EEstudou-se a interação de 4 níveis de potássio (0, 60, 120 e 180 pp, de K) com 3 regimes de água no solo (capacidade de campo, deficiência hídrica e excesso hídrico). Durante 5 dias, em 2 épocas (início de pré-floração (R5) e início de formação de vagens (R7)) em feijoeiro CV IAC-carioca cultivado em latossolo vermelho-amarelo álico. A aplicação de doses de K ao solo diminuiu a duração do estádio de enchimento de vagens e do ciclo total das plantas em solo em capacidade de campo. A maturação fisiológica das sementes foi retardada pela deficiência hídrica no solo nos estádios R5 e R7 e pelo excesso hídrico no estádio R5. Os regimes de água afetaram o consumo de água, altura e matéria seca produzida pelas raízes, parte aérea e grãos, número de flores abertas e vagens produzidas e extração de nutrientes pelos grãos. A época de aplicação dos tratamentos não afetou a produção de grãos. Houve maior produção de grãos com a dose 125ppm de k, com produções decrescentes para tratamentos sob deficiência e sob excesso hídrico. As doses de K afetaram o padrão de florescimento e produção de vagens com comportamentos distintos entre as 2 épocas de aplicação dos regimes de água. A deficiência hídrica foi mais crítica quando aplicada no estádio R7 do que no estádio R5

The purpose of this study was to verify the effect of the interaction between potassium levels applied to the soil and the water stress, during two reproductive stages of bean (Phaseolus vulgaris L.) cv. IAC-carioca plants. The greenhouse experiment was carried out at the University of São Paulo College of Agriculture, in Piracicaba, Brazil. Plastic pots (3,6 litres) with three plants each were used. The soil was an Orthic Hapludent. Three water regimes were applied (field capacity, water deficiency and water excesss), during five days, in two growth stages: pre-flowering (R5) and pod appearance (R7), with four potassium levels (O, 60, 120 and 180ppm). Stage duration, applied water and plant height were evaluated in each stage. The results showed that the applied potassium reduced the duration of pod filling and period of the total cycle for plants grown at field capacity. Water deficiency in the R5 and R7 stages and the water excess in the R5 retarded fruit maturation. Water consumption, plant height, root, shoot and grain dry matter, number of opened flowers and grain nutrient extraction, were all affected by the water regimes. There was an interaction between water regimes and potassium levels to plant height and root and shoot dry matter. The period in which water regimes were applied did not affect grain yield. The highest grain yield was obtained with 125ppm K, being smaller for the water deficiency treatments when compared with the field capacity ones. Nutrient export through grains was higher for the field capacity treatments, followed by the water deficiency and the water excess. The potassium rates varying from 115 to 140ppm induced higher N, K, P, Ca, Mg and s extractions. Inflorescence and pod production were affected by the potassium levels, causing different behaviour observed for the two water regimes application times. The water deficiency treatment was more critical for plants in the R7 stage (pod appearance) than in the R5 stage (pre-flowering). The number of opened flowers .and pods were the best parameters to evaluate plants under water stress