A Research on the Fruitfulness of the Reddish-Yellow Acrisol in Serra da Meruoca, Ceará, Brazil

Agriculture, to be successful, needs soil to have a potential nutrient composition that is relevant to plants. Therefore, it is necessary to identify the conditions for farming through soil analysis. Thus, this manuscript makes it possible to analyze the fruitfulness of two samples of the reddish-yellow acrisol—one with vegetation and the other without it—from Serra da Meruoca, a humid area in the semi-arid region of Ceará. Concerning the material and method, the stages were literature review, researches on cartographic bases, fieldwork, and data collection and their analysis in the laboratory. The results show that the area of acrisol with vegetation favors the practice of agriculture, a fact observed because of carbon (C), which is indicative of soil with intense cultivation, as well as calcium (Ca), which appeared in a significant level, typical of arable land. In the second sample, the acrisol without vegetation, the parameters that impose restrictions on agriculture are the pH, which contains exchangeable aluminum, indicative of high acidity that leads to a leaching process. Also, the aluminum (Al) at a low level reflected the need for dolomitic quicklime, for the amendment of a deficient soil. Therefore, studies on its fruitfulness are essential for farmers to reap the rewards according to the results obtained and analyzed.

The fourth phase was the laboratory sample preparation. The material collected consisted of 1kg of each sample taken from the arable layer (60 cm) and then taken to the soil laboratory from the Instituto Federal de Educação, Ciência e Tecnologia (Federal Institute of Education, Science, and Technology of Ceará, IFCE) in Sobral. The chemical analysis (fertility) took place according to the recommendations of the soil analysis method handbook, proposed by (EMBRAPA, 2017). Therefore, the two areas selected for the sample collection are the areas I and II, respectively. Thus, the distribution of those areas happened as follow:

Area II-(Reddish-yellow acrisol without vegetation)
Its coordinates are 03° 32 825' South latitude and 040° 27.014" West longitude, and its altitude is 670m. Arruda (2014) highlights that the preparation method of a sample is essential for the rational, sustainable, and economic use of soils. It happens through a proper recommendation of fertilizer and corrective products, which will be responsible for a considerable part of the productivity of a crop. Besides, Rocha (2016) reveals that before the collection, it is necessary to establish the objectives because the sampling is different when it is the first time in an area.

The chemical parameters (fertility) happened this way:
The pH measuring happened through a combined electrode immersed in soil suspension, liquid (water, KCl, or CaCl 2 ) in ratio 1:2.5. The electrical conductivity of this solution was approximately 2.3 mS/cm. Regarding interchangeable cations (Ca 2+ , Mg 2+ , Na + ), the extracting solution employed-KCl 1 mol/L method at pH 7-demonstrated calcium and magnesium by standardized EDTA. Through the photometers, the calibration read the levels of sodium and potassium. The hydrogen and aluminum, extracted and calculated in samples with pH below 7.0, used calcium acetate 0.5 mol/L.
Concerning carbon, its generation took place through the oxidation of soil organic matter, oxidized with a mixture of potassium dichromate, involving concentrated sulphuric acid. In these conditions, the collection happened through the Mehlich-1 solution in the flame photometer. The T value, which is the total of negative charges that the soil can adsorb, was determined by the sum of the S value and the potential acidity (H + + Al 3+ ). The acquisition of the V or V% value, which indicates the proportion of the CTC of the soil by filling itself with exchangeable bases, was in the ratio of the sum of the base and the capacity of the cation exchanges with pH 7.0, being expressed by the formula V=S/Tx100 (EMBRAPA, 2017).

