Effectiveness Of Superphosphate Research Articles

Effectiveness of Dicalcium Phosphate Compared with Superphosphate for Wheat Grown on Acidic Sandy Soils

The effectiveness of dicalcium phosphate (DCP) was compared with the effectiveness of superphosphate in a greenhouse experiment using two sandy acidic soils from southwestern Australia. Fertilizer effectiveness was determined using yield of dried shoots of 46-day-old spring wheat ( Triticum aestivum L.) plants.The DCP was about one-third as effective as superphosphate for yellow sand and one-fifth as effective for red sand; thus, about three to five times the amount of phosphorus (P) as DCP was required to produce the same yield as P added as superphosphate. Per unit of applied P, the P concentration in dried shoots was larger for soil treated with superphosphate than for soil treated with DCP. Critical P, the P concentration that was related to 90% of the maximum shoot yield, was about 0.70% (dry weight basis) for both sources of P and both soils.

The relative effectiveness of superphosphate and rock phosphate for soils where vertical and lateral leaching of phosphate occurs

Laboratory studies have shown that up to 70% reactive rock phosphate dissolves in three soil types found in the high rainfall (> 800 mm annual average) area of south-western Australia. Three field experiments were undertaken on these soils to compare reactive apatite rock phosphate from North Carolina (NCRP) with single superphosphate (SSP) as fertilizers for subterranean clover (Trifolium subterraneum) pasture. Vertical leaching of phosphorus (P) occurs in one soil, a deep, very sandy, acid peaty sand. Lateral leaching of P occurs in the second soil, a shallow (3 cm) sand over a slowly permeable sandy clay loam. No leaching of P occurs in the third soil, a uniform, permeable red sandy loam with a moderate capacity to sorb P. All the soils remained moist to very wet for the 6 to 8 month growing season. Fertilizers were applied once only to different plots over a four-year period (1992 to 1995). Each year fertilizer effectiveness was determined relative to the effectiveness of freshly-applied (current) SSP using yield and P content of dried clover herbage and bicarbonate-soluble P extracted from the soil (soil test P) as indices of effectiveness.

Long-term residual value of North Carolina and Queensland rock phosphates compared with triple superphosphate

The effectiveness of large single applications of North Carolina reactive rock phosphate, Queensland non-reactive rock phosphate, and Calciphos, were compared to the effectiveness of superphosphate in field experiments in south-western Australia for up to 11 years after application. As measured using plant yield, superphosphate was the most effective fertilizer in the year of application, and relative to freshly-applied superphosphate, the effectiveness of the superphosphate residues declined to be about 15 to 65% as effective in the year after application, and 5 to 20% as effective 9 to 10 years after application. Relative to freshly-applied superphosphate, all the rock phosphates were 10 to 30% as effective in the year of application, and the residues remained 2 to 20% as effective in the 10 years after application. The bicarbonate soil test reagent predicted a more gradual decrease in effectiveness of superphosphate of up to 70% 10 years after application. For rock phosphate, the reagent predicted effectiveness to be always lower than for superphosphate, being initially 2 to 11% as effective in the year after application, and from 10% to equally as effective 10 years later. Therefore rock phosphates are unlikely to be economic alternatives to superphosphate in the short or long term on most lateritic soils in south-western Australia.

Agronomic effectiveness of partially acidulated rock phosphate and fused calcium-magnesium phosphate compared with superphosphate

