Growth and biochemical responses of sorghum genotypes to nitrogen fertilizer under salinity stress conditions

This study was carried out to assess the efficiency of nitrogen (N) fertilizer in mitigating the harmful effects of salinity stress on growth and biochemical traits in sorghum genotypes. The experiment was conducted as a factorial trial based on the completely randomized design with four replications under the greenhouse conditions. The factors included four sorghum genotypes (KDFGS1, KDFGS23, KDFGS29 lines, and KFS2 cultivar), two salinity levels (3 and 12 dS m(-1)) and three nitrogen levels (0, 75 and 150 mg N kg(-1)soil). The results showed that application of nitrogen fertilizer increased photosynthetic pigments and K+/Na+ ratio in leaf sheath and root. Also, nitrogen dramatically decreased malondialdehyde (MDA) content. This was an indication of the reduced detrimental effects of salinity stress found in all genotypes. In addition, it was found that upon 150 mg N kg(-1) treatments, proline (Pro) and antioxidant enzymes markedly decreased in all sorghum genotypes. The highest impact of nitrogen fertilizer for reducing the negative effect of salinity stress was observed in KFS2 (known as tolerant genotype). Due to the highest Pro accumulation in KDFGS23 (known as sensitive genotype), it did not appear to be a suitable criterion for the selection of the tolerant lines/cultivars. In general, the results suggested that using a reasonable N fertilizer level could be used as an efficient tool to improve the growth of the sorghum genotypes subjected to salinity stress and this effect was more pronounced in the tolerant genotype.