Effects of Soil Water Tension on the Emergence and Growth of Cotton Seedlings1

Abstract

AbstractA laboratory study was conducted to determine the effects of soil water tension on the rate and percentage of emergence and the vigor of cotton (Gossypium hirsutum L.) seedlings in a soil environment. Pressure plate apparatus was used to bring the soil to the tensions desired. One hundred seeds were planted equal distance apart in a silt loam soil at a depth of 2.5 cm in a 30‐cm‐diameter enameled pan. The soil was compressed around the seeds to a bulk density of about 1.1 g/cm3. The pan was enclosed in a transparent plastic bag and placed in a constant temperature chamber at 25 C. The number, height, and a description of the appearance of the seedlings which had emerged were recorded daily for 4 weeks.Total emergence was not affected by changes in soil water tension between 1/3 bar and 3 bars. Emergence at 4 bars tension was significantly less than at lower tensions. The number of seedlings which emerged decreased slowly as the tension increased from 4 to 7.5 bars. A sharp decrease was observed in the emergence at a tension of 8 bars. No emergence occurred at tensions greater than 12 bars. The time required for emergence and the growth rate of seedlings was not significantly affected by changes in tension from 1/3 to 1 bar. The rate of emergence and the growth rate progressively decreased as tension increased from 2 to 4 bars. Thereafter, as tension increased, time requird for emergence increased rapidly and rate of growth simultaneously decreased sharply.