Spacing and Plant Density in the Yield Components, Nutritional Status, and Soil Fertility of Guarana Varieties Grown in Humid Tropical Amazon

Abstract

In agriculture there is a tendency to reduce spacing between plant rows, both for perennial and annual plants. Yield gains have been associated with the use of this technique. However, in the case of perennial plants, this technique was found to reduce productivity in older orchards because of the greater competition between plants caused by the increased volume of the crown and root system, resulting in lower photosynthetic efficiency, increased infestation with fungal diseases, and greater competition in nutrient uptake. In addition to yield, efficient management should consider soil fertility, nutritional status, and the growth of the guarana variety. The present study aimed to assess the effects of spacing and plant density on grain yield, soil fertility, and nutritional status of two guarana varieties (BRS Amazonas and BRS Maués). The plant density studied were 625 (4 m × 4 m), 833 (4 m × 3 m), 1,111 (3 m × 3 m), 1,666 (3 m × 2 m), 2,500 (2 m × 2 m), and 5,000 (2 m × 1 m) plants per hectare distributed in randomized block design with three replicates. The high plant density has significantly increased grain yield in the guarana varieties, with changes in launch number, trunk diameter, and crown diameter. Regarding macronutrients, in the average of the varieties, the mean foliar concentration had the following sequence: nitrogen (N) > potassium (K) > calcium (Ca) > phosphorus (P) > sulfur (S) > magnesium (Mg), whereas for micronutrients it was manganese (Mn) > iron (Fe) > boron (B) > zinc (Zn) > copper (Cu). The differences in the foliar concentrations of the varieties and in soil fertility are important tools for the selection of materials with better capacity of uptake and/or translocation of nutrients, resulting in greater grain yield.