COMPARISON OF SOIL PHOSPHORUS TEST METHODS

Abstract

Analiza biljkama pristupačnoga fosfora obavezna je agrokemijska analiza tla za procjenu plodnosti i preporuku gnojidbe, a u RH u upotrebi je najčešće AL metoda (ekstrakcija tla s amonij-laktat otopinom uz pH 3,75). Analiza AL metodom ekstrahiranog fosfora u nekim tlima (posebice karbonatnim) može rezultirati neodgovarajućim reakcijom usjeva na utvrđenu pristupačnost fosfora i preporuku gnojidbe pa je cilj ovoga rada usporediti AL metodu s 6 različitih ekstrakcijskih metoda za utvrđivanje pristupačnosti fosfora u tlu: Olsen, Morgan, Bray 1, Bray 2, CAL i DL. Svaka metoda ima različit kemizam i pH ekstrakcijske otopine: Olsen (pH 8,5), Morgan (4,8), Bray 1 i Bray 2 (2,6), CAL (4,1) DL (3,7). S ciljem usporedbe prikupljeno je i analizirano 360 uzoraka tla s područja kontinentalne Hrvatske. Analize su obuhvaćale kemijska svojstva tla kao pH, humus, AL-P2O5 i karbonati, a tla su prema kiselosti podijeljena u dvije pH grupe i pet pH grupa. Prosječno možemo reći da količina ekstrahiranoga fosfora u mg P2O5 kg-1 opada po nizu: Bray 1> DL> AL> CAL> Bray 2> Olsen> Morgan. Statistički značajna korelacija utvrđena je u svim uzorcima između AL i Olsen metode (r= 0,88), AL i Bray 1 metode (r=0,68), Olsen i Bray 1 metode (r= 0,75), te CAL i DL metode (r=0,45) U analiziranim uzorcima utvrđene su značajne količine ukupnoga fosfora, a udio organskoga fosfora u ukupnome fosforu kretao se od 0,54% do 78,29%. Regresijski modeli razvijeni u ovome radu vrlo su jednostavni i primjenjivi, jer mogu dati nove podatke već na temelju koncentracije fosfora ekstrahiranoga određenom metodom, što je dovoljno kao jedini ulazni podatak. Validacije modela dokazale su sve međuovisnosti metoda utvrđene u osnovnome setu uzoraka te potvrdile navedene preciznosti modela.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 thay 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