Sulfur/sodium bentonite prills as sulfur fertilizers. 2. Effect of sulfur-sodium bentonite ratios on the availability of sulfur to pasture plants in the field

Sulfur/sodium bentonite prills containing 5–40% of sodium bentonite were evaluated in a field experiment to determine the effects of the bentonite contents on their ability to supply sulfur to pasture plants. Comparative rates of oxidation of the elemental sulfur in the fertilizers to sulfate were deduced from plant sulfate contents and phosphate-extractable sulfate in soil (0–75 mm depth) over a period of 15 months. In grass-dominant pastures plant sulfate appeared to be more sensitive than soil sulfate to differences between S fertilizers.Increasing the proportion of bentonite in the prills from 5% to 40% increased the rate at which sulfur became available for plant uptake. At least 10% bentonite content was necessary to allow a satisfactory rate of supply to plants in the first year after application. Plant sulfate concentrations were increased by the S°/bentonite treatments for the whole of the experimental period of 467 days. In contrast gypsum only increased plant sulfate levels for about 118 days. Prills containing 40% bentonite also maintained sulfate concentrations longer than did finely divided elemental S. However oxidation of S from S°/bentonite prills lagged behind elemental S powder of similar fineness due to the delay for prill disintegration and less uniform distribution of S.In a cool-temperate climate with sufficient rainfall for significant leaching of sulfate, the optimum bentonite content of S°/sodium bentonite prills as fertilizer for pasture was about 15%. 20% sodium bentonite may be more appropriate in dry cool-temperate environments, whereas in warm moist temperate environments prills containing 10% sodium bentonite may be satisfactory.     

Effectiveness of two partially acidulated rock phosphates,coastal superphosphate and Ecophos,compared with North Carolina reactive rock phosphate and superphosphate

The effectiveness of coastal superphosphate, a partially acidulated rock phosphate (PARP) made from apatite, and Ecophos, a PARP made from calcium iron aluminium (crandallite millisite) rock phosphate, was compared in pot experiments with the effectiveness of ordinary superphosphate (OSP) and North Carolina reactive apatite rock phosphate (NCRP). There were three experiments using different lateritic soils collected in Western Australia. Fertilizer effectiveness was measured using yield of dried wheat (Triticum aestivum) tops grown for 28 days. Three successive crops were grown. The phosphorous (P) fertilizers were applied and mixed with the soils before sowing the first crop. In addition, OSP was added to extra pots before sowing crops 2 and 3 in order to measure the effectiveness of the original P fertilizers relative to freshly-applied OSP for these crops.As measured using plant yield, coastal superphosphate was the most effective P fertilizer for three crops on an acidic peaty sand (pH water 5.0). Relative to freshly-applied OSP, it was 154% as effective for crop 1, 75% as effective for crop 2, and 36% as effective for crop 3. Corresponding values for Ecophos were 44, 29 and 19%, and for NCRP, 77, 67 and 29%, with the original OSP treatment being 61 and 56% as effective for crops 2 and 3. For three crops on a lateritic gravel loam (pH 6.5), both coastal superphosphate and OSP were the most effective fertilizers, and were equally effective for crop 1, and relative to freshly-applied OSP, were about 31% as effective for crop 2, and 16 and 21 % as effective for crop 3. Corresponding values for Ecophos were 47,15 and 11%, and NCRP, 33,15 and 5%. For two crops in a loamy sand (pH 5.4), OSP was the most effective fertilizer, and, relative to fresh OSP, it was 36% as effective for crop 2. Relative to fresh OSP, the effectiveness for crops 1 and 2 of coastal superphosphate was 57 and 18%, for Ecophos 71 and 27%, and for NCRP 50 and 36%.     

The agronomic effectiveness of reactive rock phosphate,partially acidulated rock phosphate and monocalcium phosphate in soils of different pH

