Agricultural Fertilizer Research Articles

Effect of nutrient omission on grain and biomass yield of irrigated wheat (triticum aestivum) in Sekota district, Amhara region, Ethiopia

Abstract The Ethiopian government has recently imported and distributed multi-nutrient fertilizers for farmers' use without sufficient research finding. Selecting the appropriate fertilizers based on the actual limiting plant nutrients is crucial for providing timely policy direction to import only fertilizers that could limit crop yield. A field study was carried out to identify the yield-limiting plant nutrients for wheat under irrigation at two farmer’s fields in the Woleh irrigation scheme of the Amhara region of Ethiopia in the 2022 irrigation season. A total of nine treatments, including control, NPSKZnB (all), NPSKZn (all-B), NPSKB (all-Zn), NPKZnB (all-S), NPSZnB (all-K), NKSZnB (all-P), PKSZnB (all-N), and RNP (all-KSZnB), were arranged in a randomized complete block design (RCRD) with three replications. The Kekeba wheat variety was used as a test crop. The collected grain and biomass yield data were analized by using SAS software following the procedure. The analysis of result showed that the application of fertilizer had a significant effect on wheat grain yield. The highest grain yield (4443.5 kg ha-1) was obtained from NPKZnB (All-S). While the lowest grain yield was obtained from the control and nitrogen omitted treatment. There was no significant difference between and among the treatments except Control, All-N, and All-P. The grain yield was reduced by 3181.6 kg ha-1 when N was omitted and 1817.8 kg ha-1 when P was omitted over All-S (NPKZnB). This showed that nitrogen and phosphorous are yield-limiting plant nutrients for wheat under irrigation in the study area. Therefore, the government should give emphasis to nitrogen- and phosphorous-containing fertilizers to increase wheat yield.

A genome-wide investigation of the mechanism underlying the effect of exogenous boron application on sugar content and overall quality of “Benihoppe” strawberries

In recent years, the widespread application of growth regulators and nutrients to boost yield and quality of strawberry fruits has led to the rapid growth of strawberry industry globally. Although the effects of major nutrients on strawberry yield have been widely studied, investigations into the effect of trace elements such as boron remain limited. This study examined the effect of boron application on the yield and quality of “Benihoppe” strawberry fruits. Nutrient solutions with varying boron concentrations (0, 0.024, 0.048, 0.072, and 0.096 mM) were applied to the plants, and their effect on fruit quality was evaluated. The results indicated that boron application enhanced the yield per plant, nutrient composition (total amino acid and vitamin C content), antioxidant properties (total phenol) and volatile components (esters) in strawberry fruits. Specifically, treatment with 0.048 mM boron concentration significantly increased the accumulation of soluble sugars, such as sucrose, whose concentration was 154.29% higher than that of the control treated with 0 mM concentration. This enhancement is attributable to the regulated expression of sucrose phosphate synthase (maker-Fvb2-2-augustus-gene-229.38) and β-fructofuranosidase-1/2/3 (augustus-masked-Fvb5-4-processed-gene-2.0, maker-Fvb5-3-augustus-gene-272.30, and maker-Fvb5-1-augustus-gene-0.37) genes, which play crucial roles in sugar metabolism and enzyme activity. Overall, boron application enhanced the quality of “Benihoppe” strawberries. The findings of this study offer substantial theoretical and practical guidance for using boron fertilizers in strawberry farming.

Towards sustainable agricultural development and food security in East Asia: The role of broad money and banking credits

The existing literature has extensively explored the role of financial development in boosting agricultural output. However, there is a lack of empirical research on the effects of broad money and banking credits on food production in East Asian countries. This study addresses this gap by examining the relationship between financial variables and agriculture in selected East Asian economies from 1995 to 2019, focusing on food security. Our findings indicate that increases in broad money and financial sector credit significantly enhance long-term food security by 0.216% and 0.846%, respectively. Additionally, we observed positive correlations between food security and agricultural inputs: a 1% increase in agricultural land, fertilizer use, and renewable energy adoption improves food security by 0.219%, 0.049%, and 0.146%, respectively. Robustness checks and Granger causality tests further validate these results. This study underscores the critical role of financial resources and agricultural inputs in food security and calls for a reassessment of credit systems to mitigate any adverse effects. These findings provide important insights for policymakers aiming to strengthen food security in East Asia.

