Tropic Acid Research Articles

Synthesis of Novel Pseudo-Enantiomeric Phase-Transfer Catalysts from Cinchona Alkaloids and Application to the Hydrolytic Dynamic Kinetic Resolution of Racemic 3-Phenyl-2-oxetanone.

Naturally occurring Cinchona alkaloids such as quinidine (QD)/cinchonine (CN) and their diastereomers, quinine (QN)/cinchonidine (CD), have been recognized as pseudo-enantiomeric pairs. Utilizing these pseudo-enantiomeric alkaloids as chiral resources provides complementary enantioselectivity in many asymmetric reactions. During the screening of Cinchona alkaloid phase-transfer catalysts (PTCs) in the hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone (1) to tropic acid (2), we found that the introduction of a 4-trifluoromethylphenyl group at the vinyl terminus of BnQN significantly reduced the enantioselectivity to 41% enantiomeric excess (ee). The optimized structure of tetrahedral intermediates (TI, PTC + 1 + OH-) of hydrolysis obtained by density functional theory (DFT) calculations shows that the orientation of the quinoline and benzene rings of QD class PTC are nearly parallel to each other and to construct a greatly extended π-electron cloud surface, allowing good π-π interaction with the benzene ring of 1.

“Eco-friendly HPLC method for analysis of dipyrone and hyoscine in different matrices with biomonitoring”

A selective, precise, and accurate reversed HPLC method has been developed and validated for simultaneous separation and determination of two veterinary drugs, dipyrone and hyoscine, in their combined dosage form in the presence of their official impurities, namely 4-aminoantipyrine and tropic acid, in addition to the formulated preservative: phenol. The linearity range was found to be (1.00–35.00 µg/mL) for dipyrone and (2.50–50.00 µg/mL) for hyoscine. It exhibited a satisfactory linearity regression R (0.9999) for both drugs with LOD 0.22 µg/mL and 0.72 µg/mL and LOQ 0.65 µg/mL and 2.19 µg/mL for dipyrone and hyoscine, respectively. Additionally, the two cited drugs were also determined in the presence of dipyrone active metabolite 4-aminoantipyrine using diclofenac as an internal standard in bovine urine. The linearity range was found to be (15–75 µg/mL) for dipyrone, (2.5–60 µg/mL) for hyoscine, and (2.5–60 µg/mL) for 4-aminoantipyrine with linearity regression R (0.9999–0.9998). The LLOQ (15, 2.5, 2.5 µg/mL), LQC (45, 7.5, 7.5 µg/mL), MQC (55, 25, 25 µg/mL), and HQC (60, 50 50 µg/mL) were determined for dipyrone, hyoscine and 4-aminoantipyrine, respectively. UV detection was carried out at 220 nm. The method was validated according to the ICH guidelines, as well as according to FDA guidelines for determining both drugs in bioanalytical matrices and both proved accuracy and precision. A statistical comparison was made between the results obtained and those obtained by the reported method, showing no significant difference in accuracy and precision at p = 0.05. The suggested method was proved eco-friendly through a greenness assessment using two different tools (The analytical eco-scale scored 83, and the AGREE-Analytical Greenness Metric approach scored 0.83). The suggested method can be used in the routine work of quality control labs, screening for drug abuse, and ensuring clean sport for horse racing.

Total and Extractable Micronutrients in Tropical Acid Soils of Lampung, Indonesia

