Nanoclay Polymer Composites Research Articles

Synthesis and Evaluation of Starch-Grafted-Poly[(Acrylic Acid)-Co-Acrylamide] Based Nanoclay Polymer Composite Fertilizers for Slow Release of Nitrogen in Soil.

Nitrogen (N) losses from conventional N fertilizers contribute to environmental degradation and low N use efficiency. Highlighting the need for slow-release fertilizers (SRFs) to mitigate these problems, this study aims to develop slow-release N fertilizers using starch-grafted-poly[(acrylic acid)-co-acrylamide] based nanoclay polymer composites (NCPCs) and investigate their efficacy for slow N delivery in soil. Three types of NCPCs, NCPC(A) (poly [(acrylic acid)-co-acrylamide]), NCPC(W) (wheat starch-grafted-poly[(acrylic acid)-co-acrylamide), and NCPC(M) (maize starch-grafted-poly[(acrylic acid)-co-acrylamide) were prepared and characterized using FTIR spectroscopy and X-ray diffraction techniques. N-release behaviour of the products was assessed under two distinct soils, i.e., Assam (Typic Hapludults, pH 4.2) and Delhi (Typic Haplustepts, pH 7.9) soils. Additionally, the effects of varying soil moisture and temperature levels on N release were studied in the Assam soil. The N-release kinetics of the synthesized fertilizers were assessed using zero-order, first-order, Higuchi, and Korsmeyer-Peppas models. Degradability of the NCPCs was evaluated by measuring evolved CO2-C under various soil conditions as an indicator of microbial degradation. The results indicated that NCPC fertilizers significantly slowed down the release of N compared to urea. According to the R2 values obtained, it was evident that the first-order kinetic model most accurately describes the N release from both urea and NCPC-based N fertilizers in the studied soils. Among the formulations, NCPC(A) exhibited the lowest N release (42.94-53.76%), followed by NCPC(M) (51.05-61.70%), NCPC(W) (54.86-67.75%), and urea (74.33-84.27%) after 21 days of incubation. The rate of N release was lower in the Assam soil compared to the Delhi soil, with higher soil moisture and temperature levels accelerating the release. Starch addition improved the biodegradability of the NCPCs, with NCPC(W) showing the highest cumulative CO2-C evolution (18.18-22.62 mg g-1), followed by NCPC(M) (15.54-20.97 mg g-1) and NCPC(A) (10.89-19.53 mg g-1). In conclusion, NCPC-based slow-release fertilizers demonstrated a more gradual N release compared to conventional urea and the inclusion of starch enhanced their degradability in the soil, which confirms their potential for sustainable agricultural applications. However, soil properties and environmental factors influenced the N release and degradation rates of NCPCs.

Phosphorus Availability and Adsorption Kinetics of Novel DAP Encapsulated Nano Clay Polymer Composites (NCPCs)

Phosphorus Availability and Adsorption Kinetics of Novel DAP Encapsulated Nano Clay Polymer Composites (NCPCs)

Synthesis, characterization and evaluation of novel manganese nanoclay polymer composite and nano‐MnO2 in wheat

