Poljoprivreda (Jun 2010)
COMPARISON OF SOIL PHOSPHORUS TEST METHODS
Abstract
Soil-P test is obligate chemical analysis for soil productivity estimation and most frequent used method in Croatia is AL method (soil extraction by ammoniumlactate solution at pH 3.75). Howewer, in some soils AL method (especially calcareous) could be inaccurate for phosphorus fertilizer recommendations and crop response could be inadequate. Hence, the aim of this research was to compare 6 different P-tests: Olsen, Morgan, Bray1, Bray 2, CAL and DL. Each of these methods had a different pH of extraction solutios: Olsen (pH 8.5), Morgan (4,8), Bray 1 and Bray 2 (2.6), CAL (4.1) DL (3.7). Aiming to compare these 7 soil tests, 360 soil samples were collected from the continental part od Croatia. The soil pH, organic matter, AL-P2O5 and % CaCO3 were analyzed. All samples were grouped according to soil pH in two groups (pHKCl 6 179 samples). Phosphorus content on the average decreased: Bray 1 > DL > AL > CAL > Bray 2> Olsen > Morgan. Significant corellations were estimeted between AL and Olsen P test (r= 0.88), AL and Bray 1 P test (r=0.68), Olsen and Bray 1 P test (r= 0,75) and CAL and DL P tests (r=0.45). In the analysed samples total phospohrus content was recorded in all samples and portion of organic phosphorus in total phosporus in soil ranged from 0.54 to 78.29 %. The developed models are very simple and useful because they can predict soil phosphurus using only one soil test data. The models were validated and showed that all recorded corelations in this study were precise and approved the aforementioned models accuracy.
