The degree of weed interference depends on the density of the weeds infesting the soybean crop. The objective of this work was to evaluate the growth and mineral nutrition characteristics in soybean maintained in coexistence with increasing densities of Euphorbia heterophylla. The experiment was carried out in Jaboticabal, SP, Brazil, from October through December 2008, in pots maintained under open field conditions. The treatments consisted in submitting one soybean plant per pot to coexistence with 0, 1, 2, 4, 8 and 16 plants of E. heterophylla per pot, from sowing until the beginning of soybean flowering. At this period, only height and number of leaves were evaluated in soybean, while dry matter and macronutrient accumulation were evaluated in both species. Variation in plant height and reduction in the number of leaves and dry matter and macronutrient accumulation of soybean were observed due to the higher accumulation of dry matter and macronutrients per increasing densities of E. heterophylla. It was concluded that growth and macronutrient accumulation of soybean maintained in coexistence with E. heterophylla were reduced due to weed interference.
wild poinsettia; competition for nutrients; Glycine max
