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Subject: Soil and Water Engineering × Author: Dar, Mehraj U Din × End date: 2021 × Start date: 2021 × Type: Thesis ×
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    Simulation of Nitrate-N movement through subsurface drainage system under cropping conditions
    (Punjab Agricultural University, Ludhiana, 2021) Dar, Mehraj U Din; Singh, J. P.
    The study was conducted to simulate the NO3-N movement through subsurface drainage in a field under cropping conditions using DRAINMOD-NII model and for predicting optimum depth and spacing for minimum nitrate leaching. The nitrogen balance was estimated using DNDC model for the area installed with the subsurface drainage system at Thehri village Muktsar district of Punjab. Both the models of DRAINMOD NII (v. 6.1) and DNDC (v.9.5) (Denitrification and Decomposition model) were calibrated and validated for the 2 years study period from 2018-2020. The reliability of the models was evaluated by comparing observed and simulated values of drain flow, nitrogen loss, water table depths and relative yields for the rice-wheat cropping system. The validated DRAINMOD-NII model was used to predict the optimal depth and spacing for minimum nitrate losses. The nitrogen balance for the area under subsurface drainage system was estimated using DNDC model for rice-wheat cropping system. The statistical performance of DRAINMOD-NII model was carried out and the range of statistical parameters viz, root mean square error (RMSE), Nash Sutcliffe modeling efficiency (NSE) and correlation coefficient (R2) were obtained to be 0.12 to 9.66, 0.47 to 0.88 and 0.53 to 1 respectively during the calibration and validation periods. The values of statistical parameters for DNDC model viz; RMSE, NSE and R2 ranged from 6.8 to 8.5, 0.78 to 0.88 and 0.84 to 0.90 respectively during the calibration and validation periods. The optimal depth and spacing of subsurface drainage system for the study area was obtained to be 1.3 m and 42 m respectively using DRAINMOD-NII model for minimum nitrate loss. The overall nitrogen balance was found to be -99.44 kg N ha-1 yr-1(negative) and 69.1 kg N ha-1 yr-1 (positive) for rice and wheat crops respectively using DNDC model. DRAINMODNII model and DNDC model performed a better simulation, and could be used for efficient nitrogen management in the region.