Critical nitrogen equation for maize in Pakdasht region

The nitrogen demand during growing period is variable for plant, but most farmers use large amount of nitrogen without the knowledge of the proper time in order to achieve maximum product. This pattern of fertilizer consumption causes environmental pollution. The optimum demand of nitrogen during growing period could be determined by the critical nitrogen equation. The main objective of this study was to determine the coefficients of the critical nitrogen equation for maize in Pakdasht. Comparing these coefficients with suggested coefficients in France and China was the second objective of this research. The maize (single cross 704) for a season was planted on the farm of Aburaihan campus. The aboveground biomass (W) and its critical nitrogen concentration (Nc) were measured in six different times, from 26 days after planting to the harvesting time. The coefficients of critical nitrogen equation were determined using theory of critical nitrogen dilution curve. Finally, the equation of Nc = 2.9 W -0.27 as nitrogen critical dilution curve was proposed for maize in the Pakdasht. The results showed that the nitrogen status was mispredicted in 21% and 14% of measured data point, by France and China equations respectively while this erorr was only 9% by using the equation provided in this study. The main reasons for these errors are differences in climate and prevalent varieties of maize in different areas.