The availability of potassium in some Tasmanian soils. II. Exhaustive cropping in relation to potassium reserves in the soil

1960 ◽  
Vol 11 (5) ◽  
pp. 774 ◽  
Author(s):  
CS Piper ◽  
Vries MPC de
Keyword(s):  
Sandy Loam ◽  
South Australia ◽  
Subterranean Clover ◽  
Yield Response ◽  
Exchangeable Potassium ◽  
Severe Deficiency ◽  
Intensively Managed ◽  
High Level ◽  
Yield Responses ◽  
Severe Leaf

Five soil samples from Fingal, Tas., representing Frodsley sandy loam of varying exchangeable potassium status, were subjected to exhaustive cropping in pots and the changes in their potassium status and that of the crops measured. Three of the samples represented an area carrying improved pastures while two were from a less intensively managed property. The results were contrasted with those from two soils from South Australia (Urrbrae loam and Seddon gravelly sandy loam). The progressive removal of potassium by cropping was determined by analysis of each crop and of the soil at the end of the experiment. Uptake and removal of potassium was greatest from the soils of highest exchangeable potassium status. Potassium applied to the soils was also rapidly taken up by the crops. For the Tasmanian soils, applications of potassium gave no responses in yield until the level of exchangeable potassium in the control pots fell to 0.10-0.15 m-equiv./100 g. The higher the initial level of exchangeable potassium, the greater the number of crops before a yield response to applied potassium was obtained. In contrast, yields were maintained at a high level on Urrbrae loam and, even in the fourth crop, applications of potassium gave only a barely significant response. From Frodsley and Seddon soils only small amounts of potassium were taken up from non-exchangeable sources. From Urrbrae loam, in the absence of applied potassium, slightly more than half of the potassium taken up by the crops was derived from other than exchangeable sources. These differences were in keeping with the different amounts of potassium released to boiling nitric acid by these soils. After four crops exchangeable potassium was reduced to very low levels (0.05-0.14 m-equiv./100 g) in all five Tasmanian soils. These values were directly related to the amounts of difficultly exchangeable potassium in these soils. Exchangeable potassium in Urrbrae loam was not reduced below 0.33 m-equiv./100 g, again reflecting the higher reserve of difficultly exchangeable potassium in the illitic clay of this soil and its greater capacity to replenish the exchangeable potassium fraction. The percentage of potassium in the dry matter of the crop was closely related to the level of exchangeable potassium or exchangeable plus added potassium in the soil. Subterranean clover showing severe leaf necrosis due to potassium deficiency contained 0.55-0.63 per cent. potassium. Plants showing less severe deficiency symptoms or symptoms developing at a later stage showed 0.84-0.98 per cent. potassium. Plants with 1.20 per cent. potassium were free from symptoms and gave no further yield responses to applied potassium. Additions of potassium to the soil led to higher values in the plants, and luxury uptake was common. At least 84-95 per cent. of the applied potassium was taken up by the crops on four of the Tasmanian soils.

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.

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 mown pasture to potassium fertilizer in south-eastern South Australia

1977 ◽  
Vol 17 (88) ◽  
pp. 765 ◽  
Author(s):  
AP Meissner ◽  
AL Clarke
Keyword(s):  
South Australia ◽  
Subterranean Clover ◽  
Multivariate Regression Analysis ◽  
Magnesium Concentration ◽  
Yield Response ◽  
Regression Equations ◽  
Potassium Fertilizer ◽  
Factors Affecting ◽  
Yield And Quality

Trials lasting three years were conducted at 27 sites in the south-east of South Australia to examine the responses of mown subterranean clover-ryegrass pastures to repeated annual applications of potassium chloride. At 20 sites, yield of dry matter (DM) was increased by potassium in one or more harvests. Responses were measured in 9 out of 55 winter harvests and 42 out of 86 spring harvests; mean responses to 100 kg ha-1 KCl (-Y100) at responsive sites were 380 and 560 kg DM ha-1 in winter and spring respectively. When potassium dressing increased yield, the proportion of clover in the sward was either maintained or increased. The herbage concentration of potassium was usually increased, and its magnesium concentration sometimes depressed, by potassium application. Although the K:Mg ratio was thereby increased, especially during winter, it rarely reached 15, the value considered necessary to induce grass tetany in cattle. Multivariate regression analysis showed that the exchangeable potassium concentration (Kex) of the top 10 cm of soil, the depth of soil overlying clay or limestone, and the sand content of the topsoil were factors affecting yield response. The best regression equations, however, explained less than half of the response variations. In practice, Kex alone would have usefully diagnosed potassium responsive sites. Responses occurred often when Kexwas less than 0.2 me 100 g-1 and rarely when it was greater. The use of potassium fertilizer is likely to be worthwhile to establish new pasture, to maintain the clover content of old pasture, and to increase the yield and quality of hay, where soils have less than 0.20 me 100 g-1 Kex. Such soils are most commonly sands more than 30 cm deep.

