Estimates of Nitrate Leaching from Wheat Fields in Gorgan, of Iran

摘要

There is no estimation on the nitrate leaching from arable lands of Iran. Therefore, the CERES-wheat of DSSAT model was used to estimate the nitrate leaching from wheat fields of Gorgan. The experiment was conducted in Gorgan Northeast of Iran, during 2005-2007 years. Input data were 3 nitrogen use scenarios (N-S), 3 soil profiles (SLPs) and two Cropping Systems (CS) including rainfed (RFD) and irrigated (IRR) as well as daily weather data of this area. The amounts of fertilizer-N used in N-S-1, N-S-2 and N-S-3 were 165, 122 and 96 kg N ha~(-1), respectively. Three SLPs were defined on the basis of the analysis of hundreds soil samples. Soil samples were taken from arable lands to a 120 cm depth. The simulations were performed for a 45 years time period from 1961-2006. The average of N-leached in scenarios during 45 years estimated to be 23.6 kg N/ha/year. Cropping system and SLP had significant effects (p = 0.01) on the nitrate leaching, but the effects of N-Ss and interactions between 3 factors were not significant, statistically. The results of simulations indicated that in RFDCS and IRRCS about 16 and 31 kg N/ha/year have been leached, respectively. The N-leached rates from SLP I, II and III were 39, 19 and 13 kg N ha/year, indicating significant differences between SLPs. It can be concluded that considerable amounts of nitrate-N are leached from wheat fields in Gorgan, annually that can have important economic and environmental impacts.