NITROGEN SOURCES EFFECTS ON THE MORPHOPHYSIOLOGY, PRODUCTION AND QUALITY OF COCOA (Theobroma cacao L.) CCN-51 IN THE SOUTHERN ECUADORIAN AMAZON

Background. In the new global economy, cocoa is an important crop. However, far too little attention has been paid to the nutritional aspects. On the other hand, nitrogen is the most important nutrient in crop production, and mineral nitrogen fertilizers are the most widely used by farmers. Improving the efficiency of nitrogen uptake and utilization could potentially increase crop yields and quality, as well as reduce nitrogen fertilization and environmental pollution. Objective. Therefore, the objective of this study was to evaluate the effect of three nitrogen sources on morphological characteristics, yield and quality of CCN-51 cocoa, and soil chemical characteristics in the Ecuadorian Amazon. Methodology. A randomized design was established with 4 treatments with the same N dose, but varying the source (amide: urea, calcium nitrate, NC, and ammonium sulfate, SA), plus a control without N application. The investigated variables are soil chemical characteristics, shoot growth, fruit morphology, seed chemical characteristics, production and yield estimates, and agronomic efficiency of the sources. Results. NC maintained soil pH at 5.29 points compared to SA and urea, which acidified at a higher rate (4.32 and 3.96), leading to an increase of N and a decrease Ca in the soil. SA increased the fat content in the cocoa seed (54.1 %), with a higher number of fruits per plant (16.7) and, therefore, a better yield (0.799 t/ha). Implications. These results provide basic information on the nitrogen source effects and cocoa nutrition to be considered for future research. Conclusion. The findings suggested that NC conserves soil pH better than the other sources. SA increases production and fat content, so it can be considered the most efficient.