Correct nutrition in banana cultivation

Adequate management of plant material is of great importance for plant production, considering that soil organic matter stocks and their compartments are responsible for the supply of nutrients, soil aggregation and the flow of greenhouse gases between the surface land and the atmosphere, which influences the final product (Leite, 2003).

The main management factors that influence the content of Soil Organic Matter (SOM) are soil preparation and the succession and crop rotation systems used (Langdale et al, 1992; Bayer & Mielniczuk, 1997). In agricultural systems, the dynamics of SOM can be influenced not only by management through the selection of crops and forms of soil preparation, but also by the addition of chemical fertilizers and organic materials, which positively influence the biological processes of decomposition and mineralization. from MOS. The addition of organic materials is fundamental to soil quality, characterized by the gradual release of nutrients, which reduces processes such as leaching, fixation and volatilization, although it essentially depends on the rate of decomposition, controlled by temperature, humidity, texture and soil mineralogy. , in addition to the chemical composition of the organic material used (Zech et al.

Soil organic matter (SOM) is basically made up of carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus, with around 58% being C (carbon). The importance of organic matter in relation to the chemical, physical and biological characteristics of the soil is widely recognized. Its influence on soil characteristics and sensitivity to management practices determine that organic matter is considered one of the main parameters in evaluating soil quality (Doran & Parkin, 1994).

The contents of C (carbon) in organic forms (organic C) in the soil are directly linked to its interaction with the biosphere. Through the products of photosynthesis, much of the C enters the plant. The entry of C into the soil is mainly related to the input of residues from the aerial and root biomass of plants, release of root exudates, washing of soluble plant constituents by rainwater and transformation of these carbonate materials by soil macro- and microorganisms . All these processes are part of the biosphere (Novais et al.

Phosphorus is the macronutrient least absorbed by the banana plant, however, approximately 50% is exported by the fruits. This nutrient favors vegetative development and the root system (Borges & Oliveira, 2000). The low supply of phosphorus in the soils of the semi-arid region of Northeastern Brazil shows how important it is to study the behavior of this element in the soil, with a view to an adequate supply to plants, as such knowledge contributes to the establishment of an appropriate method for phosphate fertilizer , since the capacity of soils to adsorb phosphorus directly influences the response of plants to the application of fertilizers (Moreira et al, 2006). Correa et al (2004) believe that the reduced supply of phosphorus in this region is due both to the source material and to the strong interaction of phosphate with the soil, a phenomenon known as phosphorus adsorption, sorption or fixation.

The soil attributes most closely correlated with phosphorus uptake by plants are organic matter, available phosphorus and cation exchange capacity (Moreira et al, 2006). In this way, all management practices that aim to maintain or increase organic matter levels can result in benefits in the use of P by plants (Almeida et al.

In areas subject to conservationist soil management systems and phosphate fertilization, floods with high concentrations of P generally occur (Daniel et al, 1994). In these systems, where there are lower total losses of water and sediments due to water erosion than in conventional tillages, total P losses are generally lower, despite the higher concentration of this element on the soil surface in conservation tillages (Schick et al.

Experiment

To analyze whether or not there is a relationship between the amount of carbon and phosphorus in soil cultivated with bananas and native forest, work was carried out under climatic conditions in Chapada do Apodí, Limoeiro do Norte, Ceará.

According to Koppen's classification, Chapada do Apodi has a BSw'h' climate (hot semi-arid climate) and Galssen's classification 4aTh (hot tropical with severe drought) with average annual rainfall of 600mm to 700mm, and hyperxerophilic caatinga vegetation. The Farm's soil is classified as Eutrophic Cambisol (Embrapa, 2004).

Collections were carried out at two different times, the first was in January 2009, pre-rainy season, and the second in September, post-rainy season, as shown in Figure 1. Collection was carried out on a 2ha plot. , with four repetitions in the planting line and four more between the planting lines at depths of 0-5cm, 5-20cm and 20-40cm.

