Response to applying kaolinite particles in coffee variety Cenicafé 1 seedlings during the nursery stage

The application of kaolinite has been shown to be a viable strategy for protecting crops against excessive solar radiation and high temperatures. In coffee, this could occur during the nursery stage when the seedlings grow directly in full sun. The objective of the present study was to evaluate the effects of kaolinite particles when applied to coffee seedlings in full sun during the nursery stage and those of seedlings with no kaolinite applied grown directly in full sun and in shade. Two Coffea arabica L. variety Cenicafé 1 nurseries were established, and the following treatments were stablished: 1) K30: full sun with kaolinite at 30 g/L; 2) K60: full sun with kaolinite at 60 g/L; 3) SUN: full sun without kaolinite; and 4) SHADE: under a sunscreen with 60 % shade without kaolinite. The studied variables were dry mass, dry mass distribution, leaf characteristics, leaf physiological parameters, albedo, leaf temperature, and seedling mortality. Except for mortality, the variables were analyzed using a simple factorial design in generalized complete blocks and randomly using the Welch-James statistical test with bootstrapping. Mortality was assessed using a logistic binary response model with a X² test. The results showed that in comparison to the SHADE treatment, the SUN and K60 treatments resulted in more dry mass; in turn, the K60 treatment resulted in better RDM/TLA. In comparison to the SHADE treatment, both the K30 and K60 treatments resulted in greater increases in net photosynthesis rates, and in comparison, to the SUN treatment, these treatments also resulted in a greater increase in stomatal conductance, although only when the leaf abaxial temperature was greater than 30 °C. This result may have occurred based on the greater light reflection and the lower leaf temperatures obtained with kaolinite, in the K60 treatment. However, the seedlings that grew in full sun with and without kaolinite died three times more often than the seedlings in the shade. The previous suggests that it is not convenient to establish nurseries in full sun, with or without kaolinite, despite the physiological advantages and tolerance to high temperatures at the plant level.