Influence of phosphorus fertilization on the response of pinus genotypes to glyphosate subdoses

Previous studies have reported that phosphorus transporters are involved in glyphosate uptake by plants, so phosphorus fertilization might act as an attenuator of glyphosate effects on a possible drift. The objective of this study was to evaluate the influence of phosphorus fertilization on the initial growth of Pinus taeda genotypes submitted to glyphosate subdoses applied during two growing seasons, warm and cold. Four experiments were conducted in an open area using 10-L pots, two in the warm season (during 180 days after application on Genotypes 1 and 2) and two in the cold season (during 81 days after application on Genotypes 3 and 4). The treatments consisted of a 2 × 4 factorial scheme, with presence or absence of phosphorus fertilization (25.2 kg ha−1 P2O5) and four subdoses of glyphosate (0, 72, 144 and 288 g ha−1 acid equivalente), using five replicates. For warm season, glyphosate subdoses provided a stimulatory effect on the plant growth of both P. taeda genotypes independently of the fertilization condition. The supplementary phosphorus fertilization increased plant growth characteristic in both warm and cold season, regardless of the exposure to glyphosate subdoses. However, the plant response is dependent on the genotype. Glyphosate subdoses did not negatively affect P. taeda genotypes growth at both experimental seasons, regardless of phosphorus fertilization.