ABSTRACT The study aimed to determine the total and available amounts of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in the humid tropical acid soils of Lampung, Indonesia, and to identify the key factors affecting them. Topsoil samples were taken from 10 agricultural fields and 6 natural fields in 16 sub-districts of Lampung, Indonesia. The average total contents of Fe (26.36 g kg−1), Cu (8.97 mg kg−1), and Zn (53.24 mg kg−1) are generally below the world-soil average contents and those in other acid soils, which may be due to eluviation of Fe, Cu, and Zn into subsoil induced by high rainfall and the low natural contents of especially Cu and Zn in the parent rocks (acid volcanic rocks and sandstone). In contrast, the average total Mn content (1.20 g kg−1) is 2 to 8 times higher than that commonly found in acid soils and the world-soil average content, indicating that the parent materials may contain high Mn-bearing minerals. The total Fe, Mn, and Zn are positively correlated to the clay content, exchangeable-Ca and -Mg, and exchangeable-Mg, respectively, whereas the total Cu has no correlation to any soil properties. The amounts of available Fe, Mn, Cu, and Zn account for on average 0.38%, 6.20%, 21.50%, and 4.40% of the total contents, respectively. Around 6%, 12.5%, and 56% of the soil samples exhibit Mn, Cu, and Zn deficiency, respectively, and 25% face Fe toxicity. Total Fe and Mn are the main factors determining available Fe and Mn, respectively, whereas exchangeable-Mg and organic-C content mainly control available Cu and Zn, respectively.

Low pH adaptation of tropical exotic acid tolerance yellow maize donor lines in sub-tropical breeding programs

Soil acidity is one of the most important constraints to maize production in Angola, where both yellow and white maize is essential for food and feed requirements. In this study, four yellow acid soil tolerant donor lines from the International Maize and Wheat Improvement Centre (CIMMYT)—Colombia were crossed with ten yellow elite lines adapted to the mid-altitude climatic conditions developed by CIMMYT—Zimbabwe, in order to identify donor lines, which can be potential sources of acid tolerance genes in breeding programs in Angola and within the mid-altitude climatic zones. The two groups of parents were crossed using a line by tester mating design, yielding 36 crosses with sufficient seed, which were evaluated alongside six acid tolerant commercial hybrids, during the 2014–16 cropping seasons at nine sites, representing acid and non-acid soils in Angola and Zimbabwe. A significant (p < 0.05) line and line × tester effect for grain yield performance was observed across acid and non-acid conditions. Acid tolerance donor lines CY3 and CY1 showed the highest positive GCA effects for grain yield. In addition, crosses involving these two donor lines had the best yielding ability and stability under both acid and non-acid conditions. For instance, the crosses CH142464 (ZY2 × CY3) and, CH142447 (ZY2 × CY1) were the best combinations for grain yield performance under both acid and non-acid soil conditions, and were stable compared to the commercial check hybrids. Crosses involving the acid tolerant donor lines mostly flowered earlier than the commercial checks. Overall, the data showed the potential of tropically-adapted exotic yellow maize acid tolerance donor lines in improving productivity of sub-tropical maize under both low-pH and well-managed soil conditions.

Enhanced ophthalmic bioavailability and stability of atropine sulfate via sustained release particles using polystyrene sulfonate resin

Atropine sulfate (ATS) eye drops at low concentrations constitute a limited selection for myopia treatment, with challenges such as low ophthalmic bioavailability and inadequate stability. This study proposes a novel strategy by synthesizing ophthalmic sodium polystyrene sulfonate resin (SPSR) characterized by a spherical shape and uniform size for cationic exchange with ATS. The formulation of ATS@SPSR suspension eye drops incorporates xanthan gum and hydroxypropyl methylcellulose (HPMC) as suspending agents. In vitro studies demonstrated that ATS@SPSR suspension eye drops exhibited sustained release characteristics, and tropic acid, its degradation product, remained undetected for 30 days at 40 °C. The ATS levels in the tear fluids and aqueous humor of New Zealand rabbits indicated a significant increase in mean residence time (MRT) and area under the drug concentration–time curve (AUC0-12h) for ATS@SPSR suspension eye drops compared to conventional ATS eye drops. Moreover, safety assessment confirmed the non-irritating nature of ATS@SPSR suspension eye drops in rabbit eyes. In conclusion, the cation-responsive sustained-release ATS@SPSR suspension eye drops enhanced the bioavailability and stability of ATS, offering a promising avenue for myopia treatment.

