Root Growth of Cotton as Measured by P32 Uptake¹

Abstract

Abstract Development of the root system of cotton ( Gossypium hirsutum L.) under irrigated conditions was measured by uptake of P 32 variously placed throughout the soil in dissolvable gelatin capsules. Corrections were made for small differences in P32 availability within the soil profile as determined from a greenhouse study. The tap root grew at an average rate of 2.5 cm per day to a depth of 183 cm, the deepest placement. Lateral roots grew at one‐half this rate. The basic framework of the root system was established by the onset of flowering approximately 10 weeks after planting as evidenced by measurable activity at all placements, although twothirds of the total activity on this date was confined to the top 30 cm. Root activity at the lower depths intensified as the season progressed. This resulted in relatively uniform activity through the first 122 cm and significant activity down to 183 cm at the end of the 130 days