Evaluation of the Interactive Effects of Nitrogen Sources and Sodium Bicarbonate on The Growth and Some Morpho-Physiological Characteristics of Garlic in Hydroponic System

Soil salinity and alkalinity seriously affect about 932 million hectares of land globally, reducing productivity in about 100 million hectares in Asia. Plants in alkaline soil must cope with physiological drought and ion toxicity, and also maintain intracellular ion balance and regulate pH outside the roots. Alkaline stress result into decrease in chlorophyll concentration, stomatal conductance and transpiration rate and inhibite the growth of plant. Nitrogen sources affect the pH of nutrition solution, which can affect plant growth, so nitrate increases the pH of nutrient solution while ammonium decreases pH of nutrition solution.

In order to evaluate the effect of nitrogen sources on vegetative growth, physiological and chlorophyll fluorescence of white and purple garlic genotypes under sodium bicarbonate stress, an experiment was carried out as factorial base on completely randomize desigen with three factors; sodium bicarbonate at three levels (0, 10 and 20 mM), nitrogen sources (5 mM ammonium sulfate, ammonium nitrate and calcium nitrate in nutrient soulotion) and genotypes (white and purple) with three replications in 2017 in Greenhouse of Faculty of a Agriculture, University of  Vali-e-asr Rafsanjan.

The results showed that shoot and root fresh and dry weight decreased by increasing sodium bicarbonate from 10 mM to 20 mM in nutrient solution and application of ammonium nitrate and ammonium sulfate sources decreased the negative effect of sodium bicarbonate on shoot and root fresh and dry weights. Among nitrogen sources, ammonium sulfate produced the highest soluble sugar content in both garlic genotypes. Proline content was enhanced by increasing sodium bicarbonate concentration in nutrient solution. The highest photosynthetic pigments were absorbed in plant that nourished by ammonium nitrate and ammonium sulfate, respectively. The sources of nitrogen, sodium bicarbonate and their interaction had no significant effect on chlorophyll fluorescence parameters, but genotype had significant effect on these traits.

According to the results of this experiment, the use of ammonium sulfate and ammonium nitrate sources has a better performance on growth and yield of garlic under bicarbonate stress conditions.