Recent trends in nitrogen cycle and eco-efficient nitrogen management strategies in aerobic rice system

Impacts of Land Use on Soil Nitrogen-Cycling Microbial Communities: Insights from Community Structure, Functional Gene Abundance, and Network Complexity

This study investigates the effects of different land-use types (forest, arable land, and wetland) on key soil properties, microbial communities, and nitrogen cycling in the Lesser Khingan Mountains. The results revealed that forest (FL) and wetland (WL) soils had significantly higher soil organic matter (SOM) content compared with arable land (AL), with total phosphorus (TP) being highest in FL and available nitrogen (AN) significantly higher in WL. In terms of enzyme activity, AL and WL showed reduced activities of ammonia monooxygenase (AMO), β-D-glucosidase (β-G), and β-cellobiosidase (CBH), while exhibiting increased N-acetyl-β-D-glucosaminidase (NAG) activity, highlighting the impact of land use on nitrogen dynamics. WL also exhibited significantly higher microbial diversity and evenness compared with FL and AL. The dominant bacterial phyla included Actinobacteriota, Proteobacteria, and Acidobacteriota, with Acidobacteriota being most abundant in FL and Proteobacteria most abundant in WL. Network analysis showed that AL had the most complex and connected microbial network, while FL and WL had simpler but more stable networks, suggesting the influence of land use on microbial community interactions. Regarding nitrogen cycling genes, AOA-amoA was most abundant in AL, while AOB-amoA was significantly enriched in FL, reflecting the influence of land use on ammonia oxidation. These findings highlight how land-use types significantly affect soil properties, microbial community structures, and nitrogen cycling, offering valuable insights for sustainable land management.

Preparation of slow-release fertilizer derived from rice husk silica, hydroxypropyl methylcellulose, polyvinyl alcohol and paper composite coated urea

There is a growing trend toward utilizing agricultural waste to create value-added products, addressing environmental concerns associated with their disposal. This study focuses on developing slow-release fertilizers (SRFs) using amorphous silica derived from rice husk, hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol (PVA), waste paper, and urea. Experimental optimization was carried out using the response surface methodology central composite design (RSM-CCD). The optimal formulation included 8.63 g of silica, 1.04 g of HPMC, and 0.27 g of PVA. Two SRFs were prepared under these conditions: SRF1, consisting of silica, HPMC, and PVA, and SRF2, which additionally incorporated coated waste paper. Characterization techniques such as Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD) Scanning Electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis were used to examine the materials. The rice-husk-derived silica exhibited a pore size of 2.140 nm and a BET surface area of 690 m2/g, providing an excellent surface for nutrient encapsulation. Although the addition of coated waste paper minimally influenced the slow-release behaviour of SRF2, however the other components effectively reduced nutrient leakage by trapping the nutrients. The swelling behaviour of the SRFs was analyzed in different media after 72 h, showing values of 2.66, 2.54 (g/g) in distilled water, 2.20, 2.58 (g/g) in pH 4, and 1.86, 3.09 (g/g) in pH 9 solutions. The swelling kinetics aligned with Scott's second-order kinetic model. Urea release tests in water revealed a release of 94 % and 97 % at 24 h for SRF1 and SRF2, respectively, compared to 98 % release of pure urea within 1 h. SRF2 demonstrated optimal nutrient release after 48 h. The release kinetics followed the first-order kinetic model for both SRF1 and SRF2, highlighting their potential as effective slow-release fertilizers.

Partial replacement of inorganic fertilizer with organic inputs for enhanced nitrogen use efficiency, grain yield, and decreased nitrogen losses under rice-based systems of mid-latitudes

In the rice-based system of mid-latitudes, mineral nitrogen (N) fertilizer serves as the largest source of the N cycle due to an insufficient supply of N from organic sources causing higher N losses due to varying soil and environmental factors. However, aiming to improve soil organic matter (OM) and nutrients availability using the best environmentally, socially, and economically sustainable cultural and agronomic management practices are necessary. This study aimed to enhance nitrogen use efficiency (NUE) and grain yield in rice-based systems of mid-latitudes by partially replacing inorganic N fertilizer with organic inputs. A randomized complete block design (RCBD) was employed to evaluate the effects of sole mineral N fertilizer (urea) and its combinations with organic sources-farmyard manure (FYM) and poultry compost-on different elite green super rice (GSR) genotypes and were named as NUYT-1, NUYT-2, NUYT-3, NUYT-4, NUYT-5, and NUYT-6. The study was conducted during the 2022 and 2023 rice growing seasons at the Rice Research Program, Crop Sciences Institute (CSI), National Agricultural Research Centre (NARC), Islamabad, one of the mid-latitudes of Pakistan. The key objective was to determine the most effective N management strategy for optimizing plant growth, N content in soil and plants, and overall crop productivity. The results revealed that the combined application of poultry compost and mineral urea significantly enhanced soil and leaf N content (1.36 g kg- 1 and 3.06 mg cm- 2, respectively) and plant morphophysiological traits compared to sole urea application. Maximum shoot dry weight (SDW) and root dry weight (RDW) were observed in compost-applied treatment with the values of 77.62 g hill- 1 and 8.36 g hill- 1, respectively. The two-year mean data indicated that applying 150 kg N ha⁻1, with half provided by organic sources (10 tons ha⁻1 FYM or poultry compost) and the remainder by mineral urea, resulted in the highest N uptake, utilization, and plant productivity. Thus, integrated management of organic carbon sources and inorganic fertilizers may sustain the productivity of rice-based systems more eco-efficiently. Further research is recommended to explore root and shoot morphophysiological, molecular, and biochemical responses under varying N regimes, aiming to develop N-efficient rice varieties through advanced breeding programs.

