development of an alternative to the olsen test for determining corn plant-available phosphorus in calcareous soils

In this research, several chemical extractants and modified olsen methods were studied in 25 surface-calcareous soils (0-30 cm) for determining available phosphorus (p) for corn (zea mays l.) plant. in this experiment, the highest correlation was obtained between extracted p by olsen and colwell methods (nahco3-extractable p) and dry weight of corn shoot (r =0.67 and 0.75, p<0.01, respectively). therefore, effects of varying effective conditions of extraction such as the period of shaking, the concentration and ph of nahco3 solution on the amount of p extracted from the soil and its correlation with growth parameters of the corn plant was investigated. the results showed that increasing the ph of nahco3 solutions: soil ratio, shaking period and concentration of nahco3 solution significantly increased the extracted p from the soils, but could not significantly increase the correlation between p extracted from the soil and growth parameters of the corn plant. the highest correlation was obtained between modified olsen method (with 4-hour shaking period and the solution: soil ratio of 6) and shoot dry weight (r=0.75, p<0.01) which was not significantly different (δr=0.08) using olsen’s test (0.5hour shaking time and solution: soil ratio of 20). the results of this study showed that p buffering capacity (pbc) could be the best method for predicting the available p by the corn plant.

توسعه روش جایگزین آزمون اولسن جهت تعیین فسفر قابل جذب ذرت در خاک‌های آهکی

در این تحقیق، برخی عصاره­گیرهای شیمیایی و روش­های تغییر یافته اولسن در 25 خاک آهکی سطحی (030 سانتی متر) برای تعیین فسفر قابل جذب گیاه ذرت  مورد مطالعه قرار گرفت. در این آزمایش، بیشترین همبستگی بین فسفر استخراج شده توسط روش­های اولسن و کالول (فسفر قابل عصاره­گیری با محلول بی کربنات سدیم) و وزن خشک بخش هوایی ذرت مشاهده شد( r =0.67,0.75 وp