Showing papers in "Soil Science in 1968"

Coagulation of Humic Colloids by Metal Ions

Abstract: METAL-ORGANIC INTERACTIONS WERE STUDIED USING AN ALKALI SOLUBLE FRACTION OF PEAT (ASF) TO REPRESENT THE SOLUBLE HUMIC SUBSTANCES. ELEMENTAL AND INFRARED ANALYSES OF THE STANDARD ASF WERE MADE AFTER FREEZE-DRYING THE SOLUTION. THE COMPOSITION WAS SHOWN TO BE SIMILAR TO THE AVERAGE COMPOSITION OF ORGANIC MATTER EXTRACTED FROM VARIOUS SOIL HORIZONS FROM MANY DIFFERENT LOCALITIES. INFRARED SPECTRA OF THE LYOPHILLIZED STANDARD ASF CONTAIN A FEW SHARP BANDS INDICATING HYDROXYL AND CARBOXYL FUNCTIONAL GROUPS, SIMILAR TO THE SPECTRA OF MANY SOIL ORGANIC EXTRACTS. COAGULATION VALUE OR CRITICAL CONCENTRATION OF AN ELECTROLYTE WAS DETERMINED BY INTERPOLATING THE VALUE BETWEEN THE CONCENTRATION IN THE TEST TUBE THAT PRODUCED PRECIPITATION AND THE CONCENTRATION IN THE SUBSEQUENT TUBE WHERE NO PRECIPITATION COULD BE DETECTED. COAGULATION STUDIES INVOLVING THE ALKALI'S SOLUBLE FRACTION OF PEAT WITH ADDED MONOVALENT IONS (LITHIUM, SODIUM AND POTASSIUM), DIVALENT IONS (MAGNESIUM AND CALCIUM), AND TRIVALENT IONS (IRON, ALUMINUM, AND ASSISIUM) DEMONSTRATED THE FOLLOWING: (1) THE AMOUNT OF MONOVALENT, DIVALENT, AND TRIVALENT IONS REQUIRED TO EFFECT COAGULATION GENERALLY AGREES WITH THE THEORETICAL, AND (2) FOR MONOVALENT OR DIVALENT IONS, THE COAGULATING POWER INCREASES AS THE RADIUS OF THE HYDRATED ION DECREASES. THIS ALKALI SOLUBLE FRACTION OF PEAT CAN BE CONSIDERED AS A NEGATIVE HYDROPHILIC COLLOID OR A POLYELECTROLYTE AND THE STABILITY OF METAL-ORGANIC ASSOCIATIONS CAN BE EXPLAINED BY THE FUOSS EFFECT AND THE DOUBLE-LAYER THEORY OF COLLOID COAGULATION. IT IS CONCLUDED THAT THE COLLOIDAL PROCESS MAY BE RESPONSIBLE FOR MUCH OF THE METAL TRANSPORT IN PODZOLIZATION THAT IS OFTEN ATTRIBUTED TO CHELATION, AND COORDINATION COMPLEXES.

Alkali Versus Acid Extraction Of Soil Organic Matter

Abstract: INFORMATION IN THE LITERATURE SUGGESTS THAT ALKALI EXTRACTION MODIFIES SOIL ORGANIC MATTER. TO UNCOVER SUCH EFFECTS, SOIL SAMPLES TAKEN FROM A PODZOL BH HORIZON WERE EXTRACTED AT ROOM TEMPERATURE WITH 0.5 N NAOH UNDER N SUBSCRIPT 2 AND WITH 0.1 N HCL. FOLLOWING PURIFICATION, EACH EXTRACT WAS CHARACTERIZED BY ULTIMATE AND FUNCTIONAL GROUP ANALYSIS, BY INFRARED SPECTROSCOPY AND BY GEL FILTRATION ON SEPHADEX G-50 G-25. THE EXPERIMENTAL DATA SHOWED THAT THE CHARACTERISTICS OF THE TWO EXTRACTS WERE PRACTICALLY IDENTICAL, AND THAT ALKALI EXTRACTION HAD EITHER CAUSED NO MODIFICATIONS OR, AT MOST, ONLY VERY SLIGHT ONES IN THE ORGANIC MATTER INVESTIGATED. IT IS LIKELY THAT DAMAGING EFFECTS ASCRIBED IN THE LITERATURE TO ALKALI EXTRACTION HAVE BEEN EXAGGERATED, ESPECIALLY AS THESE APPLY TO SOIL HUMIC COMPOUNDS. /AUTHOR/

Calibration and evaluation of a wide-range gravimetric method for measuring moisture stress

Abstract: A METHOD IS PRESENTED OF USING FILTER PAPER AS A PASSIVE GRAVIMETRIC MOISTURE STRESS SENSOR WITH ROUTINE GRAVIMETRIC SOIL MOISTURE SAMPLING PROGRAMS. FILTER PAPER USED AS AN INDIRECT GRAVIMETRIC MOISTURE STRESS SENSOR MAKES IT POSSIBLE TO OBTAIN A MOISTURE STRESS VALUE FOR EACH GRAVIMETRICS SOIL MOISTURE SAMPLE. IT IS CONCLUDED THAT THE METHOD IS VERSATILE, ACCURATE, CONVENIENT, AND ECONOMICAL. IT WAS EFFECTIVE OVER THE ENTIRE STRESS RANGE FROM 0.001 BARS TO 1,500 BARS, AND FROM 1 TO 1,500,000 CENTIMETERS OF WATER (PF 0 TO 6.2). IT CAN BE USED BY ANYONE CONDUCTING AT GRAVIMETRIC SOIL MOISTURE CONTENT SAMPLING PROGRAM EITHER AS CONTROL FOR NEUTRON MOISTURE MEASUREMENTS OR IN LIEU OF THEM. MOISTURE STRESS MAY BE DETERMINED BY THIS FILTER PAPER METHOD WITH AN ACCURACY THAT IS COMPARABLE TO OR BETTER THAN THE ACCURACY OF OTHER METHODS WITH LIMITED RANGES. /AUTHOR/