AbstractBackgroundManganese (Mn) deficiency due to nutrient mining by high yielding cereal–cereal cropping patterns and forgetfulness of Mn fertilizer applications becomes potential challenge in crop production.AimNano‐enabled Mn fertilizers can be safer and more nutrient efficient than conventional Mn fertilizers (nutrient use efficiency ≈ 1%–3%). However, studies about nano‐Mn fertilizer synthesis and their behaviour in soil–plant system are rare.MethodsIn this study, two novel nano‐Mn fertilizers, that is nano‐MnO2 (NMO) and manganese nanoclay polymer composites (Mn‐NCPC), were synthesized, characterized (dynamic light scattering, X‐ray diffraction, Scanning electron microscopic and energy‐dispersive X‐ray, Fourier transform infrared spectroscopy etc.) and investigated for their impact on growth, yield and nutrient acquisition by wheat crop (Triticum aestivum L., variety HD‐2967) in a pot culture experiment. Treatment comprised 25%, 50% and 100% of recommended dose of Mn (RDMn) through NMO along with 100% RDMn through MnSO4·H2O (MS). Effect of exposure route was also investigated using foliar spray of NMO at tillering stage. Mn‐NCPC was found to be most efficient Mn fertilizer in terms of yield, Mn uptake and use efficiency by wheat crop.ResultsNano‐sized formulations improved the solubility of Mn in soil due to its higher active surface area (NMO) and slow‐release behaviour (Mn‐NCPC); thus, minimal losses happened due to the fixing of Mn in oxide/hydroxide forms. Application of 25% RDMn through NMO fertilizers maintained equitant diethylenetriamine pentaacetate Mn content to 100% RDMn through MnSO4·H2O. Mn‐NCPC stimulated the soil enzymatic activities, namely dehydrogenase, acid–alkaline phosphatase activities. Mn‐NCPC and NMO at 100% RDMn recorded 3.51% and 5.20% improvement in grain yield, respectively, when compared to MnSO4·H2O 100%.ConclusionsMn fertilizer doses can be reduced up to 25% of RDMn when applied through NMO or Mn‐NCPC fertilizers. However, effects of Mn‐NCPC and NMO need to be critically evaluated in long‐term field experiments in various cropping systems especially under cereal–cereal sequences for economic profitability and wide‐scale farmer's adaptability.

Effect of Nitrogen Fertilizers Applied through Nano Clay Polymer Composites on Nitrogen Use Efficiency of Rice

Nitrogen (N) is an essential nutrient for crop growth. However, excessive nitrogen fertilizer application leads to environmental losses. In this study, an attempt was made to reduce the nitrogen losses by loading of urea and urea ammonium nitrate (UAN) into Nano clay polymer composites (NCPCs) to act as slow release N fertilizers. To achieve the objectives of the present study, five N fertilizer treatments (T1-control, T2- N applied through urea, T3- N applied through UAN, T4- N applied through NCPC loaded with urea and T5- N applied through NCPC loaded with UAN) were assessed using three rice genotypes namely IR-64, Nagina 22 and MTU 1010. Results of the greenhouse study indicated that the UAN loaded NCPC treatment was more effective in terms of increasing the grain yield, nitrogen uptake, agronomic use efficiency and apparent nitrogen recovery by 36.9%, 51.0%, 64.2%, and 92.0% over urea, respectively. Amongst the genotypes, MTU 1010 was recorded with highest gran yield followed by IR-64 and Nagina-22.

Synthesis, Characterization and Controlled Release Pattern of Novel Fe-Containing Nanoclay Polymer Composites (Fe-NCPC) in Non-calcareous and Calcareous Soil

Synthesis, Characterization and Controlled Release Pattern of Novel Fe-Containing Nanoclay Polymer Composites (Fe-NCPC) in Non-calcareous and Calcareous Soil

Synthesis and mechanical properties of HDPE based Nano-Clay polymer composites for industrial applications

ABSTRACT Polymer-based composite structures have a unique advantage over other materials, given that the reinforcement has the necessary properties. Natural fibre-based composites are new materials domains that have emerged in engineering applications in the recent past due to the extensive availability of natural fibres that are less expensive, low density, and biodegradable. Several researchers explored natural fibres’ use as reinforcements in various polymer matrices to improve mechanical and tribological properties. In this context, the adoption of bi-directional silk fibres appears to be very beneficial, and minimal research for structural applications is recorded in this regard. In the present analysis, bi-directional silk fibre is used as a reinforcement medium in a plain-woven fabric with High-Density Polyethylene (HDPE) matrix, with a varying Nano-Clay (NC) percentage from 0.1 to 1 % wt. The compression moulding process is used to process test specimens, and these specimens are further studied for the characterisation of Mechanical Properties. The tensile samples are analysed for fracture analysis by using the Scanning Electron Microscopy (SEM).

