abstract the increasing of yield per unit area is usually achievable by improving the soil fertility level through using (chemical) fertilizers. the purpose of the present research was to evaluate the 6 extraction methods including olsen, morgan, ammonium bicarbonate-dtpa, colwel, bray and mehlich 3 in order to specify a suitable extractant(s) for estimating available phosphorus through using 2...

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, cal...