Nitrogen Assimilation and Growth of Cotton Seedlings under NaCl Salinity and in Response to Urea Application with NBPT and DCD

Salinity stress and inefficient nitrogen fertilization adversely affect cotton growth and yield. The effect of salinity on the growth and stress response of cotton seedlings and the effect on N-use efficiency from the use of the inhibitors of urease (NBPT) and nitrification (DCD) under salinity stress were studied in growth chambers. The study consisted of three levels of salinity low (0.45dSm1), moderate (8dSm1) and high (16dSm1) and five N treatments unfertilized control, 100% N rate with urea, 80% N rate with urea, 80% N rate with urea +NBPT and 80% N rate with urea +NBPT+DCD. The results indicated that salinity stress reduced plant growth (low leaf area and plant dry matter), decreased N assimilation (low NR, GS and protein), increased plant stress response (high GR and SOD), and decreased leaf chlorophyll, stomatal conductance and quantum yield. Addition of NBPT to urea improved N uptake by 22% under low salinity; however, this effect was not observed with increasing salinity. No benefit of addition of DCD was observed in any of the parameters collected. In conclusion, salinity stress hindered the performance of the additive NBPT and negatively affected the growth and physiology of cotton.