OS SOLOS-SEDIMENTOS DA REGIÃO CENTRAL DO ESTADO DO ACRE (FEIJÓ-TARAUACÁ), SUA APTIDÃO AO CULTIVO DE ABACAXI E A RELAÇÃO COM OS SEDIMENTOS FLUVIAIS ATUAIS
Authors:   pós-graduação do PPGG/UFPA, Belém, Pará, Pereira Patricia , Costa Marcondes ,   Universidade Federal do Pará, Belém,Pará, Brazil
Published: February 2025

Acre state is located in the southwest of Brazilian Amazonia. More than 80% of its territory is covered by rock of “Solimões Formation” which is predominantly constituted of fossiliferous silty-argillaceous rocks, intercalated with sandstones, and its sources is the lands of “butTresses andeans”. In Acre state there are spots of soil of good fertility, mainly in the central area (Feijó-Tarauacá). However, it is well noted that some cultivars have exaggerated development in size, such as banana, watermelon and mainly pineapple “The Giant of Tarauacá”, that without artificial fertilizer neither manure, occurring only in a few specific places in this central region, that insinuating a great fertilization region, because of the big size and weighting up to 33 pounds. This natural fertilization is also recognized in the beach sediments (point bar) of the rivers that drain the state of Acre. The objective of this study is the soil fertilization in the region Feijó-Tarauacá, the origins and relations with sediments from the source sub-Andean, carried and deposited via fluvial system along the time of the development of the “Solimões Formation” and its reworking. In the establishment of this study, there was as election of eighteen points of sampling in the soil, picking-up samples in two levels of profundity (0-10 and 10-20cm), eight of this points of sampling are in cultivated areas of “The Giant of Tarauacá” located in the Cologne Treze de Maio, seven points along the road BR-364 between Feijó and Tarauacá, two points in an area of “primary” forest near to Tarauacá and one point in a cultivated area of “purple pineapple” near to Feijó in the Cologne Três Corações, and one pineapple of “The Giant of Tarauacá” in the Cologne Treze de Maio. In the fluvial system it was samples waters, at the same time suspension and bottom sediments in nine stations along of the micro-basins of Tarauacá and Envira rivers, limited to the region of Tarauacá-Feijó-Envira. The soil analyze consists of a granulometric separation (sands, silts and clays); mineral identification by x-ray diffraction (XRD); chemical analysis (major and trace elements) and nutrients (P, Mg, Ca, K, Na, Fe, Mn, Cu e Zn), as well as Al available and organic matter. The pineapple sample “The Giant of Tarauacá” was submitted to a analyze of Ca, Mg, P, Na, K, Fe, Mn, Cu, Zn and Hg. The physical-chemical parameters in situ (pH, temperature, STS, TDS, turbid, transparency) and chemical compound chlorate, sulfate, phosphate, ammonia, nitrite, and nitrate were measured. The contents of metal dissolved in water and metal adsorbed in suspension sediment were determined by ICP-MS. The bottom sediments were submitted to analyze of nutrients. The result reports shows that the soils in the region of Feijó-Tarauacá are shallowly development of where the horizons are easily confused to sediments of source rocks. The predominance is silt-clays, and the variety allows distinguishing three groups of soils: 1- silt-clay with sands between 4 – 20%; 2- sand-silt-clay; and 3- silt-clays with sands until 4%. All soils in Cologne Treze de Maio, where the pineapple “The Giant of Tarauacá” are cultivated, corresponds to the soil group #1. The mineralogy dominant in the soil-sediments studied is represented by smectite (33 to 61%) and quartz (21 to 34%) followed by illite, kaolinite, a few albite and microcline and calcite sometimes. The soils of Cologne Treze de Maio have the highest contents of smectite and quartz. The chemical analysis shows that these soils are mainly constituted of SiO2, Al2O3, and also of Fe2O3, and other like K2O3, CaO, and MgO, compatible with the mineralogy. The high level of SiO2 makes a relation of the countenance of quartz, and when allied to the Al2O3 also reflects the abundance of clays-minerals. The soils of Cologne Treze de Maio have high contents richer in MnO, CaO and P2O5. The normalization with the Earth upper-crust revels that soil-sediments in the region Frejó-Tarauacá are poor of MgO, CaO, Na2O, K2O e P2O5; enriched of TiO2; equivalents of SiO2, Al2O3 and Fe2O3; and are also enriched of MnO only in the soils sampled in the Cologne Treze de Maio. When normalized with the post-Achaean Australian Shales (PAAS) the soil-sediments are equivalents of CaO and SiO2 and maintain enriched of MnO in the samples of soil from the Cologne