Biomass Production and Mineral Nutrient Accumulation by Weeds and Sweet Orange Trees in the Amazonian

Accumulation of biomass and competition for nutrients can be used as parameters to identify species with higher potential for competition and, thus, with larger interference in crops. Consequently, studies addressing these parameters are important to weed science since they are the main factors that negatively affect the growth and productivity of cultivated plants. The objective of this research was to identify the species of weed plants with the largest potential of biomass production and accumulation of mineral nutrients in their leaves, which in turn, lead to higher interference in orange crops. In the floristic survey, 30 species of weed plants were identified and 14 botanic families, totaling 1341 sampled specimens. The phytosociological analysis showed, as per the importance value (IV), that the most representative weed species in the study area were as follows: Conyza bonariensis (L. (Cronquist)), Spermacoce latifolia Albl., Paspalum conjugatum PJ Bergius, Pueraria phaseoloides (Roxb.) Benth., Mollugo verticillate L., Peperomia pelucida (L.) Kunth, Euphorbia heterophylla L., Paspalum multicaule Poir and Waltheria corchorifolia Pers. Among these, the species with the highest production of biomass and accumulation of mineral nutrients in their tissues were S. latifolia, P. phaseoloides, P. conjugatum and C. bonariensis. This result suggests that these species are of high competitive potential against orange crops due to their high capacity for biomass and micronutrients accumulation.