This paper describes the development of an environment-friendly, slow-release fertilizer of the micronutrient iron. The compound is water insoluble, and is based on a polymeric phosphate structure. Kinetics and solubility of products in the goethite [FeO(OH)]-H3PO4 and [FeO(OH)]-MgO-H3PO4 systems were studied at 170-300 °C. Polymerization patterns were complex. The presence of Mg as additive, improved product properties. The fertilizer was prepared by polymerization of goethite, magnesium oxide and phosphoric acid to an optimized chain length at 200 °C, followed by neutralization with magnesia. The fertilizer was soluble in citrate and DTPA. A significant increase in the yield of wheat and uptake of iron was observed at a dosage of 2 kg/ha Fe as the slow-release fertilizer. © 2009 Elsevier B.V. All rights reserved.

P K CHANDRA

K GHOSH

C VARADACHARI

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Chemical Engineering Journal

This paper describes a new water-insoluble molybdenum compound that has been developed as a slow-release fertilizer. The compound is an inorganic polymer formed by inclusion of molybdenum within a long-chain polyphosphate structure. It was designed by a process of "reverse engineering" of the molecule. Synthesis involved reaction of phosphoric acid with magnesium oxide, molybdenum trioxide, and sodium carbonate at 275°C. Kinetics of reaction revealed complex multistage processes. X-ray diffraction patterns showed a crystalline nature with short-range as well as long-range ordering. The magnesium sodium polymolybdophosphate had ideal slow-release characteristics; it had low water solubility and high citrate solubility and was powdery, free flowing, and nonhygroscopic. Field testing showed an 80% increase in yield of green gram at a low dose of 0.04 kg/ha Mo. Nodulation increased by over 161%, and N content of gram increased by 20%. The slow-release fertilizer would provide an effective, low-cost, and environmentaly friendly alternative to Mo fertilization. © 2008 American Chemical Society.

Journal of Agricultural and Food Chemistry

New slow-releasing molybdenum fertilizer

Development of a new slow-release micronutrient fertilizer of iron - manganese is described. Studies include formulation, synthesis, kinetics, characterization, and testing. The compound is a partially polymerized, iron-manganese - magnesium polyphosphate, which is produced at 200 °C by reaction of iron, manganese, and magnesium oxides with phosphoric acid, followed by neutralization to pH 5.6. Polymerization is optimal at 21.2% with an Fe/Mn/Mg/P molar ratio of 1:0.51:1.15:7.33. Condensation kinetics show multistage processes with plateau formation at the end of each stage. The compound is crystalline with new XRD patterns indicative of a regular arrangement of polyphosphate chains. ESR spectra reveal Mn predominantly in the IV state. The product has ideal slow-release characteristics of low water solubility but high citrate and DTPA solubility, indicating high bio-availability of the micronutrients. Plant trials with chilli show a 45.6% increase in yield, at Fe 2 kg/ha - Mn 1 kg/ha as the slow-release fertilizer. The compound appears to be a promising, environmentally friendly alternative for Fe - Mn fertilization. © 2007 American Chemical Society.

Industrial and Engineering Chemistry Research

Development of a novel slow-releasing iron - Manganese fertilizer compound

Evaluation of chain lengths of polymeric phosphates is essential for the characterization of polyphosphate-based fertilizers. The titrimetric method, which is the most reliable and simple means of determining number average chain lengths (ñ), cannot be applied to solutions containing micronutrient ions. In this investigation, methods have been proposed for the elimination of metal ion interference prior to the titrimetric determination of the average chain length of polyphosphate solutions. When Cu2+, Fe3+, Mn2+, Mg2+, or Mo6+ are present in the solutions, solvent extraction of their complexes with 8-hydroxyquinoline at appropriate pH, prior to titration, was very effective. The interference due to Zn2+ was conveniently masked by the addition of potassium ferrocyanide and the titration carried out in the presence of the insoluble complexes. These methods do not introduce any perceptible additional error in the determination of ñ. They can also be conveniently combined when more than one interfering ion is present in the polyphosphate solution. These methods, therefore, offer a rapid, simple, and reliable means for analyzing micronutrient polyphosphate fertilizers.

Removing Micronutrient Metal Cation Interferences Prior to Titrimetric Determination of Polyphosphate Chain Length

The development of a new type of slow-releasing copper fertilizer which is based on a short-chain polyphosphate structure, is described. Kinetics of polymerization of cupric phosphate at various Cu:P ratios and temperatures were studied, and the products were characterized. The desired fertilizers were formulated by selecting the appropriate copper polyphosphates and then neutralizing them to improve their properties. The fertilizers were analyzed by chemical methods, IR, XRD, solubility studies, and plant growth experiments. They were observed to have short-chain P-O-P linkages and contain amorphous as well as crystalline phases. Their water solubility was &lt;5%, but in organic complexants, like citric acid or diethylenetriaminepentaacetic acid, solubilities were &gt;90%, thereby indicating excellent plant availability. Plant growth experiments showed that copper calcium polyphosphate is an efficient source of copper, comparable to CuSO4; however, lower dosages are required with the former than with the latter.

Novel Slow-Releasing Micronutrient Fertilizers. 2. Copper Compounds

A new concept for slow-releasing micronutrient compounds is proposed, based on the short-chain polyphosphate framework. The development of a zinc fertilizer, the first of such compounds, is described. Kinetic studies indicate that zinc phosphates polymerize in several linear stages. The polyphosphates are, in general, extremely water soluble and hygroscopic; moreover, those with lower solubility contain a high proportion of unavailable Zn2+. Initially, it was not possible to obtain a zinc polyphosphate having low water solubility and high nutrient availability. Solubility and hygroscopicity were attributed to free acid groups on the polyphosphate chain; neutralization of these groups indeed removed these undesirable characteristics. The fertilizers formulated have an average chain length of 2.35, contain some crystalline phases, have low water solubility, and are almost completely soluble in dilute HCl, citrate, diethylenetriaminepentaacetate, etc. Plant experiments indicate that the zinc polyphosphate is either equivalent to or better than ZnSO4. © 1993, American Chemical Society. All rights reserved.

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ISSN	1385-8947