A new approach to the interpretation of soil tests for phosphate response by grazed pasture

Saunders, William; Sherrell, C. G.; Gravett, I. M.

doi:10.1080/00288233.1987.10430479

Cited by 25 publications

(35 citation statements)

References 19 publications

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“…At the other extreme, the probability of response to fertiliser K is low (B0.1) if the soil QTK is about 10. This approach is similar to that used by Saunders et al (1987) when assessing the likelihood of pasture response to fertiliser P based on soil Olsen P levels, and the broad and general conclusion from this approach is similar to that expressed by Hogg (1957)*that pasture Fig. 2 Relationships between QTK and the probability of pasture response to applied K for different soil groups.…”

Section: Pasture Production Functionsmentioning

confidence: 78%

The diagnosis and correction of potassium deficiency in New Zealand pastoral soils: a review

Edmeades

Morton²,

Waller

et al. 2010

New Zealand Journal of Agricultural Research

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Field-trial data from a database comprising records of 804 potassium (K) fertiliser trials were used to define the production functions relating exchangeable soil K (quick test K (QTK) 0Á75 mm) to the relative response to fertiliser K applications, for the major soil groups in New Zealand. For all soil groups for which there were sufficient data, the production functions were generally flat in the range QTK 5Á10, and thus the estimated relative pasture production at QTK 5 and QTK 10 were similar. The critical QTK levels to achieve 97% maximum production were relatively well defined, being 6 (5Á8) for sedimentary soils (brown and pallic) and brown soils, and 7 (5Á10) for pumice soils. The data for the allophanic soils were unstable and the best estimate was 6 (5Á10). For the remaining soils groups (podzols and raw soils, organic, recent and gley soils) for which there was much less data, the relationships were essentially flat over the range QTK 2Á10. The probability of pasture responses to applied K increased as soil QTK decreased from 10. For the sedimentary and volcanic soils (including both allophanic and pumice) the probability was about 70Á80% at soil QTK B2. The comparable probabilities were 50Á60% for the recent and gley soils, and 30Á43% for the podzols and raw soils. A feature of the response functions was that some trials were not responsive to fertiliser K despite having low soil QTK. In most cases this could not be attributed to soil K reserves as measured by the soil TBK test (sodium tetra-phenol-boron extractable which measures exchangeable K plus plant-available but non-exchangeable K). Other possible reasons for this feature in the data are discussed, including uptake of K from below the soil sampling depth and the temporal effects of clover responses to applied K. Soil K buffer capacities*the amount of fertiliser K over and above maintenance required to increase soil QTK by 1 unit (DK)*ranged from 50 to 150 kg K ha (1 (average 124) for sedimentary soils. For some soils (developed organic soils, gleyed soils and podzols), fertiliser K had very little effect on QTK (0Á75 mm). It is not clear whether these differences are due to differences in leaching of K from the sampling depth, differences between soils in their ability to absorb and retain applied K or indeed the result of errors in the measurement of this parameter. Estimated maintenance K requirements (i.e. the amount of applied K required to maintain soil QTK levels) increased with increasing soil QTK from 4 to 10, from 0Á150 kg K ha(1 yr (1 to 100Á300 kg K ha (1 yr (1 in situations where losses of K were extreme due to the removal of all harvested clippings. Given the uncertainties in predicting K responses and the amount of fertiliser K required to correct K deficiency, practical suggestions are offered as to how best to diagnose and manage soil K deficiency. Areas for future research to improve the prediction of pasture responses to fertiliser K are also included.

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Section: Pasture Production Functionsmentioning

confidence: 78%

The diagnosis and correction of potassium deficiency in New Zealand pastoral soils: a review

Edmeades

Morton²,

Waller

et al. 2010

New Zealand Journal of Agricultural Research

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“…sufficient data, are given in Fig. 2 A-F. Quite clearly, there is considerable variability in the relationships between relative yield and Olsen P, as noted by Saunders et al (1987) and Sinclair et al (1997). In all cases the size of the confidence intervals decreases as the Olsen P level increases, a feature noted by Saunders et al (1987) (see Fig.…”

Section: Pasture Production Functionsmentioning

confidence: 89%

“…This research, together with the more comprehensive study by Saunders et al (1987) concluded that a modified Olsen test (Olsen et al 1954), based on extracting a volume rather than a weight of soil (dried and sieved soil and Olsen P = µg P cm -3 soil), gave the best correlation with either plant yields or plant P uptake. This was so despite the fact that it was originally developed for alkaline soils and that most New Zealand soils are acid (mostly pH < 6.0).…”

