Phosphorus fertilization and planting dates on the chemical seeds composition of two dry bean cultivars/Adubacao fosfatada e epocas de cultivo na composicao quimica de sementes de cultivares de feijoeiro

Phosphorus is a limiting nutrient in common bean grain yield and may influence the chemical composition of seeds. The aim was to assess the effects of phosphorus fertilization and planting dates ('water 'and 'dry') in the seeds chemical composition of two dry bean cultivars. A field experiment was carried out in Botucatu (SP) in a randomized block design with five replications. Two dry bean cultivars 'Carioca Precoce' e 'IAC Carioca Tybata' were evaluated in growing 'water' and 'drought' in six levels of [P.sub.2][O.sub.5] (0, 30, 60, 90, 120 and 150kg [ha.sup.-1]) applying superphosphate at planting row. It was assessed seed samples to determine the levels of N, P, K, Ca, Mg, S, Cu, Mn, Fe, Zn, total and reducing sugar and protein. The phosphorus in the soil alters the seeds chemical composition, increasing contents of P and decreasing Ca and Cu contents. The K and Fe contents showed minimum point at a level of 69.9 and 66kg [ha.sup.-1] of [P.sub.2][O.sub.5], respectively. It was observed that occurred increase in contents of N, P, and protein of seeds in the growing season 'drought'. The cultivar 'Carioca Precoce' showed higher N content and protein of seeds than 'IAC Carioca Tybata'. There is interaction between cultivar and growing season for the content of S, Mn, Fe, Ca, Mg, Cu, total and reducing sugars. Key words: Phaseolus vulgaris, macronutrients, micronutrients, seed quality. O fosforo (P) e um nutriente limitante na produtividade do feijoeiro e pode influenciar na composicao quimica de sementes. O trabalho objetivou avaliar os efeitos da adubacao fosfatada e de epocas de cultivo ('aguas' e 'seca'), na composicao quimica de sementes de duas cultivares de feijoeiro. O experimento foi realizado em Botucatu (SP), no delineamento de blocos ao acaso com cinco repeticoes. As cultivares de feijao 'Carioca Precoce' e 'IAC Carioca Tybata' foram avaliadas no cultivo 'das aguas' e 'da seca' sob seis doses de [P.sub.2][O.sub.5] (0; 30; 60; 90; 120 e 150kg [ha.sup.-1]) com aplicacao de superfosfato triplo no sulco de semeadura. Amostras de sementes foram analisadas para determinacao dos teores de N, P, K, Ca, Mg, S, Cu, Mn, Fe, Zn, acucar total e redutor e proteina. A adubacao fosfatada alterou a composicao quimica das sementes, incremento nos teores de P e reducao de Ca e Cu. Os teores de K e Fe apresentam ponto de minima nas doses de 69,9 e 66kg [ha.sup.-1] de [P.sub.2][O.sub.5], respectivamente. O cultivo na epoca 'da seca 'favorece os teores de N, P e pro