The area around Brasilia, Brazil is representative of millions of hectares in the tropics with very acid soils of extremely low fertility. The unfavorable water supplying properties of these soils together with the occurrence of wet season dry periods and limitations to root growth due to aluminum toxicity make water management a critical factor for successful crop production in the region. Research was conducted at the Brasilia Experiment Station to determine how water affects the crop production process. Climatic limitations to agricultural production were studied through analyses of daily rainfall records for 42 years. These revealed that one may expect one dry spell of 13 days or longer per wet season (November to March). Dry spells will exceed 3 weeks one year in seven. Dry spells were most prevalent during late December and January. Tensiometers, gypsum blocks, and gravimetric soil samples from three locations were used to develop depth- and site-specific relationships between soil-water tension and soil-water content. Because local clayey Oxisols are highly aggregated and structurally stable, their soil-water properties resemble those of sands. Available water storage is limited to 10-15% by volume, with 2/3 released between 1/10 and 1 bar of tension. One dry and three wet season experiments were planted to corn, with two depths of limestone incorporations and several levels and types of water management. Due to excessive aluminum, almost 85% of the soil-water use occurred in the top 45 cm.