Production and Characterization of Nanotechnology-Based, Eco-Friendly New Generation Organic Fertilizer Coatings for the Agricultural Sector

Polymer Use Classifications in Agriculture There are numerous different classifications for polymer applications in the agricultural sector. Film and greenhouse coverings, superabsorbent polymers, polymers with controlled drug release properties, polymers used for removing metal ions from soil and water, biodegradable polymers used in agriculture, and polymers with friction-reducing effects are named among the main categories. Polymers are present in every area of agricultural production in our daily lives. Organic fertilizer coverings facilitate sowing and spacing in agriculture. Efficient and productive labor savings significantly increase seed germination rates. They create a high-yield covering. They are suitable for cotton, onions, carrots, purslane, cauliflower, spinach and others. These liquid fertilizer-reinforced polycaprolactone (PCL) composites were produced by electrospinning. The study provided morphological characterization (SEM, Scanning Electron Microscopy) and mechanical (Tensile Test) analysis of the composite structure. The resulting composite material could demonstrate environmentally friendly organic fertilizer covering beneficial to agriculture. Organic fertilizer coverings facilitate sowing and spacing in agriculture. Reduction of waste seed amounts and uniform, efficient labor savings significantly increase seed germination rates. They create a covering property that provides high productivity. They are suitable for cotton, onions, carrots, purslane, cauliflower, spinach and others. Due to the nature of seed tape, growers generally may have far fewer options in terms of what crop varieties they are able to grow. Moreover, the purchase cost of seed tape is much higher than the cost of purchasing conventional seed packets. The preparation stages of seed tapes can be tedious and exhausting for those preparing them. Comprehensive quality control in practical agricultural application cannot be achieved for this reason. Figure 1.1 shows the current seed tape preparation problems. [caption id="attachment_105136" align="aligncenter"] Figure 1.1. Current seed tape preparation problems[/caption] Polycaprolactone (PCL) is a synthetic polymer that is semi-crystalline with adjustable pore sizes, has good mechanical properties and is easily processable [1]. PCL has a hydrophobic structure and is therefore a polymer whose degradation process proceeds very slowly. Degradation time can vary between 1 and 2 years. Due to its slow degradation and long-term preservation of its physical properties, it is a preferred polymer in long-term drug release systems and in vivo implants [2]. PCL, which has biocompatible and biodegradable properties, is frequently used in many medical fields such as wound dressings, surgical sutures and tissue scaffolds. In addition to this, PCL, which is extensively used in drug delivery and medical applications, is a highly compatible polymer for various tissues such as cartilage, bone, cardiovascular tissue, tendons and nerve-like tissues [3]. The chemical structure of PCL is shown in Figure 1.2. [caption id="attachment_105137" align="aligncenter"] Figure 1.2. PCL chemical structure [3][/caption]  A composite is defined as a new material comprising two or more materials that are chemically and physically distinct, combined to take advantage of their superior properties, and possessing better properties than the materials it encompasses [4]. For biomaterials produced as composites, it is important to utilize the superior mechanical and biological properties of the components in the materials [5]. Electrospinning essentially consists of the combination of three main components. It is composed of a power source, feeding sections and a layer that collects the fibers. This combining center has moving and stationary connecting centers in flat or cylindrical shapes. With an electrospinning device having these functions, polymeric nanofiber materials at various intervals can be produced. The electrospinning method allows fiber formation through electrical field force applied to solutions via high voltage [6]. Seed tape production containing polymer and liquid fertilizer using nanotechnological electrospinning technique can provide a solution to the problems experienced. Through the electrospinning technique, seed tape has been produced at reasonable cost with easy production that can serve as a beneficial source for agriculture. The time and labor losses spent in the preparation stages of seed tapes currently in use will be eliminated through nanotechnological application. It is a natural and modern tape that allows healthy agriculture, blocks the passage of harmful bacteria and pests, and is breathable. The desired seed tape for healthy agriculture exhibits homogeneous property distribution thanks to nanotechnology compared to existing seed tapes, so the same properties are realized throughout the seed tape by nanofibers. In this study, polycaprolactone (PCL) composites reinforced with liquid fertilizer were obtained using the electrospinning technique. The resulting composite material could demonstrate environmentally friendly tape and organic fertilizer covering properties beneficial to agriculture.

