عنوان مقاله [English]
In this study, P critical level for corn plant (Zea mays L.) was determined using PBC in 25 combined soils samples from different fields of East Azerbaijan province. To calculate the PBC, current soil P test methods such Olsen,Colwel, Soltanpur and Schowab, Kelna2 and iron impregnated strips as a quantity factor (Q) and the methods of soluble P measurements such as distilled water, calcium chloride and Paauw method as a intensity factor(I) was used. According of the results, the method of PBC (Olsen-P/ Paauw-P) compared to other methods for calculating PBC, was the best method to predict of P uptake by corn plant. The high correlation of PBC (Olsen-P/ Paauw-P) data with the shoot content of phosphorus was confirmed. PBC linear correlation with shoot P content was separated in two positive and negative parts and the positive value of the correlation was 0.91** and negative value was -0.89**. Critical level of soil P for corn with PBC method based on 90 % relative dry matter was determined 2.2, 2.44 and 1.19 by using graphical Cate–Nelson, Cate–Nelson analysis of variance and Mitscherlich-Bray methods, respectively. Mitscherlich-Bray equation coefficient C1 and C, for PBC, were 0.08411 and 0.0122 respectively.