PENDEKATAN TEKNIK KOMUNIKASI DALAM PENYULUHAN PENGGUNAAN PUPUK ORGANIK BAGI PETANI SAYURAN KANGKUNG DI KELURAHAN MATABUBU KECAMATAN POASIA KOTA KENDARI

This study aims to determine and analyze the communication techniques of extension workers in counseling the use of organic fertilizers for farmers, and to know the knowledge of farmers in the use of organic fertilizers in Matabubu Village, Poasia District, Kendari City.This research was conducted in July 2023. The population in the study will be informants, because kale farmers in Matabubu Village amounted to 7 people, as well as 1 extension agent in charge of Matabubu Village. Data collection techniques consist of observation, in-depth interviews, documentation and literature. The focus of the research includes: extension communication techniques (informative communication, persuasive communication and instructive communication), farmers' knowledge during related extension (source/content of organic fertilizer, benefits of organic fertilizer, how to make organic fertilizer and use of organic fertilizer). The analysis used in this research is qualitative descriptive analysis. The results showed that the communication techniques used consisted of informative, persuasive and instructive communication techniques that had been implemented by extension workers. As well as, farmers' knowledge in the use of organic fertilizer for kale vegetables in general have known, but the process of making organic fertilizer, farmers do not know

Projecting atmospheric N2O rise until the end of the 21st century: an Earth system model study

Abstract Nitrous Oxide (N2O) is a potent greenhouse gas with a centennial-scale lifetime that contributes significantly to global warming. It is emitted from natural and anthropogenic sources. In nature, N2O is released mainly from nitrification and denitrification from the ocean and terrestrial systems. The use of agricultural fertilizers has significantly increased the emission of N2O in the past century. Here, we present, to our knowledge, the first coupled ocean and terrestrial N2O modules within an Earth System Model. The coupled modules were used to simulate the six Shared Socioeconomic Pathways scenarios with available nitrogen fertilizer inputs. Our results are compared to projections of atmospheric N2O concentrations used for
SSPs scenario experiments. Further simulations were prescribed with this available
N2O concentrations. We report three main drivers for terrestrial N2O uncertainties:
atmospheric temperature, agricultural fertilizers input and wetland extent. We project
an atmospheric N2O concentration range from 401 to 418 ppb in six SSPs simulations with a robust lack of sensitivity to equilibrium climate sensitivity. We found a large difference between our low emission scenarios N2O concentrations by 2100 compared to the concentration provided for SSPs experiments. This gap is likely explained by strong mitigation assumptions that were not accounted for in this study, which would require a substantial decrease of agricultural N2O emissions, and the lack of atmospheric N2O dynamics. The coupled model and the simulations prescribed with N2O concentrations showed a difference between -0.02 and 0.09 ◦C by 2100. Our model simulation shows a lack of sensitivity to climate mitigation efforts projecting similar N2O concentration in low and high mitigation scenarios. Further improvements in Earth system models should focus on the impact of oxygen decline on N2O dynamics in the ocean and the representation of anaerobic soils and agricultural dynamics on land, including mitigation methods on nitrogen fertilizers.

The dynamic relation between fertilization, precipitation and the diffusion of agricultural non-point pollution in Hainan Island

With the increasing demand for crops, the excessive application of fertilizers has gradually become a significant factor affecting water quality. Therefore, studying the relationship between agricultural fertilizer runoff and water quality is crucial for the sustainable development of agricultural production. The present study sets up a new dynamic model of nitrogen fertilizer loss, introducing variables such as precipitation, fertilization application during dry and rainy seasons, and their lagged and interaction terms. The paper analyzed the issue of fertilizer runoff under the complex interactions of various factors, including spatial and temporal scales and climatic conditions, and explored the relationship between agricultural activities and water quality changes in the context of sustainable development. Due to Hainan Island’s independent river system, which is free from transboundary pollution, and its low level of industrial pollution, it provides an excellent sample for assessing the impact of agricultural non-point source pollution on water quality. Based on watershed monitoring data from Hainan Island, this study draws the following conclusions: 1. Precipitation exhibits a pronounced seasonal influence on total nitrogen concentration. 2. Nitrogen fertilizer enters into water bodies through precipitation, resulting in a lag effect on total nitrogen concentration. 3. The influence of grain and tropical crops on nitrogen loss is less significant, while cash crops will trigger the nitrogen overloading of rivers in scenarios where they account for a high proportion of the planting structure of the sown area.