Asymmetric Boracarboxylation of Styrenes Using Carbon Dioxide

AbstractThe boracarboxylation reaction has potential for the production of natural products and drug candidates, but the development of an asymmetric version of this transformation is challenging. We report an enantioselective boracarboxylation of styrenes, enabled by a copper catalyst containing chiral phosphines. Our experimental conditions provide yields between 31–76% and enantiomeric ratios from 80:20 up to 98:2 for electron‐rich styrenes. Oxidation of a boracarboxylation product gives (S)‐tropic acid, an intermediate towards several tropane alkaloids. A computational analysis of the mechanistic details shows a complex pattern of competing reaction pathways, highlighting challenges encountered when developing asymmetric reactions using CO2.

Cobalt-Catalyzed Enantioselective Hydroboration of α-Substituted Acrylates.

Even though metal-catalyzed enantioselective hydroborations of alkenes have attracted enormous attention, few preparatively useful reactions of α-alkyl acrylic acid derivatives are known, and most use rhodium catalysts. No examples of asymmetric hydroboration of the corresponding α-arylacrylic acid esters are known. In our continuing efforts to search for new applications of earth-abundant cobalt catalysts for broadly applicable organic transformations, we have identified 2-(2-diarylphosphinophenyl)oxazoline ligands and mild reaction conditions for efficient and highly regio- and enantioselective hydroboration of α-alkyl- and α-aryl- acrylates, giving β-borylated propionates. Since the C-B bonds in these compounds can be readily replaced by C-O, C-N, and C-C bonds, these intermediates could serve as valuable chiral synthons, some from feedstock carbon sources, for the synthesis of propionate-bearing motifs including polyketides and related molecules. Two-step syntheses of "Roche" ester from methyl methacrylate (79%; er 99:1), arguably the most widely used chiral fragment in polyketide synthesis, and tropic acid esters (∼80% yield; er ∼93:7), which are potential intermediates for several medicinally important classes of compounds, illustrate the power of the new methods. Mechanistic studies confirm the requirement of a cationic Co(I) species [(L)Co]+as the viable catalyst in these reactions and rule out the possibility of a [L]Co-H-initiated route, which has been well-established in related hydroborations of other classes of alkenes. A mechanism involving an oxidative migration of a boryl group to the β-carbon of an η4-coordinated acrylate-cobalt complex is proposed as a plausible route.

Integrated Ca, Mg, Cu, and Zn supply upregulates leaf anatomy and metabolic adjustments in Eucalyptus seedlings

Adaptive responses to abiotic stresses such as soil acidity in Eucalyptus—the most widely planted broad-leaf forest genus globally—are poorly understood. This is particularly evident in physiological and anatomical disorders that inhibit plant development and wood quality. We aimed to explore how the supply of Ca and Mg through liming (lime), combined with Cu and Zn fertilization (CZF), influences physiological and anatomical responses during Eucalyptus grandis seedlings growth in tropical acid soil. Therefore, related parameters of leaf area and leaf anatomy, stomatal size, leaf gas exchange, antioxidant system, nutrient partitioning, and biomass allocation responses were monitored. Liming alone in Eucalyptus increased specific leaf area, stomatal density on the abaxial leaf surface, and Ca and Mg content. Also, Eucalyptus exposed only to CZF increased Cu and Zn content. Lime and CZF increased leaf blade and adaxial epidermal thickness, and improved the structural organization of the spongy mesophyll, promoting increased net CO2 assimilation, and stomatal conductance. Fertilization with Ca, Mg, Cu, and Zn positively affects plant nutrition, light utilization, photosynthetic rate, and antioxidant performance, improving growth. Our results indicate that lime and CZF induce adaptive responses in the physiological and anatomical adjustments of Eucalyptus plantation, thereby promoting biomass accumulation.

Network pharmacology and molecular dynamic simulation integrated strategy for the screening of active components and mechanisms of phytochemicals from Datura innoxia on Alzheimer and cognitive decline

