Optimum use of municipal wastewater for wheat productionâ__

This study was carried out to investigate the effects of municipal wastewater of north Isfahan, south Tehran(Varamin area) and agricultural fields of Astane Ghods Razave located in holy city of Mashhad on soil and wheat plant. Some wheat fields under wastewater and wells irrigation were selected and soil samples were collected before planting and after harvest.Plants samples were also taken at the harvest time. In south Tehran(Varamin area), in addition to the above mentioned experiment, a Split plot experiment with three replicate on wheat plant essential nutrients were studied.The main factor was nitrogen with source of Urea in four levels including ;control(N0),50% and 75% of recommended soil test(N90,N135) and recommended soil test(N180). The sub factor was phosphorus and potassium with source of triple super-phosphate and potassium sulfate in three levels including;control(P0K0) ,phosphorus 50% less than conventional farmers use and potassium 50% less than recommended soil test(P12K13) and phosphorus base on conventional farmers use and potassium base on recommended soil test(P24K25). The results in north Isfahan showed that long term irrigation, may cause heavy metal accumulation in soil as well as limitation on COD and TSS of municipal wastewater.The soil organic matter content,total nitrogen,available phosphorous,available pottasium and heavy metals in soil irrigated with wastewater were higher than the soil irrigated with wells water. It is important to clarify that diminishing the limitations of north Isfahan wastewater is necessary for optimum use of municiple wastewater in agriculture lands. The results of Mashhad showed that although the highest grain and straw yield obtained in municiple wastewater irrigation with 3878 and 14530 Kg.h-1 respectively,but three was not significant difference in municiple wastewater and wells water irrigated fields.The highest thousand grain weight of 39.7 gram obtained in mixing of two source of wastewater and wells water irrigation.The final infiltration rate in wastewater, well water and mixing two source of water was 1.17,0.83 and 0.66 cm.hr-1 respectively.It seems that higher organic matter in wastewater caused soil aggregate and structural stability and increased infiltration rate. The results of Varamine first experiment showed that elements of Pb,Cu , Zn and Cd,Ni were increased significantly in contaminated lands. Also,the elements of Cd and Pb were increased significantly in plants.The amount of Cd and Pb in contaminated soils were several times of normal levels in soil. The results of the second experiment showed that grain and straw yield , thousand seed weight, length of ear and number of grain in ear weren t significant in nitrogen, phosphorus and potassium treatments and their interactions. Based on the resuls, it could be concluded that in wheat fields under wastewater irrigation the rate of nitrogen, phosphorus and potassium fertilizer may decrease considerabily,without significant yield loss. Keywords: wastewater,heavy metals,wheat,nitrogen phosphorus, potassium