The effect of sodicity on cotton: plant response to solutions containing high sodium concentrations

Abstract

Solution culture was used to investigate whether the high solution Na concentrations and Na:Ca ratios found in sodic soils could directly affect the early growth and nutrient uptake of cotton ('Gossypium hirsutum' L.). Cotton was grown in nutrient solutions with three Na:Ca ratios (46:1, 4:1 and 0.2:1 m'M') and three electrical conductivities (EC) (2.5, 4.25 and 6 dS m⁻¹) combined in a factorial design with four replicates. Most cotton growth parameters (including shoot and root dry weight, fruit number and weight) were unaffected by increasing solution EC or Na:Ca ratio, but at the highest Na concentration (56.6 m'M'), plant height was reduced. It was concluded that young cotton has the ability to tolerate solution Na concentrations up to those found in moderately sodic soils. Increasing solution Na:Ca increased plant root and shoot concentrations and plant accumulation for Na, and decreased them for Ca. Increasing EC also increased plant Na concentration and accumulation. Shoot K and P concentrations decreased with EC, but actually increased as the sodicity (Na:Ca ratio) of the nutrient solution increased. The results suggest that the low K and P concentrations commonly found in cotton grown in sodic soils are not a direct result of Na:Ca ratio in the soil solution.