A strategy for multi-nutrient application in integrated granules using

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Agricultural and Environmental Chemistry

A strategy for multi-nutrient application in integrated granules using zein as a coating layer Ricardo Bortoletto-Santos, Fábio Plotegher, Vanderlei Roncato, Rafaela F. Majaron, Vinicius F. Majaron, Wagner Luiz Polito, and Caue Ribeiro J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b01319 • Publication Date (Web): 21 Aug 2018 Downloaded from http://pubs.acs.org on August 22, 2018

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Journal of Agricultural and Food Chemistry

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Title: A strategy for multi-nutrient application in integrated granules using zein

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as a coating layer

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Authors: Ricardo Bortoletto-Santos1,2; Fábio Plotegher1; Vanderlei Roncato2,

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Rafaela F. Majaron3; Vinicius F. Majaron3; Wagner L. Polito2; and Caue Ribeiro1*

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Instrumentação, Rua 15 de Novembro 1452, Centro, São Carlos, São Paulo, 13560-

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970, Brasil. Phone/Fax: +55 (16) 2107 2800.

Laboratório Nacional de Nanotecnologia para o Agronegócio (LNNA), Embrapa

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Carlos, Avenida Trabalhador São-Carlense, 400, Arnold Schimidt, São Carlos, Zip

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Code: 13566-590, SP, Brazil. Phone/Fax: (16) 3373-9976.

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Washington Luiz, km 235, São Carlos, SP, CEP: 13565-905, Brasil

Instituto de Química de São Carlos, Universidade de São Paulo, Campus de São

Universidade Federal de São Carlos, Departamento de Química, Rodovia

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Number of Tables: 3

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Number of Figures: 7

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Corresponding Author:

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Dr. Caue Ribeiro

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Embrapa Instrumentação

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Rua XV de Novembro, 1452

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São Carlos, SP - Brazil - CEP 13560-970

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Phone: +55 (16) 2107 2915

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Fax: +55 (16) 2107 2902

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e-mail: [email protected]

ACS Paragon Plus Environment


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Abstract

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The efficiency of phosphate fertilizers is strongly limited by the acidity and high iron

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content and aluminum-based compounds in soils due to high P fixation. Coatings

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have been proposed as an alternative solution to reduce P losses by controlling the

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fertilizer release, but the literature is not conclusive about the most adequate material

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for that purpose. Herein we report a novel Zn-based coating for monoammonium

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phosphate (MAP) granules comprising ZnO nanoparticles and zein as a bi-coating

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structure. Samples were prepared by dispersing ZnO and zein on the MAP surface

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and characterized, comparing the release in neutral and acidic solutions over time.

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Coating thickness/quality determined the nutrient release by a physical barrier effect.

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The results show that the zein coating overprotection avoids a fast nutrient release,

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keeping the local acid medium necessary to suppress ZnPO4 precipitation. A range

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of 2.5 to 10.0 wt % of zein was studied, indicating that 2.5 wt % coatings just present

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significant release control, which is similar until 10.0 wt % coating.

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Keywords: Release, fertilizer, eco-friendly, phosphate, zinc.

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INTRODUCTION

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Currently, the importance of increasing food production is highlighted mainly

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due to its direct correlation with world population growth. In addition, modern

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agriculture is characterized by intensive land use, which does not allow it to increase

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productivity and cultivated area at same scale. The use of fertilizers is imperative to

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keep simultaneously soil fertility and high crop yields.1 Besides macronutrients,

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micronutrients are worthy of study due to their essential functions for plants, although

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they are required in smaller quantities. The constant use of soil, rain leaching as well

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as the lack of crop rotation lead to reduced levels of these nutrients in soils,

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especially in those which are poor in organic matter such as tropical soils.2-5 One of

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the most necessary micronutrients in tropical soils is Zn2+, which is generally applied

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as soluble zinc salts, for example, ZnSO4.

