Soil decompression when sowing

Direct sowing using a guillotine or machete at a greater depth becomes one of the solutions to urgently resolve soil decompression, in addition to ensuring greater water absorption for the planted crop.

The agricultural sector in the last 20 years has undergone many beneficial changes, which have contributed not only to increased productivity, but also to the practicality of the farmer. This statement was associated with remembering the times when the soil was cultivated in the minimum cultivation system or conventional system, as it is known, as it was necessary to spend a good amount of time turning the soil and preparing it to implement some culture, not to mention the use of some pesticides, such as trifluralin, which needed to be incorporated with the grid.

Currently, we live with the Direct Planting System (SPD) management, which provides several benefits to the soil, and, mainly, to the environment, by reducing water erosion, although currently there are erosion problems also in SPD, due to the use inadequate management.

SPD, compared to the conventional preparation system (SPC), retains more moisture, enabling the crop to be more resistant to drought and dry periods; there is a reduction in soil erosion, reducing the loss of soil and fertilizers, which contribute to the environmental sustainability of the system, an increase in organic matter, which triggers improvements in the physical structure and CTC (cation exchange capacity).

Not long ago, seeders were equipped with systems that aimed to open the furrows larger, allowing them to be used at different depths with the aim of solving a problem found in several experiments, soil compaction. In many regions where the practice of silage and crop-livestock integration is found, this problem is even more aggravating, due to the uncontrolled traffic of agricultural machinery and implements and the presence of excess animals, especially on rainy days. This compaction also occurs in routine crop management practices, for example: use of a large agricultural harvester, in high humidity without controlling its traffic.

In compacted soils there is less development of the root system, which results in a smaller volume of soil explored by the roots and, consequently, less absorption of water and nutrients. In dry years, the problem is more common due to the lack of water available for the plants, causing a significant decrease in productivity.

Such problems extend to the area of ​​agricultural mechanization, due to the increase in traction force, seen by the increase in tractor skidding, the increase in fuel consumption, the reduction in sowing depth, the irregular cutting of the vegetation cover caused by the reduction in performance of the furrowing mechanism if it is poorly adjusted.

The soil can be correlated with a bank, however, of tension, which receives the action of pressure, whether via rolling or trampling, and stores it until a point is reached where there are restrictions on the development of plants.

For some years now, the team at the Soil Machine and Plant Relationship Laboratory at the Federal Institute of Education, Science and Technology – Campus Sertão has been studying these issues in order to seek techniques that help maintain the principles of the direct planting system. Analyzing the data obtained largely from research on the physical properties of the soil, it is clear that the problem of compaction is between 7cm and 15cm and, given this, the use of the guillotine furrower or machete furrowed at a greater depth can improve the development environment. roots, resulting in increased productivity. Research has been carried out seeking to quantify and qualify the effects of this technique.

UNCOMPACKING

When talking about different working depths of the fertilizer furrower, the first things that come to mind are fuel consumption, the power required to pull it and whether it will have an impact on productivity. Given this, three types of management were tested by the research team. One of the management methods is the direct planting system with the fertilizer furrowing rod at 7cm at sowing, called SPD7 and considered as a control. The other management operated at a depth of 11cm, SPD11, considered as a physical improvement strategy, and the third was soil subsoiled 14 months ago, called minimum cultivation (CM), and this operation was carried out with an implement equipped with a disc. straw cutting, curved rod adjusted to 25cm depth and deroster roller.

The test was carried out in the IFRS Campus Sertão experiment area, in a soil classified as Red Nitisol, which has more than 60% clay, and which had white oat straw desiccated 30 days before sowing.

The seeder was configured for summer, with seven rows spaced 45cm apart, guillotine-type fertilizer furrowing rod, the popular little boot. The tractor to pull the implement had 95hp of nominal power, with assisted front-wheel drive (TDA) on. The engine speed in the test was kept constant at 1.600rpm, with the average speed resulting in 5,3km/h.

The slippage, fuel consumption and soybean productivity in Table 1, which demonstrates that the slippage in SPD11 was much higher than SPD7 and close to CM, which highlights the action of the high soil resistance on the breaking mechanisms at the depth above the commonly used (7cm every year). Comparing the SPD11 with the CM, there was not much difference, both being above the 12% considered maximum for 4RM (4x2TDA) tractors, a popular layout. The reduction in slippage is achieved by adding metallic weight, as the test tractor did not have one. 

Minimum tillage showed intermediate slippage between the three managements with 15,37% slippage, but much higher than the direct planting system at 7cm, which showed slippage of 4,88%, this because it presents a “lighter” soil, with less resistance, generating consumption slightly higher than sowing, at 11cm.

Analyzing as a whole, the direct planting system with guillotine at 11cm generates higher consumption and greater slippage, but when it comes to cost/benefit, diesel consumption was higher, but productivity also increased. Considering the soybean price of R$60,00/bag, SPD11 would result in R$279,54 more than SPD7, and R$405,13 more than CM, this is a very attractive income for the farmer, considering that the difference in diesel consumption does not reach R$ 3,00/h.

When compaction is present in the crop and becomes a problem in the development of planted crops, direct sowing with a guillotine or machete at a greater depth becomes one of the solutions to first resolve soil decompression. This generates a higher initial cost when compared to more superficial sowing, but it gradually improves the physical conditions of this soil, through the use of direct sowing at greater depth.

In addition to the greater productivity in SPD11 management, this directly influenced the accumulation of water in depth, that is, achieved by breaking the compacted layer, as can be seen in Figure 1, which demonstrates the behavior of soil water content after two days of rain, always measuring humidity for five consecutive days, thus detecting soil drying.

A fact observed in this research is the sudden loss of water through the subsoil (CM), which demonstrates the action of the implement on the structure; it reduces the density and strength of the soil, but affects its porosity, which results in this condition. SPD11, throughout the entire soybean development cycle, presented higher humidity, which must have been one of the factors that contributed to the increase in productivity.

David Peres da Rosa, Daelcio Vieira Spadotto, Diego Fincatto, Felipe Pesini, IFRS Sertão; Rodrigo Zeni, Fapeg

 

Article published in issue 165 of Cultivar Máquinas.