Results and Discussion
Based on the literature review, fieldwork, soil sample collection, and data analysis, it was possible to analyze the fruitfulness of the reddish-yellow acrisol with the presence of vegetation and without it. The chemical parameters analyzed are as follows carbon, organic matter, pH, phosphorus, calcium, magnesium, sodium, aluminum. Below is the table with the results extracted in the laboratory.
It is important to emphasize that it is relevant to describe each chemical element (fertility) presenting its characteristics for soil analysis, namely: Soil organic matter (SOM) is commonly heterogeneous and consists of animals and plants remain, that is, residues in a specific environment (Fontana, 2017). Thus, organic matter is an essential source of nutrients for plants. According to Van Raij and Battaglia (1991, p. 82), the organic matter present in the soil reflects the balance between the losses and gains that exist in each case, being factors influencing the vegetation coverage, soil texture, management, drainage, acidity, and other elements. It is worth remembering that the organic matter is heterogeneous and composed of animal remains.
Soils, when placed for agricultural use, end up suffering a decrease in organic matter content, reaching the lowest content. It portrays new conditions for the balance of oxidized organic matter and the one added to the system by the remains of decomposed organics (Van Raij & Battaglia, 1991, p. 82).
Besides influencing the survival and production of plants, pH also impacts the physical, chemical, and biological components. In the soil, it points to the active acidity, which is common, and there is the suspension of the soil in water (Van Raij & Bataglia, 1991, p. 87). Mehlich (1948) highlights that the pH is one of the simplest measures made in the soil, however, very important, reflecting in a set of complexity focused on the reactions in the system involving soil and solution. It is useful when related to the properties that compose the soil.
Moreira (2006, p. 7) defines the phosphorus adsorption as the phenomenon in which soluble forms become weaker or even insoluble when they come into contact with the solid phase of the soil. From a different point of view, the phosphorus forms compounds that present low solubility in soils, linked in various combinations to chemical elements such as aluminum, iron, organic matter, among others (Van Raij & Bataglia, 1991, p. 84).
Potassium (K) is one of the elements knows as soil base along with magnesium and sodium. The reason for this is because it has an alkaline content (Van Raij & Bataglia, 1991, p. 85). Furthermore, Diniz (2001) stresses that the amount of water in the soil becomes essential for the availability of potassium for the roots, an element taken directly from the land. It means that the water interferes with the diffusion of potassium and controls Ca 2+ as well as Mg 2+ .
Calcium (Ca) provides the reduction of acidity in the soil and also influences the improvement of plant roots since plants with high calcium contents are resistant to the toxicity of these elements (Aquino, 2000, p. 135). Magnesium (Mg) is a cationic and secondary macronutrient that has relevance to the development of plants.
Magnesium (M) is present in both exchangeable and non-exchangeable ways, and in soil solution, found many times in younger soils, in primary minerals (Ca 2+ and Mg 2+ ). Thus, according to Aquino (2000), magnesium is part of chlorophyll and is an enzymatic activator, that is, more than half of the magnesium is fixed in the leaves, thus forming chlorophyll.
Sodium (Na) is beneficial when it comes to growth. So, its benefits are significant where there are problems filling potassium (Aquino, 2000). Aluminum (Al) is a constituent of the clay particles of the soil and in the solution, but it can cause a series of problems concerning the development of the plants when absorbed.
Miguel (2010) points out that one of the symptoms presented by aluminum in plant growth is the root reduction, considered sensitive, thus occurring the difficulty for plants to absorb water, as well as its nutrients deep in their surface rooting.
Therefore, H+Al is the hydrogen content associated with aluminum in the soil, whose function is to determine the potential acidity, as well as the exchangeable acidity, where the hydrogen content or non-exchangeable acidity is the difference between H+Al and Al³ + . The neutral solution of calcium acetate absorbs the potential acidity (Van Raij & Bataglia, 1991, p. 86).
However, the sum of bases (SB) is the representation of the summation of the interchangeable cations contents, except H + and Al³ + (SB = Ca² + + Mg² + + K + ) (EMBRAPA, 2017). Base saturation is a more viable indicator for general indications of soil fertility, used as an additive in soil nomenclature (EMBRAPA, 2017).
The cation exchange capacity (CEC) is the number of negative charges a soil has. So, if much of the CEC has essential cations, such as Ca² + , Mg² + and K + , then the soil is adequate for plant nutrition (Roquin, 2010).
Base saturation (V%) is for the recommendations of the need for liming, as well as fertilizers. They improve the fertility of the soil so that the plants can find the nutrients they need to achieve high yields (Roquin, 2010).
The exchangeable sodium percentage (ESP) is a relevant parameter in determining the ability of a soil to expand and contract. In these conditions, it demonstrates the ratio of sodium to other adsorbed cations.
The percentage of saturation per aluminum (m%) demonstrates the fraction or even the percentage of the effective CEC of the interchangeable acidity or Al. Thus, Lopes and Guilherme (2004, p. 10) point out that the more acid the soil, the higher can be the exchangeable aluminum content, the higher the saturation percentage