The agronomic effectiveness of two partially acidulated rock phosphate (PARP) fertilizers, made from either North Carolina or Moroccan apatite rock phosphate, and a fused calcium-magnesium phosphate (thermal phosphate or TP), was compared with the effectiveness of superphosphate in two glasshouse experiments. A different lateritic soil from Western Australia was used for each experiment. Oats (Avena sativa) were grown in one experiment and triticale (×Triticosecale) in the other. Fertilizer effectiveness was measured using (i) yield of dried tops, (ii) P content (P concentration in tissue multiplied by yield) of dried tops, and (iii) bicarbonate-extractable soil P (soil test value). The following relationships differed for the different fertilizers: (i) yield of dried tops and P content in the dried tops; (ii) yield and soil test values. Consequently the fertilizer effectiveness values calculated using yield data differed from those calculated using P content or soil test data. Freshly-applied superphosphate was always the most effective fertilizer regardless of the method used to calculate fertilizer effectiveness values. For one of the soils, as calculated using yield data, relative to freshly-applied superphosphate, the PARP and TP fertilizers were 15 to 30% as effective for the first crop, and 20 to 50% as effective for the second crop. The second soil was more acidic, and for the first crop the PARP and TP fertilizers were 80 to 90% as effective as freshly-applied superphosphate, but all fertilizers were only 5 to 15% as effective for the second crop. For each soil, the two PARP fertilizers had similar fertilizer effectiveness values. Generally the TP fertilizer was more effective than the PARP fertilizers.

Residual value of superphosphate for wheat and lupin grain production on a uniform yellow sandplain soil

In a field experiment on a sandplain soil in a low rainfall (326 mm per annum) Mediterranean environment of south-western Australia, the effectiveness of superphosphate applied in 1986 was measured in three subsequent years relative to freshly-applied superphosphate each year, using grain (seed) yields of wheat (Triticum aestivum) and lupins (Lupinus angustifolius). The wheat and lupins were grown in rotation and both crops were grown each year starting in 1986. Bicarbonate-soluble phosphorus was determined on soil samples taken in mid June from where the P treatment was applied in 1986 only. These soil test values were related to the grain yields produced that year.

Lupin grain yields and fertiliser effectiveness are increased by banding superphosphate below the seed

Five field experiments with lupins (Lupinus angustifolius) measured the effectiveness, for production, of 4 superphosphate placements either: (i) drilled with the seed to a depth of 4 or 5 cm; (ii) applied to the soil surface (topdressed) before sowing; or (iii) banded 2.5-5 cm and 7.5-8 cm below the seed while sowing. Levels of applied phosphate (P) from 0 to 36 kg P/ha were tested. In all experiments lupin grain yield responded to the highest level of superphosphate applied. At this P level, the average grain yield from all trials was 1.16 t/ha for the deepest banded treatment. This was 0.38 t/ha (49%) better than P drilled with the seed, and 0.62 t/ha (115%) better than P topdressed. Relative to superphosphate drilled with the seed and regardless of the lupin cultivar or the phosphate status of the soil, the effectiveness of superphosphate was increased by 10-90% by banding below the seed, and decreased by 30-60% by topdressing. Increasing the levels of superphosphate drilled with the seed generally reduced the density of seedlings and reduced early vegetative growth, probably due to salt or P toxicity. However, during the growing season, the plants treated with high levels of superphosphate recovered, so that eventually yields of dried tops and grain responded to increasing superphosphate drilled with the seed. In each experiment there was a common relationship between yield and P content in lupin tissue, regardless of how the superphosphate was applied, suggesting that lupins responded solely to P, and other factors did not alter yield. We recommend that farmers band superphosphate 5-8 cm below the seed while sowing, rather than continue the present practices of either drilling the fertiliser with the seed, or topdressing it before sowing.

Cultivation reduces fertilizer residual effectiveness and affects soil testing for available phosphorus

