Cooperative adsorption involving anions and cations, termed ion‐pair adsorption (IPA), is reported to increase the retention of some ions in certain soils. Sulfate and calcium can exhibit such interaction, and this affects their movement through the soil. Ion‐pair adsorption is shown here in miscible displacement experiments with a variable‐charge soil. The relevance of IPA under more realistic conditions is further investigated in a pot experiment. Rapeseed (Brassica napus) was grown at two different irrigation regimes and with two sulfur fertilizer sources. Calcium sulfate (CaSO4·2H2O) was used to induce IPA in contrast to potassium sulfate (K2SO4). The results suggest that IPA reduces sulfate and calcium leaching only in the short term. Continued irrigation dissipates the differences between the two fertilizer sources. Final soil ion concentrations and the plant uptake could not be related to IPA, evidencing the short‐term relevance of IPA. The influence of IPA on the bioavailability of calcium and sulfate to plants still demands further study.

Potassium sulfate

10.1080/00103620903173814

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Citations (1)

Globalisation of water management

Agricultural Water Management (2000)

Brent Clothier

Emerging Technologies

10.1016/s0378-3774(00)00091-3

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Citations (1)

The impact of soil carbon management on soil macropore structure: a comparison of two apple orchard systems in New Zealand

European Journal of Soil Science (2009)

M. Deurer D. V. Grinev Iain M. Young Brent Clothier Karin Müller

Summary We analysed the long‐term effect of the addition of organic carbon (C) on the macropore structure of topsoils. For this purpose we compared the top 50 mm in the tree rows of an organic apple orchard with those in an adjacent conventional orchard with the same soil type, texture and previous land‐use history in New Zealand. After 12 years the topsoils of the organic orchard had 32% more soil organic carbon (SOC) sequestered than those of the conventional, integrated orchard because of regular compost applications and grass coverage. We quantified the macropore structure (macropores = pores > 0.3 mm) of nine undisturbed soil columns (43 mm long, 20 × 17 mm in the plane) within each orchard using 3D X‐ray computed tomography. The macroporosity (7.5 ± 2.1%) of the organic orchard soil was significantly greater than that of the integrated orchard (2.4 ± 0.5%). The mean macropore radius was similar in the organic and integrated systems, with 0.41 ± 0.02 mm and 0.39 ± 0.01 mm, respectively. The connectivity of macropores tended to be greater in the organic than in the integrated system, but this was not statistically significant. The pronounced soil C management in the organic orchard increased both the formation of macropores by roots and a larger fresh weight of anecic earthworms, and the stabilization of the macropore structure was increased by a larger aggregate stability and microbial biomass compared with those of the integrated orchard. We simulated the diffusion through the measured pore structures of segments of the soil columns. The segments had the length of the mean aggregate size of the soils. The relative diffusion coefficients at this aggregate scale were significantly greater in the organic (0.024 ± 0.0009) than in the integrated (0.0056 ± 0.008) orchard. In a regression analysis with both the porosity and connectivity of macropores as significant variables, 76% of the variability of the relative diffusion coefficients was explained in the integrated, and, with the porosity as the only significant factor, 71% of the variability in the organic orchard. We hypothesize that a greater relative diffusion coefficient at the aggregate scale would reduce nitrous oxide (N 2 O) production and emission in a wet soil and suggest that soil C management combats climate change directly by sequestering C and indirectly in the form of a reduction of N 2 O emissions, by creating more macropores.

Macropore

Orchard

Soil carbon

Soil structure

10.1111/j.1365-2389.2009.01164.x

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Citations (89)

Cation transport during unsaturated flow through two intact soils

European Journal of Soil Science (1997)

Iris Vogeler D. R. SCOTTER Brent Clothier R. W. TILLMAN

10.1046/j.1365-2389.1997.00105.x

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Citations (6)

Advances in Soil Ecosystem Services: Concepts, Models, and Applications for Earth System Life Support

Vadose Zone Journal (2013)

David A. Robinson Bethanna Jackson Brent Clothier Estelle Dominati S.C. Marchant

The ecosystem services approach is gaining wide acceptance at the policy‐making level as a framework for integrating science and policy regarding the natural environment. It is important that soil science clearly articulates how knowledge and understanding of the vadose zone soils can be transmitted through this framework into the decision‐making process. Competition between food production, living space, and maintaining habitat for all of earth's life‐forms has never been so intense, so the need for soil security and vadose zone protection is paramount. Soil management can no longer be thought of in terms of single function management but instead needs to be considered and managed in the context of the multiple functions it offers. In this 10th anniversary issue of the journal, we assess progress in the development of a coherent soil ecosystem services framework using the natural resource management stock‐flow and fund‐service resource approach. We go on to examine some of the areas where the application of an ecosystems approach is gaining traction, which include national and local decision making as well as support for legal arguments in court.

