Effect of sodium chloride and manganese in irrigation water on cotton growth

Brackish water is used widely for agriculture around the world. The elevated NaCl and Mn content in brackish water can impose toxicity stress on crops, including cotton (Gossypium hirsutum L.). However, there have been no previous studies of the combined effects of NaCl and Mn on cotton growth. This study presents greenhouse pot experiments with 30 different NaCl and Mn conditions. The results show that the cotton vegetative growth tends to be highest when both NaCl and Mn concentrations in irrigation water were low. In contrast, the cotton reproductive growth parameters were higher for elevated NaCl and Mn concentrations in irrigation water. There was an antagonistic relationship for the combined effect of NaCl and Mn on cotton growth and yield. The Mn content in cotton leaves increased with increasing Mn concentration in the 4.5–72 µmmol L⁻¹ range when the NaCl concentration was low. Na content in cotton leaves generally increased as NaCl concentration in irrigation water increased. However, the excess Mn concentration in irrigation water inhibited the absorption of Na. The ratios of K/Na and Ca/Na in the cotton plant generally decreased as NaCl concentration in irrigation water increased. This led to lower tolerance of cotton plants to NaCl stress. The antagonistic characteristics between NaCl and specific trace elements for cotton growth and yield indicated that the micronutrients in saline water can alleviate salt damage. This suggests that using saline water for irrigation carefully may produce adequate cotton yield with lower quality water while minimizing soil salinization.