feasibility study of phosphorus buffering capacity (pbc) application for estimation of corn available phosphorus in some calcareous soils

abstract 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.