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A good solution to overcome micronutrient deficiency in soils lies on its

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simultaneous application with macronutrients as a coating, since coatings are

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frequently applied on fertilizer granules.6 This would minimize the need for specific

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micronutrient application, but it is challenging in terms of nutrients kinetic availability,

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as well as concerning the relative amounts of nutrients that need to be released to

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soil. Despite some products are an indicative of market tendency, the interaction of

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Zn2+ with phosphate ions (leading to zinc phosphate, a poorly soluble material)

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strongly limits any solution focused on these two nutrients, since the final product

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could reduce the available of Zn2+ and phosphate due to precipitation.7

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In this study, we proposed a novel strategy to produce a Zn-based coating for

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monoammonium phosphate (MAP) granules using ZnO nanoparticles and zein, a

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prolamine derivative from maize. These materials were selected considering that

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ZnO nanoparticles are less soluble than zinc salts but can be dissolved by the acid



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environment created by MAP dissolution. At the same time, the zein coating avoids a

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fast nutrient release, sustaining the local acidic medium necessary to suppress

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ZnPO4 precipitation.

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MATERIALS AND METHODS

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Coating of fertilizer with micronutrients and zein.

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MAP granules (Monoammonium Phosphate Standard, gently provided by

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Adubos Vera Cruz Ltda.), with average diameter of 3 mm, were coated in a

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laboratory coater under rotation speed of 30 rpm using 50 g of a commercial

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micronutrient suspension based on Zincite (ZnO) and water (gently provided by

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Produquimica). The material was homogenized for 10 min until drying and completely

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separation of the granules. Next, the MAP granules coated with ZnO were coated

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again with an ethanolic zein solution (1:3).8 The zein to fertilizer proportion was 2.5%

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in a mass basis. The process was repeated layer upon layer until 10.0% in mass,

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using heated air flow between 60 – 80 oC to dry the material. Table 1 shows the

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sample nomenclatures.

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Physical and Chemical Characteristics of the Coatings

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Characterizations

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Thermogravimetric analyses (TGA) were performed on an equipment Q500

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(TA Instruments, United States) using synthetic air flow rate at 60 mL min-1. Samples

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were heated up to 800 oC using a continuous heating rate of 10 oC min-1. Differential

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scanning calorimetry (DSC) analyses were conducted in a Q2000 calorimeter (TA

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Instruments, United States). Samples were placed in an aluminum crucible and


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heated at a continuous heating rate of 10 oC min-1 from –50 to 200 oC under inert

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nitrogen atmosphere.

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In order to obtain qualitative results of the groups present in the materials,

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MAP uncoated, all fertilizers coated with ZnO and different amounts of zein (MAPZ0

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to MAPZ100) as well as pure zein (in form of powder or film) were analyzed in a

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spectrophotometer with a Fourier Transform Infrared Spectrometer - Vertex 70 model

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and Bruker (Fourier Transform Infrared Spectrometer - FTIR). The analysis also used

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the Attenuated Total Reflectance (ATR) with diamond crystal in the frequency range

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from 4000 to 400 cm-1 with a 4 cm-1 resolution.

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The morphology of the micronutrient particles and the layer formed on the

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granules were observed by scanning electron microscopy (SEM) using a JSM 6510

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microscope (JEOL, Japan). Imaging was carried out using an accelerating voltage of

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10 kV and secondary electron detector.

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The dispersion of the micronutrient particles of the layer on the fertilizer

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granules were observed by high-resolution X-Ray tomography (Micro-CT) analysis

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using a scanner SkyScan 1172 (Bruker, Germany) operating with voltage of 59 kV,

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current 167 µA, rotation step of 0.3 degree and image reconstruction by NRecon

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software.

