Effects of calcium particle films and natural shading on ecophysiological parameters of conilon coffee

Abstract

Conilon coffee (Coffea canephora Pierre ex A. Froehner) is an important agricultural crop in Brazil due to its high economic value. This plant species is sensitive to the effects of high levels of solar radiation and temperature, which could limit its wide cultivation in the Brazilian Northeast region. However, management practices such as shading could increase the feasibility of its cultivation. This study aimed to evaluate the effects of different shading methods and the use of calcium particle films on the conilon coffee ecophysiological parameters in the coastal flatland the State of Sergipe, Brazil. The field experiment was carried out as randomized block design with four treatments: i) Natural shading (intercropping coffee and banana plants), ii) Artificial shading with 10% w/v CaCO3 particle films; iii) Artificial shading with 20% w/v CaO particle films; and iv) and control (without shading), and four replicates. Measurements were performed 7, 21 and 35 days after film application at 9:00 h and 12:00 h. Individual parameters, gas exchange efficiency, chlorophyll a fluorescence and maintenance of film coverage on leaves were evaluated. Artificial shading with particle films promoted greater physiological stability of the coffee plants during diurnal meteorological oscillations as compared to the control, resulting in higher rates of liquid photosynthesis (A), better control on stomatal conductance (gs) and transpiration (E). Improvement was also observed in the plant water use efficiency (WUE and IWUE) and in the reduction of leaf temperature. Calcium particle films were more efficient in providing protection to the photosystems and improving photochemical efficiency and energy conversion for photophosphorylation than natural shading. However, the results were more pronounced at 21 days after film application and more persistent for treatment with 20% CaO film. Therefore, calcium particle films are useful tools to alleviate coffee plants stress under adverse climate conditions.