Tissue testing to assess the sulfur requirements of subterranean clover on very sandy soils in high rainfall areas of south-western Australia

2003 ◽  
Vol 43 (11) ◽  
pp. 1311 ◽  
Author(s):  
M. D. A. Bolland ◽  
J. S. Yeates ◽  
B. J. Codling ◽  
M. F. Clarke
Keyword(s):  
Western Australia ◽  
Field Experiments ◽  
Relative Yield ◽  
Subterranean Clover ◽  
Ground Level ◽  
Total N ◽  
High Rainfall ◽  
Significant Yield ◽  
Yield Responses ◽  
Ratio Range

Tissue testing was studied in field experiments between 1979 and 1985 to predict when sulfur (S) fertiliser was required for pastures in high rainfall (>650 mm annual average) areas of south-western Australia. The pastures comprised about half subterranean clover and annual ryegrass (Lolium rigidum Gaud.), the major pasture species in the region. Tissue testing was done for each species, using: (i) whole shoots, the present method used by commercial laboratories in Western Australia; (ii) youngest open leaves (legumes, YOLs) or youngest expanded blades (grass, YEBs); (iii) old leaves and blades (leaves that were not YOLs or YEBs); and (iv) stems (left after removal of YOLs, YEBs, old leaves and blades). Dried tissue was measured for total S, sulfate S, the total nitrogen : total S ratio and the sulfate S : total S ratio. For each pasture species, tissue test values were related to yield of dried herbage of that species measured for plants cut at ground level. Fertiliser nitrogen was not applied in the experiments.Annual ryegrass showed no significant yield responses to applied fertiliser S for all harvests in all experiments. Subterranean clover showed significant yield responses for most harvests of all experiments. At each site in each year, yield responses to applied S tended to become larger as the growing season progressed. For subterranean clover critical S values related to 90% of the maximum (relative) yield varied for different harvests of the same experiment within and between years, and for different experiments in the same and different years. As determined from all data, critical S values were similar for all plant parts (whole shoots, YOLs, old tissue, stems), with no consistent, systematic trend with plant age, and were: total S, range 0.10–0.30% S, mean 0.23%; sulfate S, range 0.01–0.14%, mean 0.04%; total N : total S ratio, range 11–30, mean 19; sulfate S : total S ratio, range 0.01–0.48, mean 0.27. The exception was that total S was lower for clover stems, the range being 0.06–0.20%, and mean 0.13%. Therefore, % total S in clover shoots can continue to be used as an indicator of sulfur deficiency in subterranean clover in the region.

Soil and tissue tests to predict pasture yield responses to applications of potassium fertiliser in high-rainfall areas of south-western Australia

2002 ◽  
Vol 42 (2) ◽  
pp. 149 ◽  
Author(s):  
M. D. A. Bolland ◽  
W. J. Cox ◽  
B. J. Codling
Keyword(s):  
Western Australia ◽  
Field Experiments ◽  
Relative Yield ◽  
Subterranean Clover ◽  
Test Method ◽  
Yield Response ◽  
Soil Test ◽  
Test Procedures ◽  
Pasture Production ◽  
Yield Responses

