Determination of the critical level of copper for corn in some soils of East Azerbaijan province

The purpose of this research was the determination the critical level of copper for corn in 21 soils of East Azerbaijan province. In a greenhouse experiment, corn plant (Zea mays L.) single cross 704 variety, cultivated in two levels of Cu, zero and 7.5 mg Cu kg-1 soil with three replications. After the 60 days (end of the growth period), before harvesting chlorophyll index of leaf were measured, then plant harvesting and wet and dry weight in shoot and copper content were measured. Critical level of soil Cu for corn with DTPA and AB-DTPA methods were measured by using plant response column order procedure, graphical Cate-Nelson, Cate-Nelson analysis of variance (ANOVA) and Mitscherlich-Bray. According to the results, by application of copper, significant increases in corn shoot dry weight, concentration and content of Cu occurred. Critical level of soil Cu for corn with DTPA method based on 90 % relative yield, was determined as 1.46, 1 and 1.70 (mg Cu kg-1 soil) by using plant response column order procedure, graphical Cate-Nelson, Cate-Nelson analysis of variance (ANOVA) and Mitscherlich-Bray, respectively and for AB-DTPA method was 1.50, 1.80 and 2.94 (mg Cu kg-1 soil), respectively. The Mitscherlich-Bray equation coefficients C for these methods were 0.5874 and 0.3397 kg soil mg-1 Cu, respectively. In this research, the Cate-Nelson analysis of variance method was not the appropriate for determination of critical level of Cu for corn. Drawing the plot by the Excel softwar and correlation coefficients with statistical analysis by using SPSS software was performed.