Water relations in highly calcareous very gravelly soils

This study was undertaken because of the many irrigated acres of highly calcareous very gravelly soils in Western Montana and the uncertainties of permeabilities and available water capacities associated with them.Infiltration rates were recorded on large 9.3 square meter (100 square foot) plots in July 1975.Soil water was determined gravimetrically 2.5, 5, 9, and 16 days after saturation.The substratum of these soils contains 80 percent (by weight) rock fragments so samples for moisture were taken by excavation with a backhoe.Bulk density for soil horizons containing a large amount of rock fragments was determined by a sand-fill excavation method.Saturated hydraulic conductivity was 2.5 to 3.5 centimeters per hour.The "field moisture capacity" available for plant use was 13.5 centimeters for the Gravel soil and 19.3 centimeters for the Musselshell soil.Although the surface was covered to prevent evapotranspir-ation, these very gravelly soils continued to lose significant amounts of gravitational water for 16 days after saturation.If plants were allowed to use the free water during this period, very little gravitational water may have been lost TABLE OF CONTENTS Continued I f Musselshell 20" ring water intake data.Ig Musselshell 12" ring water intake data.Ih Musselshell in filtra tio n curves . . . .Ii Musselshell total water intake curves . 2 Basic Soil-Water D a t a .....................