Alzheimer’s disease (AD) ranks as the most prevalent neurodegenerative disorder with dementia and it accounts for more than 70% of all cases. Despite extensive reporting on the experimental investigation of Datura innoxia (DI) and its phytochemical components in the treatment of AD, the urgent need for elucidation of the principle of multi-mechanism and multi-level treatment of AD remains. In this research, molecular docking and network pharmacology were used to evaluate active compounds and molecular targets of DI for the treatment of AD. The phytochemical compounds of DI were obtained from the Indian Medicinal Plants, Phytochemistry, and Therapeutics (IMPPAT) as well as the Traditional Chinese Medicine System Pharmacology (TCMSP) databases. The screening includes the 28 most abundant components of DI and the Swiss Target Prediction database was used to predict targets of these compounds. The GeneCards database was used to collect AD-related genes. Both DI and AD targets were imported into a Venn diagram, and the 28 overlapped genes were identified as potential DI anti-AD targets. The results showed that Dinoxin B, Meteloidine, Scopoline, and Tropic acid had no effect on AD-related genes. Furthermore, the GO enrichment analysis indicates that DI influences molecular functions and biological processes such as learning or memory and modulation of chemical synaptic transmission as well as the membrane raft and membrane microdomain. The KEGG pathway analysis revealed that the key pathways implicated in DI's anti-AD actions include serotonergic synapse, IL-17 signaling pathway, and AGE-RAGE signaling pathway in diabetic complications. Based on the STRING and Cytoscape network-analysis platforms, the top ten anti-AD core targets include APP, CASP3, IL6, BACE1, IL1B, ACE, PSEN1, GAPDH, GSK3B and ACHE. The molecular docking and molecular dynamic simulation of the top two molecules against the top three target proteins confirmed the strong binding affinity and stability at the docked site. Overall, our findings pave the path for further research into the development and optimization of potential anti-AD agents from DI. Communicated by Ramaswamy H. Sarma

Hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone to chiral tropic acid.

Tropic acid was synthesized in a good yield and with high enantioselectivity (81% ee) under non-biphasic conditions via the novel hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone (tropic acid β-lactone) in the presence of a chiral quaternary ammonium phase-transfer catalyst and strongly basic anion exchange resin as the hydroxide ion donor.

Response of growth performance and yield of butternut squash(Cucurbita moschata Duch Ex Poir) cultivar Waltham under differentdosages of bokashi application

Butternut squash, also known as Cucurbita moschata, is a variety of pumpkin with promising commercial potential. However,most of the soils in the tropics are acidic and lack organic matter.The addition of organic material such as bokashi is essential inimproving the low soil pH and soil quality. Therefore, this study aimed to elucidate the effects of different rates of bokashi application on the growth performance and yield of butternut squash cultivated on tropical acid soil. A planting experiment was carried out from July until October 2022. A total of 36 planting beds were prepared, and each bed was constructed in 100 cm x 400 cm, consisting of 8 plants bed-1. The experiment was arranged in a Randomized Complete Block design. A total of three different rates of bokashi were applied to the soil prior to planting, namely 0 (control), 4,000, and 8,000 kg ha-1. A 12,000 kg ha-1 of commercial peat moss (Holland Free Peat) was also applied to compare bokashi and peat moss (the common planting medium used in most planting activities). The maximum plant height growth and leaf production for butternut squash was around 7-8th week. Application rate of 8,000 kg ha-1 bokashi contributed to significantly highest plant height (352.1 cm), number of leaves (86 leaves), and yield of Waltham butter squash per plant (1.5 kg plant-1). Multiple planting cycles should be carried out further to elucidate the bokashi's residual effect on nutrient supply to butternut squash cultivation.

Investigation of three Sulfobutylether-β-cyclodextrin bonded magnetic nanoparticles in enantioselective Liquid-Liquid extraction

Chiral recognition ability of five racemic drugs/intermediates in enantioselective liquid–liquid extraction of functionalized magnetic nanoparticles was studied, which were synthesized by three different bonding methods using SBE-β-CD as functional molecule. The synthesis of three functionalized magnetic nanoparticles using SBE-β-CD as a functional molecular were studied and the functionalized magnetic nanoparticles were characterized by thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The loading amount of SBE-β-CD on the surface was determined to be functionalized magnetic nanoparticles II (13.04 %) > functionalized magnetic nanoparticles I (7.15 %) > functionalized magnetic nanoparticles III (less than 6.22 %). Enantioselective liquid–liquid extractions of five racemates were optimized using the three functionalized magnetic nanoparticles as chiral extractant, respectively, and the ideal chiral extractant for each enantiomer was found. Functionalized magnetic nanoparticles III was found to be the best chiral extractant for trans-paroxol and N-methyl duloxetine, with the optimum enantioseparation factors of 1.824 and 1.480, respectively, while functionalized magnetic nanoparticles I was ideal for fluoxetine, tropic acid and acetyltropic acid, with the optimum enantioseparation factors of 1.201, 1.226 and 1.484, respectively.

