Adequacy of tractors to increase crop production

Evaluation shows behavior of the tractor and harrow set, soil disturbance acting with different ballast configurations.

The use of tractors and agricultural implements can contribute to increasing crop production and improving the yield of labor employed in the field, enabling rural producers to obtain a better financial return on their activity. On the other hand, when this equipment is used inappropriately, it can cause serious economic and environmental problems. Thus, the basic factors of suitability of the tractor to the implement and the conditions of the soil to be worked must be considered during the planning and execution of operations, minimizing losses in operational efficiency of the mechanized set. As well as the degradation of soil physical quality indicators.

The versatility of the tractor in relation to the operations it can perform in the field requires adjustment and/or adaptation for each operation, seeking to achieve greater efficiency in each of these. Among the main adjustments are work speed, power required by the implement, types, slip rate, tire inflation pressure and addition of ballast to the tractor structure.

In soil disturbance operations, it is essential to adapt the tractor/implement set to the conditions of the land to be worked. Above all, those related to soil physics, such as humidity at the time of disturbance, slope and vegetation cover in the area.

Considering the aspects listed above, work was carried out to adapt the tractor to the soil disturbance activity on the Barretense farm, located in the municipality of Altamira, Southwest of the state of Pará, in an area of ​​1,5 hectares formed by Yellow Oxisol of Texture Clay-Sandy Loam, with gentle relief, average slope of 4%, which had been fallow for around five years.

In the experiment, the operational performance of the agricultural tractor was evaluated under different ballasting conditions. The soil was disturbed, followed by analysis of the proposed treatments on some physical properties of the soil.

A 4x2 TDA agricultural tractor was used, with a power of 63kW @ 1.900rpm; equipped with 12.4-24 R1 front and 18.4-30 rear tires, inflated to 24 and 26 PSI, respectively. The turning implement used was an intermediate harrow measuring 1,5m in working width, equipped with 26” diameter discs, operating at a depth of 0,30m.

The treatments followed the following configuration: L1 = tractor without ballast; L2 = 75% liquid ballast and 100kg of metal ballast on the rear axle and 64kg of metal ballast on the front axle; L3 = 75% liquid ballast and 200kg of metal ballast on the rear axle and 128kg of metal weights on the front axle; L4 = 75% liquid ballast and 300kg of metal weights on the rear axle and 192kg of metal ballast on the front axle.

The slip index, operating efficiency and fuel consumption were measured and the physical quality indicators, density, macroporosity and microporosity of the soil were determined.

PERFORMANCE ON THE FIELD

Table 1 presents the operational performance results of the tractor and harrow set, followed by the results of the soil physical quality indicators, based on the proposed ballasting arrangements.

Based on literature reference values, operational efficiency results were well below the minimum rate of 70%. This behavior can be explained based on the following hypotheses: small working width of the implement or shape of the field, both implying a greater number of headland maneuvers. Or, even, due to the lack of prior planning of the operation, which is directly related to the level of technical knowledge of the team that will coordinate and execute it. 

Regarding the slip index (I.P) results (Table 1), except in L1, the other treatments obtained results below the range between 8 and 12%, considered adequate for the configuration of the tractor used in this test. According to parameters in Table 2, the behavior of I.P in treatments L2 and L3, below 8%, is directly related to excess ballast. Condition that in the routine operation of a property may cause excessive fuel consumption, which in this test (Table 1), is within the average for operation under the conditions carried out or even premature wear of the wheelsets, overload and damage to some bearings and axles of the transmission system.

Both the lack and excess of ballast are harmful from a mechanical, economic and soil conservation point of view. Therefore, the same ballast condition is not universal for all operations. Therefore, it is necessary to adopt technical parameters and adjust the tractor to the conditions of the proposed operation.

As a form of guidance, when ballasting, the distribution of the ballast over the machine structure must be considered. The type of tractor and the way the implement is attached to it must be considered, following the parameters contained in Table 3.

Table 5 contains the results of the evaluation of the ballast configurations proposed in this work, focusing on some indicators of soil physical quality. This result, according to the literature, is close to the maximum acceptable limit, which guarantees the root development of most crops of economic value.

Soil density is an indicator of the physical quality of the soil, which indicates how much soil mass, considering the pore spaces, is contained in a given volume. Maximum acceptable values ​​can vary from 1,60g/cm³ at 1,80g/cm³, for clayey and sandy, respectively.

In this work, with the configurations used in just one agricultural cycle, the values ​​obtained do not represent an impediment to the root development of crops. However, in research under similar conditions, conducted in bean producing areas in the Northeast of Pará, under Yellow Oxisol, medium texture, it was found that, after five years, there was an increase in soil density and the formation of a compacted layer below the 30cm deep, directly influencing the development of the crop's root system.

Regarding macroporosity and microporosity (Table 5), the results were similar to those found in the ungraded soil (control), varying from 0,30m/m³ at 0,34m/m³ and 0,17m/m³ at 0,19m/m³, macroporosity and microporosity, respectively. These results are well above the minimum condition of 0,10m/m³ for macroporosity, as described in numerous studies that address issues inherent to soil/machine interaction.

Finally, to carry out mechanized agricultural operations in the most economical way possible, it is recommended that the producer, together with technical assistants from the private or public sector, before carrying out the operations, jointly evaluate and plan them. Considering, above all, the issues inherent to operational quality control, measuring slippage, monitoring and periodic adjustment of tire inflation pressure, in accordance with the recommendations of the equipment manufacturers, and correctly adjusting the implements.

Weight/power ratio

A parameter that must be considered when adapting tractors is the weight/power ratio, information that indicates how many kilograms of each power unit (horsepower or kilowatt) will be responsible for displacing during tractor activity. This information must be obtained after ballasting the tractor, with values ​​that should vary between 50kg/c.v and 60kg/c.v, according to Table 4, considering the characteristics of the operation to be carried out.

Light operation: (low traction requirement). For example: light harrowing, spraying, mowing, etc. 

Average operation: (intermediate traction requirement). Examples include intermediate harrowing, sowing, planting, etc.

Heavy Operation: (heavy traction requirement). It is the one that demands the most from the tractor, such as sublogging, scarification, destumping, etc.

Ronilson de Souza Santos, FEA/UFPA-Altamira; Jairo de Souza Neres, Semat-Altamira Environmental Analyst; Jefferson Sandi

Kleber Pereiraanças, FCA-Unesp/Botucatu-SP

Article published in issue 163 of Cultivar Máquinas.