Monitoring long‐term changes in reserve potassium in some New Zealand soils using a modified sodium tetraphenyl‐boron method

Carey, Peter; Metherell, A. K.

doi:10.1080/00288233.2003.9513547

Cited by 13 publications

(10 citation statements)

References 14 publications

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“…Instead, the large variability indicated that a comprehensive sampling regime would be required to estimate Step K for each field. Carey and Metherell (2003) reached a similar conclusion in a study of long-term fertilizer trials conducted on New Zealand soils with sedimentary parent materials.…”

Section: The Second Surveysupporting

confidence: 59%

Plant available potassium in New Zealand steep-land pasture soils

2006

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Section: The Second Surveysupporting

confidence: 59%

Plant available potassium in New Zealand steep-land pasture soils

2006

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“…Cox et al (1999) showed in a pot trial study that shorter extraction times using NaTPB may be preferable to longer-term extractions as a measure of plant available-K. However, extrapolations to the field from pot trials can prove problematic for a variety of reasons (Carey and Metherell 2003a).…”

Section: Soil Test Methodologymentioning

confidence: 99%

“…The unexplained portion of the K balance is assumed to be mainly due to changes in soil K below the standard sampling depth (0-7.5 cm) (Carey and Metherell 2003a). The methodology for extraction of reserve K using NaTPB differs from cation exchange-based soil test methodologies such as QTK in that the removal of K from soil mineral interlayers is kineticallycontrolled (Chute and Quirk 1967;Cox and Joern 1997).…”

Section: Soil Test Methodologymentioning

confidence: 99%

“…The critical quick test K value for pastures on sedimentary soils is believed to be generally in the 0.3 to 0.4 cmol K/kg soil range (measured in the top 7.5 cm). However, it is well known that certain low QTK soils do not respond to applied K, probably because of the release of K from the reserve pool (Carey and Metherell 2003a;Syers 1998). The quantity of reserve-K in soils is strongly related to the content of clay and/or fine clay (Goulding 1987;Metson 1980) but it has also been shown that using strong acid to decompose the 2:1 lattice structure of micaceous minerals can overestimate plant available K (Newman and Brown 1966).…”

Section: Introductionmentioning

confidence: 98%

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An improved procedure for routine determination of reserve-K in pastoral soils

2010

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Non-exchangeable K (reserve K) can be an important source of K for plant uptake in micaceous soils but testing for reserve K is laborious and expensive and involves use of potentially hazardous chemicals. Our objectives were to (1) identify a cheaper and more reliable reserve K test that is amenable for routine use by commercial laboratories, and (2) quantify the response of grass-clover pasture to applied K in soils differing in reserve K. We measured the release of reserve K using different combinations of the K-precipitant, sodium tetraphenyl boron (0.033 to 0.2M), and extraction time (1 to 16 h). Copper chloride was used to decompose the Ktetraphenyl boron precipitate rather than the more toxic mercuric chloride or acetone. Based on data obtained for soils with a wide range of reserve K values, a test involving extraction of soil (1-g) in 0.1 M Na-tetraphenyl boron for 4 h was selected as the best option for routine use because it generally gave similar values to the current test (thus the same diagnostic criteria may be applicable) and it provided a better fit with operational requirements of commercial laboratories. Pasture K responses, in the presence and absence of applied N, were measured over a single growing season (pasture harvested at intervals of 1-2 months, depending on growth rate) at seven sites in Canterbury, New Zealand with reserve K (measured using the current test) ranging from 0.5 to 2.3 cmol c /kg (all sites were low in exchangeable K, <0.33 cmol c /kg). The size of the K response depended on the clover content of the pasture and only one site with a high clover content responded consistently to K throughout the season. Clover content increased at all sites following K addition, confirming that a major benefit of pasture K fertilization is in improving clover production. Our results suggest that there may not be a unique critical threshold for reserve K that can be applied to all pastures; rather, the value below which a production response to K is obtained may depend on the amount of clover in the pasture.

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“…While K exch can reach steady state at a low level when K balance is negative for a long time (Blake et al 1999, Madaras andLipavský 2009), a decrease of K reserves is clearly measurable in K non-exch pool (Carey and Metherell 2003, Andrist-Rangel et al 2007. K exch monitoring therefore might not give a true impression about the development of soil K reserves (Madaras 2014).…”

mentioning

confidence: 99%