Combined effect of sodium chloride and boron in irrigation water on cotton growth

The NaCl and B levels of brackish water are higher than those of fresh water. Cotton (Gossypium hirsutum L.) is probably affected by simultaneous NaCl and B stress when irrigated with brackish water, but little is understood regarding the combined effect of NaCl and B on cotton growth and the absorption of nutrient elements. Cotton growth and nutrient element content were measured at different NaCl and B concentrations in pot experiments. Cotton growth parameters varied with different NaCl and B concentrations in irrigation water. Cotton stem dry weight (DW) and lint yield decreased with an increase of NaCl concentrations from 15 to 75 mmol L^–1 at the B toxicity stress in irrigation water. An antagonistic relationship for the combined effect of NaCl and B on cotton growth was revealed by the experiments. Boron content in cotton leaves increased with an increased B concentration in the 0.046 to 0.736 mmol L^–1 range. The combined effect of NaCl and B accelerated the Na accumulated in cotton leaves when NaCl and B were present in high concentrations. The reduction of K and Ca uptake potential at increased NaCl concentrations resulted in lower K⁺/Na⁺ and Ca²⁺/Na⁺ ratios, thereby inhibiting cotton vegetative growth and lint yield. Brackish water with a total dissolved solid (TDS) content of 1.49 to 1.68 g L^–1 moderately promoted cotton growth.