<i>Urochloa brizantha</i> competition on initial growth, physiology, and use of macronutrients in <i>Caryocar brasiliense</i>

Abstract Forest recovery using Caryocar brasiliense (pequi) seedlings faces problems related to weed competition. Despite its relevance, weed competition has been little studied, especially in relation to its coexistence with Urochloa brizantha , which is considered the main forage crop cultivated in Brazil and an invasive problem in conservation areas. Thus, in this study, we aimed to evaluate the competitive aspects, initial growth, and physiological responses of C. brasiliense that coexist with U. brizantha at different densities. The treatments were composed of pequi tree seedlings, in the center of a 12‐dm 3 pot, with varying numbers of U. brizantha plants used as competitors, at densities of 0 (control), 14, 28, and 42 weeds m −2 . C. brasiliense plants maintained under competition with U. brizantha showed a reduction in photosynthetic rate (45%–73%), instantaneous water use efficiency (55%–70%), electron transport rate (18%–50%), and stomatal conductance (40%–66%), regardless of weed density. The coexistence with U. brizantha reduced the relative accumulation of macronutrients. The coexistence of U. brizantha , regardless of density, affects the physiology, use of macronutrients, and growth of C. brasiliense . In reforestation of C. brasiliense , attention should be paid to controlling U. brizantha to avoid competition with plants of interest.