2. Materials and Methods 2.1. Materials

80,000 g/mol polycaprolactone (PCL), liquid fertilizer, dimethylformamide (DMF) organic solvent as support material in the electrospinning environment to dissolve the polymer, and wax paper were used.

2.2. Method Preparation of Composite Solutions

PCL polymer solution was prepared using a heated magnetic stirrer at the desired temperature and stirring speed. 10 ml of PCL solution was taken into a beaker and four different compositions were obtained with 1%, 5% and 8% liquid fertilizer. The solutions were subjected to the values given in Table 2.1 and brought into suitable form for nanofiber production by the electrospinning method. Table 2.1 shows the parameter values of the composite solutions. [caption id="attachment_105138" align="aligncenter"] Table 2.1. Preparation values of composite solutions[/caption]  

Composite Production by Electrospinning Method

The prepared 10% PCL, 10% PCL-1% liquid fertilizer, 10% PCL-5% liquid fertilizer and 10% PCL-8% liquid fertilizer composite mats were obtained by the electrospinning method according to the values in Table 2.2. The FYTRONIX electrospinning device image is given in Figure 2.1. The production stages of composites by electrospinning technique are shown in Figure 2.2.

Characterization Method

Nanofiber membranes placed in holders were examined with a Thermoscientific Phenom XL G2 desktop microscope and photographs were taken. For SEM analysis of composite nanofiber membranes, images magnified x12,000 times at 15 kV potential were examined. Nanofiber sizes were determined by measuring an average of 200 nanofibers using the device software on the obtained images. [caption id="attachment_105140" align="aligncenter"] Figure 2.1. FYTRONIX electrospinning device image[/caption]   Samples of 1x4 cm were prepared for mechanical characterization studies of composite nanofiber membranes. A digital micrometer (795.1 MEXFL-25, Starrett, USA) was used to measure the thickness of composite nanofiber membranes cut to appropriate dimensions. The obtained thickness values were entered into the analysis program prior to mechanical analysis and used to determine the elastic modulus. The mechanical properties of the formed nanofibers were determined with a Zwickline (Zwick/Roell Ltd., Germany) analyzer. Tests were conducted at room temperature. Samples are separated from the substrate material and fixed to the device clamps. Mechanical properties were determined with the device set at 500 N load, 5 mm/min tensile speed and 10 mm jaw spacing.

3. Results 3.1. Morphological Characterization

Nanofiber formation was observed in all samples. The average fiber diameter of PCL mats was determined to be in the range of 150-300 nm. As the liquid fertilizer amount increased, PCL fibers gradually became thinner. The Thermoscientific Phenom XL G2 desktop microscope image is shown in Figure 3.1. SEM morphology images of the composites are given in Figure 3.2, Figure 3.3, Figure 3.4 and Figure 3.5.

3.2. Mechanical Characterization

According to the results of nanofiber thickness measurements performed before the mechanical test, it was determined to be in the range of 0.01-0.18 mm. The test procedure was performed at a constant tensile speed of 5 mm/min with 10 cm jaw spacing, and strength values are shown in Figure 3.6. As the liquid fertilizer amount increased, the strength increase in the composites resulted from both the high load-bearing capacity of the polymeric (PC) matrix and the homogeneous distribution of different material additives in the composite [7]. When evaluating the study results, composite production was successfully accomplished using the electrospinning technique. It was observed that as the liquid fertilizer amount increased, PCL fibers became thinner and surface area increased. This is consistent with the tensile tests applied to the composites. Through the resulting composite structure, agricultural sector materials will acquire the property of organic fertilizer covering beneficial to agriculture. As a continuation of our studies: drug loading capacity tests can be conducted to investigate the possibility of use in the pharmaceutical industry, nanoparticle studies can be performed to conduct preliminary work for other problems in the agricultural sector, continuation of studies in different applications will be provided and field applicability will be determined. We thank FYTRONIX for their contributions to material procurement and determination of mechanical properties in production of nanofiber membranes.

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  Erdi Buluş Metallurgy and Materials Engineer Materials Technology Specialist Istanbul Arel University ArelPOTKAM (Polymer Technologies and Composite Application and Research Center) Gülseren Sakarya Buluş Specialist Nurse Silivri District Health Directorate