Differential Growth Behavior of Cotton Varieties at Adequate and Deficient Levels of Nitrogen and Phosphorus.

Abstract

Seven cotton (Gossypitn hirsuturn L.) varieties were evaluated for growth and utilization efficiency of nitrogen (N) and phosphorus (P), in hydroponics using modified Johnson's solutions containing adequate (6.0 mM N and 0.20 mM P), and deficient levels of N (0.8 mM) and P (0.01 mM). Substantial differences were observed among varieties for accumulation of shoot dry weight (SDW), relative reduction in shoot biomass due to N-deficiency (NSF), and uptake by shoot in case of N, and root dry weight (RDW), root:shoot ratio (RSR), relative reduction in shoot biomass due to P-deficiency (PSF), concentration in shoot and uptake by shoot in case of P. Variety SLS-1 exhibited the minimum stress at N-deficiency (NSF = 34%) as well as P-deficiency (PSF = 59%) among all the varieties. A negative correlation (r =0.555, n =35) between SDW and RSR in P-stressed plants suggested increase RDW production at the cost SDW. Utilization efficiency in varieties remained unchanged in case of N-deficiency stress and decreased in case of P-deficiency stress as compared to control, and in both the cases differences among varieties remained statistically non-significant. Nutrient level X variety interaction was significant for all the parameters studied in case of P, whereas for N, the interaction was significant only for shoot dry weight, stress factor and uptake by shoot.