Modification of a maize simulation model under different water, nitrogen and salinity levels

Document Type: Research Paper

Authors

Irrigation Department, Shiraz University, Shiraz, I.R. of Iran

Abstract

Irrigation, salinity and nitrogen (N) are the three major limiting environmental factors in
maize yield potentials especially in arid and semi-arid regions. An integrated water and N Maize
Simulation Model (MSM) was modified for salinity conditions using 2009-2010 field
experiments data in southwest of Iran. Irrigation levels were: I1=1.0ETc+0.25ETc as normal
leaching amount, I2=0.75I1 and I3=0.5I1, salinity of irrigation water: S1=0.6, S2=2.0 and S3=4.0
dS m-1 and N fertilizer rate: N1=0, N2=150 and N3=300 kg N ha-1. Data of the first and second
year were used to calibrate and validate the modified model, respectively. The MSM model was
modified by including the combined effects of water and salt stresses using different water
uptake functions. Furthermore, N uptake via mass flow process was also modified. By this
modification, the soil salinity was also estimated by the model. Calibration/validation results
showed that the water uptake function of Homaee and Feddes led to a better estimation of all
parameters than those obtained by other water uptake functions. Based on the NRMSE and d
indices, the modified MSM model presented a very good to fair estimation of soil water content,
salinity and N, evaporation, transpiration, evapotranspiration, leaf area index, total dray matter,
N uptake and grain yield. Besides, under saline irrigation water there was much higher risk to
the groundwater contamination by nitrate leaching.


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