Soil preparation system to avoid compaction

Six different soil preparation systems were tested to find out which one is the most compact and which is the least aggressive to the soil.

In the agricultural exploration process there is concern about the correct use of soil preparation systems. With the constant use of agricultural machinery in producing areas and the recent increase in their size, combined with the failure to monitor tire width, the soil has received a considerable load of pressure that can result in a process of degradation of its quality. This reduction in quality is mainly reflected in physical characteristics of the soil, such as the appearance of compacted layers, especially if, during mechanized operations, soil moisture is not taken into account.

Soil preparation systems have the basic objective of providing a favorable environment for seed development. However, some of these systems have shown their negative effects, over time, on the process of crop development and production.

Among the most used tillage systems are: conventional, reduced, conservation and direct planting. The conventional tillage system traditionally uses plowing followed by harrowing for loosening and leveling. The reduced tillage system is characterized by a reduction in the number of operations in the area, resulting in fewer machine passes, and can be characterized by a single harrow pass. In some situations, the use of scarifiers is considered reduced, or minimal. . The conservation system is characterized by maintaining the soil's vegetation cover at least 30% after preparation operations, which is normally achieved when scarifiers are used, equipped with a cutting disc for straw and a de-clogging roller. For purposes of understanding, the terms scarification and subsoiling are used in this article, considering that scarification takes place up to a depth of 0,40 m and, below 0,40 m, subsoiling takes place.

The direct planting system, where there is no soil disturbance in the total area, involves sowing on crop residues. The purpose of such crop residues is to protect the soil and, for this purpose, seeder-fertilizers are used with a cutting disc for straw and a furrowing rod (boot) to prepare the soil only in the sowing row.

In the direct planting system, the inadequate use of crop rotation, combined with the lack of adequacy of the mass and machinery tires, has caused the appearance of compacted layers over the years. Therefore, producers have used equipment with rods to remove compacted layers, aiming to improve the physical characteristics of the soil.

Therefore, the study of management systems such as direct tillage, scarified direct tillage, crossed scarified direct tillage, conventional tillage, reduced tillage and conservation tillage, can help producers define the best system for their area, especially in relation to the process of soil compaction.

With this objective, a study was conducted at FAECA – Experimental Farm of Agricultural Sciences of the Federal University of Grande Dourados – UFGD in the municipality of Dourados (MS), on the influence of soil preparation systems on the compaction process in distroferric Red Oxisol texture clayey (62,23% clay, 20,43% silt, 17,34% sand).

The experimental area was conducted for more than 10 years with a direct planting system, however, before the installation of this experiment, it was prepared with a disc plow (0,30 m deep), followed by declogging-leveling harrowing (0,15 m deep). ), followed by subsoiling with 5-rod equipment (0,50 m deep) and new declogging-leveling harrowing (0,15 m deep). The function of this preparation was to eliminate physical problems in the soil and level the land. To establish a cover crop, oat was sown (60 seeds per meter at 0,04 m depth with a spacing of 0,20 m between rows), which was subsequently desiccated and handled with a straw crusher to implement this experiment.

When preparing the plots of the soil preparation systems, after crushing the oats, a five-rod scarifier was used, with a narrow nozzle from 0,08 m to 0,40 m deep (scarification treatments); mouldboard plow cut 0,40 m deep (conventional preparation); declogging-leveling harrow, off-set, drag type, with 20 discs of 0,51 m in diameter (20”), at a depth of 0,15 m (conventional, reduced and cross scarified preparation).

The treatments were composed of six management systems: direct planting (PD), scarified direct planting (PDe), crossed scarified direct planting (PDec), conventional tillage (PC), reduced tillage (PR) and conservation tillage (PCs).

In this study, the direct planting system used the succession of crops with soybeans in the summer and safrinha corn in the winter, as mobilization in the summer and no type of soil mobilization in the winter sowing. Scarified direct planting (PDe) received only one scarification operation. Cross scarified direct planting (PDec) received two scarifications and a leveling harrow to break clods and level the soil. The conventional tillage (PC) received a plow and four declogging-leveling harrows. The reduced preparation (PR) received only a declogging-leveling harrowing. The conservation preparation (PCs) was a scarification operation and a declogging-leveling harrowing.

In order to characterize the water content in the soil, samples were collected randomly in the plots. Figure 1 shows the water content in the soil at the time of collecting data on soil mechanical resistance to penetration. 

