Dinâmica de potássio no sistema solo-planta em cana-soca sob condições edafoclimáticas de cerrado
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2018-11-26
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Universidade Federal de Goiás
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The sugarcane crop stands out as the most used renewable energy source in Brazil presenting high yields and good adaptation to Brazilian soil and climate conditions. Due to the high biomass production, the nutrient uptake from soil is also high. Among them, Potassium (K) has important functions related to the physiological processes in plant tissues, being the most extracted nutrient by sugarcane crop. Due to low natural K contents in tropical soils, it is necessary to complement it with fertilizer applications in order to meet the crop demands and achieve high yields. Therefore, the objective of this study was to evaluate the dynamics of potassium in the soil-plant system during the first sugarcane ratoon period as a function of potassium nutrition under the Cerrado of Goias edaphoclimatic conditions. The experiment was conducted at the Goiasa Plant, in Bom Jesus de Goiás, GO, during the 2017/18 season, in a dystrophic RED LATOSOL, clayey texture (440 g clay kg-1), using the variety IAC 91-1099. Treatments consisted of five K2O rates, (0 (control), 50, 100, 150 and 200 kg K2O ha-1), with five replicates. We evaluated: the climatic water balance for the area; the soil (up to 0.8 m) and plant K content (leaf and stem); biometric variables (plant height, stem diameter, number of tillers and leaf area); physiological variables (photosynthesis, transpiration, stomatal conductance, internal CO2 concentration and relative chlorophyll index); stem yield and technological quality. Also, decomposition rate and K release by the sugarcane straw as well as K balance in the soil-plant system were evaluated. Data were submitted to analysis of variance, and polynomial regression analysis was performed for the significant variables. The increase in Potassium fertilizer rate intensified the movement of the K+ ion in soil to the depth of 0.80 m with a 55% increase in K content between the control treatment and the 200 kg K2O ha-1 rate, in an evaluation performed at 180 days after sprouting, and a 20% increase at the end of the experiment. Sugarcane straw provided 79.25 kg K ha-1 to the soil, requiring approximately 70 days so 50% of this total would be available. There was a reduction of about 49.03% in straw production over 300 days, requiring 345 days so half of this material would decompose. K balance in the soil-plant system, for the annual application of 150 kg K2O ha-1 resulted in soil K balance of 133.22 kg ha-1 year-1, being the treatment that most contributed to increase soil K contents. Although the K rates in this experiment did not influence sugarcane growth, they presented a significant effect on physiological variables such as transpiration and photosynthesis. The higher K input in the soil as a function of the treatments did not result in differences in stem yield, however, when thinking about the sustainability of the productive system for sugarcane crops, the 150 kg K2O ha-1 rate increased soil K contents.
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ANDRADE, A. F. Dinâmica de potássio no sistema solo-planta em cana-soca sob condições edafoclimáticas de cerrado. 2018. 87 f. Dissertação (Mestrado em Agronomia) - Universidade Federal de Goiás, Goiânia, 2018.