Nitrogen preference and genetic variation of cotton genotypes for nitrogen use efficiency.

Background: Although nitrogen (N) availability is a major determinant of cotton production, little is known about the importance of plants' preference for ammonium versus nitrate for better growth and nitrogen use efficiency (NUE). We aimed to assess the growth, physiology, and NUE of contrasting N-efficient cotton genotypes (Z-1017, N-efficient and GD-89, N-inefficient) supplied with low and high concentrations of ammonium- and nitrate-N.

Results: The results revealed that ammonium fed plants showed poor root growth, lower dry biomass, N content, leaf chlorophyll and gas exchange than those under nitrate irrespective of the concentration.