Evaluation of Potential Nitrate and Ammonium Accumulation in the Soil Profile under Irrigation and Manure Treatments with the LEACHM Model

Bahmani, Omid; Broomand Nasab, Saeed; Behzad, Majid; Naseri, Abd Ali

Evaluation of Potential Nitrate and Ammonium Accumulation in the Soil Profile under Irrigation and Manure Treatments with the LEACHM Model

Document Type : Original Articles

Authors

¹ epartment of Irrigation, Faculty of Agricultural, University of Bu Ali Sina, Hamedan.

² epartment of Irrigation, Faculty of Water Sciences Engineering, University of Shahid Chamran, Ahvaz.

³ Department of Irrigation, Faculty of Water Sciences Engineering, University of Shahid Chamran, Ahvaz.

Abstract

Nitrate (NO3-N) and ammonium (NH4-N) leaching from agricultural soils can represent substantial losses of nitrogen (N) fertilizer, but a large variation in N losses has been reported. The objectives of this study were to assess the accumulation and movement of nitrate and ammonium in the soil profile over the study period under different irrigation and fertilizer conditions. So, N concentration and its leaching were studied under three N fertilizer and three irrigation treatments during 2007 Khuzestan Province, Iran. The irrigation treatments consisted of full irrigation (I1) and 85 (I2) and 70 (I3) percent of I1. Also, the N treatments were 150 (N1), 250 (N2) and 350 (N3) kg/ha. Soil sampling was conducted in June, July, August and September from the soil surface to 1.2 m depth at intervals of 0.3 m depth. We used the LEACHM model for nitrate (NO3-N) and ammonium (NH4-N) simulation, and their comparison with measured data. The amount of application of nitrogen and irrigation treatments indicated their important role in the accumulation of nitrate and ammonium in the soil profile. In this study, a high concentration of NO3-N was observed in I3N3 and also a high concentration of NH4-N accrued in the I3N3 and I3N2 treatment. After some time, Nitrate leached to subsurface depths and by the end of sampling (September) the concentration at the 0-30 cm depth was zero. The model was calibrated with a change in nitrification, denitrification and N volatilization for the three N treatments and model accuracy was increased after calibration so that Willmott's index for NO3-N and NH4-N after calibration was 0.56 to 0.98 and 0.76 to 0.96, respectively.

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