EXCHANGEABLE AND WATER-SOLUBLE POTASSIUM IN SOILS AND DEGREE OF SATURATION IN RELATION TO TOMATO YIELDS

1959 ◽  
Vol 39 (2) ◽  
pp. 129-135 ◽  
Author(s):  
R. L. Halstead ◽  
H. B. Heeney
Keyword(s):  
Sandy Loam ◽  
Clay Content ◽  
Field Trials ◽  
Water Soluble ◽  
Degree Of Saturation ◽  
Yield Response ◽  
Clay Loam ◽  
Exchangeable Potassium ◽  
Potassium Fertilizer ◽  
Prince Edward County

In 33 field trials on soils varying in texture from sandy loam to clay loam in Prince Edward County, Ontario, exchangeable potassium, per cent potassium saturation, and water-soluble potassium were significantly correlated with yield response of tomatoes to potassium fertilizer on the sandy loam soils, but there was no correlation within the loam and clay loam groups. The mean c1 value in the modified Mitscherlich equation relating exchangeable potassium to yield response within the sandy loam group was 0.00555 and the coefficient of variation was 19.8 per cent. The corresponding coefficients for c1 values based on per cent potassium saturation and water-soluble potassium were of greater magnitude. The amounts of potassium soluble in boiling 1 N HNO3 were not related to yield response.Exchangeable potassium and the non-exchangeable form soluble in boiling 1 N HNO3 increased, whereas water-soluble potassium decreased with increasing clay content of the samples. Water-soluble potassium was significantly correlated with per cent potassium saturation within the sandy loam and loam groups.

Studies on the fertility of seddon soil (Kangaroo Island, South Australia). 1. The response of subterranean clover to various phosphatic fertilizers.

1955 ◽  
Vol 6 (4) ◽  
pp. 398 ◽  
Author(s):  
AG Tyson
Keyword(s):  
Phosphorus Content ◽  
Sandy Loam ◽  
South Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Phosphate Deficiency ◽  
First Year ◽  
Phosphate Availability ◽  
Second Year ◽  
Phosphatic Fertilizers

Seddon gravelly sandy loam from Kangaroo Island has proved to be grossly deficient in both total and available native phosphorus. Growth of subterranean clover (Trifolium subterraneum L.) in this soil is virtually nil unless phosphatic fertilizers are applied to it. Experiments with eight different phosphatic fertilizers showed that thermal phosphates of the Rhenania type were slightly superior to monocalcic phosphate as a source of plant phosphorus on Seddon soil. Both types of phosphate were equally efficient in the contrasting Urrbrae loam. Rock phosphate proved to be an extremely poor source of plant phosphorus. In the first year the availability of monocalcic phosphate applied to the Seddon soil was 20 per cent. or half that of material applied to the Urrbrae loam. The comparative residual value in the second year of applied phosphate was greater, however, in the Seddon soil than in the Urrbrae loam. Yields and phosphate availability were influenced by seasonal variation, but the phosphorus content of the plant material was nearly constant in different years for any particular yield from the same soil. The requirement for phosphorus at yields below the maximum was greater, however, in plants growing on Urrbrae loam than on Seddon soil. At maximum yields the ratio N/P205 was constant for plants from the two soils, but this did not hold where phosphorus was in minimum supply. The availability of residual phosphate from Seddon soil to which small annual additions of fertilizer had been made over 12 years was markedly lower than that from virgin soil to which phosphate had been added 12 months previously. The lower availability from the partially developed soil has been tentatively ascribed to the concurrent accumulation of organic matter. Results support the practice of making small annual applications of superphosphate to Urrbrae loam but it would appear that greater overall production could be obtained from Seddon soil by heavier initial applications. Amounts of P205 as low as 0.17-0.20 per cent. were found in the dry matter of subterranean clover growing on Seddon soil. Values below 0.3 per cent. are considered to be indicative of phosphate deficiency.

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.