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Solubilization tests

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The solubility of the fertilizer was evaluated under two conditions: deionized

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water (18.2 MΩ cm) and citric acid solution (2.0% wt), which is a standard condition

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used in tests of phosphate chemical fertilizers recommended by Brazilian Ministry of

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Agriculture, Livestock and Supply (MAPA).9,10 Both experiments were performed at

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room temperature (23 oC) to assess the nutrient release rate as a function of time.3



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Experiments were carried out for 30 days following the model described by Pereira et

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al. (2012), in which a beaker containing a known mass of the coated material was

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immersed in a larger beaker containing water or citric acid solution, under constant

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stirring, hence ensuring homogeneous release.11 For each experiment, 500 µL

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aliquot parts were taken periodically at every 24 hours over ten days and then at

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every 48 hours until the twentieth day. Aliquots were further taken at twenty-fifth day

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and the last one at the thirtieth day. These aliquots were used for phosphorus and

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zinc release determinations.

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Determination of solubilized phosphorus

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Phosphorus determination was based on a method reported by Murphy and

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Riley (1962),12 modified by Drummond and Maher (1995),13 also recommended by

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MAPA for phosphorus quantification in chemical fertilizers.10 This method consists of

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phosphorus complexation with antimony and molybdenum. The blue complex was

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quantified by UV-Vis colorimetric method using a Femto® spectrophotometer with a

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fixed wavelength at 880 nm. Zinc determination was done by flame atomic absorption

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spectroscopy (FAAS) using a Perkin Elmer model PinAAcle 900T with flame

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composed of synthetic air (10 mL) and acetylene (2.5 mL) and wavelength at 213.86

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nm.

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RESULTS AND DISCUSSION

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Figure 1 shows the FTIR spectra of free zein film (self-supported) and different

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MAP/ZnO coated granules, where it is possible to see that all coated materials have

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similar spectra. Comparing the spectra of zein powder and film, one can see that the

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processing condition did not alter the zein structure, as expected. However, in the


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MAP/ZnO surface, it is noteworthy that the main zein peaks are suppressed or

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shifted, indicating some interaction between zein and ZnO as well as this is in fact

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the material in contact with zein. We pointed out three regions of the spectrum that

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are correlated to zein amides I, II and III. One can see that these bands are the most

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intense for this material. The first region is in approximately 1643 cm-1, where the

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C=O stretching vibration band of peptide groups is observed together with C–N

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stretching contributions. The second region refers to amide II, in the range of 1537

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cm-1, characterized by deformations in the plane of the N–H bond of the peptide

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groups.17 The third region is associated with amide III vibration of peptide groups

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present in zein as well as different conformations due to decomposition of these

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groups in a set of secondary structures, in the region of 1242 cm-1. In addition, a set

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of bands, in the range between 3100 - 2800 cm-1, is associated with the C–H

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vibrations of CH3 and CH2 groups derived from fatty acids and/or side chains of some

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amino acids. All these peaks are strongly suppressed in MAP coated sample spectra,

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indicating the surface interaction. A band in the zein film spectrum at 3288.5 cm-1 is

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also observed, which is characteristic of N–H stretching, which is shifted to 3222.7

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cm-1 in coated sample spectra. It is important to note that the amine bands of proteins

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generally correspond to overlaps of several vibration bands of different secondary

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structures of proteins such as α-helices and β-sheets.18

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The degradation behavior of the coating and its thermal stability were

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evaluated by the TG and DTG curves shown in Figure 2. It can be seen that zein

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present four mass loss events, the second event being responsible for the largest

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mass loss, approximately 60%. The first loss event is associated with loss of solvent

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adsorbed on the material (54 °C), while the other mass loss events relate to the

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degradation of the protein structure (322 °C, 506 °C and 563 °C) - approximately 60,



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20 and 10 %, respectively.19,20 In addition, DSC curve (Figure 3) shows a peak at

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89.6 °C which is attributed to the loss of solvent visualized in the TG curve (Figure 2)

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and the presence of Tg at 159.7 ºC, as shown in Figure 3.21-23

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Figure 4 shows the cut in the z-axis = 1 mm obtained from the Micro CT

