Due to their great nutritional value, herbs play an important role in the family's daily food basket in many countries. They also contain different types of vitamins, minerals and cellulosic materials which play a very important role in human health (Peyvast, 2009). The greenhouse production industry and plant production in hydroponic systems has grown a lot in recent years. This production method can provide high quality products every year and free from residual pesticides and herbicides for farmers and growers (Mairapetyan, 1999; Dorais, et al. 2001). The root environment in hydroponic systems always has enough water, air and food. This system increases the uptake and metabolic activities of roots which leads to high growth rate of plants (Mairapetyan. 1999; Dorais et al. 2001; Manukyan, et al. 2004). To provide adequate levels of nutrients to plants it is necessary to use accurate nutritional programs (Iersel and Kang, 2002). Different concentrations of nutrient solution have been published based on fertilizer recommendations and selected based on experience, plant species and cultivars, growth stage and plant breeding system (Schwarz, et al. 2002). The effect of different concentrations of nutrient solution was examined on the growth, yield and quality of basil and stated that the best growth and maximum yield of basil are achieved with the standard solution or with half the concentration of the standard solution ( Suh, et al. 1999). Effect of different concentrations of nutrient solution on sage plants expressing that the concentration of nutrient solution has a significant effect on plant root and shoot dry weight. (Kang and Iersel, 2004). Udagawa (1995) compared different concentrations of nutrient solution on dill in the center of a sheet of paper. Iersel, (2004) and Udagawa (1995) in similar experiments stated that the concentration of nutrient solution has a significant effect on the root, shoot of dill and thyme dry weight. Such results were not observed in our study on basil plants. Conclusion Herbs such as watercress and basil do not need much concentration of nutrient solution and a moderate amount of all elements is more beneficial for them. Watercress and basil respond differently to the concentration of ammonium in the nutrient solution. Ammonium has a positive effect on watercress while basil shows a negative response to ammonium, which is why a nutrient solution with a low concentration of ammonium has been proposed for basil production in the nutrient film technique. On the other hand nutrient solution containing adequate concentration of ammonium proposed for watercress production. However, the adequate concentration of this ion will have to be tested in future experiments.