Ameliorative effects of potassium nutrition on yield and fiber quality characteristics of cotton (Gossypium hirsutum L.) under NaCl stress

Cotton (Gossypium hirsutum L.) being moderately tolerant to salinity has been extensively grown in arid and semiarid regions where soil salinization is a major threat to plant growth and soil productivity. Excess salts in the growth medium may interfere with growth processes of cotton, leading to a severe decline in yield and fiber quality characteristics. Adequate mineral nutrient status of plants can provide an important strategy to improve plant tolerance to salinity. A pot experiment was planned to evaluate the ameliorative effects of additional potassium (K) applied at 50 and 100 mg K2O kg(-1) soil as potassium sulfate against NaCl stress of 100 and 180 mM in cotton. The experiment was conducted according to completely randomized design with five replications. NaCl caused a significant (P <= 0.05) increase in shoot sodium (Na+) and chloride (Cl-) with a corresponding decrease in shoot K+, K+: Na+ ratio, calcium (Ca2+) and magnesium (Mg2+). Plant growth, yield and fiber quality characteristics were also declined significantly by increasing external NaCl concentration. Additional K reduced shoot Na+ while increased K+, K+: Na+ ratio, Ca2+ and Mg2+ with the consequent improvement in plant growth, lint yield and yield attributes as well as fiber quality characteristics at both levels of NaCl. Results revealed that K nutrition improved shoot K+: Na+ ratio by 116 and 246% at NaCl100 while 188 and 294% at NaCl180 with K-50 and K-100, respectively as compared to NaCl treated plants without additional K. Likewise, lint yield was improved by 38.27 and 60.49% at NaCl100 while 75.12 and 136% at NaCl180 with K-50 and K-100, respectively compared to NaCl stressed plants without additional K. Ameliorative effects of K against NaCl stress were relatively more prominent at higher K application at both NaCl levels. In conclusion, K-induced decrease in Na+, increase in Ca2+, K+, K+: Na+ ratio, relative water content and membrane stability index provide protective mechanisms against NaCl stress. However, the results need to be confirmed under field conditions and the economic feasibility should be worked out.