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characterizations. It is possible to observe the clearest contrast in the granule

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contour of the samples MAPZ0 and MAPZ100. This is due to the lower transmission

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of X-rays of the zinc oxide applied to the fertilizer granule surface. Such feature is not

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observed for MAP0 due to the lack of zinc oxide in its coating. The zein layers are not

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possible to observe in the images, because they are organic compounds and exhibit

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high X-ray transmission than the other materials. However, Figure 5 shows a cross-

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sectional SEM image of the MAPZ100 granule in which the zein layer (yellow)

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applied on the zinc oxide layer (blue) covering MAP granule surface (green) is

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observed.

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The results of phosphorus release in water are presented in Figure 6a. It is

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noted that the variation in coating content correlates directly with the release profile.

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It is also noted that for all materials, the amount of phosphorus released was above

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80% of the total coated value, and the release levels off after 50 h in all cases. This

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relates a controlled release but not an irreversible phosphate interaction with coating

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materials. It important to observe that uncoated granules, MAP0 and MAPZ0, exhibit

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similar phosphorus release behavior. This indicates that P release is exclusively

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dependent on MAP solubilization, evidencing that the presence of micronutrient does

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not interfere on P release (phosphorus release delay). The release occurs through

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the coating porosity without any influence of ZnO. However, it is observed that

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materials containing low zein contents (MAPZ25) present a slightly delayed

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phosphorus release, reaching dissolution of 70-80% over 50 h. The uncoated


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fertilizer reached 85% of phosphorus released in approximately 2.5 h. Thus, the zein

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coating has a significant ability to delay the phosphorus release. Finally, it can be

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seen that thicker coatings (above MAPZ75) implied in a slight delay in the first 50 h,

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releasing 60 % of the fertilizer. Therefore, the physical barrier effect becomes more

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significant allowing the system to achieve a total phosphorus release in 500 h.

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The results of phosphorus release in citric acid solution presented in Figure 6b

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showed that the medium acidification accelerates the fertilizer release when the zein

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levels are low (below MAPZ75). This fact can be evidenced by observing, for

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example, that materials with low zein content, MAPZ25 and MAPZ50, reached 80%

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phosphorus released within 50 h. Also, medium acidification does not significantly

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interfere on coatings with high biopolymer content (MAPZ100). The sample

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MAPZ100 achieved 70% phosphorus released in approximately 100 h, under both

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immersion test conditions. This is due to the fact that the physical barrier generated

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by higher zein levels presents better uniformity and, consequently, smaller porosity

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and cracks, avoiding the fast contact of the immersion solution with the fertilizer.

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Figure 7 shows the release profile of Zn2+ in citric acid solution since ZnO has

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low solubility in water so that equilibrium in water is reached in release percentage

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less than the real one. In addition, the graphic containing the Zn2+ release in water is

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shown in Supplementary Figure S1. The results show that the coating strategy, allied

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to the use of ZnO instead of Zn salts, was efficient in avoiding the Zn reaction with

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phosphate, leading to insoluble precipitates. Consistently to Figure 6, all the

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materials showed high Zn solubilization levels (up to 80% of the estimated content).

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However, the most remarkable difference was the role of zein coating in the release

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process: for thicker coating (MAPZ100) the Zn2+ release was significantly delayed

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compared with all the other conditions, indicating that zein coating quality determines



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the Zn2+ release by a physical barrier effect. However, the little zein-coated granules

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did not present initial delay (up to 40% of zinc released) significantly different from

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the uncoated granules (MAPZ0), with a delay in zinc availability after 24 h. After this

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time the best biopolymer barrier effect is obtained as well as the best retention for

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MAPZ75 when compared with MAPZ25 and MAPZ50. This similarity indicates that

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ZnO dissolution is continuously promoted even in the inner coating, releasing Zn2+

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ions to the medium through the pores and cracks of the zein coating.