Zincated Nanoclay Polymer Composite (ZNCPC): Effect on DTPA-Zn, Olsen-P and Soil Enzymatic Activities in Rice Rhizosphere

ABSTRACT Zinc (Zn) is the most deficient micronutrient globally resulting in malnutrition and requires improved mode of delivery for increased nutrient use efficiency. An innovative fertilizer formulation, Zincated nanoclay polymer composite (ZNCPC), containing a total 6.59% Zn was evaluated in a pot experiment in comparison with ZnSO4 using rice (Oryza Sativa L.) (PRH 10 variety) as a test crop. The ZNCPC was applied in two doses [5.0 mg Zn kg−1 (T1) and 2.5 mg Zn kg−1 (T2)] whereas ZnSO4. 7 H2O was applied at single dose (5.0 mg Zn kg−1) (T3) in Zn deficient soil along with a control (without application of Zn) (T4). Effects of two modes of Zn application were evaluated under maximum tillering (MT) (55 days after transplanting) and panicle initiation stage (PI) (70 days after transplanting) on DTPA Zn, Zn uptake, Olsen-P, P uptake and soil enzymatic activities in rhizosphere and non-rhizosphere soil. Treatment T1 increased DTPA-extractable Zn content in rhizosphere soil to 157% in PI stage in comparison with T3. Stimulation of soil enzymes activity namely, dehydrogenase, acid and alkaline phosphatase was recorded in rhizosphere soil. Our study demonstrates that ZNCPC could potentially to be novel and innovative fertilizer formulation to increase Zn uptake in rice.

Variation in Soil Microbial Population and Soil Enzymatic Activities Under Zincated Nanoclay Polymer Composites (ZNCPCs), Nano-ZnO and Zn Solubilizers in Rice Rhizosphere

Zinc deficiency is a major problem in production of rice crop, resulting in low grain Zn content. Use efficiency of conventional Zn sources (ZnSO4·7H2O) is very low. Therefore, technological interventions for increasing Zn use efficiency need to be explored. Nanoformulations of Zn, i.e. zincated nanoclay polymer composites (ZNCPCs), nano-ZnO (foliar application) and zinc solubilizer (Azospirillum brasilense), were compared with ZnSO4·7H2O (soil and foliar application) in rice (Oryza sativa var. Rajendra Mahsuri) rhizosphere at various phenological growth stages (maximum tillering, panicle initiation and harvesting). Effect of various Zn carriers on soil microbial population, enzymatic activities, DTPA-Zn content and Zn uptake was documented in pot experiment in Zn-deficient soil (DTPA-extractable Zn 0.48 mg kg−1). DTPA-extractable Zn content in soil at harvesting stage was found to be maximum in T6 (3.50 mg kg−1) followed by T4 (3.46 mg kg−1). Microbial population (bacteria, actinomycetes, fungi and zinc-solubilizing bacteria) was recorded to be highest in T4 (RDF + Azospirillum brasilense) followed by T6 (ZNCPC) at panicle initiation, maximum tillering and harvesting stages. Dehydrogenase activity was higher at maximum tillering stage in T6 (ZNCPC) followed by that in T4. Acid and alkaline phosphatase activities were found to be maximum at panicle initiation stage in T6 followed by T4 treatment. ZNCPC and zinc solubilizers stimulated soil microbial population consequently increasing the soil enzymatic activities and resulted in release of DTPA-extractable Zn in the rice rhizosphere. Maximum zinc uptake was recorded in treatment T6 (ZNCPC) Zn (303.42 mg kg−1). ZNCPC proved to be a promising fertilizer in increasing Zn use efficiency in rice rhizosphere. Findings of the present investigation need to be further evaluated in long-term field experiment to identify its cost/benefit ratio.

Response of polymers and biofertilizers on soybean (Glycine max) yield under rainfed condition

A field experiment was conducted to find out the response of polymers and biofertilizers on yield and quality of soybean (Glycine max L. Merrill) under rainfed condition at the Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India during 2015-16. The experiment was laid-out in split-plot design consisting three levels of polymer (Control, 5 kg/ha Nano clay-polymer composite (NCPC) and 5 kg/ha Hydrogel) in the mainplots and four levels of biofertilizer inoculation (Control, Rhizobium japonicum, Phosphate Solubilising Bacteria (PSB) and Mycorrhiza) were taken in sub-plots with three replications. Results indicated that the application of polymer @ 5 kg NCPC/ha improved growth parameters, yield attributes, yields, nutrient content, uptake, quality of seed in terms of protein and oil content. However, the application of 5 kg/ha Hydrogel was statically at par on all the parameters. Moreover, amongst the biofertilizers response was found significant on the growth parameters, yield attributes, yield quality parameters, nutrient content and their uptake. Their conjoint application is beneficial to farmers for sustaining the crop productivity in the rainfed condition of eastern Uttar Pradesh, India.