The agronomic effectiveness of superphosphate and two rock phosphates that had been applied once only to the soil surface 8 to 12 years previously was measured in a field experiment with oats on a lateritic soil in south-western Australia. The soil was either undisturbed or cultivated with a rotary hoe before sowing. The rock phosphates were Christmas Island C-grade ore (C-ore, a calcium ironaluminium rock phosphate), and C-ore calcined (heated) at about 500°C (Calciphos). Cultivation reduced the effectiveness for all three fertilizers by 20 to 50%. The effectiveness of phosphorus (P) applied as superphosphate decreased with increasing period from time of application whereas the effectiveness of the rock phosphates increased but they were always much less effective than superphosphate. The relationship between grain yield and P concentration of plant tissue (i.e. the internal efficiency of P use curve) was similar regardless of fertilizer type, year of application of fertilizer, and whether or not the soil was cultivated. Thus differences in fertilizer residual effectiveness were solely due to the amount of P taken up by the plants. Values of bicarbonate-soluble P (i.e. soil test for P values) for superphosphate treated soil were reduced by about 20 to 25% when the fertilizer was incorporated into the soil whereas for the rock phosphate treated soils the values were little affected by cultivation. The relationship between yield and soil test for P values varied depending on cultivation treatment and fertilizer. We conclude that cultivation decreases the effectiveness of residual fertilizer P and that cultivation and fertilizer type influence the accuracy of yield prediction from soil test values.

Reactive rock phosphate fertilizers and soil testing for phosphorus: The effect of particle size of the rock phosphate

North Carolina rock phosphate (NCRP) (highly carbonate—substituted apatite) was ground to produce three samples with different particle size distributions. The effectiveness of these fertilizers was compared with the effectiveness of superphosphate in a field experiment and three glasshouse experiments using lateritic soils from south-western Australia. Non-reactive Queensland rock phosphate (low carbonate-substituted apatite from the Duchess deposit) was also used in the pot experiments. Bicarbonate-soluble phosphorus extracted from the soil is widely used in Western Australia to predict plant yields from previously-applied fertilizer dressings. For both field and pot experiments bicarbonate-extractable phosphorus (soil test value) was measured and related to subsequent plant yields.

The long-term residual value of rock phosphate and superphosphate fertilizers for various plant species under field conditions

In three, long-term field experiments on different lateritic soils in south-western Australia, the effectiveness of superphosphate and rock phosphate fertilizers applied 10 years (one experiment) or 4 years previously was measured relative to the effectiveness of freshly-applied superphosphate (relative effectiveness or RE) using several different plant species. For the species comparisons, RE values were estimated using the initial slope of the relationship between yield and the level of P applied. In addition, RE values were also determined for different levels of application to test whether RE values for previously-applied fertilizer changed with increasing level of application. Soil samples were collected 3–5 months before sowing for a soil test for phosphate (P) and the soil test values were related to plant yields measured later that year. At each site, the RE value of previously-appliedrock phosphate was calculated using initial slopes and was mostly consistently low and was similar (0.04–0.18) for all plant species. The exceptions were that the RE value about doubled for barley in one experiment and for another experiment the effectiveness of calcined (heated) C-grade ore (Calciphos) was about 2–3 times that of the untreated (i.e. unheated) fertilizer. In most cases, the RE value of previously appliedsuperphosphate at each site was similar (0.23–0.34) regardless of plant species. The exceptions were that the RE value was about double for barley in one experiment and about half for triticale in another. Rock phosphates applied 4 or 10 years previously were between about one twentieth to one quarter as effective as freshly applied superphosphate. Superphosphate applied 4 or 10 years previously was between about a quarter to one third as effective as freshly-applied superphosphate. At each site, the yield of each species was closely related to the P content of plant tissue and the relationship was independent of the fertilizer type or when the fertilizer was applied. At each site and for each plant species, the RE value of the previously-applied rock phosphate was estimated for different levels of application and generally decreased with increasing level of application, whereas the RE value for previously-applied superphosphate mostly remained approximately constant. At each site, the relationship between yield and soil test values (i.e. soil test for P calibrations) differed depending on the fertilizer type and the plant species.

High phosphorus concentration in Trifolium balansae and Medicago polymorpha seed increases in herbage and seed yields in the field

Seed of Trifolium balansae and Medicago polymorpha, of the same size (mean ± s.d., T. balansae 0.8 ± 0.01 mglseed, M. polymorpha 3.6 ± 0.05 mg/seed) but with increasing phosphorus (P) concentration in the seed (T. balansae 0.34 to 0.63% P, M. polymorpha 0.40 to 0.64% P), were sown in field experiments as singlestrain, dense, ungrazed swards on 2 different soil types (a sand and a lateritic gravel sand) in south-western Australia. Different amounts of superphosphate were drilled with the seed (5-40 kg P/ha for the sand, and 15-100 kg P/ha for the lateritic gravel sand). Increasing P concentration in seed increased yields of dried herbage measured at each harvest, and also increased seed yields (measured for M. polymorpha only). Increasing P concentration in the seed increased the effectiveness of superphosphate drilled with the seed, so that less fertiliser was required to produce the same yield as P concentration in the seed increased.