Dairy and beef pastures in the high (>800 mm annual average) rainfall areas of south-western Australia, based on subterranean clover (Trifolium subterraneum) and annual ryegrass (Lolium rigidum), grow on acidic to neutral deep (>40 cm) sands, up to 40 cm sand over loam or clay, or where loam or clay occur at the surface. Potassium deficiency is common, particularly for the sandy soils, requiring regular applications of fertiliser potassium for profitable pasture production. A large study was undertaken to assess 6 soil-test procedures, and tissue testing of dried herbage, as predictors of when fertiliser potassium was required for these pastures. The 100 field experiments, each conducted for 1 year, measured dried-herbage production separately for clover and ryegrass in response to applied fertiliser potassium (potassium chloride). Significant (P<0.05) increases in yield to applied potassium (yield response) were obtained in 42 experiments for clover and 6 experiments for ryegrass, indicating that grass roots were more able to access potassium from the soil than clover roots. When percentage of the maximum (relative) yield was related to soil-test potassium values for the top 10 cm of soil, the best relationships were obtained for the exchangeable (1 mol/L NH4Cl) and Colwell (0.5 mol/L NaHCO3-extracted) soil-test procedures for potassium. Both procedures accounted for about 42% of the variation for clover, 15% for ryegrass, and 32% for clover + grass. The Colwell procedure for the top 10 cm of soil is now the standard soil-test method for potassium used in Western Australia. No increases in clover yields to applied potassium were obtained for Colwell potassium at >100 mg/kg soil. There was always a clover-yield increase to applied potassium for Colwell potassium at <30 mg/kg soil. Corresponding potassium concentrations for ryegrass were >50 and <30 mg/kg soil. At potassium concentrations 30–100 mg/kg soil for clover and 30–50 mg/kg soil for ryegrass, the Colwell procedure did not reliably predict yield response, because from nil to large yield responses to applied potassium occurred. The Colwell procedure appears to extract the most labile potassium in the soil, including soluble potassium in soil solution and potassium balancing negative charge sites on soil constituents. In some soils, Colwell potassium was low indicating deficiency, yet plant roots may have accessed potassum deeper in the soil profile. Where the Colwell procedure does not reliably predict soil potassium status, tissue testing may help. The relationship between relative yield and tissue-test potassium varied markedly for different harvests in each year of the experiments, and for different experiments. For clover, the concentration of potassium in dried herbage that was related to 90% of the maximum, potassium non-limiting yield (critical potassium) was at the concentration of about 15 g/kg dried herbage for plants up to 8 weeks old, and at <10 g/kg dried herbage for plants older than 10–12 weeks. For ryegrass, there were insufficient data to provide reliable estimates of critical potassium.

Response of annual pastures to applications of limestone in the high rainfall areas of south-western Australia

2002 ◽  
Vol 42 (7) ◽  
pp. 925 ◽  
Author(s):  
M. D. A. Bolland ◽  
D. G. Allen ◽  
Z. Rengel
Keyword(s):  
Soil Ph ◽  
Western Australia ◽  
Field Experiments ◽  
Sandy Loam ◽  
Subterranean Clover ◽  
Italian Ryegrass ◽  
Yield Response ◽  
Pasture Production ◽  
High Rainfall ◽  
Yield Responses

The yield response of long-term pastures growing on acidified soil to applications of limestone (0, 2.5, 5.0, 7.5 and 10.0 t/ha with adequate magnesium fertiliser, and 0 and 5 t/ha with no magnesium fertiliser) was measured in 5 field experiments on different representative soils of the high rainfall areas of south-western Australia. After application, limestone was incorporated 1 cm deep in 3 experiments, 3 cm deep in 1 experiment, and 7 cm in another experiment. The pastures comprised subterranean clover (Trifolium subterraneum), and annual and Italian ryegrass (Lolium rigidum and L. multiflorum), the dominant species found in intensively grazed dairy and beef pastures of the region. Yields were measured when ryegrass plants had 3 leaves per tiller, which is when pastures in the region are grazed to maximise utilisation by cattle.Subsoil acidity was a problem at 4 of the 5 sites, and was so severe at 1 site that, despite having the lowest soil pH to 50 cm depth, there was no yield response to limestone incorporated to 3 cm deep. Applications of fertiliser magnesium had no significant effect on pasture production, soil pH, aluminium and manganese, or concentration of magnesium in dried herbage in any of the 5 experiments. Increasing amounts of limestone consistently: (i) increased soil pH, by between 1–2 pH units in the top 5 cm of soil, and 0.5–1.0 of a pH unit in the 5–10 cm soil profile; and (ii) decreased, by up to 84–98%, the amount of exchangeable aluminium in the 0–5 and 5–10 cm soil profiles. During 3 years (1998–2000) there were: (i) no yield responses to limestone for a total of 9 assessments on a sand, or 11 assessments on a sandy gravel; (ii) 2 significant (P<0.05) yield responses to limestone, from a total of 8 assessments on a loamy clay and from 9 assessments on a loam; (iii) 9 significant yield responses from a total of 13 assessments on a sandy loam (2 from 5 assessments in 1998, 3 from 4 assessments in 1999, and all 4 assessments in 2000). The sandy loam had the largest amount of exchangeable aluminium in the top 5 cm of soil [about 1.6 cmol(+)/kg, accounting for 35% of the exchangeable cations]. Increasing limestone applications did not induce deficiency or toxicity of any nutrient elements in subterranean clover or ryegrass dried herbage and, for dried herbage of bulk samples of both species, had no effect on dry matter digestibility, metabolisable energy and concentration of crude protein.