Nano zinc carriers influences release kinetics of zinc and iron in a laboratory incubation experiment under Inceptisol and Alfisol

Zinc (Zn) deficiency is a widespread phenomenon globally. Conventional Zn fertilizers viz zinc sulfate (ZnSO4· 7H2O) reported to have very low use efficiency (1–5%). Hence, technological interventions in increasing Zn use efficiency are of utmost important. Keeping this in view, a laboratory incubation study was undertaken to evaluate the effect of various Zn carriers on release kinetics of zinc and iron under Inceptisol and Alfisol. Zincated nanoclay polymer composite (ZNCPC), nano zinc oxide (n-ZnO), Zn-citrate were compared with conventional one i.e., zinc sulfate. ZNCPC attributed highest DTPA-Zn content at 45 days of incubation in Inceptisol (2.99 mg kg−1) and at 60 days of incubation in Alfisol (2.36 mg kg −1). Zn citrate was found another efficient Zn carrier followed by ZNCPC but superior over n-ZnO as per as the Zn availability and control release behavior is concern. Thus, ZNCPC was found to be the most efficient Zn carrier as compared to conventional zinc sulfate and other nano Zn carriers. High aspect ratio of n-ZnO curbs its soil application.

Field evaluation of Zincated nanoclay polymer composite (ZNCPC): Impact on DTPA-extractable Zn, sequential Zn fractions and apparent Zn recovery under rice rhizosphere

Zinc (Zn) deficiency is a widespread phenomenon globally. Conventional Zn fertilizers (ZnSO4·7H2O) are reported to have very low use efficiency of applied Zn (1–5%). Hence, technological interventions in increasing Zn efficiency are of utmost importance. Keeping in this background, the present investigation was undertaken with the objectives of evaluating ZNCPC (Zincated nanoclay polymer composites), Nano ZnO and ZnSO4·7H2O on various fractions of soil Zn and agronomic parameters under rice rhizosphere in field experiment for two consecutive growing seasons. Nano Zn carriers (ZNCPC at three doses 100%, 75% and 50%) and nano ZnO were evaluated in comparison with ZnSO4·7H2O in a field experiment under rice (Rajendra Mahsuri) rhizosphere. DTPA Zn was significantly increased under 100% ZNCPC (1.99 mg kg−1). Sequential Zn fractionation revealed that under ZNCPC treatments there was significant increase of water soluble, exchangeable and organically bound Zn, whereas there was significant increase of residual and specifically adsorbed Zn under ZnSO4·7H2O. Grain Zn content was maximum under 100% ZNCPC treatment (40.57 mg kg−1) followed by nano ZnO (34.71 mg kg−1). Maximum AZR (Apparent Zn recovery) was found in case of 100% ZNCPC (26.35%) followed by 75% ZNCPC (21.22%) and nano ZnO (18.73%). ZNCPC was found to be promising Zn formulation for increasing Zn use efficiency. Nano ZnO at foliar spray was also proved to be effective in increasing the grain Zn concentration. However, ZNCPC and nano ZnO need to be evaluated in long-term experiment in various soil types and cropping system for evaluating benefit: cost ratio and wide scale farmers’ adaptability.

Mitigating nitrous oxide emission using nanoclay-polymer composites in rice-wheat cropping system

ABSTRACT A study was conducted in lab for synthesizing and characterizing the behavior of the nanoclay-polymer composites (NCPCs). Furthermore, greenhouse experiments carried out to investigate the effects of NCPCs application on crop yield, nutrient uptake, soil nitrogen availability and N2O emission. Wheat flour (WF), sodium alginate (Na-Alg) and acrylic acid (AA)+ acrylamide (Am) (AA+Am) NCPCs were synthesized via free radical polymerization and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), SEM-energy dispersive X-ray (SEM-EDX) and transmission electron microscopy (TEM). At lower dose NCPCs, resulted in significantly equal grain yield in rice and wheat with 100% urea treatment with reduced amount of N2O emissions. Yield-scaled N2O emissions of rice and wheat under T9 [NCPC (AA+AM+Clay) (75% N of RDF) + PK (full dose)] treatment was respectively 19.8 and 25.5% lower than urea treatment. These findings demonstrate that there is a great potential to increase crop yields with lower N2O emissions through use of innovative fertilizer technique in India.

