Eficiência do uso da radiação em cultivos de milho em Alagoas

Abstract

R E S U M OO milho foi cultivado em três sistemas de manejo: i) cobertura de capim; ii) plástico na entrelinha e iii) cultivo tradicional (solo nu). Com o objetivo de determinar a eficiência do uso da radiação (EUR) mediram-se componentes da radiação solar (incidente e transmitida) em dossel de milho. A irradiação fotossintética (HF) incidente foi considerada equivalente a 44% da irradiação solar global. A HF transmitida (HF T ) foi estimada utilizando-se a lei de Beer para radiação aplicada a um dossel vegetal (HF T = HF exp(-k IAF)), com coeficiente de extinção da luz (k) ajustado de uma função exponencial, que relacionou a fração da HF T (HF T/ HF) e o índice de área foliar (IAF). A HF interceptada (HF I ) foi calculada por diferença (HF I = HF -HF T ). Estimou-se a EUR por meio de regressão linear, forçada a passar pela origem, entre o acúmulo de matéria seca (MS) e a HF I . O k foi de 0,628 com coeficiente de determinação de 0,88. A EUR das plantas da parcela coberta com plástico foi de 3,85 g de MS MJ -1 de HF I , que mostrou eficiência superior à dos demais tratamentos (solo nu 3,31 g MJ -1 e capim 3,58 g MJ -1); entretanto, esta conferiu menor IAF e, consequentemente, teve menos HF I acumulada, o que resultou na menor produção de MS. Radiation use efficiency in corn crop in Alagoas A B S T R A C TMaize was cultivated under three management systems: i) mulching (grass cover); ii) plastic cover in the inter rows and iii) traditional cultivation (bare soil). The components of the incident and transmitted solar radiation in a maize canopy were measured in order to determine the radiation use efficiency (RUE). The photosynthetic irradiation (HF) was considered as 44% of the solar global irradiation. The transmitted HF (HF T ) was estimated using Beer's law applied to a plant canopy (HF T = HF exp (-k LAI)), with the light extinction coefficient (k) by fitting an exponential function, which related the fraction of HF T (HF T /HF) and leaf area index (LAI). The intercepted HF (HF I ) was calculated by the difference (HF I = HF -HF T ). The RUE was estimated using a linear regression (forced to pass through the origin) between the dry matter accumulation (DM) and HF I . The k was 0.628 with the determination coefficient of 0.88. The plants RUE in plots covered with plastic was 3.85 g DM MJ -1 of HF I , showing a higher efficiency compared to other treatments (bare soil 3.31 g MJ -1 and grass 3.58 g MJ -1

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Research Article Productive performance and multivariate interrelations of open-pollinated and hybrid maize in Brazil

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