Additional degradants in the impurity profile of atropine low-dose ophthalmic solution

WHO has identified the increase in myopia as the world's greatest threat to vision health due to its association with vision-threatening complications like myopic macular degeneration, retinal detachment, cataract and open angle glaucoma. Pharmacological treatment with atropine is assessed as one of the best option in op-tical approaches to the control and inhibit of myopia progression. The aim of this study was to develop analytical method for quality control of 0.1 mg/mL atropine ophthalmic solution. UPLC analytical method for simultaneous determination of atropine sulfate monohydrate and its related substances described in Eur. Ph. and for additional impurities was developed. For method development low-dose of atropine formulations with a wide range of pH 4.5-6.6 were tested and the impact of formulation pH on the impurity profile was noted. The ionized form of tropic acid was observed in our studies in all buffered formulations with pH above 5. Additionally two isomers of atropine N-oxide were observed in the tested preparation with pH 6.6 in the presence of an oxidizing agent and were just possible to integrate with our new developed UPLC method. The ionized form of tropic acid was already defined in Berton et al. publication (1) and observed in the buffered formulation with pH 6.0. Our result complement and extend the impurity profile of atropine in wider pH range of atropine ophthalmic solutions.

Qualitative identification and quantitative comparison of Physochlainae Radix from different regions based on chemometric methods.

Physochlainae Radix (PR) is an essential herbal medicine that has been generally applied for treating cough and asthma. In this study, a comprehensive strategy for quality evaluation of PR from different origins was established by integrating qualitative identification, quantitative analysis, and chemometric methods. A total of 58 chemical components were identified by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS), and a sensitive and rapid UHPLC-QqQ-MS/MS method was established for the simultaneous determination of 12 compounds. In addition, multivariate statistical analysis was applied for discriminant analysis to compare the differences among 30 batches of PR samples. The results showed that the 30 batches of PR collected from four provinces could be clustered into three categories, in which scoparone, protocatechuic acid, tropic acid, and scopolin were important components to distinguish the primary and non-primary producing areas, as well as superior and inferior products of PR. Chemometric results were consistent and validated each other, and systematically explained the intrinsic quality characteristics of PR. This study first demonstrated that LC-MS combined with multivariate statistical analysis, provided a comprehensive and effective means for quality evaluation of PR.

Atropine-eluting silicone contact lenses for myopia control.

Myopia, also known as nearsightedness, is one of the prime reasons for vision impairment worldwide. Atropine in topical ophthalmic solutions (e.g., 0.01% atropine sulfate eye drops) is the primary medical treatment for controlling myopia, especially for pseudomyopia or true myopia in rapid progress. However, aqueous atropine solution is unstable and easily breaks down to tropic acid, which will result in vision blur. Drug-eluting contact lenses (CLs) have been explored as a potentially superior alternative to effectively control the drug release and improve the drug efficacy. In this work, an atropine-eluting contact lens was developed by encapsulating an atropine implant in a silicon-based contact lens, towards functioning in vision correction and controlling myopia. The safety and effectiveness of this atropine-eluting contact lens were verified with rabbit and guinea pig models. The results showed that the lenses reduced the side effects like mydriasis and no other adverse events were observed in rabbit eyes. More importantly, atropine-loaded lenses could effectively delay the progress of form-deprivation myopia with guinea pig eyes as the model. Thus, we concluded that atropine-eluting CLs prepared by implantation technology may be an option for the treatment of myopia.

Monomer-Promoting Asymmetric Kinetic Resolution-Alternating Copolymerization To Afford AAB-Type Copolyesters.

