The effects of drought stress on the phosphorus (P) and potassium (K) uptake dynamics of summer maize (Zea mays L.) throughout the growth cycle were studied. Field trials were conducted under a completely randomized design with three field water capacity (FC) regimes: 75 % FC was well watered and considered to be the control, 55 % FC represented moderate stress (MS), and 35 % FC represented severe stress (SS). The water regimes were applied from the third leaf stage until maturity. Drought stress induced sharp decreases in total K and P uptake of maize organs at different developmental stages and, in particular, detrimentally affected the nutrient uptake capability of roots. SS caused more deleterious effect than MS on both total K and P uptake by plant organs. The results suggested maize plants differ in their ability to maintain nutrient uptake under drought stress, and it is highly dependent on the intensity and duration of drought stress and the developmental stage. The decrease in total K and P uptake caused by both MS and SS was accompanied by reduction in biomass production in drought-stressed tissues. The biomass allocation patterns in response to drought stress fluctuated strong mostly because of competitive changes in the shoot and roots at different stages, thus the root:shoot ratio increased at some stages and decreased at other stages. SS induced a dramatic reduction in the harvest index (HI), whereas MS slightly decreased HI. Thus, water limitation caused lower K and P uptake and HI.
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