The objective of this study was to evaluate the Kelowna multiple element extractant and some EDTA and DTPA modifications for simultaneous determination of potassium and sodium in acid and calcareous soils. To that end, the relationships between K and Na concentrations extracted with 1 N NH4OAc and the Kelowna multiple element extractant (0.25 N HOAc + 0.015 N NH4F) were assessed. However, relationships between K and Na concentrations removed by the modified Kelowna multiple element extractants containing either EDTA or DTPA (KEDTA & KDTPA with NH4F; and AAEDTA & AADTPA without NH4F) were evaluated by comparing values against those obtained with the Kelowna extractant. Addition of these complexing agents was of interest because of their potential in enabling simultaneous extraction of available Zn. The procedures were evaluated by contrasting K and Na concentrations extracted from 100 Canadian soils — half which had pH values between 4.1 and 6.9 (H2O) and a second group with values between 7 and 9.6 — by means of graphing, regression and correlation techniques. Potassium and sodium concentrations removed by the Kelowna extractant ranged from 25 to 510 μg and from 10 to 1420 μg mL−1 soil, respectively. The Kelowna and its EDTA and DTPA modifications extracted K and Na as effectively from acid as calcareous soils. This conclusion was supported by the similar regression slopes obtained when relating concentrations of K and Na removed from these soil groups by the multiple element extractants against those removed by 1 N NH4OAc (r-values ≥ 0.97**). However, the new multiple element extractants removed an average of about 20% less K than 1 N NH4OAc from these soils, though similar Na levels. The lower K levels removed from the Kelowna extractant, or by one of its modifications, may require that soil test interpretation norms be adjusted to compensate for the lower values when using one of these to determine K-availability. A significant correlation was found between extracted Na levels and 1:2 vol/vol water-extract conductivities (r ≥ 0.83**) suggesting that "higher" Na levels may be soluble instead of exchangeable. Some Na test interpretations are discussed in the text. Key words: EDTA, DTPA
The influence of base saturation and fertility treatments on yield and cation composition of oats grown on two British Columbia soils high in organic matter was studied in the greenhouse. Increased base saturation significantly increased: the yield of oat forage on the Alouette soil (an organic soil), calcium uptake on both soils, magnesium content of oats grown on the Pitt soil, and tissue potassium with the Alouette soil.The yield decreased significantly when nitrogen was added to the Alouette soil. Nitrogen significantly increased tissue calcium on the Pitt soil. The magnesium and potassium content of oats was not influenced by nitrogen.With the Pitt soil there was a consistent (but not significant) trend showing that phosphorus increased yields. For the Alouette soil the interaction between phosphorus and base saturation significantly increased calcium absorption. Phosphorus tended to increase calcium uptake from both soils. Tissue magnesium increased significantly when phosphorus was added to the Pitt soil.There was a tendency (not significant) with both soils for yield to decrease as potassium was applied. When potassium was added to the Pitt soil there was a marked tendency for tissue magnesium to increase. A reverse trend occurred with the Alouette soil. Potassium fertilization of both soils significantly increased potassium absorption.
The influence of soil moisture regimes and P sources on the response of alfalfa to P was studied in the growth chamber. Surface samples of two calcareous British Columbia soils, Machete stony sandy loam and the Nisconlith clay loam were used. Alfalfa yield and P uptake were highest when soil moisture tension was allowed to reach a maximum of 2.0 bars and subsequently reduced to 0.2 bars. The P sources were almost equally available with this regime. Calcium metaphosphate and anhydrous dicalcium phosphate produced the highest yields. P content of alfalfa was highest with monoammonium phosphate on the Machete soil. Monocalcium phosphate resulted in the highest tissue P with the Nisconlith soil. Amount of P removed from the soil, with the exception of hydroxyapatitc, was not markedly influenced by P source. Hydroxyapatitetreated soil released the lowest amount of NaHCO3‐extractable P.
A laboratory study was conducted on two calcareous soils which had beeu previously cropped with lucerne. Equilibrium soil solutions were obtained from soil samples which were taken after the last harvest of lucerne. Monocalcium phosphate (r/npCa + pH,PO,) and lime (pH -I/zpCa) potentials and dicalcium phosphate potentials (pCaHPO,) were calculated from pH, Ca and P measurements in these solutions.A plot of the lime and phosphate potentials on a solubility diagram showed that all the experimental values were near or above the solubility curve for dicalcium phosphate dihydrate. There was little difference between all phosphorus sources on the Machete soil, and between the treatments on the Wisconlith soil. Lime potentials of the two soils were similar, Phosphate potentials of the Machete soil were lower than those of the Nisconlith soil. The moisture regimes tested did not affect the lime and phosphate potentials of either soil.Dicalcium phosphate potential of hydroxyapatite was significantly higher than for all the other sources on the Machete soil, and also that of monoammonium and monocalcium phosphate on the Nisconlith soil. The lowest pCaHPO, values occurred with the Nisconlith soil Moisture did not influence pCaHPO, on either soil.
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