Soil Acidification, its Measurement and the Processes Involved

Helyar, K. R.; Porter, WM; Robson, A. D.

doi:10.1016/b978-0-12-590655-5.50007-4

Cited by 190 publications

(173 citation statements)

References 36 publications

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“…There is wealth of information on the processes of soil acidification (Helyar and Porter 1989); however, the causes of subsoil acidification are poorly understood. In general, soil acidification results from natural weathering processes and imbalances within the carbon (C) and nitrogen (N) cycles.…”

Section: Subsoil Aciditymentioning

confidence: 99%

Subsoil constraints to grain production in the cropping soils of the north-eastern region of Australia: an overview

Dang¹,

Dalal²,

Routley³

et al. 2006

Aust. J. Exp. Agric.

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Section: Subsoil Aciditymentioning

confidence: 99%

Subsoil constraints to grain production in the cropping soils of the north-eastern region of Australia: an overview

Dang¹,

Dalal²,

Routley³

et al. 2006

Aust. J. Exp. Agric.

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“…However, further acidification due to bases removed by product removal or movement of cations associated with nitrate production may intensify the soil acidity problem. Although the rate of these acidifying processes is slow under natural conditions, agricultural production systems undergo accelerated soil acidification as a result of anthropogenic inputs and outputs (Helyar, 1976;Helyar & Porter, 1989;Sumner & Noble, 2003). The factors that contribute to soil acidification include the initial soil pH, soil buffering capacity, and the acidification rate (Hill, 2003).…”

Section: Introductionmentioning

confidence: 99%

Assessing the potential soil acidification risk under dryland agriculture in the Mlondozi district in the Mpumalanga Province of South Africa

Rensburg

Claassens

Beukes

et al. 2009

South African Journal of Plant and Soil

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The farming community in the Mlondozi district in the Mpumalanga Province of South Africa has been part of a government liming intervention with the objective to ameliorate the serious soil acidity problem in the district. The current study was undertaken in order to evaluate the impact of the liming intervention and the risk of reacidification of the soil due to natural and agricultural activities. Acid production in the 0-250 mm depth varied from a measured 0.21 to 10.31 (mean 3.70 kmol H + ha -1 year -1 ) in crop production sites. Approximately 190 kg lime ha -1 yr -1 is required to maintain current soil pH levels under crop production. The rate of pH decline for the top 0-250 mm depth was between 0.051 and 0.918 (mean 0.237) pH units year -1 . In the absence of remedial lime applications, pH(H 2 O) values in most of the area are projected to decrease to the critical value of 5.68 or lower within 4 years. The upper and lower critical pH(H 2 O) were found to be between ca. 5.73 and 5.68. Below the lower critical value a reduction in crop production can be expected and above the upper critical value, accelerated acidification takes place. Soils with an extractable Al and acidity of <0.180 and <0.253 cmol (+) kg -1 soil, respectively, a clay content of 26%, and an ECEC value of 3.29 cmol (+) kg soil -1 , or high initial soil pH values, are more at risk to accelerated acidification than soils with lower extractable Al and acidity, higher clay contents and higher ECEC values.

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“…Excess cation removal (moBVpot) = Y * (LC -SA) ( 1 ) 245 where Y is total dry matter yield (kg per pot), ZC is the sum of charge from legume cation uptake (Ca 2+ , Mg 2+ , K + , and Na + , mol+ kg" 1 DM), and IA is the sum of charge from uptake of anions by the legume (H 2 PO 4 -, SO 4 2 -, and Cl", mol+ kg" 1 DM). This procedure is analogous to the calculation of organic anion removal as described by Helyar & Porter (1989) and Jarvis & Robson (1983), which assumes that the charge surplus created by excess cation uptake by plants is counterbalanced either by the formation of organic anions or by the export of H + into the rhizosphere, thereby maintaining plant electroneutrality.…”

Section: Calculationsmentioning

confidence: 99%

“…Note that this approach ignores charge contributions arising from the uptake of soil N as either NH 4 + or NO3"; differentiating between uptake in these two forms is experimentally very difficult, and for convenience N-cycling effects are calculated from the net inputs and exports of N to the plantsoil system (Helyar & Porter 1989;de Klein et al 1997). As stated above, NO3" leaching in this experiment was eliminated by only watering pots to 75% of their field moisture capacity, and the net acidity arising from N-cycling effects was therefore zero.…”

Section: Calculationsmentioning

confidence: 99%

“…Soil acidification is a natural process, but the rates at which it occurs are enhanced by intensive farming practices, mainly through the increased net removal of basic nutrients from the soil-plant system plus the greater losses of oxidised forms of nitrogen via nitrate leaching associated with intensive agriculture. Helyar & Porter (1989) describe a theoretical framework for estimating the net input of protons into a system, which is made up of three distinct components: carbon-cycle effects, nitrogen cycling effects, and the direct inputs of acidic products, e.g., fertilisers containing the reduced forms of plant nutrients. Bolan et al (1991) use a similar approach to estimating soil acidification rates in legume-based pastures.…”

Section: Introductionmentioning

confidence: 99%

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Soil acidification through carbon cycling in legumes: A pot experiment examining the contributions from white clover, lotus, Caucasian clover, and lucerne

Monaghan

Morrison

Sinclair

1998

New Zealand Journal of Agricultural Research

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Soil acidification, induced by the growth of four legume species (white clover, lotus, lucerne, or Caucasian clover), was examined in a glasshouse pot trial at initial soil pH levels of either 4.5, 5.0, or 5.5. White clover and lotus out-yielded lucerne and Caucasian clover at all soil pH levels, particularly at the lowest level of pH 4.5. The acidity produced as a result of this legume growth was shown to approximately correspond to the removal of excess cation over anion nutrients by the plants. Averaged over all three soil pH levels, plant excess cation concentrations decreased in the order: white clover > Caucasian clover > lucerne > lotus. With the exception of white clover, there was no evidence of any consistent change in excess cation concentrations as soil pH decreased, indicating that the rate of excess cation removal did not decrease as soil pH declined. Although white clover was shown to have a higher excess cation concentration than the other three legumes, plant yield was the major determinant of legume-induced soil acidification, rather than legume species excess cation concentration.

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Soil Acidification, its Measurement and the Processes Involved

Cited by 190 publications

References 36 publications

Subsoil constraints to grain production in the cropping soils of the north-eastern region of Australia: an overview

Subsoil constraints to grain production in the cropping soils of the north-eastern region of Australia: an overview

Assessing the potential soil acidification risk under dryland agriculture in the Mlondozi district in the Mpumalanga Province of South Africa

Soil acidification through carbon cycling in legumes: A pot experiment examining the contributions from white clover, lotus, Caucasian clover, and lucerne

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