Residual effectiveness of superphosphate is greater than that of rock phosphate fertilisers for lateritic soils in south-western Australia

The residual values of granular reactive rock phosphate (highly carbonate-substituted apatite from North Carolina, USA.), partially powdered low-reactive Queensland rock phosphate (low carbonate-substituted apatite from the Duchess deposit), and granular triple superphosphate were measured in 3 experiments on different lateritic soils in different climatic regions of south-western Australia (Gibson, South Bodallin, West Dale). Finely powdered calcined crandallite-millisite rock phosphate from Christmas Island (Calciphos) was included in one of the experiments. The fertilisers were applied once only in May 1984 and their residual value measured over 3 years (1984-1986) using yield and phosphorus content of the following species each year: experiment 1 (Gibson), barley in years 1 and 2 and oats in the third year; experiment 2 (South Bodallin), triticale in all 3 years; experiment 3 (West Dale), subterranean clover in years I and 2 followed by oats in year 3. Relative to triple superphosphate (TSP) applied each year, the effectiveness of superphosphate in year 1 (year of application) in the experiment at Gibson decreased by about 40% between years 1 and 2, and by a further 5% between years 2 and 3. The corresponding values for the experiment at South Bodallin were 75% and 5%, and at West Dale 50% and 25%. All rock phosphates were much less effective than TSP in year 1, being 5-30% as effective as TSP. Effectiveness of rock phosphates remained low over the 3 years, being 5-20% as effective as newly applied TSP. Although the effectiveness of TSP decreased, it continued to be 50% as effective as newly applied TSP after 3 years. Residual TSP and both freshly applied and residual rock phosphates did not support the same maximum yield as freshly applied TSP despite well defined yield plateaux being obtained in each case. At each harvest, the relationship between yield and phosphorus content of plants was similar for all fertilisers so that the smaller maximum DM and grain yield and reduced effectiveness of the rock phosphates were largely due to less phosphorus being taken up by plants.

The effectiveness of rock phosphate fertilisers in Australian agriculture: a review

Plant responses to apatite rock phosphates and Calciphos, a calcined calcium iron-aluminium rock phosphate fertiliser, have been measured in many pot and field experiments in Australia, but there is no consistent view of the agronomic effectiveness of these fertilisers. Quantitative indices of the effectiveness of freshly applied rock phosphates relative to freshly applied superphosphate (relative effectiveness or RE values) have been calculated from the data for 164 Australian pot and field experiments on the basis of the substitution value of the rock phosphates for superphosphate. RE values range from <0.1 to 2.5, with the mean value for apatite rock phosphates being 0.26 compared with 0.42 for Calciphos. Statistical analysis of the data demonstrate that variations in RE values were primarily due to systematic differences in experimental design and fertiliser solubility, and not to differences in soil pH, plant species, the capacity of the soil to adsorb P and mean annual rainfall. All RE values >0.4 were obtained from experiments in which only 1 or 2 levels of fertiliser were applied to soils that were poorly responsive to applied P; thus it was not possible to define the complete response curves required to obtain precise values of RE. In most cases, RE values were < 0.4 for experiments in which several levels of fertiliser P were applied to highly P-responsive soils so that complete response curves were defined and precise values of RE estimated. The effectiveness of previously applied rock phosphate (i.e, residual value) remained low and approximately constant for several years after application, being 5-30% as effective as freshly applied superphosphate for the various experiments. The corresponding average value of the relative effectiveness of superphosphate declined by 40% in the first year after application, by a further 15% in the second year, and by a further 30% over the remaining 6 years. However, the magnitude of these declines in relative effectiveness differed substantially between individual sites. The residual value of both the superphosphate and rock phosphate fertilisers appears not to have been systematically influenced by soil type, soil pH, the capacity of the soil to adsorb P, mean annual rainfall, and whether the fertilisers were topdressed or were incorporated. However, there is a need for additional experiments to investigate the influence of these factors on fertiliser effectiveness. It is concluded that, on the basis of published data, rock phosphate fertilisers cannot be regarded as economic substitutes for fertilisers containing water-soluble P for most agricultural applications in Australia. This is because, relative to freshly applied superphosphate, the fertiliser effectiveness of rock phosphates is low in the year of application and it remains low in subsequent years so that uneconomical, very high rates of application of rock phosphate are required.

