Interactive effect of salicylic acid and nitrogen application management on wheat growth and yield in saline soils- A case study in Anbar Olum, Golestan province

Salinity is one of the major constraints prevailing in the environment that affects not only plant growth but also agriculture productivity and soil fertility. Salinity stress causes nutritional and hormonal imbalance, ion toxicity, oxidative and osmotic stress and increase susceptibility of plant to diseases. In this regard, research has shown that salicylic acid causes resistance in plants to environmental stresses, including salinity. Nitrogen also has a direct effect on plant yield due to its significant role in plant establishment and photosynthetic and physiological abilities.

In order to investigate the effects of salicylic acid and nitrogen fertilizer application rates at different salinity levels on growth of wheat cv. Morvarid, an experiment was conducted as a split plot factorial based on a randomized complete block design with four replications in the fields of Mazraeh-E-Nemooneh located in Anbarolum, Aq Qala city, Golestan province. The main factor included three soil salinity levels (3-4 below wheat tolerance threshold (control), 9-11and 13-15 dS/m) and sub factors included two levels of salicylic acid (0 and 1.5 mM) and three levels of nitrogen fertilizer (urea) included 30% N less than soil test recommendation, N based on soil test recommendation and 30% N more than soil test recommendation, respectively. Salicylic acid was foliar applied twice at 2 weeks intervals in the tillering stage. Nitrogen treatments were applied in three stages- before planting and twice as top dressing at the tillering and stem elongation stages. Plant dry weight and height, grain yield, number of spike, number of grains per spike, thousand seed weight and spike length were measured.

The results showed that the effect of different levels of salinity on yield and its components were significant. With increasing the salinity, yield and yield components decreased (p≤0.01). However, yield and yield components increased as N fertilizer consumption increased (p≤0.01). So that the highest grain yield was in the +30% of soil test recommendation treatment (N3), which was significantly different from the other levels. Application of calicylic acid increased all parameters of yield and its components except for number of grains per spike and spike length (p≤0.01). The interactive effect of salinity and nitrogen showed that application of N fertilizer more than the soil test recommendation level up to moderate salinity level (9-11 dS/m) was increased yield and yield components but at high salinity level (13-15 dS/m) reduced these traits. Also, nitrogen application with salicylic acid improved these traits under low and moderate saline conditions, but could not have a significant effect on them at high salinity level.

Therefore, the application of salicylic acid and nitrogen fertilizer management to some extent alleviated the adverse effects of salinity up to moderate salinity levels and improved plant growth and yield by increasing plant tolerance to salinity. At high salinity condition, it is better to reduce the use of nitrogen fertilizer.