Living copolymerization of mixed monomers can enrich the diversity of copolymer materials with well-defined performance via controlling both monomers and stereosequences. However, periodic sequence-controlled living copolymerization of same-type monomers with more than two components in synthetic polymer science remains a challenge. In this work, a new method of monomer-promoting asymmetric kinetic resolution-alternating copolymerization can let a tricomponent mixture of l-lactide (S,S-LA or l-LA) and two enantiomeric isomers of racemic tropic acid cyclic esters (tropicolactone) be polymerized into sequence-controlled -(ASASBS)n- type biodegradable copolyesters (the subscript S presents the configuration and A and B present lactic acid units and tropic acid units, respectively), and diblock copolymers of -(ASASBS)n-b-(ARARBR)n- can further be obtained upon addition of R,R-LA (d-LA). Compared to previous asymmetric kinetic resolutions of racemic chemicals via polymerization or organic reactions, no enantiopure catalyst/initiator is required in this system. After the resolution and alternating copolymerization of S,S-LA and rac-tropicolactone, the ee value of unreacted tropicolactone can reach 99.4%. The alternating probability between tropicolactone and lactide monomers is more than 96% in periodic sequence polymers of -(ASASBS)n-. The tetracomponent mixture of rac-lactide and rac-tropicolactone can be copolymerized into an alternating copolymer with a -((ASASBS)x-ran-(ARARBR)y)n- structure, in which the stereoselective linkage probability of 95% after S,S-lactide (R,R-lactide) followed by S-tropicolactone (R-tropicolactone) keeps very high too.

Compounded 0.01% Atropine-What's in the Bottle?

To describe the labeling, packaging practices, and characteristics of compounded 0.01% ophthalmic atropine. A convenience sample of parents of children who had previously been prescribed low-concentration atropine for myopia management were randomized to obtain 0.01% atropine ophthalmic solution from one of nine compounding pharmacies. The products were analyzed for various important quality attributes. The main outcomes were labeling practices, concentration of atropine and degradant product tropic acid, pH, osmolarity, viscosity, and excipients in 0.01% atropine samples obtained from nine US compounding pharmacies. Twenty-four samples from nine pharmacies were analyzed. The median bottle size was 10 mL (range 3.5-15 mL), and eight of nine pharmacies used clear plastic bottles. Storage recommendations varied and were evenly split between refrigeration (33%), room temperature (33%), and cool, dark, dry location (33%). Beyond use dates ranged from 7 to 175 days (median, 91 days). Median pH of samples was 7.1 (range, 5.5-7.8). Median measured concentration relative to the prescribed concentration was 93.3% (70.4%-104.1%). One quarter of samples were under the 90% minimum target concentration of 0.01%. An inconsistent and wide variety of formulation and labeling practices exist for compounding 0.01% atropine prescribed to slow pediatric myopia progression.

Co-Composted Chicken Litter Biochar Increases Soil Nutrient Availability and Yield of Oryza sativa L.

Intensified cultivation of rice has accelerated weathering of most tropical acid soils leading to significant loss of base cations. In most developing countries, rice yield is low and this results in its production being costly because productivity versus labor is low. The objectives of this study were to (i) enhance soil chemical properties, nutrient uptake, and grain yield of rice grown on a mineral tropical acid soil using agro-wastes; (ii) determine the agro-waste (chicken manure, cow dung, forest litter, and Leucaena) that has the potential to significantly increase rice yield; and (iii) determine the residual effects of the organic soil amendments produced from the agro-wastes on soil and rice productivity. The treatments used in this three-cycle field study were (i) soil without amendments (S0); (ii) prevailing recommended rates for fertilizers (NPK-Mg); (iii) biochar–forest litter compost (OSA1); (iv) biochar–chicken litter compost (OSA2); (v) biochar–cow dung compost (OSA3); (vi) biochar–Leucaena compost (OSA4); and (vii) biochar–Leucaena–chicken litter compost (OSA5). Standard procedures were used to determine the plants’ rice growth, grain yield, plant nutrient concentrations and uptake, and selected soil chemical properties. The use of organic soil amendments (OSA1 to OSA5) significantly improved the soil chemical properties, rice plant growth, nutrient uptake, and grain yield compared with the prevailing method of cultivating rice (NPK-Mg). The application of organic soil amendments reduced the use of inorganic N, P, K, MgO, and trace elements fertilizers up to 25%, 100%, 64%, 100%, and 100%, respectively. The organic soil amendments with Leucaena significantly increased rice grain yield of OSA5 at 11.17, 13.11, and 10.06 t ha−1 in the first, second, and third cropping cycles, respectively. The residual effect of the organic soil amendments also improved rice plant growth, nutrient uptake, and rice grain yield although these were slightly reduced as compared to those of the two previous cropping cycles, the afore-stated treatments were superior to the prevailing method of cultivating rice (NPK-Mg). Transforming agro-wastes into organic soil amendments can improve tropical mineral acid soils and rice productivity.

