Initial growth of Brachiaria subquadripara Hitchc. em diferentes condicoes nutricionais

The objective of this study was to evaluate the initial growth of emergent plants of Brachiaria subquadripara under different conditions of availability levels of the nutrients nitrogen (N), phosphorus (P), and potassium (K) provided to the plants via nutrient solution in a greenhouse. The treatments consisted of five concentrations of N (0, 42.0, 84.0, 126.0, and 168.0 mg [L.sup.-1]), five concentrations of P (0, 6.2, 12.4, 18.6, and 24.8 mg [L.sup.-1]) and five concentrations of K (0, 46.8, 93.6, 140.4, and 187.2 mg [L.sup.-1]) which were adapted from a base solution. The results showed that the initial growth of plants was slow up to 21 days after transplantation (DAT) and it increased in accordance with increments in N, P, and K concentrations in the nutrient solution up to the end of the study (35 DAT). The Relative Growth Rate and the Net Assimilation Rate of the B. subquadripara plants were larger when the N, P, and K concentrations were of 84.0, 18.6, and 46.8 mg [L.sup.-1], respectively. These results suggest that this species can develop in environments considered hypereutrophic. Key words: Urochloa subquadripara Umchloa arrecta aquatic plant weed eutrophication water reservoir Propos-se, neste trabalho, avaliar o crescimento inicial emergindo Brachiaria subquadripara em diferentes condicoes de disponibilidade dos nutrientes nitrogenio (N), fosforo (P) e potassio (K) via solucao nutritiva em casa-de-vegetacao. Os tratamentos se constituiram de cinco doses de N (0, 42,0, 84,0 126,0 e 168,0 mg [L.sup.-1]), cinco doses de P (0, 6,2, 12,4, 18,6 e 24,8 mg [L.sup.-1]) e cinco doses de K (0, 46,8, 93,6, 140,4 e 187,2 mg [L.sup.-1]) adaptadas a solucao base. Os resultados demonstraram que o crescimento inicial das plantas foi lento ate os 21 dias apos o transplante (DAT) e crescente de acordo com os aumentos das concentracoes de N, P e K em solucao nutritiva ate o final do experimento (35 DAT). A Taxa de Crescimento Relativo e a Taxa de Assimilacao Liquida da B. subquadripara foram maiores nas concentracoes de 84,0, 18,6 e 46,8 mg [L.sup.-1] de N, P e K, respectivamente. Esses resultados sugerem que esta especie pode se desenvolver em ambientes considerados hipereutroficos. Palavras-chave: Urochloa subquadripara Urochioa arrecta planta aquatica planta daninha eutrofizacao reservatorios hidreletricos