Uso de algas e adubação fosfatada no crescimento de mudas de eucalipto

Abstract

The seaweed Ascophyllum nodosum is used as a plant stimulant due to its rich composition of macro and micronutrients, carbohydrates, amino acids, and growth promoters, thus improving seedling growth. To accelerate root development after transplanting, seedlings have been immersed in a solution containing monoammonium phosphate (MAP) fertilizer prior to planting. This fertilizer is recommended for use at the beginning of the growing season, when phosphorus availability is crucial for root system establishment in the field. Therefore, the objective of this study was to evaluate the effect of doses of seaweed extract (Ascophyllum nodosum), combined or not with monoammonium phosphate, on the initial growth of clonal eucalyptus seedlings. A randomized block design was used in a 2:6 factorial scheme, where six doses of A. nodosum (0; 10; 20; 30; 40 and 50 mL L-1) were tested, applied by immersion of the seedling root ball, in the presence or absence of MAP (15 g L-1), with four replicates. Each plot consisted of two eucalyptus seedlings (clone H13). At 90 days after transplanting, the following were measured: collar diameter (CD), total height (HT), root length (CR), relative chlorophyll index (IRC), leaf area (AF), dry mass of shoot (MSPA), root (MSR) and total (MST). For DC, the highest values were reached at doses of 32.8 mL L-1 associated with MAP and 17.1 mL L-1 in its absence. The highest HT was observed using the dose of 34.2 mL L-1 in association with MAP. The highest CRI values were obtained with 19.1 mL L-1 and 33 mL L-1, when associated or not with MAP, respectively. For MSPA, the highest values were achieved with doses of 29.7 mL L-1 and 26.0 mL L-1, in the presence or absence of MAP, respectively. While for MSR, the highest values were observed using 33.6 mL L-1and 43.8 mL L-1, in the presence or not of MAP, respectively. Thus, it can be concluded that the use of A. nodosum associated with phosphate fertilizer influences the initial growth of eucalyptus seedlings. The isolated use of the extract favored root length (CR), root dry mass (MSR) and total dry mass (MST), while the association with MAP enhanced the production of collar diameter (DC), total height (HT), number of leaves (NF), leaf area (AF), relative chlorophyll index (IRC) and dry mass of the aerial part (MSPA).