Brachiaria decumbens, commonly known as surinam grass, is considered an important weed, very aggressive and difficult to control in areas where it was introduced as forage grass and later became a crop. Dry matter production and macronutrient distribution and accumulation in B. decumbens were evaluated under greenhouse conditions. The plants were grown in pots filled with washed and sieved river sand, and irrigated daily with Hoagland & Arnon complete nutrient solution at 50% of the original concentration. The first evaluation was performed 20 days after emergence (DAE) of seedlings and the others every 14 days. Dry matter of every plant part was determined. The material was ground and analyzed for macronutrient content. The results indicated plant growth throughout the experimental phase. The largest accumulation occurred at 160 DAE, when the plant accumulated 38.27 grams of dry mass. At 160 DAE, around 37.37% of the dry biomass was accumulated in the roots, 37.54% in the stems and sheath and 25.09% in the leaves. Total macronutrient accumulation increased up to 146 days after emergence. At 76 DAE ( period of greater competition between the weeds and most of the annual cultures), a surinam grass plant accumulated 1.32 grams of dry mass; 40.8 mg of K; 18.2 mg of N; 6.3 mg of Ca; 5.2 mg of Mg; 2.68 mg of P and 2.4 mg of S.
weeds; B. decumbens; macronutrients