Single and coastal superphosphates are equally effective as sulfur fertilisers for subterranean clover on very sandy soils in high rainfall areas of south-western Australia

2003 ◽  
Vol 43 (9) ◽  
pp. 1117
Author(s):  
M. D. A. Bolland ◽  
J. S. Yeates ◽  
M. F. Clarke
Keyword(s):  
Western Australia ◽  
Field Experiments ◽  
Maximum Yield ◽  
Sandy Soils ◽  
Subterranean Clover ◽  
Water Soluble ◽  
Single Superphosphate ◽  
Suitable Alternative ◽  
High Rainfall ◽  
Coastal Superphosphate

To reduce leaching of phosphorus (P) from fertilised pastures to shallow estuaries in the high rainfall (>800 mm annual average) areas of south-western Australia, and to supply extra sulfur (S) for subterranean clover (Trifolium subterraneum L.) in pasture, 'coastal superphosphate' was developed as a possible alternative P and S fertiliser to single superphosphate. Coastal superphosphate is made by adding phosphate rock and elemental S to single superphosphate as it comes out of the den before granulation. It has about 3 times more sulfur (S) and one-third the water-soluble P content than single superphosphate. Four long-term (5-year) field experiments were conducted in south-western Australia to compare the effectiveness of single and coastal superphosphate as S fertilisers for subterranean clover pasture grown on very sandy soils that are frequently S deficient after July each year due to leaching of S from soil. Seven different amounts of S were applied as fertiliser annually. Fertiliser effectiveness was assessed from clover herbage yield and S concentration in dried herbage. Fertiliser nitrogen was not applied in these experiments as this was the normal practice for pastures in the region when the research was conducted.Both coastal and single superphosphates were equally effective per unit of applied S for producing dried clover herbage and increasing S concentration in herbage. Previous research on very sandy soils in the region had shown that coastal superphosphate was equally or more effective per unit of applied P for production of subterranean clover herbage. It is, therefore, concluded that coastal superphosphate is a suitable alternative S and P fertiliser for clover pastures on very sandy soils in the region. The concentration of S in dried clover herbage that was related to 90% of the maximum yield (critical S) was about 0.20–0.35% S during August (before flowering) and 0.15–0.20% S during October (after flowering).

Comparing different sources of sulfur for high-rainfall pastures insouth-western Australia

2003 ◽  
Vol 43 (10) ◽  
pp. 1221 ◽  
Author(s):  
M. D. A. Bolland ◽  
J. S. Yeates ◽  
M. F. Clarke
Keyword(s):  
Western Australia ◽  
Field Experiments ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Residual Value ◽  
Single Superphosphate ◽  
Pasture Production ◽  
Leaching Losses ◽  
S Deficiency ◽  
Different Sources

The dry herbage yield increase (response) of subterranean clover (Trifolium subterraneum L.)-based pasture (>85% clover) to applications of different sources of sulfur (S) was compared in 7 field experiments on very sandy soils in the > 650 mm annual average rainfall areas of south-western Australia where S deficiency of clover is common when pastures grow rapidly during spring (August–November). The sources compared were single superphosphate, finely grained and coarsely grained gypsum from deposits in south-western Australia, and elemental S. All sources were broadcast (topdressed) once only onto each plot, 3 weeks after pasture emerged at the start of the first growing season. In each subsequent year, fresh fertiliser-S as single superphosphate was applied 3 weeks after pasture emerged to nil-S plots previously not treated with S since the start of the experiment. This was to determine the residual value of sources applied at the start of the experiment in each subsequent year relative to superphosphate freshly-applied in each subsequent year. In addition, superphosphate was also applied 6, 12 and 16 weeks after emergence of pasture in each year, using nil-S plots not previously treated with S since the start of the experiment. Pasture responses to applied S are usually larger after mid-August, so applying S later may match plant demand increasing the effectiveness of S for pasture production and may also reduce leaching losses of the applied S.At the same site, yield increases to applied S varied greatly, from 0 to 300%, at different harvests in the same or different years. These variations in yield responses to applied S are attributed to the net effect of mineralisation of different amounts of S from soil organic matter, dissolution of S from fertilisers, and different amounts of leaching losses of S from soil by rainfall. Within each year at each site, yield increases were mostly larger in spring (September–November) than in autumn (June–August). In the year of application, single superphosphate was equally or more effective than the other sources. In years when large responses to S occurred, applying single superphosphate later in the year was more effective than applying single superphosphate 3 weeks after pasture emerged (standard practice), so within each year the most recently applied single superphosphate treatment was the most effective S source. All sources generally had negligible residual value, so S needed to be applied each year to ensure S deficiency did not reduce pasture production.