Treze de Maio, that are poor of other elements. When compared with soil of the central region of the Amazonia, the soil- sediments of the region Feijó-Tarauacá are enriched of MgO, CaO, Na2O, K2O, Fe2O3 and MnO and similar with other oxides. The chemical index of alteration (CIA) indicates soil-sediments of low chemical alteration, a slightly superior than beach sediments from Acre and from the rivers Marañon-Solimões but compared to the CIA of smectites probably related to the high concentrations of this clay-mineral on the matter studied. The fertilization analyzes demonstrate high concentration of K, Ca, Mg, Fe, Mn and Zn, medium and high contents of P and of organic matter, showing that these soil-sediments has high cation exchange capacity (CEC), saturation of base above of 75% and low saturation by Al. However, the soils of the Cologne Treze de Maio highlight from others because of a fertilization standard higher than other soils studied, even after successive plantations of corn, rice, and giant pineapple. This high standard of fertility suggests that despite evidenced fertility spots in the soils in the region of Acre, especially in the soils of Feijó-Tarauacá, in fact in this area, inserted in the largest spots, there are “micro-spots” of soils with more fertility. These micro-spots are of empiric knowledge of few agriculturists that knows how to distinguish one area from other of less degree of fertility, cultivating banana, corn, rice, bean, and the exuberant pineapples “The Giant of Tarauacá”. The origin of fertility of the region Feijó-Tarauacá is intrinsic relational to the geological distinct characteristics in the region, that probably is relate to the oscillations in the process of deposition along the time of establishment of Solimões Formation, mainly with a rich mineralogy in clay-mineral 2:1 like the smectites, more abundant in the soils of giant pineapple plantation, been the main responsible for the high index of CEC of the soils. The giant pineapple sampled analyzed weighted 4 times more than a commercial pineapple. The pulp pH is 4.1. Its nutritional content shows high contents of chemical elements in all parts of the pineapple analyzed (peel, pulp, center), in the peel concentrates the most elements, found in the following proportional order K> P> Ca> Mg> Mn> Na> Fe > Zn >Cu. When comparing it with the pineapples consumed in Colombia and in Mexico, it shows that only the contents of Na and Mg of “The Giant of Tarauacá” meets the average of other pineapples, other elements are found in a great contents, and the highlight is the values of P that is 22 times highest than one in the pineapple from Colombia, and the Mn element which is 18 times highest than one in the pineapple from Mexico. The average contents of Hg (55 ppb) in the soils analyzed is below of the worldwide meaning, however it is double of the average values found in the beach sediments from the rivers Envira, Tarauacá and Juruá, while the values of Hg (6 to 16 ppb) in the giant pineapple is like the one found in the lives and berries of bean cultivated in these beaches. The high contents of Mn available in the soils and in the giant pineapple insinuates that contributes together with K and P elements, for the exaggerated growth of cultivars planted in the soils of micro-spots. High contents of nutrients of soils analyzed also were observed in the rivers that drain this region. The bottom sediments from the Envira River are richer in nutrients than one in Tarauacá River, insinuating that soils derived from Solimões Formation drained by the Envira River seems to be richer in nutrients. The fluvial waters in the season of high-water (winter) enriched itself of organic matter in suspension until 8 times more than in summer, the inverse happen with the total solid solute (TDS), that in the dryness season it is 3 times more (TDS) than in the period of high-water. The contents of metals available in the suspension sediments are in the following decreasing order Fe, Al, Mg, Mn, Na, Ti, Ba, Zn, Sr, Cu, B, Li, Sn, Pb, Rb, etc, (Ca e K not analyzed). The smallest meanings of these elements are found mainly in the Jurupari River, affluent of Envira River, except Se, Sn, Rb, Sb, and Cs. These suspension sediments are relative rich of nutrients explaining the mineralogy of fluvial waters and in conjuncts the fertility in the point bar, thus shows that the sediments of Solimões Formation in fact are the mainly source of fertility of the actual bodies in the point bar and in the flood plain of Acre state, also for the sediments of older terrains, where pineapple “The Giant of Tarauacá” is cultivated, among other cultivars.