Nitrogen (N) and potassium (K) are the major nutrients required for coffee plants growth and development. Soil water deficit reduces nutrients uptake, causing negative effects on photosynthesis and water relations of plants. Within certain limits, the increase in N and K concentration in soil solution could result in higher nutrient uptake, softening physiological disturbs caused by the water deficit. This study aimed to evaluate water relations and photosynthesis of young coffee plants grown in 16 L pots in a greenhouse. Treatments were three N and three K doses: conventional (urea 12 g plant -1 and KCl 4 g plant -1), doubled and tripled; and two water regimes: irrigated (soil at field capacity) and non-irrigated. Thus, treatments were arranged in a factorial 3*3*2, with three replicates in a completely randomized design. Water stress effects on leaf water potential and relative water content are softened by increase in N and K doses. However, transpiration, stomatal conductance and net photosynthesis are decreased by water stress, regardless of N and K doses. Increase in K doses reduces transpiration and stomatal conductance, regardless of water regime. This study suggests that increases in N and K could partially protect young coffee plants against the water stress, as they contribute to mitigate negative effects in plant water status; however, they do not prevent a decrease in net photosynthesis.