Data on the soil's mechanical resistance to penetration (RP) were also collected using an impact penetrometer model IAA/Planalsucar-Stolf, developed by Stolf et al. (1983), adapted by KAMAQ with placement of a ruler for measurement (Stolf et al., 2011) up to a depth of 0,55 m, in the soybean harvest. In order to identify areas of greater resistance in the profile after traffic, a collection mesh measuring 0,225 m wide x 0,10 m deep was used within the traffic lane (seven lines of the soybean seeder). The seeder-fertilizer, with seven seeding lines spaced 0,45 m apart, deposited soybean seeds in each preparation system.

The average data on resistance to penetration - compaction (Figure 2) indicate that the system with conventional preparation (PC) presented a higher value when compared to the others. Systems that use furrowing rods (scarifiers), such as scarified direct planting, crossed scarified direct planting and conservation tillage, presented the lowest resistance values, showing the beneficial effect of using these equipment in removing compacted layers.

The direct planting and reduced tillage systems presented compaction values ​​very close to conventional tillage. It is possible to see that the effects of plowing and harrowing of conventional tillage are momentary and that, after the first traffic in the area, resistance values ​​increased, even surpassing the values ​​of systems without mobilization or with minimal mobilization.

The resistance data were verified in the soil profile using a collection mesh with a maximum width equal to the width of the seeder, up to a depth of 0,60 m. The data from this collection were analyzed by geostatistics and the adjustment of the spherical semivariogram was verified, with a range varying from 33,2 to 69,9 cm, for all management systems. Spatial dependence was considered strong for all management systems. Cross validation showed a good coefficient of determination for all management systems, with the exception of the direct planting system.

The soil profile maps for each system indicated the effect of management on the compaction process. This indicates that soil management systems result in different levels of soil compaction.

According to Ribeiro (2010), when compiling works on RP in typical eutrophic Red Latosol, the values ​​of penetration resistance levels can be classified as: low (0 to 2 MPa); medium (2 to 4 MPa); high (4 to 6 MPa) and very high (above 6 MPa).

According to the compaction isoline maps (MPa) for the management systems (Figure 3), the direct planting (PD) system presented resistance (compaction) values ​​considered high (4 to 6 MPa – yellow band) in the soil layer. 0,05-0,35 m. On the other hand, the scarified no-tillage (PDe) and cross-scarified no-tillage (and PDec) systems presented high values ​​just below the 0,40 m layer, evidencing the scarification action as effective in removing compacted layers, which can be a recommendation for use for direct planting systems that have compacted layers. It can be seen that, in the direct planting system, compaction is concentrated in a layer of 0,05-0,35 m, indicating that subsoiling must be carried out at a depth of up to 0,45 m. In this case, an increase of 0,10 m is recommended as a safety margin for removing the compacted layer.

The conservation preparation (PCs), by also carrying out the scarification operation with a harrow, presented high values ​​of resistance to penetration below the 0,35 m layer. It is noted, in this system, that the thickness of the layer with medium resistance (2 to 4 MPa) is greater compared to conventional planting. The latter suffers the effects of leveling harrowing and compression caused by traffic and the action of the harrow discs, and presented high compression values ​​across the entire length of the profile (4 to 6 MPa). The reduced preparation showed high compaction values ​​(4 to 6 MPa) below the 0,15 m layer.

It is observed in the maps of the scarified no-tillage system and the crossed scarified no-tillage system (Figure 3) that they did not show differences between them in terms of values ​​and layers. This may be an indication that from a soil quality point of view, a second scarification operation is not necessary. Furthermore, there is an increase in the cost of the operation and the time spent on this new operation.

Therefore, it can be used as an indication of management in agricultural areas that the use of scarification in direct planting is beneficial for reducing the compaction normally existing between the 0,05-0,35 m layers and that a second scarification operation does not is necessary, as the results indicate that there is no difference between the use of one and two interventions. The use of conventional tillage (plowing and harrowing) and its benefits are not very significant, as after a few months the compaction values ​​return to the area. The use of systems with minimum disturbance, such as reduced preparation using a grid, means that the highest compaction values ​​are concentrated below the 0,15 m layer, increasing the thickness of the compacted layer. 

Jorge Wilson Cortez, Paulo Henrique Nascimento de Souza, Maurício Viero Rufino, Renan Miranda Viero, Eduardo de Freitas Rodrigues, UFGD; Nelci Olszevski, UNIVASF

Article published in issue 147 of Cultivar Máquinas.