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

Abstract

<span>Irrigation, salinity and nitrogen (N) are the three major limiting environmental factors in<br /><span>maize yield potentials especially in arid and semi-arid regions. An integrated water and N Maize<br /><span>Simulation Model (MSM) was modified for salinity conditions using 2009-2010 field<br /><span>experiments data in southwest of Iran. Irrigation levels were: I<span>1<span>=1.0ET<span>c<span>+0.25ET<span>c <span>as normal<br /><span>leaching amount, I<span>2<span>=0.75I<span>1 <span>and I<span>3<span>=0.5I<span>1<span>, salinity of irrigation water: S<span>1<span>=0.6, S<span>2<span>=2.0 and S<span>3<span>=4.0<br /><span>dS m<span>-1 <span>and N fertilizer rate: N<span>1<span>=0, N<span>2<span>=150 and N<span>3<span>=300 kg N ha<span>-1<span>. Data of the first and second<br /><span>year were used to calibrate and validate the modified model, respectively. The MSM model was<br /><span>modified by including the combined effects of water and salt stresses using different water<br /><span>uptake functions. Furthermore, N uptake <span><em>via </em><span>mass flow process was also modified. By this<br /><span>modification, the soil salinity was also estimated by the model. Calibration/validation results<br /><span>showed that the water uptake function of Homaee and Feddes led to a better estimation of all<br /><span>parameters than those obtained by other water uptake functions. Based on the NRMSE and d<br /><span>indices, the modified MSM model presented a very good to fair estimation of soil water content,<br /><span>salinity and N, evaporation, transpiration, evapotranspiration, leaf area index, total dray matter,<br /><span>N uptake and grain yield. Besides, under saline irrigation water there was much higher risk to<br /><span>the groundwater contamination by nitrate leaching.</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><br /><br class="Apple-interchange-newline" /></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>