Responses of intensively grazed dairy pastures to applications of fertiliser nitrogen in south-western Australia

2007 ◽  
Vol 47 (8) ◽  
pp. 927 ◽  
Author(s):  
M. D. A. Bolland ◽  
I. F. Guthridge
Keyword(s):  
Western Australia ◽  
Dry Matter ◽  
Maximum Yield ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Growing Season ◽  
Mineral Elements ◽  
Italian Ryegrass ◽  
Total N ◽  
Dry Matter Digestibility

For the first time, we quantified pasture dry matter (DM) responses to applied fertiliser nitrogen (N) for intensively grazed, rain-fed, dairy pastures on sandy soils common in the Mediterranean-type climate of south-western Australia. The pastures are composed of subterranean clover (Trifolium subterraneum L.) and annual and Italian ryegrass (Lolium rigidum Gaud. and L. multiflorum Lam.). Six rates of N, as urea (46% N), were applied to 15 m by 15 m plots four times during 2002 and after each of the first 5–7 grazings in 2003 and 2004, throughout the typical April–October growing season. Total rates of N applied in the first year of the experiments were 0, 60, 120, 160, 200 and 320 kg N/ha, which were adjusted in subsequent years as detailed in the ‘Materials and methods’ section of this paper. The pastures in the experiments were rotationally grazed, by starting grazing when ryegrass plants had 2–3 leaves per tiller. The amount of pasture DM on each plot was measured before and after each grazing and was then used to estimate the amount of pasture DM consumed by the cows at each grazing for different times during the growing season. Linear increases (responses) of pasture DM to applied N occurred throughout the whole growing season when a total of up to 320 kg N/ha was applied in each year. No maximum yield plateaus were defined. Across all three experiments and years, on average in each year, a total of ~5 t/ha consumed DM was produced when no N was applied and ~7.5 t/ha was produced when a total of 200 kg N/ha was applied, giving ~2.5 t/ha increase in DM consumed and an N response efficiency of ~12.5 kg DM N/kg applied. As more fertiliser N was applied, the proportion of ryegrass in the pasture consistently increased, whereas clover content decreased. Concentrations of nitrate-N in the DM consistently increased as more N was applied, whereas concentrations of total N, and, therefore, concentration of crude protein in the DM, either increased or were unaffected by applied N. Application of N had no effect on concentrations of other mineral elements in DM and on dry matter digestibility and metabolisable energy of the DM. The results were generally consistent with findings of previous pasture N studies for perennial and annual temperate and subtropical pastures. We have shown that when pasture use for milk production has been maximised in the region, it is profitable to apply fertiliser N to grow extra DM consumed by dairy cows; conversely, it is a waste of money to apply N to undergrazed pastures to produce more unused DM.

Taxonomic and pathogenic characteristics of a new species Aphanomyces trifolii causing root rot of subterranean clover (Trifolium subterraneum) in Western Australia

2010 ◽  
Vol 61 (9) ◽  
pp. 708 ◽  
Author(s):  
Tiernan A. O'Rourke ◽  
Megan H. Ryan ◽  
Hua Li ◽  
Xuanli Ma ◽  
Krishnapillai Sivasithamparam ◽  
...  
Keyword(s):  
New Species ◽  
Western Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Root Disease ◽  
Molecular Characteristics ◽  
Root Pruning ◽  
High Rainfall ◽  
South West ◽  
A New Species