Increases in soil water content decrease the residual value of superphosphate

In pot experiments, levels of superphosphate incorporated through the whole soil were incubated for 30 days in 2 lateritic soils from south-western Australia at 1 of the following 5 soil water contents: air-dry for 30 days, at field capacity for 10 or 30 days, and flooded for 10 or 30 days. The soils were then air-dried for 30 days and the residual value of the superphosphate relative to freshly applied superphosphate was measured using 30-day-old triticale (x Triticosecale cv. Tyalla) and wheat (Triticum aestivum cv. Gamenya) plants. Soil samples were collected just before sowing from each pot for measurement of bicarbonate-extractable phosphorus (P) levels which were compared with the DM yield of plant tops. For all treatments there was a common relationship between the P concentration (data not shown) or P content in the tops and the DM yield. This shows that the treatments can be considered as different dilutions of the same fertiliser. Less P was taken up by plants as the moisture content and period of contact with moist soil increased, and this limited yield. The effectiveness of superphosphate incubated in dry soil was similar to the effectiveness of freshly applied superphosphate. Incubation in moist soil reduced the effectiveness of superphosphate for plant growth, by about 50% for soils incubated at field capacity and 70% for flooded incubated soils. As calculated from the P content of plant tops, the effectiveness of superphosphate incubated in dry soil was similar to the effectiveness of freshly applied superphosphate, and the effectiveness of superphosphate decreased by about 55% for soils incubated at field capacity and 75% for flooded incubated soils. The amount of P extracted by sodium bicarbonate from soil sampled just before sowing was also influenced by the incubation treatments, and decreased in the following order: freshly applied = air dry incubated > field capacity incubated > flooded incubated. Thus the bicarbonate-soluble P extracted from the soil qualitatively paralleled the yield results. However, compared with the yield results, the decreases were not as marked. When the bicarbonate-extracted P results were compared with subsequent yields of triticale or wheat, separate calibration curves were required for the different incubation treatments.

Effectiveness of superphosphate and crandallite-millisite rock phosphates on a deep, very sandy soil as assessed by plant growth and soil extractable phosphate

The initial and residual effectiveness of superphosphate, Christmas Island C-grade ore (C-ore) and 500�C heated (calcined) C-ore (Calciphos) was measured on a deep, very sandy soil near Badgingarra, W.A. Different levels of each fertiliser were applied once only in May 1980. Yields of lupins (1980 and 1983) and subterranean clover (1981) were used to determine the effectiveness of the fertilisers, and in 1986 the residual value of the fertilisers was measured for wheat, oats, and barley, relative to freshly applied superphosphate. Samples of the top 10 cm of soil were collected each January-February for soil tests for P which were compared to plant yields measured in the following spring (Aug.-Dec.). Superphosphate was the most effective fertiliser, though its effectiveness declined by about 50% between years 1 and 2, and by a further 25% between years 2 and 4. C-ore was only about one-tenth as effective as superphosphate in the year of application, and its effectiveness declined by about 40% between years 1 and 2, and by a further 15% between years 2 and 4. Calciphos was about one-fifth as effective as superphosphate in the year of application, and its effectiveness declined by about 40% between years 1 and 2, and remained approximately constant between years 2 and 4. In 1986, the effectiveness of 1980 applied superphosphate was between about one-quarter to one-fifth as effective as freshly applied superphosphate for wheat, oats and barley, and the 1980 applied C-ore and Calciphos were about 15% as effective as freshly applied superphosphate. The amount of P extracted by sodium bicarbonate from soil fertilised with superphosphate decreased by about 50% between years 2 and 3, by a further 20% between years 3 and 4, and by a further 15% between years 4 and 7. For soil treated with Calciphos, the amount of extractable P doubled between years 2 and 3 and thereafter remained approximately constant. Very little P was extracted from soil fertilised with C-ore. Separate calibration curves were required in most cases for the relationship between yield and soil test values for superphosphate and rock phosphate in 1981 and 1983, and for each fertiliser and species in 1986. A substantial amount of superphosphate-added P (50-70%) and about 20% of rock phosphate-added P had leached below 50 cm of the topsoil 6 years after application.

