Influence of Tree Shade on the Growth and Chlorophyll Content of Arabica Coffee Plants Established in an Agroforestry System at Southern Manabí, Ecuador

The experiment was developed under production conditions on a farm in the Santa Ana city, south-central region of the province of Manabí, Ecuador, in a mountainous area of approximately 300 meters above sea level. Coffee (Coffea arabica, sp.) production is carried out in a context of peasant family agriculture, with an agroforestry system with coffee trees of the Sarchimor variety planted at 1.5 x 1.5 m, interspersed with tree species typical of the dry forest. The system involves manual weed control, without fertilization, irrigation, phytosanitary control, or shade regulation. In this scenario, and during an experimental period of 90 days (03/08/2022 - 26/10/2022), phenological variables of coffee trees maintained in a study area of 50 x 50 m at a high (S1: 51-70%) and low (S3: 1-30%) shade level was compared with those obtained at an intermediate shade level considered as standard (S2: 31-50%). The phenological variables related to vegetative development (Total Branches) of coffee plants showed higher values in S2 compared to S1 and S3. These results are related to the higher photosynthetic activity associated with the higher intensity of incident solar radiation, although the relationship is not linear. In our results, flowering and fruiting were not affected by the level of shade, nor were their precursors, such as nodes per productive branch and productive nodes per productive branch. On the other hand, coffee plants at full sun exposure in S1, without shade, decreased chlorophyll measured in SPAD units, as a possible compensation for the increase in photosynthetically active uptake in that condition.