Abstarct: A field experiment was conducted as split plots factorial layout baxsed on a randomized complete block design with three factors and three replications at the Research Station, Faculty of Agriculture, the Ferdowsi University of Mashhad (Iran) during growing years of 2015-2016 and 2016-2017. Three levels of irrigation (100, 70, and 40 percent of water requirement) were assigned as main plots and the combination of three levels of biochar (0, 10, and 20 t.ha^-1) and two levels of chemical fertilizers (without and with chemical fertilizer) were allocated as sub plots. Recommended dose for nitrogen, phosphorus, and potassium was 150 kg.ha^-1, 75 kg.ha^-1and 100 kg.ha^-1, respectively. The results showed that biochar was significantly influenced electrical conductivity and soil available phosphorus just in first year but soil saturated moisture, organic carbon, total nitrogen percent, potassium and microbial respiration were affected in two years.The highest biochar effect on soil characteristics was found in the 20 t ha^-1 biochar application treatment. 100 percent of water requirement was significantly influenced the yield and yield components of black seed. Application of biochar had no effect on plant hight, number of stem branches, follicle number, 1000-seed weights and harvest index. Biochar in first year was significantly influenced the seed number per plant and seed weight per plant but in second year biochar increased yield, yield components and biological yield. 10 t ha^-1 level of biochar had more effect on yield and yield components compared to 20 t ha^-1 level. 40 percent of water requirement was significantly influenced the protein and essential oil percent but had reverse effect on oil percent. 10 t ha^-1 level of biochar had more effect on quality charactriestics compared to 20 t ha^-1 level. Combined use of fertilizer and biochar were more affected on plants growth than biochar or fertilizer alone. The interaction between biochar, chemical fertilizer and water requirements significantly affected the seed and straw yield. The significant increase of grain yield, straw yield observed in 70% water requirement+10 t.ha1- biochar+ with chemical fertilizer by 1257 and 5116 kg ha^-1 respectively. As a result, the current study confirmed that the biochar application may help in increasing of black seed production through the improving some physical and chemical properties of the soil due to its high porosity and high water retention capacity. This in particular, in arid and semi-arid areas, where reduces the amount of water consumed and increases water yields for plants that are under water stress. This means that, by using the biochar in soil, only 70% water irrigation required. These results may use for water saving in agriculture in arid and semi-arid conditions.