Evaluation of zincated nanoclay polymer composite in releasing Zn and P and effect on soil enzyme activities in a wheat rhizosphere

AbstractZinc deficiency in soil is a widespread global phenomenon, resulting in smaller Zn content in cereal grains, particularly in wheat. Conventional fertilizers (ZnSO4·7H2O or ZnSO4· H2O) resulted in low recovery efficiency (1–5%). An innovative fertilizer formulation was synthesized using nanoclay (having at least one dimension <100 nm), copolymer (acrylic acid and acrylamide as monomers), N,N‐Methylenebisacrylamide (NNMBA) as a crosslinking agent and ammonium persulphate (APS) as initiator. Zinc was added as Zn‐citrate during polymerization reactions. The product was named zincated nanoclay polymer composite (ZNCPC) containing 6.59% total Zn. The nanocomposite was evaluated in a laboratory incubation experiment and the data showed that it acted as a controlled release Zn formulation. Two doses of ZNCPC (5.0 mg Zn kg−1 and 2.5 mg Zn kg−1) were tested in pot experiments and compared with ZnSO4·7H2O (5.0 mg Zn kg−1) in two Zn‐deficient soils (Soil I and Soil II) at the crown root initiation (CRI) and heading initiation (HI) stages in rhizosphere (with plants) and non‐rhizosphere (without plants) soil. The nanocomposite significantly increased DTPA‐extractable Zn (DTPA‐Zn), Olsen‐P and enzyme activities in rhizosphere soil. Citrate released during degradation of ZNCPC in soil solubilized native or applied P, which in turn increased Olsen‐P content in soil. Zinc content in wheat biomass at the HI stage increased to 88 and 87% in Soils I and II, respectively, compared to ZnSO4·7H2O. There were positive and significant correlations among DTPA‐Zn, Olsen‐P and soil enzyme activities across growth stages and soil types. The ZNCPC proved to be an innovative and promising fertilizer formulation in a wheat rhizosphere that needed to be evaluated in a long‐term field experiment for its benefit:cost ratio and widespread adaptability. To explore an increase in Zn use efficiency the novel ZNCPC formulation was applied in a wheat rhizosphere. As there was an increase in DTPA‐Zn, Olsen‐P and soil enzyme activities, ZNCPC proved to be an innovative promising fertilizer formulation.Highlights To explore an increase in Zn use efficiency. Novel ZNCPC formulation was applied in wheat rhizosphere. Increase in DTPA extractable Zn, Olsen‐P and soil enzyme activities. ZNCPC proved to be an innovative promising fertilizer formulation.

Nanoclay polymer composites loaded with urea and nitrification inhibitors for controlling nitrification in soil

ABSTRACTNanoclay polymer composites (NCPCs) were synthesized with partially neutralized acrylic acid and bentonites and loaded with urea and nitrification inhibitors (NIs) to act as a slow release carrier of nitrogen (N). The resulting product was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The XRD of NCPCs revealed that the bentonite layers were completely exfoliated and dispersed in the composite after the polymerization. The water absorbency of pure polymer (Acrylic acid + Acrylamide) was 197.53 g g−1 and 137.75 g g−1 by nanocomposite (8% nanobentonite) in distilled water. The nitrification inhibition ability of these NCPCs was evaluated by incubation study for 60 days in laboratory at 28°C and 50% water-holding capacity. The Schiff base -NCPCs were most effective at inhibiting nitrification (30–87%) compared to dicyandiamide and Neem oil. A column study was performed to know the movement of NH4-N and NO3-N at three different depths. Result showed that the Schiff base -NCPC decreased nitrate movement by 78.5% at the depth of 5 cm in soil column. The slow release of nitrogen and good water retention capacity confirmed that these NCPCs can be viably exploited for application in agriculture.

