Synthesis of a Novel Polymer Nitrification Inhibitor with Acrylic Acid and 3,4-Dimethylpyrazole

A Poly(Acrylamide-co-Acrylic Acid)-Encapsulated Nitrification Inhibitor with Good Soil-Loosening, Phosphorous-Solubilizing, and Nitrogen Fixation Abilities and High-Temperature Resistance

3,4-dimethylpyrazole (DMPZ), when used as a nitrification inhibitor, exhibits volatility, poor thermal stability, high production costs, and limited functionality restricted to nitrogen fixation. To address these limitations and introduce novel phosphorus-solubilizing and soil-loosening abilities, herein, a poly (acrylamide-co-acrylic acid)-encapsulated NI (P(AA-co-AM)-e-NI) is synthesized by incorporating linear P(AM-co-AA) macromolecular structures into NI systems. The P(AA-co-AM)-e-NI demonstrates an obvious phase transition from a glassy state to a rubbery state, with a glass transition temperature of ~150 °C. Only 5 wt% of the weight loss occurs at 220 °C, meeting the temperature requirements of the high-tower melt granulation process (≥165 °C). The DMPZ content in P(AA-co-AM)-e-NI is 1.067 wt%, representing a 120% increase compared to our previous products (0.484 wt%). P(AA-co-AM)-e-NI can effectively reduce the abundance of ammonia-oxidizing bacteria and prolong the duration during which nitrogen fertilizers exist in the form of ammonium nitrogen. It can also cooperatively enhance the conversion of insoluble phosphorus into soluble phosphorus in the presence of ammonium nitrogen (NH4+-N). In addition, upon adding P(AA-co-AM)-e-NI into soils, soil bulk density and hardness decrease by 9.2% and 10.5%, respectively, and soil permeability increases by 10.5%, showing that it has a good soil-loosening ability and capacity to regulate the soil environment.

Oxygen Availability Governs the Mitigating Effect of 3,4-Dimethylpyrazole Phosphate on Nitrous Oxide Emissions from Paddy Soils under Various Water Managements

Alternate wetting and drying (AWD) frequently triggers nitrous oxide (N2O) emissions from paddy fields, while the inhibitory effect of 3,4-dimethylpyrazole phosphate (DMPP) on N2O under various water managements remains uncertain. Here, we evaluated the effects of DMPP on N2O emissions and associated biological indicators under three water managements: continuous flooding (CF), mild AWD (Mi-AWD), and moderate AWD (Mo-AWD). The Mi-AWD and Mo-AWD practices increased N2O emissions by 2- and 0.9-fold compared to the CF treatment, respectively, due to enhanced oxygen availability, facilitating coupled nitrification-denitrification. DMPP application notably reduced N2O emissions in the AWD treatments, attributed to the reductions in nitrifier abundances, nitrification rates, and nitrate accumulation. Nevertheless, DMPP failed to suppress nitrification and, thereby, N2O emissions in the CF treatment. Overall, DMPP effectively mitigates N2O emissions under oxygen-rich AWD rather than anaerobic CF conditions, highlighting that the trade-offs between water-saving irrigation and N2O mitigation can be overcome via nitrification inhibitors application.

Effective strategy to improve nitrification inhibitor efficiency and minimize environmental risk with microenvironments created by ecofriendly biocomposites

Over half the global population depends on food grown with synthetic nitrogen fertilizers, but much of this nitrogen is lost as nitrates, N2O and NH3, harming the environment and health and incurring substantial environmental costs. Practical technologies aimed at enhancing nitrogen efficiency to reduce these losses promised considerable societal benefits. Nitrification inhibitors (NIs) can help reduce these losses, but their effectiveness varies, often lasting only weeks or days, for the strategy to improve NIs efficiency reducing environmental pollution that are still poorly contrived. Therefore, this study developed a novel approach by ecofriendly alginate and polyphenols to create a microenvironment (SANMP), which increased NIs based on DMPP stability at temperatures between 70 and 125 °C (47%-77% increase), in compound fertilizers (1.4%-11% increase), and in soils with a wide pH range of 5.6-7.9 (21%-27% increase). Enhanced stability can significantly increase environmental benefits in agriculture. SANMP reduces N2O emissions by 89% relative to nitrogen fertilizer-only treatments and a further 26% decrease compared to traditional DMPP formulations. Analysis of the chemical structure of alginate-metal-polyphenol hybrid materials demonstrated that DMPP immobilization, achieved through pore filling, chelation, and electrostatic attraction, significantly reduced its degradation from high temperatures, pH fluctuations, environmental ions, and soil microbial activities. The novel microenvironment offers an effective solution to the problems of high cost and unstable inhibition efficiency of DMPP, thus improving its environmental and agricultural benefits. This technology promises to offer solutions for nutrient management strategies that are efficient, highly beneficial to the environment and cost-effective.

Synthesizing a Water-Soluble Polymeric Nitrification Inhibitor with Novel Soil-Loosening Ability

Nitrification inhibitor is essential for increasing the nitrogen utilization efficiency of agricultural plants, thus reducing environmental pollution and increasing crop yield. However, the easy volatilization and limited functional property is still the bottleneck of nitrification inhibitors. Herein, a novel water-soluble polymeric nitrification inhibitor was synthesized through the copolymerization of acrylamide and bio-based acrylic acid, which was synthesized from biomass-derived furfural, and the complexation of carboxyl groups and 3,4-dimethylpyrazole. The results showed that the nitrification inhibitor was an amorphous polymer product with a glass transition temperature of 146 °C and a thermal decomposition temperature of 176 °C, and the content of 3,4-dimethylpyrazole reached 2.81 wt%, which was 115% higher than our earlier product (1.31 wt%). The polymeric nitrification inhibitor can inhibit the activity of ammonia-oxidizing bacteria effectively, thus inhibiting the conversion of ammonium nitrogen to nitrate nitrogen and converting the insoluble phosphate into soluble and absorbable phosphate. By introducing a copolymer structure with a strong flocculation capacity, the polymeric nitrification inhibitor is further endowed with a soil-loosening function, which can increase the porosity of soil to improve the soil environment. Therefore, the nitrification inhibitor can be used in water-soluble and liquid fertilizers, as well as in high tower melting granulated compound fertilizers.

A Novel High Temperature Resistant and Multifunctional Nitrification Inhibitor: Synthesis, Characterization, and Application

The industrialized nitrification inhibitors are not suitable for compound fertilizer fabrication through high tower melt granulation process due to their poor resistance to high temperature. In this paper, a novel high temperature resistant and multifunctional nitrification inhibitor (HTRMFNI) was synthesized. The HTRMFNI is a polymer product with the complex of silicic acid and 3,4-dimethylpyrazole (DMPZ) wrapped inside the polymer and the effective content of DMPZ is 0.484 wt %. The HTRMFNI presents good nitrification inhibitory performance and rapid phosphate-solubilizing ability. The decomposition temperature of HTRMFNI is ∼212 °C, satisfying the temperature requirements for the high tower melt granulation process. The fabricated compound fertilizer presents good nitrogen immobilization performance but loses the phosphate-solubilizing ability, possibly due to the damages of carboxyl functional group on the wrapping polymer by the high melting temperature. Moreover, the addition of HTRMFNI did not affect the physicochemical properties and the overall performance of the compound fertilizer.