Subterranean clover (Trifolium subterraneum) is grown extensively as a pasture legume in agronomic regions with Mediterranean-type climates in parts of Africa, Asia, Australia, Europe, North America and South America. Root diseases of subterranean clover, especially those caused by oomycete pathogens including Aphanomyces, Phytophthora and Pythium, greatly reduce productivity by significantly decreasing germination, seedling establishment, plant survival and seed set. For this reason, experiments were conducted to determine the species of Aphanomyces causing root disease on subterranean clover in the high-rainfall areas of south-west Western Australia. The effects of flooding, temperature and inoculum concentration on the development of root disease on subterranean clover caused by this Aphanomyces sp. were also investigated as was its host range. Morphological and molecular characteristics were used to identify the pathogen as a new species Aphanomyces trifolii sp. nov. (O’Rourke et al.), which forms a distinct clade with its nearest relative being A. cladogamus. A. trifolii caused significant lateral root pruning as well as hypocotyl collapse and tap root disease of subterranean clover. The level of disease was greater in treatments where soil was flooded for 24 h rather than for 6 h or in unflooded treatments. The pathogen caused more disease at 18/13oC than at lower (10/5oC) or higher (25/20oC) temperatures. The pathogen caused more disease at 1% inoculum than at 0.5 or 0.2% (% inoculum : dry weight of soil). In greenhouse trials, A. trifolii also caused root disease on annual medic (M. polymorpha and M. truncatula), dwarf beans (Phaseolus vulgaris) and tomatoes (Solanum lycopersicum). However, the pathogen did not cause disease on peas (Pisum sativum), chickpea (Cicer arietinum), wheat (Triticum aestivum), annual ryegrass (Lolium rigidium) or capsicum (Capsicum annuum). A. trifolii is a serious pathogen in the high-rainfall areas of south-west Western Australia and is likely a significant cause of root disease and subsequent decline in subterranean clover pastures across southern Australia.

Assessment of the phosphorus and sulphur status of subterranean clover pastures. 3. Plant tests

1969 ◽  
Vol 9 (38) ◽  
pp. 329 ◽  
Author(s):  
D Bouma ◽  
K Spencer ◽  
EJ Dowling
Keyword(s):  
Leaf Area ◽  
Field Experiments ◽  
Correlation Coefficients ◽  
Subterranean Clover ◽  
Growing Season ◽  
Yield Response ◽  
Leaf Analysis ◽  
South Wales ◽  
Soluble Phosphorus ◽  
Yield Responses

Field experiments were carried out in south-eastern New South Wales to establish the relationships between three plant tests for phosphorus and for sulphur, and the yield responses of subterranean clover pastures to applied phosphorus and sulphur. Subterranean clover plants (CV. Mt. Barker), sampled early in the growing season of 1963 and on five occasions at approximately monthly intervals in 1964, were analysed for total and soluble phosphorus and for total and reducible sulphur. The third plant test involved a comparison of the leaf area responses measured seven days after transfer to appropriate nutrient solutions of clover plants sampled in the field plots at the beginning of each growing season. Correlation coefficients (R) varying from 0.546 to 0.908 were obtained for the curvilinear regression of relative yields on total phosphorus contents of the clover, but only under conditions of an adequate sulphur supply. The correlation coefficients for soluble phosphorus were generally lower and differed greatly between samplings. The correlation coefficients for the curvilinear regressions of yield responses on the total or reducible sulphur content of clover, under conditions of ample phosphorus supply, were never less than 0.606 at the end of the season, and for some of the earlier samplings were as high as 0.947. The correlation coefficients (r) between leaf area responses and yield responses to phosphorus were 0.576 and 0.716, and those for sulphur 0.710 and 0.692 in 1963 and 1964 respectively. In contrast to those based on leaf analysis, the relationships between leaf area responses and yield response for each one of the elements were not affected by the level of supply of the other element.

Phosphate and potash requirements of sugar cane in relation to soil chemical analysis and soil type

1966 ◽  
Vol 6 (23) ◽  
pp. 409
Author(s):  
ICR Holford
Keyword(s):  
Sugar Cane ◽  
Soil Type ◽  
Field Experiments ◽  
Soil Phosphorus ◽  
Soil Test ◽  
Mitscherlich Equation ◽  
Percentage Yield ◽  
Significant Yield ◽  
Highly Correlated ◽  
Yield Responses

The superphosphate and potassium chloride requirements of sugar cane were studied in relation to soil test levels on 25 different soil types in Fiji. Soil phosphorus was determined by a modified Truog method and soil potassium by extraction with 0.5N acetic acid. Percentage yields of sugar cane in fertilizer field experiments harvested over a five-year period were highly correlated with soil test levels in the control plots. The regressions of percentage yield on soil test level were curvilinear, and a modified Mitscherlich equation gave an excellent fit to the points. Critical soil test levels were found to exist, below which soils gave significant yield responses to applied nutrients. Critical soil test levels ranged over 5 to 20 p.p.m, for phosphorus and 51 to 150 p.p.m. for potassium. Within the deficient range of each nutrient there were only weak relationships between optimum fertilizer requirements and soil test levels. There was some evidence to suggest that soil type may be a useful complementary criterion for predicting fertilizer requirements.

