Care of the soil preparation system

Soil preparation directly interferes with its microbial activity and the development of the crops that will be planted, requiring the producer to take care so that the preparation system used impacts the physical properties of the soil as little as possible.

The soil preparation system directly influences its physical and biological properties, in addition to providing an environment for the establishment of crops. When choosing the type of soil preparation, elements such as the root development of the crop and environmental factors must be considered.

Soil microbiota can be used as an indicator of soil quality through microbial activity and biomass. According to Marchiori Junior and Melo (2000), soil preparation, as well as the establishment of new crops, imposes a new condition on the soil/microorganism system. By analyzing microbiological activity, it is possible to monitor whether the activity implemented in the soil is impacting or interfering with soil quality (Alves et al.

In basal respiration, microorganisms decompose the organic matter available in the soil and release carbon dioxide. Thus, by quantifying the CO₂ released by respiration can determine the microbial activity of the soil. A high microbial respiration rate may indicate high microbial activity when microorganisms are decomposing soil organic matter, but it may also indicate, in the long term, a disturbance such as the loss of organic carbon from the soil to the atmosphere (Cunha et al, 2011) . The analysis of soil basal respiration must be carried out in conjunction with other types of analysis, such as the metabolic quotient.

The metabolic quotient represents the respiration rate of microorganisms per unit of microbial biomass. This ratio, when it presents high values, indicates that microorganisms in the soil are degrading carbon from their own cells, indicating that the environment is under stress (Islam; Weil, 2000). A balanced soil/microorganism system releases less CO₂ by respiration and incorporates more carbon into your cells, consequently, the metabolic quotient decreases. To evaluate how different mechanized soil preparation systems can interfere with its microbiological activity depending on the soil's metabolic quotient, work was carried out in an experimental area at the Federal University of Viçosa, Minas Gerais. The soil is classified as dystrophic Red Yellow Argisol (Embrapa, 1999). To carry out the experiment, the following types of soil preparation were used as treatments: direct planting (PD), conventional planting (PC) and minimum cultivation (CM). Direct planting was established by one plowing and two harrowing, minimum cultivation by one pass with a scarifier and direct planting by one pass with the direct planting seeder-fertilizer.

To carry out the experiment, a Valtra Valmet tractor, model 800, with auxiliary front-wheel drive and 59kW of nominal power was used. In direct planting, a direct planting seeder-fertilizer was used with three planting rows, brand Seed-Max, model 2123. In conventional planting, a reversible disc plow with three 26' discs, brand Imaf, model UP 328, was used. and a 24 disc leveling harrow, in tandem, Baldan brand. In minimum cultivation, a five-rod spring scarifier, Massey Ferguson 226, was used.

The microbiological analyzes were carried out at the Organic Matter Laboratory, of the Soil Department of the Federal University of Viçosa. Collections were carried out in triplicate, in depth ranges from 0m to 0,10m and from 0,10m to 0,20m, using a Dutch auger, in three stages, before soil preparation, after preparation and 14 days after soil preparation. soil preparation. Carbon, microbial biomass, basal soil respiration and metabolic quotient were determined.

RESULTS OBTAINED IN TESTS

Direct planting was the only system that showed a statistical difference between depths, with the highest value of microbial biomass carbon being found at the most superficial depth (667,98mg/kg) and the lowest in the depth range of 10cm – 20cm ( 385,98mg/kg). Direct planting is a system that contributes to low soil mobilization, which promotes lower losses of nutrients, consequently favoring the accumulation of organic matter in the soil. Furthermore, as the depth increases, the carbon values ​​of the soil Microbial biomass decreased due to lower rates of biodegradable organic carbon at these depths.

The other soil preparation systems did not differ statistically between depths. In the depth range of 0cm to 10cm, conventional preparation presented a lower average microbial biomass carbon at this depth (443,93mg/kg).

Baseline breathing showed no statistical difference at 5% probability. Alves et al (2011) studied the influence of different systems on microbial activity and did not observe statistical differences in relation to basal soil respiration in the types of soil management, agricultural crop integration, native vegetation and native vegetation in recovery.

The increase in basal respiration values ​​after soil preparation is linked to the disturbances that the soil and microbial populations suffer.

The highest metabolic quotient means were found in direct planting, before soil preparation, with conventional planting being the type of preparation that presented the lowest qCO value.₂ (Table 1).

No statistical differences were found between before and after soil preparation, probably due to the fact that sample collections were carried out shortly after the implement passed through the soil.

After 14 days of soil preparation, the conventional tillage system obtained the highest average qCO₂ (7,37mg/kg/day). These results represent the specific respiration of soil microorganisms. When the metabolic quotient is high, microorganisms are oxidizing carbon from their cells, consequently, the soil/microorganism system is under stress.

Replacing vegetation accelerates the decomposition of plant residues and thus the value of the metabolic quotient increases. Thus explaining the increase in the metabolic quotient 14 days after soil preparation in the conventional planting system.

Conclusions

After obtaining the data presented, it is possible to conclude that the greatest microbiological interference was detected 14 days after soil preparation, in the conventional tillage system. Another important finding is that direct planting was the soil preparation system that least interfered with soil microbial activity.

Juliana Pinheiro Dadalto, Haroldo Carlos Fernandes, Mauri Martins Teixeira, Raquel Santana Milagres, Federal University of Viçosa

Article published in issue 149 of Cultivar Máquinas.