Bertholletia excelsa saplings respond to seasonal precipitation variations by changing metabolism when fertilized with NPK in different planting systems

Fertilization with nitrogen (N), phosphorus (P), and potassium (K) can increase plant growth. How seasonal variations in water availability can affect species interactions and fertilization effectiveness is still uncertain. We investigated the effects of liming and nutrient fertilization and planting systems (monospecific and mixed planting), during low levels of precipitation on the synthesis of organic compounds such as sugars, starch, proline, total phenols, amino acids and proteins in young Brazil nut tree (B. excelsa) plants cultivated in degraded areas in Central Amazon. The pure planting + NPK treatment significantly increase in fructose leaf contents in 2021, while in 2022, the mixed planting + NPK treatment were greater leaf glucose and fructose contents. In addition, over two years, significant differences in sucrose and starch contents were observed between treatments. Concerning the seasons, sugars, glucose, fructose, and amino acids showed higher contents in the dry period during the two years of study. PCA revealed was a clear distinction between plants in the rainy and dry periods, which evidences the remarkable plasticity of the metabolism of B. excelsa. Our findings suggest that high levels of soluble sugars, mainly glucose, and amino acids would improve its ability to osmoregulate and osmoprotect against water changes allowing greater adaptability. It was also observed that pure planting, with the addition of NPK, increased the height and diameter of the plants. Our research contributes to understanding carbon and nitrogen metabolism in support of the growth of B. excelsa planted in different planting systems during the low precipitation period in the Amazon, aiming at improving sustainable forestry plantations for Brazil's nut trees.