Granular reactive apatite rock phosphate is not an effective phosphorus fertilizer in the short term on lateritic soils in south-western Australia.

1986 ◽  
Vol 26 (2) ◽  
pp. 217 ◽  
Author(s):  
MDA Bolland ◽  
AJ Weatherley ◽  
RJ Gilkes ◽  
JW Bowden
Keyword(s):  
Western Australia ◽  
Rock Phosphate ◽  
Field Experiments ◽  
Maximum Yield ◽  
Subterranean Clover ◽  
Phosphate Fertilizer ◽  
Carbonate Apatite ◽  
Rock Phosphates ◽  
Fertilizer Effectiveness ◽  
Eastern Australia

The effectiveness, as a phosphate fertilizer, of granular reactive rock phosphate (carbonate substituted apatite from North Carolina, U.S.A.), granular triple superphosphate and partly powdered Duchess non-reactive rock phosphate (low carbonate apatite from north-eastern Australia) was compared in three field experiments on different soil types in different climatic regions of south-western Australia. Calciphos (finely ground calcined crandallite rock phosphate from Christmas Island) was included in one experiment. The rock phosphates were incorporated into the soil and their effectiveness was compared with both topdressed and incorporated superphosphate. Different species were grown at each site (barley, triticale and subterranean clover). As determined on the basis of relative amounts of fertilizer required for constant yield, the effectiveness of all the rock phosphates relative to incorporated superphosphate was very low at each site throughout the growth of each species. Fertilizer effectiveness of rock phosphates was about one-fifth that of superphosphate for barley, and one-tenth for triticale and clover. The maximum yield obtained from rock phosphate was generally 88-100% that obtained from superphosphate. Incorporation did not greatly affect the effectiveness of superphosphate.

Field evaluation of a leaf test for assessment of the phosphorus status of subterranean clover and for prediction of its response to phosphorus

1985 ◽  
Vol 25 (2) ◽  
pp. 331 ◽  
Author(s):  
EJ Dowling ◽  
D Bouma
Keyword(s):  
Field Experiments ◽  
Relative Yield ◽  
Leaf Tissue ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Field Evaluation ◽  
Close Relation ◽  
Critical Value ◽  
Late Winter ◽  
Phosphorus Status

A series of field experiments (5 phosphorus levels x 6 replicates) on the southern Tablelands of New South Wales was used, firstly, to confirm the suitability of a modified test for inorganic phosphorus (Pi) concentrations in fresh clover (Trifolium subterraneum) leaves as an index of the current phosphorus status of subterranean clover-based pastures; and, secondly, to evaluate the usefulness of Pi as a predictor of responses to phosphorus applications. A close relation (R2 = 0.910) was found between Pi in healthy green leaf tissue sampled in winter and field responses to phosphorus measured at the same time. The fitted curve had a critical value of 154 ppm Pi at 90% of the fitted asymptote for relative yield. Close relations were also found between total herbage yield measured over the season and Pi in leaf tissue sampled in late autumn and early winter (R2 = 0.896) and in leaves sampled in late winter and early spring (R2= 0.877). Critical values were 160 and 153 ppm Pi respectively. The relation was less close for the third sampling (seed set and flowering, R2= 0.809) and the critical value had declined to 118 ppm Pi. It is concluded that Pi determined in clover leaf samples provides a simple measure of the current phosphorus status of subterranean clover-based pasture, and of its likely response to phosphorus. A critical value of 150 ppm Pi is confirmed for assessing the current phosphorus status, and is also proposed for predictive purposes. The method described for the estimation of Pi is a further simplification of the method presented previously. It is also more rapid and achieves a saving of 80-90% in chemicals. The correlation coefficient for the straight line relationship between the two methods was 0.956 (68 observations).

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