improving water/fertilizer use efficiency of hydroponically cultured greenhouse tomato by partial root zone drying, deficit irrigation and hydrogel amendment

soilless culture of greenhouse vegetables has been a fast developing section in iran during recent years. most growers fertigate plants without enough knowledge about plant water requirements. since some soilless substrates have low water retention capacity, wasting a great amount of nutrient solution can be occurred due to poor management. in this research work, effects of hydro gel amendment and partial root zone drying were studied on hydroponically cultured greenhouse tomato and water/ fertilizer use efficiency. results showed that plants treated by partial root zone drying had lower yield than those irrigated normally, but their water/fertilizer use efficiency was improved. according to the results, prd showed better results than deficit irrigation treatment probably due to better absorption of water and fertilizer from substrate. incorporating hydro gel into media could improve coarse perlit physical properties and increased its water holding capacity. this can be resulted in more availability of water and fertilizer to plant root and increment of yield and water/fertilizer use efficiency. hydro gel showed better results on water/fertilizer use efficiency values under deficit irrigation compared to normal irrigation conditions.