The chemical analyzes carried out were routine, following the Embrapa manual. Assimilable phosphorus was extracted by Mehlich-1 solution and organic carbon was extracted by potassium dichromate.

The averages were submitted to Minitab where the coefficient of correlationde Pearson. This coefficient measures the degree of correlation between metric scale elements. According to Correa (2003) these values ​​can be between -1 and 1. If the value is 1, it is a perfect positive correlation, one grows, the other too; if the correlation is -1, perfect negative correlation, while one increases, the other decreases; finally, if it is equal to 0, there is no correlation for this test, however, there may be for another test. More specifically, the same author reports correlation criteria that are:

Results

Figures 1 and 2 represent the results obtained in the test. Initially, a different behavior is noticed between the areas of study. According to Correa (2003), none of the indices obtained have a strong correlation, however, in some situations there is a medium correlation.

Figure 1 - Phosphorus/carbon correlation in the cultivated area. A: 0-5cm; B: 5-20cm; L:20-40cm

The C/P relationship in the cultivated area is shown in Figure 1. It can be seen that at a depth of 0-5cm the correlation between carbon and phosphorus was medium positive, that is, the more organic carbon is present in the soil, there is a tendency to have more assimilable phosphorus at this depth. In areas with greater deposition of organic residues in the soil and with a large number of roots, there is an increase in population and microbial biomass activity (Cattelan & Vidor, 1990). Microbial biomass also represents the central compartment of the C cycle in the soil and can function as a reserve compartment for nutrients, including organic P, or as a catalyst in the decomposition of organic C. In this way, the quantity and quality of plant residues deposited on the soil can considerably alter its microbial population. (Souza, 2008).

At a depth of 5cm-20cm the behavior was similar to the more superficial depth, positive correlation, with a correlation index between organic carbon and assimilable phosphorus, however, with values ​​lower than those in the 0cm-5cm layer, possibly due to the decrease in carbon at depth bottom.

At the last depth studied in the cultivated area, 20cm-40cm, the behavior was different from previous depths. The index was positive, however, almost neutral.

Analyzing Figure 2, it can be seen that the behavior of the C/P relationship between depths is different from the area with banana, with the correlation at depths 0-5cm and 20-40cm being negative, that is, the larger one element, the smaller the other. element and, at depth 5-20cm, it was practically neutral.

The different behavior in the areas studied can be attributed to the management adopted. In the native forest, no type of soil correction is carried out according to the plants' needs and no type of irrigation is carried out, with water being supplied only through rain, resulting in less deposition of material due to the scarcity of precipitation. plant on the soil surface. When the soil is decomposed, recovery hardly occurs, that is, with the decomposition of organic matter in soils with native caatinga forest, the plant material only recovers in the post-rain period. There is a particularity about phosphorus, as it is an element that is easy to “lose”, becoming immobilized, unavailable to the plant. One of the ways to store it is through organic matter in the soil, as there is no immediate replacement of carbon in the soil, When organic matter is decomposed, carbon decreases and phosphorus that was immobilized by SOM is released and becomes available to the plant, which explains the predominant negative correlation in the area with native forest.

In cultivated areas there is fertilization and soil correction, aimed at the plant's needs, adequate management of crop residues and correct irrigation, providing the plant with ideal conditions for production. In this way, there is a constant deposition of crop residues in the soil, always having an acceptable and high amount of organic carbon in the soil and consequently of assimilable phosphorus, since the SOM will always be decomposing. Hence the positive correlation in cultivated areas.

Figure 2 - Phosphorus/carbon correlation in native forest. A: 0-5cm; B: 5-20cm; L: 20-40cm

Conclusion

In the area cultivated with bananas, a positive correlation was obtained between carbon and phosphorus, that is, when one increases, the other will also increase.

Proper management of organic matter is necessary to maintain and store assimilable phosphorus in the soil, as it prevents this nutrient from binding to other elements and remaining unavailable to the plant indefinitely.

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