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Analysis of coating role on the nutrients release process was conducted using

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the kinetic parameters obtained from a modified Ritger-Peppas model.14-15 Parameter

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values for phosphorus release and zinc release are reported in Table 2 and 3,

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respectively. The diffusional process (or diffusional exponent) can be obtained from

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equation 1

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Mt/M∞=k(t-to)n

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Where Mt/M∞ is the release ratio at a given time t and/or equilibrium state,

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considering the total amount available for release; k is the velocity constant which

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depend on the kind of material and the permeation medium; t0 is the induction time,

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i.e., the necessary period to observe any appreciable solute release; and n is the

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release order, which provides information about the transport mechanism

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determining the release process. In addition, n values between 0.5 and 1.0 indicate a

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Fickian release, i.e., diffusion through coating (as a semipermeable membrane) is

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predominant while n > 1.0 indicates that the release is governed by the coating

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structure, which changes during the process allowing solute diffusion by channels or

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structural pores.15-16

(1)

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The parameters suggest that there is a direct relationship between nutrients

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release behavior and coating thickness. In the phosphorus release case, the kinetic


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model indicates that materials MAPZ25 to MAPZ75 have similar diffusional

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characteristics when compared with uncoated material (MAP0), with n values from

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0.5 to 1.0. In addition, the acidic medium accelerates the phosphate release, as

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expected, by fastening the salt dissociation. However, one can notice that the acidic

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medium reduces the variation among the different coating conditions, except for

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MAPZ100, which also shows the slower release condition in neutral medium. This is

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an important feature of the coated system, since indicates that the release is favored

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by acidic conditions like expected by organic acid production in roots – in other

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hands, when the nutrient is easily absorbed by plants. Therefore, phosphate source

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is effectively protected by coating even in moist conditions, avoiding immobilization.

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On the other hand, for MAPZ100 sample a non-Fickian behavior was

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observed (n>1.0) indicating that the release only takes place after some modification

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in coating structure. Since zein is poorly soluble in water,8,23 this may indicate that

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release will occur only after some granule swelling (through small zein layer pores),

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which may damage the coating, resulting in cracks formation for release. In addition,

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n values for MAPZ100 in P release (1.13) indicate that the coating imposes a

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continuous diffusion barrier for phosphate dissolution. It is noteworthy that coated

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samples differ mainly in k values, indicating that this process velocity is governed by

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coating thickness. In fact, one could note that increasing coating thickness reduces

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the nutrient release rate. This indicates that the release happens through the open

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porosity but there are less pores/cracks for MAP dissolution with increasing coating

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thickness. In any case, this is happening only after a significant time, which indicates

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a good fertilizer granule protection behavior. The initial retention time (t0) also

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significantly increases for MAPZ75 and MAPZ100, indicating that the coating needs

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change its structure to allow the fertilizer release.



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The application of the same kinetic model for Zn2+ release (Table 3) indicates

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smaller variations of diffusional behavior among the materials, with n of

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approximately 0.5 (indicating a simple diffusional behavior).14,15 However, MAPZ100

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showed a totally different behavior, with very long retention time and a large

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diffusional barrier (n = 1.20 and 1.83 in neutral and acidic medium, respectively). This

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shows the importance of complete coating of the ZnO nanoparticles by zein, since

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this effectively retarded the ZnO dissolution. Interesting, in all the samples the ZnO

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nanoparticles (in citric acid solution) tend to maximum dissolution, indicating that the

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zein coating does not suppress this behavior as well as reveals that the acidic

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medium is necessary to promote effective Zn release.

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CONCLUSIONS

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In summary, we have showed that zein/ZnO co-coating for MAP may be an

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efficient strategy for simultaneous micro- and macronutrient delivery with synergic

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effects for both nutrients. MAP granules coated with ZnO leads to a good

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adhesiveness and homogeneous protection of the fertilizer, synergistically acting to

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zein coating, which is essential for proper simultaneous P and Zn release.

