The aim of this work was to study the effect of sub-doses of herbicide nicosulfuron on the levels of chlorophyll and growth of marandu-grass in an forest-livestock integration system. The treatments consisted of eucalyptus consortium with sorghum (BRS 655 hybrid) and forage Urochloa brizantha cv. Marandu (marandu-grass) at 12×2 and 12×3 m spacings in agroforestry systems, in addition to sorghum + marandu-grass and marandu-grass in monoculture. The doses of nicosulfuron applied at the marandu-grass were 0, 15 and 30 g ha-1. At 30 and 120 days after the application of nicosulfuron, chlorophyll a and chlorophyll b were measured usinf a portable chlorophyll meter, with six measurements per plant. Afterwards, the total chlorophyll content and chlorophyll a/b were calculated. We also measured the mass of the total dry matter of marandu-grass and growth rate of the culture. Marandu-grass plants cultivated in monoculture showed higher quantities of chlorophyll and the highest growth rates. The levels of chlorophyll a, b and chlorophyll a/b and the growth rate of marandu grass were similar between systems integrated with eucalyptus (12x2 and 12x3 m). The increase of herbicide dose negatively influenced on chlorophyll content in marandu-grass in all treatments evaluated. The use of nicosulfuron in doses of 25 and 50 g L-1 reduced the growth rate of marandu grass only when grown in monoculture