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

Long-term availability of phosphorus from calcined rock phosphate compared with superphosphate

The phosphorus supply from single dressings of three rates of superphosphate and Christmas Island C-grade ore calcined at either (a) 500�C or (b) 900�C were compared in a long-term field trial by measuring (i) bicarbonate-extractable phosphorus and (ii) dry weight of tops of a subterranean clover based pasture in spring each year. For superphosphate, the bicarbonate-extractable phosphorus decreased with time, whereas for the two calcined products, the amount of bicarbonateextractable phosphorous, although initially low, increased slightly with time. As measured by herbage yield, the effectiveness of superphosphate decreased from the first to the second year and thereafter changed little with time. The effectiveness of the two calcined products tended to increase with time. Superphosphate was much more effective than the two calcined products throughout the trial. The effectiveness of both calcined products were similar, despite the fact that the fertilizers differed in their proportions of total phosphorus which was soluble in neutral ammonium citrate. The bicarbonate soil test did not always predict the same future pasture production for the three phosphorus sources, indicating that different soil test calibration curves are needed for each source.

Poorly soluble phosphates in Australian superphosphate: their nature and availability to plants

Australian superphosphates contain approximately 20 % of their phosphorus content as residual apatite and two water-insoluble phosphates, Ca(Fe0.12Al0.88)H(HPO4)2F2.2H20 and (Fe1.88Al1.12) (K0.28Na0.72)H8(PO4)6.6H20 that result from the use of impure rock phosphates. These compounds resemble phosphates occurring in American and New Zealand fertilizers, and comprise the acid and citrate soluble phosphorus fractions that are determined by statutory chemical tests. Glasshouse trials with wheat indicate that they are less effective phosphorus sources than monocalcium phosphate and will probably reduce the agronomic effectiveness of superphosphate.

Relationship between a soils ability to adsorb phosphate and the residual effectiveness of superphosphate

Twenty-two unfertilized soils from four localities in south-western Australia were used in a pot trial. In March powdered, single superphosphate was applied to the surface of eight of the pots at a range of levels. All the pots were kept moist until August when subterranean clover seed was sown and fresh superphosphate was applied to the previously unfertilized pots. Response curves were fitted to the yields and from the coefficients of the curves the relative effectiveness of the March and the August applications was calculated. For most of the soils, the March application was between 50 and 60% as effective as the August application. There was a small but significant trend for the relative effectiveness to increase as the soils' ability to adsorb phosphate from solution (�P) increased. There was a close relationship between the effectiveness of the August application and the inverse of �P. Since �P is a measure of the distribution of phosphorus between the solid and the solution phases in the soil, it was argued that the decreased effectiveness of the March application could be explained by a change in the distribution of phosphate. An incubation experiment showed that such a redistribution occurred and that the proportional change was little affected by �P. This seemed to explain the small effect of �P on decrease in effectiveness.

The Effectiveness of Superphosphate Top‐dressed on Established Meadows

The Effectiveness of Superphosphate Top‐dressed on Established Meadows