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Phosphate release was efficiently controlled for systems with >2.5% weight zein,

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which could be regularly released in acidic conditions until 10.0% weight, indicating

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that this interval can be used to adjust the desired Zn/phosphate proportion in

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application. In addition, it is important to note that P and Zn2+ liberation are

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independent and do not interfere with each other as well as granules coated with zein

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above 10% wt also provided a delay in the Zn2+ release. This simple coating strategy

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is similar to other industrial processes, which supports its adequacy for large scale

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fertilizer applications.


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FUNDING

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The authors thank the financial support given by CAPES, FAPESP

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(2017/11149-6), CNPq (402.287/2013-4), SISNANO/MCTI, FINEP and Embrapa

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AgroNano research network.

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CORRESPONDING AUTHOR

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*Embrapa Instrumentação (CNPDIA), Rua XV de Novembro 1452, São Carlos, SP,

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13560-970, Brazil. Phone: +55 16 2107 2915; E-mail: [email protected]

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[18] Duodu, K. G.; Tang, H.; Grant, A.; Wellner, N.; Belton, P. S.; Taylor, J. R. N.

361

FTIR and Solid State 13C NMR Spectroscopy of Proteins of Wet Cooked and

362

Popped Sorghum and Maize. J. Cereal Sci. 2001, 33, 261-269.

363

[19] Rosa, C. G. A.; Maciel, M. V. O. B.; Carvalho, S. M.; Melo, A. P. Z.; Jummes, B.;

release.

J.

Appl.

Polym.

Sci.

2016,


33,

133,

43790.


Page 16 of 27

16

364

Silva, T.; Martelli, S. M.; Villetti, M. A.; Bertoldi, F. C.; Barreto, P. L. M.

365

Characterization and evaluation of physicochemical and antimicrobial properties of

366

zein

367

Physicochem. Eng. Aspects. 2015, 481, 337–344.

368

[20] Han, Y-L.; Xu, Q.; Lu, Z-Q.; Wang, J-Y. Preparation of transparent zein films for

369

cell culture applications. Colloids Surf. B: Biointerfaces. 2014, 120, 55-62.

370

[21] Ali, S.; Khatri, Z.; Oh, K. W.; Kim, I.; Kim, S. H. Zein/Cellulose Acetate Hybrid

371

Nanofibers: Electrospinning and Characterization. Macromolecular Research. 2014,

372

22, 9, 971-977.

373

[22] Chen, L.; Subirade, M. Elaboration and characterization of soy/zein protein

374

microspheres for controlled nutraceutical delivery. Biomacromolecules. 2009, 10,

375

3327–3334.

376

[23] Forato, L. A.; de Britto, D.; Scramin, J. A.; Colnago, L. A.; Assis, O. B. G.

377

Propriedades mecânicas e molhabilidade de filmes de zeínas extraídas de glúten de

378

milho. Polímeros. 2013, 23, 1, 42-48.

nanoparticles

loaded

with phenolics

monoterpenes.

379


Colloids

Surf. A

Page 17 of 27


17

380

FIGURES

381 382

Figure 1. Fourier-transform Infrared Spectroscopy (FTIR) spectra of zein powder,

383

zein film, MAP uncoated (MAP0), MAP coated with ZnO (MAPZ0) and MAP+ZnO

384

coated with zein at 2.5, 5.0, 7.5 or 10.0% by weitgh (MAPZ25 to MAPZ100).

385



Page 18 of 27

18

386

2.

Thermogravimetric

analysis

(TGA)

curves

and

their

derivative

387

Figure

388

thermogravimetric (DTG) curves of pure zein, MAP uncoated (MAP0) and MAP+ZnO

389

coated with zein at 10.0% (MAPZ100).

390


Page 19 of 27


19

391 392

Figure 3. Differential scanning calorimetry (DSC) curve of pure zein, MAP uncoated

393

(MAP0) and MAP coated with zein at 10.0% (MAPZ100).

