ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We derive a new optimization principle that can be used, first, to predict accurately water intake into a soil when air movement is not negligible. The principle is also useful for solving the transport equation numerically, by avoiding numerous iterations. Finally, analytical approximations can be greatly improved when the principle is taken into account.These three applications of the optimization principle are illustrated by comparison with an exact solution using Brutsaert's technique.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We investigated the effect of temperature on K availability using quantity-intensity (Q/I) analyses and on K selectivity on the Ap and B21t horizons of a Kalmia sandy loam (Tppic Hapludults), an Evesboro loamy sand (Typic Quartipsamments), and a Matapeake silt loam (Typic Hapludults) from the Delaware Coastal Plain. The predominant mineral suite of the <2-μm clay fraction consisted of vermiculite, mica, and chloritized vermiculite, with lesser quantities of kaolinite and quartz. Quantity-intensity analyses revealed that as temperature increased from 0 to 40°C, the amount of K adsorbed by the soils decreased. For similar initial electrolyte concentrations, ΔK (K concentration difference between initial and equilibrium solutions) decreased, while the activity ratio of K+to (Ca2++ Mg2+)1/2, orARk, increased. Thus, to maintain an equal amount of K on the soil as temperature increased, a higher ratio of K+to (Ca2++ Mg2+)1/2in solution was needed. The equilibrium potassium activity ratio (ARek), which is a measure of available K, increased in the soil horizons as temperature increased. The labile K parameter, (ΔK0), changed little with temperature, though the potential buffering capacity (PBCk), which is related to the CEC of the soil, decreased with increased temperature. Potassium selectivity coefficients (kK), based on the Gapon equation, decreased with increased temperature, indicating decreased K sorption relative to Ca2+and Mg2+, with increased temperature. As temperature increased from 0 to 40°C, the quantity of K in the equilibrium solution increased from an average of 19.3 to 20.9 moles/liter and from 14.0 to 17.0 x 10−4moles/liter in the Ap and B21t horizons, respectively, of the three soils. The amounts of Ca and Mg in solution, however, decreased as temperature increased.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Natural soil materials react with derivatives of benzene in water under saturated conditions slowly, with equilibration times of up to 5 days. The Freundlich isotherm equation fits best those water-phenol-soil systems in which few soil properties dominate. For the fine-textured B horizon soils used in this experiment, percentage iron oxides and solution pH were found to be the most important factors related to adsorption of these phenols by soils. Molokai clay had the highest adsorption rate of simple phenols. Slightly soluble phenols, such as dimethyl and dichloro phenols, seem to be able to react better with soils than the more readily soluble phenols, such as cresols, phenol, andp-nitrophenol. In comparing Hammett (σ) and hydrophobic (π) constants with the laboratory results, we found that a high degree of correlation seems to exist between them and the behavior of these organics in soils.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We studied the relationship between the K+buffer power and the critical K+concentration of the soil solution in pot experiments with Italian ryegrass. Critical K+concentration is defined as that K+concentration of the bulk soil solution below which plants respond by a yield increase when K fertilizer is applied. The K+concentration of the soil solution was measured indirectly by means of the electro-ultrafiltration technique. The K+buffer power was obtained by plotting the exchangeable K+against the K+concentration of the bulk soil solution. The steepness of the resultingcurve reflects the K+buffer power.Nine soils differing widely in clay content, CEC, and K+buffer power were used for the investigation. A very close correlation (r2= 0.908) was found between the K+buffer power and the critical K+concentration of the soil solution. This relationship was reflected by a hyperbola (y=c/x), indicating that the critical K+concentration was lower the higher the K+buffer power was.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Most andic soils are fertile and support good tree growth by virtue of favorable nutrient and water availability. Western Montana has some andic soils that are low in nutrient content and, because of underlying gravels that allow excessive drainage, are droughty. Before the drought problem was recognized, the area was fertilized. These soils are deficient in Ca, Cu, K, Mg, Zn, and total N. Fertilizer added to known volumes of andic soil in Leach tubes showed that not all deficiencies can be remedied by adding the deficient ions. Adding 1000 ppm Ca made some calcium available, but released considerable Mg. Magnesium added to soil at 300 ppm released calcium from the soil. Adding potassium did not result in high levels of available potassium. Calcium and magnesium fertilizer released some manganese from andic soils. Copper in solution was nearly all available, and in some soils more copper was released than was added. Iron added to these soils increased iron availability 2.5 to 3 times in excess of what was added. Manganese fertilizer was readily retrieved with 1NNH4OAc extractant. Zinc retrieval was poor, but phosphate retrieval with 1NNH4F was good.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We examined the sorption of three nitrogen-heterocyclic compounds (acridine, bi-quinoline, and dibenzocarbazole) on 14 soils and sediments with a wide range of properties. The compounds produced linear sorption isotherms (Kp=Cs/Cw). When sorption was expressed on a constant organic carbon basis (Koc=Kp÷ organic carbon), theKocvalues obtained were in good agreement withKocvalues predicted fromKoc-SandKoc-Kowrelationships established for other classes of compounds. This study expands these relationships to include N-heterocyclics, particularly the lower, water-soluble members of this family.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We describe several methods for calibrating different neutron moisture meters. The simplest was found to be that of calibrating one “master” probe and comparing other probes with this under similar field conditions over a range of soil water contents. If several probes are available initially, plastic absorbers of various thicknesses can be used as secondary standards to establish a regression equation for the different probe. From the slope and intercept values obtained, a reference regression equation can be developed that can be used to calibrate other probes in the laboratory.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The alkaline permanganate digestion method has been widely used for assessing the available nitrogen pool in soils. We report that simple laboratory experiments have shown that the standard method does not include nitrate and nitrite, but that a simple modification, involving the use of Devarda's alloy, allows inclusion of nitrate and nitrite. This modification is desirable if the method is to be used for assessing available nitrogen in tropical upland soils that experience pronounced wet and dry seasons. Results with soil on our experimental farm showed that the nitrate content of the soil contributed 10 to 40 percent of the available nitrogen assessed by the modified method.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We derive a mathematical expression (fourth-degree polynomial) to calculate the average of the maximum and minimum soil temperatures at a 10-cm depth for any day of the year at 15 locations in France. Coefficients for the equations are tabulated.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID