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BORON TOXICITY IN IRRIGATED COTTON (GOSSYPIUM HIRSUTUM L.)

NIAZ AHMED¹, MUHAMMAD ABID¹ AND FIAZ AHMAD²

Abstract: Boron toxicity is a serious concern in irrigated agriculture throughout the world for sustainable crop production. A greenhouse experiment was conducted to determine the critical level of boron (B) toxicity for cotton in soil and plant tissues in an arid climate. B levels of 0, 0.5, 1.0, 2.0, 3.0, 5.0, 10.0, 15.0, 20.0 and 25.0 mg kg^-1 were applied in solution form to soil before the sowing of the crop. Toxicity symptoms (yellowing and necrosis in patches between veins and tips and margins of leaves) first appeared on older leaves at 5 mg B kg^-1 soil level and increased in severity with increasing levels. Dry matter yield declined significantly (p≤0.05) with increasing levels of B. The maximum dry matter yield (29.10g/pot) was recorded at 2 mg B kg^-1 soil level. The 90% of the maximum dry matter yield was obtained at B level of 5 mg kg ^-1 soil. At 5 mg B kg ^-1 soil, leaf tissues maintained contents at 198 mg B kg^-1 dry weight. The concentration of B in various plant parts was found in the order of leaves>shoot>root.  The addition of higher levels of B caused significant (p≤0.05) reduction in N, Ca²⁺, Mg²⁺, Mn²⁺, Zn²⁺ and Fe²⁺ contents   whereas P, K⁺ and Cu²⁺ contents increased significantly (p≤0.05) in leaf tissues.

¹University College of Agriculture, Bahauddin Zakariya University, Multan, Pakistan

²Central Cotton Research Institute, Multan, Pakistan-60500