , did not leave plant material on the surface and severely damaged the soil, so the scarifier and subsoiler were developed for these new systems.

There are currently two valid theories about the difference between scarification and subsoiling. The first, by Martuchi (1987), is divided into light scarification (5cm – 15cm), heavy scarification (15cm – 30cm) and subsoiling (30cm <). The second methodology, Asae (1982), says that an activity carried out up to 40cm is scarification and that an activity carried out above 40cm is subsoiling. Both theories are accepted, with equipment being classified according to the depth at which it can work.

Some models of subsoilers come equipped with cutting discs to work mainly in areas with dense straw.
Some models of subsoilers come equipped with cutting discs to work mainly in areas with dense straw.


Deivielison Ximenes Siqueira Macedo, Viviane Castro dos Santos, Leonardo de Almeida Monteiro, Enio Costa, Rafaela Paula Melo, Henryque Candido Fernandes do Nascimento, UFC


Article published in issue 159 of Cultivar Máquinas. 

Cultivar Newsletter

Receive the latest agriculture news by email

LS Tractor February