Effect of nitrogen, potassium and phosphorus on the yield, growth and nutrient status of ixodia daisy (Ixodia achillaeioides ssp. alata)

1994 ◽  
Vol 34 (5) ◽  
pp. 681 ◽  
Author(s):  
NA Maier ◽  
G Barth ◽  
M Bennell
Keyword(s):  
Plant Growth ◽  
Field Experiments ◽  
Biomass Yield ◽  
South Australia ◽  
Nutrient Status ◽  
Growth And Yield ◽  
Yield Response ◽  
Total Biomass ◽  
Extractable P ◽  
Yield Responses

The effect of annual applications of nitrogen (N), potassium (K) and phosphorus (P) on the yield, growth and nutrient status of Ixodia daisy (Ixodia achillaeioides ssp. alata) grown on a silty loam, was investigated in field experiments conducted during 1989-91 in the Mount Lofty Ranges, South Australia. The experimental design was a randomised block with 3 replications. The N and K treatments, at annual rates up to 200 kg N/ha and 150 kg K/ha, were applied as 2 equal side-dressings. The P treatments, at rates up to 200 kg/ha, were broadcast as 1 annual application. To assess plant nutrient status we sampled the fifth leaf below the growing terminal of 50 stems in October and whole stems at harvest. As rate of applied N increased, there was a significant (P<0.05) increase in total biomass harvested, number of 3040 and 41-50 cm stems, total number of marketable stems, plant height and width. Annual N application rates of 75-110 kg/ha were required for 95% of maximum biomass yield and number of marketable stems. The application of K did not significantly (P>0.05) affect yield or plant growth. First and second order interactions between N, K and year were not significant. Plant growth and yield responses to P applied as superphosphate were inconsistent and the interaction between P and year was not significant (P>0.05). Coefficients of determination (r2) for relationships between N, K and P concentrations in the fifth leaf samples v. total biomass yield and total stem number, were in the range 0.13-0.52 for the combined 1990 and 1991 data. Based on sensitivity, reproducibility and occurrence of the Piper-Steenbjerg effect, we concluded that N, K or P concentrations in the fifth leaf sampled in October, or in whole stems at harvest, were not reliable indicators of the nutrient status of Ixodia daisy. The application of N and P did not affect the concentration of minor or micronutrients in the fifth leaf. In contrast, the application of K increased calcium (Ca), magnesium (Mg) and sulfur (S) concentrations by 14.3, 33.3 and 12.2%, respectively. For a high density planting (13,000 plants) we estimated that for N, P and K, 69.4, 6.2 and 83.2 kg/ha, respectively, are removed in marketable stems. The application of P increased extractable-P concentrations in the surface (0-15 cm) soil from 22 to 73 mg/kg. We suggest that for surface (0-15 cm) soils, extractable-P and extractable-K concentrations in the ranges 15-95 and 210-260 mg/kg, respectively, are adequate and indicate that a yield response to the application of these nutrients in fertiliser may not occur.

Influence of lime rate and particle size on soil pH and vegetative and seed yields of subterranean clover in the South East of South Australia

1994 ◽  
Vol 34 (3) ◽  
pp. 367 ◽  
Author(s):  
TJV Hodge ◽  
DC Lewis
Keyword(s):  
Particle Size ◽  
Soil Ph ◽  
South Australia ◽  
Subterranean Clover ◽  
The South ◽  
Lime Application ◽  
Lime Particle ◽  
Rate Interaction ◽  
Yield Responses ◽  
Seed Yields

The effect of 2 rates (2, 4 t/ha) and 5 particle size grades of applied lime on vegetative and seed yields of subterranean clover on an acid siliceous sand in the South East of South Australia is reported. The movement of the lime down the soil profile was assessed through its effect on soil pH. Vegetative yield responses to lime were recorded in 4 of 5 harvests; there was a significant particle size x rate interaction at 2 harvests. When seed yield was significantly increased by lime application, the particle size treatments were not significantly different. Vegetative and seed yields were not increased by doubling the lime rate. Five years after mixing lime in the top 2.5 cm of soil, there was a significant particle size x rate x depth interaction for soil pH. Soil pH was significantly increased to a depth of 12.5 cm by the application of 4 t/ha of lime, with the finer lime particle sizes causing the greatest increase in soil pH at depth

Moisture and nitrate conservation and reponses to following after medic ley in the Wimmera

1972 ◽  
Vol 12 (57) ◽  
pp. 414 ◽  
Author(s):  
CL Tuohey ◽  
AD Robson ◽  
DR Rooney
Keyword(s):  
Protein Content ◽  
South Australia ◽  
Grain Protein Content ◽  
Yield Response ◽  
Grain Protein ◽  
Minor Importance ◽  
Nitrate Accumulation ◽  
Large Yield ◽  
Yield Responses