394



Page 20 of 27

20

395 396

Figure 4. Microtomography analyses of granules – MAP0 (without coating), MAPZ0

397

(zinc coated) and MAPZ100 (zinc and zein coated).

398


Page 21 of 27


21

399 400

Figure 5. Scanning Electron Microscopy (SEM) of the section containing the

401

interface between the fertilizer (green), ZnO (blue) and zein coating (yellow).

402



Page 22 of 27

22

403 404

Figure 6. Phosphorus release in water (a) and citric acid solution (2.0% wt) (b) from

405

MAP uncoated (MAP0), MAP coated with ZnO (MAPZ0) and MAP+ZnO coated with

406

zein at 2.5, 5.0, 7.5 and 10.0% by weight (MAPZ25 to MAPZ100). Vertical bars are

407

standard deviations.

408


Page 23 of 27


23

409 410

Figure 7. Zn release in citric acid solution (2.0% wt) from MAP uncoated (MAP0),

411

MAP coated with ZnO (MAPZ0) and MAP+ZnO coated with zein at 2.5, 5.0, 7.5 and

412

10.0% by weight (MAPZ25 to MAPZ100). Vertical bars are standard deviations.

413 414 415



Page 24 of 27

24

TABLES

416 417

Table 1. Sample nomenclatures.

418 Material

Nomenclature

MAP (uncoated)

MAP0

MAP+ZnO

MAPZ0

MAP+ZnO+Zein 2.5%

MAPZ25

MAP+ZnO+Zein 5.0%

MAPZ50

MAP+ZnO+Zein 7.5%

MAPZ75

MAP+ZnO+Zein 10.0%

MAPZ100

419 420

Table 2. Kinetic parameters of modified Ritger-Peppas model for phosphorus release

421

in water and acidic (citric acid solution, 2.0% wt) conditions.

422

Neutral Material

k (h-1) x 10-3

n

Acidic t0

k (h-1)

(h)

x 10-3

n

t0 (h)

MAP0

82.52

0.81 ± 0.05

0

-

-

-

MAPZ0

85.95

0.80 ± 0.05

0

105.80

0.80 ± 0.06

0

MAPZ25

43.36

0.73 ± 0.09

0.5

92.25

0.81 ± 0.08

0.5

MAPZ50

17.94

0.91 ± 0.09

0.5

27.81

0.82 ± 0.09

0.5

MAPZ75

15.33

0.81 ± 0.09

3.0

19.19

0.86 ± 0.06

2.0

MAPZ100

6.42

1.13 ± 0.17

4.0

7.20

1.11 ± 0.19

4.0

423 424


Page 25 of 27


25

425

Table 3. Kinetic parameters of modified Ritger-Peppas model for zinc release in

426

neutral and acidic (citric acid solution, 2.0% wt) conditions Neutral

Acidic

-1

Material

k (h ) -3

x 10

-1

n

t0 (h)

k (h ) x 10-3

n

t0 (h)

MAPZ0

1.87

0.75 ± 0.04

0

60.85

0.66 ± 0.08

0

MAPZ25

2.50

0.78 ± 0.08

0

63.11

0.57 ± 0.04

0

MAPZ50

1.75

0.73 ± 0.05

1.0

75.39

0.65 ± 0,07

0

MAPZ75

1.34

0.75 ± 0.04

-

45.92

0.60 ± 0.03

1.0

MAPZ100

3.89

1.20 ± 0.08

-

7.11

1.83 ± 0.14

72.0

427



Page 26 of 27

26

SUPPLEMENTARY FIGURE

428

429 430

Supplementary Figure S1. Zn2+ release in water from MAP coated with ZnO

431

(MAPZ0) and MAP+ZnO coated with zein at 2.5, 5.0, 7.5 and 10.0% by weight

432

(MAPZ25 to MAPZ100).

433


Page 27 of 27


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434

TOC Graphic

435


A strategy for multi-nutrient application in integrated granules using

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