Effect of Nano Clay inclusions on Mechanical Properties of Thermoplastics

The polymer has been widely used nowadays in many fields. Their properties make them useful in many engineering applications. Owing to their poor mechanical properties in engineering applications are seldom found. Hence, in the present study, it is aimed to enhance the mechanical properties of thermoplastics to enable their usage in engineering applications such as automotive bumpers, gears, etc. Recently many researchers tried to improve the mechanical properties of polymers using Nano clay inclusions. In the present study polypropylene (PP), Acrylonitrile butadiene styrene (ABS) and high-density polyethylene (HDPE) thermoplastics polymers are considered. Nano clay included polymer composites are fabricated with an intention to enhance their mechanical properties. Often these materials are subjected to various testing procedures and mechanical properties of these composites are to be studied. Hence, in the present work PP, ABS and HDPE Nano clay composites are fabricated using twin-screw extruders for blending Nano clay in different percentages to study the effect of Nano clay weight fraction on these properties. Samples fabricated using injection molding process. The samples are fabricated at different weight percentages of nanoclay and Often these materials are exposed to certain testing like tensile and fatigue. More after the mechanical properties of PP, ABS and HDPE with Nanoclay polymer composites were observing and how much percentage of strength increasing when comparing with the pure samples. Among the selected thermoplastics ABS Nanocomposites exhibit higher mechanical properties and by increasing the nanoclay weight percentage in each and every component the mechanical properties also increasing gradually and all are exhibits their better results at 5% of nanoclay with PP, ABS, and HDPE.

Citric acid loaded nano clay polymer composite for solubilization of Indian rock phosphates: a step towards sustainable and phosphorus secure future

ABSTRACTNon-renewable nature of rock phosphate (RP) reserves coupled with open ended nature of P cycle makes it imperative for maximum utilization of available P resources. In this context, use of Indian RPs from Purulia and Udaipur along with citric acid loaded nanoclay polymer composite (CA-NCPC) as P source to costly diammonium phosphate (DAP) was investigated through an incubation experiment followed by a greenhouse experiment with wheat-rice cropping sequence in a Luvisol (pH 5.14, available P 13.5 mg kg−1). Soil available P, crop yield parameters and dynamics of soil P fractions were taken to judge the efficacy of CA-NCPC in solubilizing RPs. Application of CA-NCPC and DAP resulted in 82% and 69% increase in available P over control, respectively under incubation study. Direct effect of treatment receiving CA-NCPC + RP on yield and P uptake by wheat was comparable with DAP but residual impact of CA-NCPC + RP (16.7 g pot−1) was better than DAP (13.8 g pot−1) in rice. The changes in inorganic P fractions were also significant as inclusion of RP increased calcium-P from 16.1 to 61.5 mg kg−1. Results indicated potentiality of RPs treated with CA-NCPC as an alternate P source which could prove promising amidst P scarcity.

Zincated Nanoclay Polymer Composites (ZNCPCs): Synthesis, Characterization, Biodegradation and Controlled Release Behaviour in Soil

ABSTRACTNovel zincated nanoclay polymer composites (ZNCPCs) with variable percentage of commercial bentonite and nanobentonite (8%, 10% and 12% of monomer for each case) were synthesized. Polyacrylic acid-Polyacrylamide copolymer was synthesized using N, N-Methylene bisacrylamide as crosslinker and ammonium persulfate as initiator. Clays as well as ZNCPCs were characterized by XRD, SEM, TEM and FTIR. 12% nanoclay containing formulation showed slowest release rate. ZNCPCs containing 8% clay recorded highest Zn content as well as highest equilibrium water absorbency. Biodegradation study revealed that Aspergillus spp was more effective as compared with Trichoderma spp in degradation of ZNCPCs.

Impact Assessment of Cetyltrimethylammonium Bromide Treated Organically Modified Nanoclay-Polymer Composite on Soil Enzyme Activity and Root Volume