The effect of three times of initial cultivation (August, October, February-March) on grain yield, grain protein content, moisture conservation, and nitrate accumulation was studied over a period of seven years at three sites in the Wimmera on land that had been under medic ley. Fallowing in winter (August) or spring (October) markedly increased grain yields but not grain-protein content when compared with the non-fallow control (initial cultivation in February-March). Variation in yield response to both winter and spring fallowing appeared to be associated mainly with variation in moisture conservation in the 30-60 cm layer. With winter fallowing, the nitrate that accumulated was associated with yield increases, but with spring fallowing the nitrate appeared to he associated with yield depression. However, the role of nitrate accumulation in determining yield responses to fallowing was only of minor importance. Suppression of weeds in the crop was not a factor in producing the large yield responses to fallowing since crops on both fallowed and non-fallowed areas were generally weedfree. Results obtained in the current experiments indicate that the aspects of climate suggested by work in South Australia as being the ones that determine yield responses to fallowing are not the ones which are important in the Wimmera. In this environment the most promising predictors of yield responses to fallowing appear to be April to August rainfall before commencement of the winter fallow and September rainfall before commencement of the spring fallow.

Effect of nitrogen and potassium on the yield and quality of irrigated Brussels sprouts (Brassica oleracea L. var. gemmifera) cvv. Roger and Oliver grown in South Australia

1996 ◽  
Vol 36 (7) ◽  
pp. 877 ◽  
Author(s):  
CMJ Williams ◽  
NA Maier ◽  
MJ Potter ◽  
GG Collins
Keyword(s):  
Brassica Oleracea ◽  
Sandy Loam ◽  
Total Yield ◽  
Maximum Yield ◽  
South Australia ◽  
Sprinkler Irrigation ◽  
Yield Response ◽  
Brussels Sprouts ◽  
Silty Loam ◽  
Brassica Oleracea L

This study was conducted to assess the effects of nitrogen (N) and potassium (K) on the yield and size distribution of Brussels sprouts (Brassica oleracea L. var. gemmifera) grown with sprinkler irrigation in the Mt Lofty Ranges, South Australia. The cultivars grown were Oliver and Roger which are early and mid season types, respectively. Yields of swollen axillary buds or Brussels sprouts were assessed over 4-7 harvests. Five rates of N (0, 125, 250, 375, 600 kg/ha) with 3 rates of K (0, 150, 300 kg/ha) were applied over 8 side-dressings during the 7-8-month cropping period in randomised block experiments. Four experiments were conducted during 1992-93 (sites 1 and 2) and 1993-94 (sites 3 and 4) on silty loam, loam and sandy loam soils. The effect of N and K on sprout colour was determined at sites 3 and 4. Thiocyanate concentrations in sprouts and the bitterness of sprouts, from the nil and highest K treatment, and from plants in the crop adjacent to the experimental area, were determined for sites 1 and 2. In 3 of the 4 experiments, applied N significantly (P<0.001) increased total yield of sprouts harvested. Yield increases due to applied N ranged from 51 to 78%. At site 1 (cv. Oliver), there was no yield response to applied N but at sites 2 and 4 (cv. Roger) and site 3 (cv. Oliver), 319, 377 and 383 kg N/ha, respectively were required for 95% maximum yield. At responsive sites, application of N significantly increased both yield of sprouts at all harvests except harvest 1, and yield of 20-<30 and 30-<40 g sprouts, which are the preferred size ranges. Increasing rates of N significantly (P<0.05) increased yield of 240 g or large sprouts at all 3 responsive sites. The effect of applied N on sprout colour was inconsistent. At site 4, application of N significantly (P<0.001) increased the mean colour rating of sprouts, in contrast, at site 3 the effect was not significant (P>0.05). At both sites, mean colour ratings decreased during the harvest period irrespective of N applied. Total yield, size and colour of sprouts were not significantly (P>0.05) affected by rate of applied K at any site. It was concluded that extractable K concentrations of 140-260 mg/kg in the surface (0-15 cm) soils were adequate and not limiting yield. At site 1, thiocyanate concentration in sprouts and sprout bitterness increased significantly (P<0.001) when the highest rate of K2SO4 was applied. At site 2, which had received higher rates of sulfate-based fertilisers in previous years, the effect was not significant (P>0.05). This finding suggests that application of high rates of K2SO4 to Brussels sprouts should be avoided to ensure bitterness does not adversely affect the marketability of sprouts.

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