Coeficiente de extinção da luz e eficiência do uso da radiação na cultura da soja em Rio Largo - AL

Abstract

The objective of this work was to determine the light extinction coefficient and the efficiency of the use of radiation in the soybean crop in the municipality of Rio Largo in the state of Alagoas. The state of Alagoas is also a soybean producer, but it differs from other regions in that its crop is produced in the autumn/winter period. For its cultivation it is necessary to understand its biotic and abiotic factors that can influence productivity. The research was carried out at the Campus of Engineering and Agricultural Sciences (CECA) of the Federal University of Alagoas (UFAL). Glycine max (L.) Merril and its Monsoy cultivars: M6210, M6410, M8349, AS3730, Bmx-Potência and BRS-9383. During the cultivation period, some equipment was used, such as the pyranometer with the purpose of measuring global solar irradiance (Rg), the Quantum Sensor/RFA, for measuring transmitted photosynthetically active irradiance and the Datalogger CR1000 Campbell Scientific with the purpose of recording each five minutes the measurement of transmitted radiation. The data obtained were tabulated in the Excel 2013 office package program. To obtain the light extinction coefficient, it was necessary to calculate the Leaf Area Index (LAI). To obtain the LAI, it was necessary to determine the leaf area (AF) using a manual method. There are several PA evaluation methods that can be direct, indirect, destructive and non-destructive. In this work, the methodology was configured as direct and non-destructive because the measurement took place in the field without removing the plant structures. The calculation of the radiation use efficiency (EUR) was obtained from the relationship between the plant dry mass (DM) of the aerial part and the photosynthetically active irradiation intercepted (RFAint) accumulated during the cultivation, which was determined through linear regression. DM was determined after the process of drying the plant structures in a forced ventilation oven at a temperature of 65 oC for 72 hours. The light extinction coefficient was determined to be 0.77 and the maximum LAI value obtained was 6.34. The AS3730 variety had the lowest LAI value, however, it was the one with the most EUR. After analyzing and comparing the studies, it was possible to verify some factors that influenced the different results found in the literature. Palavras-chaves: Glycine max (L.) Merrill; Leaf Area Index; cultivars.