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The rugged Hill Country of Central Texas is part of the extensive Edwards Plateau region. Significant portions of the Texas Hill Country overlie the Glen Rose Formation, which is characterized by a stair‐step topography formed by the weathering of interbedded carbonate materials having different weathering susceptibilities. This process has sculpted the strata into a series of “risers” and “treads” that mimic stairways. In this paper, we document the soil hydrology within the riser–tread catena. Our results are counterintuitive in that we find the highest infiltration and deepest soils on the steep riser slopes. In addition, we find that the riser subsoils are saturated or very wet for extended periods. On the basis of these findings, we suggest that (1) groundwater recharge on these hillslopes is minimal and occurs only in highly fractured zones; (2) the water‐holding capacity of the subsoils is sufficient for supporting the woody vegetation; and (3) runoff generation occurs as a combination of surface and subsurface flow, with the risers serving as sinks or recharge zones and the treads as source areas.

Energy of exchange is a measure of the intensity factor in the delivery of a balanced supply of nutrient cations from the exchange complex of the soil to the growing plant. Energies of exchange for the replacement of calcium by potassium in a soil may be computed from the cationic composition of water extracts from the soil. Cationic compositions of displaced soil solutions varied with the concentrations of soluble anions that in turn depended upon the moisture contents of the soils. But the variations were such that they reflected constant energies of exchange for each of the soils at different moisture contents. Energies of exchange for the replacement of calcium with potassium ranging from -3,500 to -4,000 calories were associated with potassium deficiencies in plants. Energies of exchange from -2,500 to -3,000 calories represented suitable balances between potassium and calcium. Energies of exchange of -2,000 calories or less were associated with excessive amounts of potassium in relation to the amounts of calcium that were present. The relationships between plant nutrition and energy of exchange appear to be universal in scope and applicable to all soils.

Century-long annual precipitation time series at 168 stations in the central United States are analyzed with special attention given to interdecadal variations. The results show statistically significant precipitation variations of interdecadal timescales in the region. In particular, one variation has a quasi 20-yr period, and another one possesses a quasi 12-yr period. The negative phases of the 20-yr variation match with the major drought periods in the region's history, that is, the 1910s, 1930s, 1950s, and the late 1970s. The positive phases of this variation correspond well to the wet periods between the dry epochs. The 12-yr variation shows an amplification after the mid-1960s, while the 20-yr variation shows a reduced amplitude following this time. Concurrent with these changes, the annual precipitation in the region has increased since the mid-1960s. A plausible mechanism connecting the interdecadal variations of annual precipitation in the central plains region and slow timescale variations in the midlatitude and subtropical North Atlantic regions is briefly discussed.

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