Ciclagem de nutrientes, características funcionais e crescimento de Bertholletia excelsa Bonpl. cultivada sob plantio puro submetido à calagem

Abstract

Technically, it is known that the application of dolomitic limestone, besides providing calcium (Ca) and magnesium (Mg), corrects the acidity of soils. On the other hand, it is also well established in the literature that the low pH values of Amazonian soils represent a limiting factor to the primary productivity of plants, either in natural systems or in planting systems. However, it is not known how liming can affect the internal cycle of nutrients in plantations and what possible impacts of this practice on the growth and the ecofunctional characteristics of individuals of Bertholletia excelsa when established in pure plantations (monoculture). This work was divided into two parts with complementary approaches to soil-plant interaction. The first part deals with the influence of liming on chemical attributes, nutritional status and nutrient cycling, with emphasis on the tree growth environment (Chapter 1), the second part was devoted to understanding the effects of liming on growth and functional characteristics of B. excelsa trees (Chapter 2). In order to do so, an experiment was carried out in pure plantation of B. excelsa at the age of 17, located in the area of Agricultural Company Aruanã, Itacoatiara, AM, with spacing of 2.5 x 1.5m between rows and individuals, respectively. The experimental design was a randomized complete block, with four treatments (Plantation submitted to two levels of liming, 0 and 2.0 t ha-1 of dolomitic limestone, treatments that were sampled in two different periods of precipitation (high and low) with 8 replicates. In the area of planting, soil fertility, litter production and decomposition, fine root production and nutrient concentration in mature leaves, litter and fine roots were analyzed. The application of dolomitic limestone reduced the presence of Al by about 90%, which was related to the increase of fine roots in the dry period and increased the availability of Ca and Mg in the soil, with reflexes in the relationship between Ca concentration and production However, liming did not affect the estimate of decomposition of this planting. In the subjects of B. excelsa were analyzed leaf area, gas exchange, chlorophyll a fluorescence, water use efficiency, light and nutrients, water potential and growth in diameter. Changes in soil chemical properties with the liming effect resulted in better functional performance for light capture, with emphasis on increases in ETR, ΦPSII, Vcmax and gs, as a consequence, higher photosynthetic rates were observed. Greater efficiency in the use of light and nutrients were also verified in the plants that received liming. In the low precipitation period, there was an increase in Vcmax and the photosynthetic rates of both treatments. At the same time, the treatment of the leaves of the control treatment showed reduction in the electron transport. The current annual increment in diameter was about 30% higher in plants that received liming. Therefore, there was an improvement in nutritional status in B. excelsa correlated with the beneficial effects of liming, the reduction of acidity resulted in greater soil volume exploration by the roots, allowing greater absorption of water and K during the period of less water availability. Ca and Mg optimized the transport of electrons that added to the improvement in the efficiency of light and nutrients use, were the factors that contributed the highest growth rates of B. excelsa. In view of the aforementioned statements, it can be concluded that liming conditioned improvements in the soil edaphic environment which induced a higher growth performance of the individuals of brazil nut tree plantations in the Amazon.