The effect of organically modified nanoclay-polymer composite was evaluated on soil enzyme activity and root volume at different growth stages viz. crown root initiation, tillering and panicle initiation of wheat (variety: HD 3059). Nanoclay-polymer composite was synthesized by in -situ polymerization of acrylic acid-acrylamide in presence of cetyltrimethylammonium bromide @ 60% neutralization degree and 0.5% cross-linker level and subsequently loaded with di-ammonium phosphate fertilizer (14 g di-ammonium phosphate per unit weight of nanoclay-polymer composite). Phosphorus loaded nanoclay-polymer composite and conventional diammonium phosphate fertilizer were applied (P dose-40 mg P2O5 kg−1 soil) to two types of soil (Alfisol and Inceptisol). Soil enzyme activity and root volume were studied independently with a factorial completely randomized design experiment. Results revealed that dehydrogenase enzyme activity in modified nanoclay-polymer composite increased by + 26.3 and + 19% over conventional fertilizer in Alfisol and Inceptisol respectively. Acid phosphatase activity (9.25 µg p-nitrophenol g−1 soil h−1) was highest at panicle initiation stage in Inceptisol whereas alkaline phosphatase activity was more at tillering in both soils. Root volume also increased by + 16.8% on applying nanoclay-polymer composite as compared to conventional fertilizer in Alfisol. The corresponding data in Inceptisol was + 13.1%. Therefore, it was concluded that nanoclay-polymer composite prepared from organoclay has a positive effect on soil enzyme activity as well as root volume.

Phosphorus Release from Rock Phosphate as Influenced by Organic Acid Loaded Nanoclay Polymer Composites in an Alfisol

The aim of the present study was to develop a strategy to solubilize low-grade rock phosphate (RP) from Purulia and Udaipur through organic acids loaded nanoclay polymer composites (NCPC) and see their effectiveness as source of P. An incubation experiment was conducted under laboratory condition to study the release pattern of P in an Alfisol from Jharkhand amended with various RPs treated with organic acid loaded NCPC for 90 days. The RPs were applied at a dose of 0, 50 and 100 mg P kg−1 soil, along with the organic acid loaded NCPC having 10 % clay which was applied at a dose of 0, 20 and 40 mg organic acid kg−1 soil. The incubation experiment showed a positive impact of the organic acids in their ability to release P from all the RP sources, and oxalic acid performed better over citric acid in solubilizing P from RPs. The two indigenous RPs maintained almost comparable available P in soil throughout the period of incubation. With increase in levels of P application, there was an increase in the amount of release of P from both the RPs. Similarly, with the increase in levels of organic acid both Udaipur and Purulia RPs showed increase in the available P in soil. This study demonstrated that availability of P from low-grade indigenous RP could be improved with the interventions of organic acid loaded NCPC which could be used as P-fertilizer and reduce the dependence on commercial fertilizers like DAP.

Solubilization of Purulia Rock Phosphate Through Organic Acid Loaded Nanoclay Polymer Composite and Phosphate Solubilizing Bacteria and its Effectiveness as P-fertilizer to Wheat

Rock phosphate (RP) reserves across the globe stand out to be a major non-renewable resource and the cost of phosphatic fertilizers is shooting up causing a burden on the farmers. This study was undertaken with the purpose of developing a strategy to solubilize low-grade RP from Purulia district of West Bengal, India through organic acids loaded nanoclay polymer composites (NCPC) and phosphate solubilizing bacteria (PSB) and to see their effectiveness as P source against commercial diammonium phosphate (DAP) using wheat as the test crop. Oxalic acid and citric acid were loaded @ 2% (w/w) in NCPC (2-mm sieved) having 10% clay (NCPC-OA and NCPC-CA). Organic acid loaded NCPC (2 g kg−1 soil) containing 40 mg acid kg−1 soil was mixed with powdered RP (100 mesh size) at three rates of P (0, 50 and 100 mg P kg−1 soil) with and without inoculation of PSB (Pseudomonas striata) and tested as source of P to wheat in a greenhouse experiment. An absolute control (without fertilizer material) and a standard P-fertilizer (DAP @ 50 mg P kg−1 soil) were also included for comparison. Results revealed that Purulia RP along with oxalic acid loaded NCPC and PSB inoculation performed significantly better than other treatments in terms of yield of wheat, P uptake and available P in soil. All the P fractions in soil showed an increasing trend due to application of Purulia RP along with organic acid loaded NCPC and PSB. The Fe-P fraction was more dominant in soil compared to other fractions. However, the Ca-P fraction showed a higher value with the increase in levels of P application. The oxalic acid loaded NCPC performed better in most of the cases compared to citric acid loaded NCPC and proved to be a more efficient solubilizer of P from RP. This study could help to utilize Purulia RP as a P source for wheat, with the interventions of organic acids and PSB and reduce the dependence on commercial fertilizers like DAP.