Soil functions

Natural Resource Management

Ecosystem Management

10.2136/vzj2013.01.0027

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Citations (55)

THE CONSTANT HEAD WELL PERMEAMETER

Soil Science (1985)

W. D. Reynolds D. E. Elrick Brent Clothier

In this paper, the constant head well per-meameter (CHWP) theory is extended analytically to account for the effects of unsaturated flow. This results in a more accurate estimate of the field-saturated hydraulic conductivity and in new methods for in situ estimation of the soil sorptivity and the α parameter of the exponential hydraulic conductivity-pressure head function. Calculations using the extended CHWP theory and “average”sand, loam, and clay soils indicate that the original CHWP theory is only slightly in error for soils exhibiting weak capillarity, but can be substantially in error for soils exhibiting strong capillarity. The extended theory successfully predicts results of previous numerical investigations of the CHWP method.

Permeameter

Sorptivity

Pressure head

Constant (computer programming)

Hydraulic head

10.1097/00010694-198502000-00011

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Citations (158)

BURGERS' EQUATION

Soil Science (1981)

Brent Clothier J. H. Knight Ian White

We present the analytical constant-flux solution to Burgers' equation. Burgers' equation is a minimally nonlinear Fokker-Planck diffusion equation, applicable to infiltration into soils with a constant diffusivity and quadratic conductivity-water content relationship. Field Bungendore fine sand has a near-constant diffusivity-water content relationship, and analytical solutions of Burgers' equation are in good agreement with field profiles of water content obtained in situ with a rainfall simulator. The solutions and experimental data all relate to nonponding infiltration with fluxes less than the saturated hydraulic conductivity; however, a wide range of elapsed times and flux rates are covered. Predicted wet-front penetration is in good agreement with the field experimental data. The complete analytical solution can be evaluated using a programmable hand calculator. The simpler "profile-at-infinity" solution is shown to be surprisingly accurate over a wide range of times, giving useful results easily. An expression for the time to ponding is also presented.

Ponding

Infiltration (HVAC)

Constant (computer programming)

10.1097/00010694-198110000-00001

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Citations (67)

The use of visible and near‐infrared spectroscopy for the analysis of soil water repellency

European Journal of Soil Science (2014)

I. Kim Reddy Pullanagari M. Deurer Ranvir Singh Keùn Huh

Summary This study investigated the potential of visible/near‐infrared reflectance spectroscopy ( V is‐ NIRS ) to predict soil water repellency ( SWR ). The top 40 mm of soils ( n = 288) across 48 sites under pastoral land‐use in the N orth I sland of N ew Z ealand, which represented 10 soil orders and covered five classes of drought proneness, were analysed by standard laboratory methods and V is‐ NIRS . Soil WR was measured by using the molarity of ethanol droplet ( MED ) and the water drop penetration time ( WDPT ) tests. Soil organic carbon content (% C ) was also measured to examine a possible relationship with SWR . A partial least squares regression ( PLSR ) model was developed by using V is‐ NIRS spectral data and the reference laboratory data. In addition, we explored the power of discrimination based on WDPT classes using partial least squares discriminant analysis ( PLS‐DA ). The PLSR of the processed spectra produced moderately accurate prediction for MED ( R 2 val = 0.61, RPD val = 1.60, RMSE val = 0.59) and good prediction for % C ( R 2 val = 0.82, RPD val = 2.30, RMSE val = 2.72). When the data from the 10 soil orders were considered separately and based on soil order rather than being grouped, the prediction of MED was further improved except for the A llophanic, B rown, O rganic and U ltic soil orders. The PLS‐DA was successful in classifying 60% of soil samples into the correct WDPT classes. Our results indicate clearly that V is‐ NIRS has the potential to predict SWR . Further improvement in the prediction accuracy of SWR is envisaged by increasing the understanding of the relationship between V is‐ NIRS and the SWR of all N ew Z ealand soil orders as a function of their physical properties and chemical constituents such as hydrophobic compounds.

Soil carbon

Soil test

10.1111/ejss.12138

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Citations (16)