Abstract
Sodium (Na) can substitute different osmoregulatory functions of potassium (K) in several crop species. Inter and
intra-specific variations in crop species have been reported for (K) uptake and use efficiency. We studied 30
cotton genotypes in hydroponics for growth response, K use efficiency and potassium substitution by sodium. The
treatments were, deficient K (0.3mM), adequate K (3.0mM) and deficient K (0.3mM) + Na (2.7mM). The cotton
cultivars differed significantly (p<0.01) in biomass production. The three treatments significantly (p<0.05) differed
in total dry matter, root: shoot ratio, total K uptake and K use efficiency (KUE) in various cotton genotypes.
Greater efficiency in total dry matter production (6.0 g plant") in NIBGE-2 and minimum (2.15 g plant") in PB-899
per unit of K concentration at deficient K was observed. At adequate K a substantial increase (45%) in mean total
dry weight was obvious compared to deficient K. At deficient K maximum K concentration (18.2 mg g'1) and total
K uptake (105 mg plant") were noted in NIBGE-2. Addition of 2.7 mM sodium to deficient K level, increased mean
total dry weight by 38% compared to deficient K only. In deficient K + Na treatment maximum total dry matter was
produced again by NIBGE-2 and minimum by MNH-786. Root: shoot ratio didn't differ by sodium addition to
deficient K. The root: shoot ratio was maximum in FH-115 and minimum in PB-843.
The results confirmed that screening of genotypes on the basis of their KUE and K substitution by Na could be an
effective approach for categorizing crops under K deficient condition for their growth and yield. Overall genotype
NIBGE-2 had the medium potential for making better growth on K deficient soils because of more total dry matter,
KUE and K, Na uptake in shoot.
Key words: Genetic variability, substitution, KUE, cotton.