The initial and residual fertilizer effectiveness of North Carolina RP (rock phosphate), monocalcium phosphate and partially acidulated RP (made from North Carolina RP at 30% acidulation), both granulated and non-granulated, were measured in a glasshouse experiment. Triticale (xTriticosecale) was grown for 30 days on a soil that had been adjusted to three pH values (4.2, 5.2 and 6.2). Two crops were grown with a six month interval between crops. The effectiveness of the different fertilizers was compared using relationships between (1) yield of dried tops and the amount of P applied and (2) P content (P concentration in tissue multiplied by yield) and the amount of P applied. For the first crop, relative effectiveness (RE) of the fertilizers was calculated relative to granulated monocalcium phosphate, the most effective fertilizer. Monocalcium phosphate was not applied to the second crop, so relative residual effectiveness (RRE) was estimated for each fertilizer relative to the residual effectiveness of granulated monocalcium phosphate.The relative effectiveness of granulated monocalcium phosphate (band application) was greater (RE = 1.00) than of North Carolina RP (0.01–0.02) and partially acidulated RP (0.45–0.76) for all three soil pH values for the first crop. Granulation and band application increased the effectiveness of monocalcium phosphate and partially acidulated RP, but reduced the effectiveness of North Carolina RP. Both non-granulated monocalcium phosphate and partially acidulated RP were less effective than granulated partially acidulated RP for both crops. For the second crop granulated monocalcium phosphate was most effective and the RRE of non-granulated partially acidulated RP (0.16–0.32) and North Carolina RP (0.19–0.28) was greater than for non-granulated monocalcium phosphate (0.12). For the more acidic soil the RE of non-granulated North Carolina RP was four times higher than for the high pH soil for the first crop and 60% higher for the second crop, but it was still poorly effective relative to granulated monocalcium phosphate. Granulated North Carolina RP was least effective among all the fertilizers for all soil pH values and for both crops.     

部分酸化磷矿一步法制复肥研究

介绍了部分酸化磷矿一步法制复合肥的肥效及水溶磷在土壤中的退化机理。说明控制化肥中适当的水溶磷比例,可以减少土壤对磷的固定,提高施肥效果。     

Greenhouse evaluation of phosphorus availability from compacted phosphate rocks with urea or with urea and triple superphosphate

The possible effect of urea hydrolysis on the availability of phosphorus (P) from phosphate rock (PR) was evaluated in two greenhouse experiments with maize, using two sources of PR — Pesca (Colombia) and Bayovar (Peru) — representing low and high chemical reactivity, respectively.In Experiment I, on a neutral Josephine silty clay loam (pH 6.2) (Typic Haplozerult), Bayovar PR compacted with urea (Bayovar PR + urea) performed better than Bayovar PR compacted with NH₄Cl (Bayovar PR + NH₄Cl) in increasing dry-matter yield at a rate of 100 mg P kg^–1 but not at rates of 50 and 200 mg P kg^–1. It was also found that the dry-matter yield obtained with compacted Bayovar PR products was significantly higher when the N ratios of urea: NH₄Cl were 1:1 or higher than when the ratios were below 1:1. Although Bray I–P can overestimate available P from PR with respect to that from TSP, a good relationship was observed between Bray I–P and dry-matter yield from various compacted Bayover PR products with a small particle size (–0.43 + 0.15 mm).In Experiment II an acid Bladen sandy loam (pH 4.5) (Typic Albaquult) was used. Finely ground Bayovar PR (– 0.07 mm) was about 66% as effective as TSP in increasing dry-matter yield, whereas Pesca PR was ineffective. When Pesca PR was partially acidulated with H₃PO₄ at 20% level (PAPR), it became 70% as effective as TSP. Granulated PAPR and Pesca PR compacted with TSP (Pesca PR + TSP) were found to be equally effective in increasing dry-matter yield when both products had the same particle size and the same water-soluble and citrate-soluble P as percent of total P, and when prilled urea was used as the N source. However, when urea was compacted with Pesca PR and TSP, the product's effectiveness was further increased by 30% and to the same level as TSP.In summary, the results tend to support the suggestion that urea hydrolysis can be beneficial in increasing the availability of P from PR to plants in soils having medium to high organic matter contents.     

Single superphosphate - reactive phosphate rock mixtures. 3. The use of concentration ratios of elements to identify the nature and amounts of unacidulated rock residues in the mixtures

Water insoluble residues (WIR) of unreactive phosphate rocks in single superphosphate-reactive phosphate rock (SSP-RPR) mixtures are considered to reduce the agronomic value of these mixtures. A technique using concentration ratios of elements to identify the quantities of WIR of ground North Carolina (NC), ground Nauru and as received NC phosphate rocks in a SSP-RPR was developed. Of 22 elements tested P/Sr ratios were found to be the only element ratios that could be used to distinguish between WIR's derived from Nauru and NC. P/Sr ratios in Nauru and NC were markedly different and provided a useful index for differentiating between the two rocks. During acidulation the P/Sr concentration ratio remained essentially constant in the WIR's from both rocks.Using the element ratio technique the percentage of total P in the SSP-RPR sample was determined to be 60-61% water soluble, 5% water insoluble Nauru, 2% water insoluble ground NC and 32-33% water insoluble as received NC.The element ratio technique developed in this study can be applied to partially acidulated P fertilizers made with rocks other than NC and Nauru provided elements which satisfy the same conditions as Sr in this study can be found.     