Co-Application of Inorganic Fertilizers with Charcoal and Sago Bark Ash to Improve Soil Nitrogen Availability, Uptake, Use Efficiency, and Dry Matter Production of Sorghum Cultivated on Acid Soils

Efficient management of N fertilizers enhances crop yields and contributes to sustainable food security. Tropical acidic soils with high Al and Fe are prone to easy loss of basic cations, such as NH4+, via leaching and erosion. Appropriate soil amendments and agronomic practices minimize the loss of fertilizer nutrients, improve soil nutrient retention, and maximize their uptake by plants. This study aimed to evaluate the effects of co-applying charcoal and sago bark ash with inorganic fertilizers on N availability, uptake, use efficiency, and dry matter production of sorghum in a tropical acid soil. The results revealed that the co-application of inorganic fertilizers with charcoal and sago bark ash increased sorghum plant height, dry matter production, N uptake and N use efficiency. The soil treated with a combination of 100% of the recommended rate of charcoal and sago bark ash (C1A1) resulted in significantly higher sorghum dry matter production, N uptake, and use efficiency compared with normal fertilization (U1). The C1A1 treatment resulted in significantly lower soil available N compared with U1. The C1A1 treatment enhanced the uptake of N by the sorghum plants, resulting in less available N in the soil after the experiment. Although the effects of co-applying charcoal and sago bark ash on soil total N were not glaring, this practice increased soil pH and total C, and reduced exchangeable acidity and Al3+. A long-term field study is recommended to confirm the effects of co-applying inorganic fertilizers with charcoal and sago bark ash on sorghum productivity, economic viability, and soil nutrient residual effects.

Dynamics of ammonia volatilization from NBPT-treated urea in tropical acid soils

The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) reduces NH3 losses from urea (UR) surface-applied to soils, but its efficacy may be lower in acidic soils. The period when urease inhibition occurs efficaciously may change with soil pH. This needs to be clarified in tropical soils which are commonly acidic. This study evaluated the effectiveness of NBPT-treated urea to delay and reduce ammonia volatilization in two soils at three pH levels. Two experiments were conducted under laboratory conditions in soils with different textures (sandy-clay and clay). The treatments consisted of three soil pH levels and two N sources (UR and UR + NBPT), with five replicates. The soil pH values were adjusted and reached values of 4.5, 5.6, and 6.4 in the sandy-clay, and 4.5, 5.4, and 6.1 in the clay soil. Ammonia volatilization was measured using glass chambers (1.5 L). In the sandy-clay soil, NH3 losses were 40-47 % of the UR-N. In the clay soil, losses were 26-32 %. The addition of NBPT to UR reduced the NH3 volatilization by 18-53 %; the inhibitor decreased the N losses under all soil pH conditions but was significantly less efficient in acidic soils (pH 4.5). The lower efficiency of the inhibitor under acidic conditions was more evident in the first few days: 50 % of the total NH3 losses occurred in less than four days in soils with pH 4.5, but in 8-11 days in soils with pH above 5.4. The rapid loss in efficiency in more acidic soils is a drawback. Using NBPT in severely acidic soils showed a relatively small advantage over untreated UR as the inhibitor did not provide extra time for fertilizer incorporation and further reduction of NH3 losses.