Section: Introductionmentioning

confidence: 99%

“…More recently the focus has been on quantifying the relationship between pasture production and soil Olsen P. Saunders et al (1987) reported results from a series of 62 pasture field trials measuring the effect of rates of P fertiliser on pasture production and Olsen P, and covering a wide range of soil groups. They recorded that the correlations between relative pasture production and soil P, using a polynomial function, were generally low (R < 0.30), although higher correlations (R > 0.8) occurred at some times on some sites.…”

Section: Introductionmentioning

confidence: 99%

“…This latter point is consistent with reports of reasonably high correlations between pasture production and Olsen P when the experiments are restricted to one site (e.g., Grigg 1977;McCall & Thorrold 1991) or a few sites on the same soil group (e.g., O'Connor & Gray 1984;O'Connor et al 2001). Given these difficulties, Saunders et al (1987) suggested a different approach. They defined a term, probable minimum yield (PMY), as the relative yield below which the observed relative yield will fall 20% of the time, for a given soil test level.…”

Section: Introductionmentioning

confidence: 99%

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Defining the relationships between pasture production and soil P and the development of a dynamic P model for New Zealand pastures: A review of recent developments

Edmeades¹,

Metherell²,

Waller³

et al. 2006

New Zealand Journal of Agricultural Research

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A database was constructed comprising records from 2255 pasture phosphorus (P), potassium (K) and sulphur (S) field trials, of which 1799 included one or several rates of P. Subsets of this data were selected based on predetermined criteria to define the relationships between relative pasture production and available soil P (0-75 mm, Olsen P in µg P cm -3 soil)-the P production functions-for the major soil groups in New Zealand. These relationships, and their 95% confidence intervals, were defined using Bayesian statistics. For those soil groups for which there was sufficient data, the production functions were well defined and gave reasonably precise estimates of the relative pasture yield for a given Olsen P. the relative pasture production is most likely (P < 0.05) to be in the range 88-94% at Olsen P 25 and 98-100% at Olsen P 50. The shape of the production functions was similar for all soil groups-the relative pasture production increased with increasing Olsen P up to an asymptote-except the pumice soils and the podzols, which showed irregularities. The production function for the podzols was also flatter. There was good agreement between the empirically derived production functions and those generated from a dynamic P model. The Olsen P level required to achieve 97% maximum production was estimated for all soil groups. These ranged from 10 to 45 depending on soil group. The critical Olsen P levels were related to the soil anion storage capacity (ASC, a laboratory measure of P buffer capacity) and to soil volume weight (g cm -3 of sieved and dried soil), although not strongly. The field measured P buffer capacity (ΔP F )-the amount of soluble fertiliser P (kg P ha -1 ) required above maintenance to increase the Olsen P (0-75 mm) level by 1 unit-was estimated for selected trials. There was reasonable agreement between these estimates and those derived from the P model (ΔP M ), and these results indicated that ΔP decreases with increasing Olsen P. The results imply that factors other than those related to soil chemical properties affect the relationship between soil P and pasture production. The factors which determine the relationship between pasture production and soil P are defined and discussed. These were assigned to two categories: those factors which affect the ability of the soil to supply P for plant uptake and those that affect the ability of the plant to acquire soil P. It is concluded that further progress towards improving our ability to predict pasture responses to fertiliser P will depend on quantifying the latter effects. Based on these results and the development of a dynamic P model, an econometric P model was developed for New Zealand pastures which enables consultants to quantify the likely agronomic, financial and investment effects of any given fertiliser strategy on a given farm or block within a farm. This was not previously possible but is essential for the sustainable use of P fertilisers in pastoral farming.

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The nutrition of grazed pastures in New Zealand

Cornforth

Sinclair

Rowarth

1993

Plant Nutrition — From Genetic Engineering to Field Practice

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A new approach to the interpretation of soil tests for phosphate response by grazed pasture

Cited by 25 publications

References 19 publications

The diagnosis and correction of potassium deficiency in New Zealand pastoral soils: a review

The diagnosis and correction of potassium deficiency in New Zealand pastoral soils: a review

Defining the relationships between pasture production and soil P and the development of a dynamic P model for New Zealand pastures: A review of recent developments

The nutrition of grazed pastures in New Zealand

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