Tailoring competitive adsorption sites of hydroxide ion to enhance urea oxidation-assisted hydrogen production

Alloys with bimetallic electron modulation effect are promising catalysts for the electrooxidation of urea. However, the side reaction oxygen evolution reaction (OER) originating from the competitive adsorption of OH- and urea severely limited the urea oxidation reaction (UOR) activity on the alloy catalysts. This work successfully constructs the defect-rich NiCo alloy with lattice strain (PMo-NiCo/NF) by rapid pyrolysis and co-doping. By taking advantage of the compressive strain, the d-band center of NiCo is shifted downward, inhibiting OH- from adsorbing on the NiCo site and avoiding the detrimental OER. Meanwhile, the oxygenophilic P/Mo tailored specific adsorption sites to adsorb OH- preferentially, which further released the NiCo sites to ensure the enriched adsorption of urea, thus improving the UOR efficiency. As a result, PMo-NiCo/NF only requires 1.27 V and -57 mV to drive a current density of ±10 mA cm-2 for UOR and hydrogen evolution reaction (HER), respectively. With the guidance of this work, reactant competing adsorption sites could be tailored for effective electrocatalytic performance.

Agriculture and environmental management through nanotechnology: Eco-friendly nanomaterial synthesis for soil-plant systems, food safety, and sustainability

Through the advancement of nanotechnology, agricultural and food systems are undergoing strategic enhancements, offering innovative solutions to complex problems. This scholarly essay thoroughly examines nanotechnological innovations and their implications within these critical industries. Traditional practices are undergoing radical transformation as nanomaterials emerge as novel agents in roles traditionally filled by fertilizers, pesticides, and biosensors. Micronutrient management and preservation techniques are further enhanced, indicating a shift towards more nutrient-dense and longevity-oriented food production. Nanoparticles (NPs), with their unique physicochemical properties, such as an extraordinary surface-to-volume ratio, find applications in healthcare, diagnostics, agriculture, and other fields. However, concerns about their potential overuse and bioaccumulation raise unanswered questions about their health effects. Molecule-to-molecule interactions and physicochemical dynamics create pathways through which nanoparticles cause toxicity. The combination of nanotechnology and environmental sustainability principles leads to the examination of green nanoparticle synthesis. The discourse extends to how nanomaterials penetrate biological systems, their applications, toxicological effects, and dissemination routes. Additionally, this examination delves into the ecological consequences of nanomaterial contamination in natural ecosystems. Employing robust risk assessment methodologies, including the risk allocation framework, is recommended to address potential dangers associated with nanotechnology integration. Establishing standardized, universally accepted guidelines for evaluating nanomaterial toxicity and protocols for nano-waste disposal is urged to ensure responsible stewardship of this transformative technology. In conclusion, the article summarizes global trends, persistent challenges, and emerging regulatory strategies shaping nanotechnology in agriculture and food science. Sustained, in-depth research is crucial to fully benefit from nanotechnology prospects for sustainable agriculture and food systems.

Effects of increased ozone on rice panicle morphology

Ground-level ozone threatens rice production, which provides staple food for more than half of the world's population. Improving the adaptability of rice crops to ozone pollution is essential to ending global hunger. Rice panicles not only affect grain yield and grain quality but also the adaptability of plants to environmental changes, but the effects of ozone on rice panicles are not well understood. Through an open top chamber experiment, we investigated the effects of long-term and short-term ozone on the traits of rice panicles, finding that both long-term and short-term ozone significantly reduced the number of panicle branches and spikelets in rice, and especially the fertility of spikelets in hybrid cultivar. The reduction in spikelet quantity and fertility because of ozone exposure is caused by changes in secondary branches and attached spikelet. These results suggest the potential for effective adaptation to ozone by altering breeding targets and developing growth stage-specific agricultural techniques.

Integration of organics in nutrient management for rice-wheat system improves nitrogen use efficiency via favorable soil biological and electrochemical responses

Introduction

The contrasting soil management in flooded-transplanted rice (Oryza sativa) and dry-tilled wheat (Triticum aestivum) poses a challenge for improving low nitrogen use efficiency (NUE) of the rice-wheat system. Integration of organics in nutrient management can bring in changes favoring efficient N uptake via changes in growing conditions and soil responses.

Materials and methods

This study reported the results of a 15-year-long experiment on integrated nutrient management (INM) systems for rice-wheat cropping. The INM included substituting ~50% of chemical fertilizers via (i) including a legume crop (Vigna radiata) in the sequence and its biomass incorporation (LE), (ii) green manuring with Sesbania aculeata (GM), (iii) farmyard manure application (FYM), (iv) 1/3 wheat stubble in situ retention (WS), and (v) 1/3 rice stubble in situ retention.

Results and Discussion

The INM strategies resulted in improved NUE compared to 100% chemical fertilizers (F). The INM had significantly higher net N mineralization and improved biological activity aligning with the NUE trends. The reductions in redox potential (Eh) and pH during rice season improved NUE under integrated management. Highly reduced conditions favored N mineralization and plant availability in form ofNH 4 + - N resulting in enhanced uptake efficiency, in rice crop. The soil organic carbon (C) significantly increased in INM, and an effect of the active C fractions was evident on the NUE of the wheat crop.

Conclusion

The results showed that these INM strategies can immensely benefit the rice-wheat system via improvement in biological health along with electrochemical changes for flooded rice, and labile-C-assisted improvement in soil conditions for wheat.