Sulfur/sodium bentonite mixtures as sulfur fertilizers. 1. The effects of S/Na-bentonite ratios on the rate of dispersion and particle size distribution of elemental sulfur dispersed from laboratory-produced prills

Sulfur/sodium bentonite fertilizer prills were made by blending between 5 and 40% by weight of a swelling sodium bentonite clay with molten sulfur (S) and chilling droplets of the mixtures in oil. The resulting prills were hard and dust free and thus offered a suitable form for elemental sulfur (S°) transportation and application. The prills were stable at normal room temperature and RH. Prill strength was much reduced by prolonged storage at 80% RH. With 15% or more bentonite the bulk resistivity was sufficiently low that no electrostatic charge build-up was likely and consequently there was little risk of spontaneous combustion.Prills containing 10% or more bentonite disintegrated when placed in water and both the rate of dispersion and the fineness of the dispersed S° particles increased bentonite content. Bentonite contents of 15–20% appeared to offer the best combination of rapid prill dispersion, fine dispersed S° particle size, and high S° content.     

The effects of nitrogen fertilizer form on the plant availability of phosphate from soil,phosphate rock and mono-calcium phosphate

A glasshouse trial using lettuce as the test crop, and laboratory incubations were used to evaluate the influence of various nitrogen fertilizers on the availability of phosphate from an unfertilized loamy sand soil and from the same soil fertilized with Sechura phosphate rock or monocalcium phosphate. The order in which nitrogen fertilizer form increased plant yield and P uptake from soil alone and from soil fertilized with the rock was ammonium sulphate > sulphurised urea > ammonium nitrate > urea > potassium nitrate. For each rock application (both 30 and 60 mg/pot) and for soil alone, increased P uptake by the plant correlated well with decreased soil pH. In soil fertilized with the soluble P form, monocalcium phosphate, the form of the nitrogen fertilizer had little effect on plant P uptake. Subsequent laboratory incubation studies showed that increased dissolution of soil-P or Sechura phosphate rock did not occur until acidity, generated by nitrification or sulphur oxidation of the fertilizer materials, had lowered soil pH to below 5.5. A sequential phosphate fractionation procedure was used to show that in soils treated with the acidifying nitrogen fertilizers, ammonium sulphate and urea, there was considerable release of Sechura phosphate rock P to the soil, amounting to 42% and 27% of the original rock P added, respectively.     

The residual value of rock phosphate and superphosphate from field sites assessed by glasshouse bioassay using three plant species with different external P requirements

A pot experiment with two lateritic soils measured the relative residual effectiveness (RRE) of superphosphate and three rock phosphate (RP) fertilizers applied six years previously in the field. Three plant species (lettuce, wheat and maize) having very different external P requirements were grown as indicators of P availability. Superphosphate had the maximum RRE (1.0) and low reactive Queensland RP had the minimum RRE (0.04–0.45) for all plant species. For one soil the RRE of reactive North Carolina RP was similar to that of superphosphate (0.87–1.04), but ranged from 0.07 to 0.30 for the other soil. The RRE of Calciphos (one soil only) ranged from 0.60 to 0.98 for all plant species.The RRE of rock phosphate decreased for the three crops in sequence maize> wheat> lettuce for a 30 days growth period. This ranking follows the increasing external P requirement of the three plant species. Very high rates of application of RP may have induced micronutrient deficiencies.     

不同工艺硫酸钾对高塔硝硫基复合肥料质量的影响

概述卤水提取工艺、曼海姆工艺、复分解工艺制取的硫酸钾的特点,并通过实验考察不同工艺硫酸钾对高塔硝硫基复合肥料质量的影响。结果表明,各种工艺的硫酸钾的物理指标和化学指标存在着区别,对高塔硝硫基复合肥料的部分理化指标会造成一定的影响。高塔硝硫基复合肥料需要根据不同类型配方的要求,选用不同工艺的硫酸钾,合理利用不同工艺硫酸钾的优点,生产出优质的高塔硝硫基复合肥料。