Seed priming enhances seed germination and plant growth in four neglected cultivars of Capsicum annuum L.

Priming is basically a water-based technique inducing controlled seed rehydration to trigger the metabolic processes normally activated during the early phase of germination. It is regarded as an ecofriendly approach alternative to fertilizers in traditional agriculture, but also a method to synchronize off-field crops and resume stored seeds, improving vigor, and allowing for a rapid, uniform seedling emergence. In this work we tested several methods of seed priming (i.e., hydro-priming, halopriming by KNO3, and acid priming with HCl) in four ancient and neglected cultivars of Capsicum annuum L., a crop species belonging to Solanaceae family cultivated worldwide. We followed germination performance, seedling growth and selected morphological traits, antioxidant production in the leaves, and protein content of the seeds. Apart from acid priming, which inhibited root emergence, both hydropriming and halopriming decreased the mean germination time in all cultivars. The best treatments were KNO3 6% for 96 h > KNO3 4% for 48 h > hydropriming for 24 h. In particular, KNO3 6% for 96 h in all four cultivars significantly increased plant growth, simple vigor index, development germination index, leaf antioxidant concentration and protein content in the seeds, in comparison to control and other priming treatments, indicating the prompt activation of pre-germinative processes.

Environmental Impact and Decompsition of Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Soils: Challenges and Future Directions

The rapid pace of urbanization and development has led to an increasing global concern over polycyclic aromatic hydrocarbons (PAHs) due to their persistent and widespread presence in the environment, posing significant threats to ecosystems and human health. PAHs originate from both natural and human-made sources and can be categorized based on their origin into pyrogenic, petrogenic, and biogenic products. Upon entering the environment, PAHs undergo various chemical and biological transformations, and their movement occurs through processes such as air-to-soil and soil-to-air transport. Composting, a green and cost-effective technology, offers a promising solution for PAH remediation. This process, which includes mesophilic, thermophilic, cooling, and maturing stages, can yield compost that is useful as fertilizer and soil amendment in agriculture. The success of composting depends on factors such as substrate bioavailability, oxygen levels, nutrient supply, and environmental conditions. While composting has shown effectiveness in reducing PAH levels, it is not without challenges, including the risk of weed infestation, greenhouse gas emissions, and odor pollution. The main obstacles in PAH remediation today are the limited bioaccessibility of PAHs and the insufficient focus on the formation of oxygenated PAHs during the process. Future research should address these challenges, particularly by improving PAH bioaccessibility and mitigating issues related to odor and greenhouse gas emissions.

A New Entrepreneurial Opportunity - The Commercial Viability of Recycling and Processing Wasted Food

Abstract: Food waste is a serious problem faced by today's society, leading not only to wasted resources but also to negative environmental and economic impacts. In order to solve this problem, a business model that uses wasted food resources to produce animal feed and agricultural fertilisers has attracted much attention. The aim of this paper is to overview the feasibility of this business model and discuss it in depth. Firstly, this paper analyses the global and Chinese food waste situation. It is estimated that about 13 billion tonnes of food are wasted globally every year, and the problem of food waste is also growing in China. Rapid urbanisation and changes in dietary structure are among the main reasons for the increase in food waste in China. The paper then analyses the impact of market demand and policy support on the business model. With the emphasis on environmental protection and sustainable development, the demand for environmentally friendly products is increasing, providing favourable conditions for the development of this business model. Meanwhile, government policy support is also an important factor in promoting the development of the business model. Finally, this paper assesses the feasibility and sustainability of the business model. Although there are some challenges associated with this model, such as technological innovation and marketing, it is expected to be successful and contribute to solving the food waste problem through the joint efforts of the government, enterprises and the community.

Agricultural Valorization of Treated Effluent from Korhogo Wastewater Treatment Plant

Aims: The main objective is to evaluate the effluents of Korhogo’s wastewater treatment plant for irrigation and fertilization in agriculture. Study Design: Characterization of outlet treated wastewaters has been firstly done. Then their suitability for irrigation has been determined and finally their fertilizing power has been assessed. Place and Duration of Study: Department of geosciences, Korhogo’s wastewater treatment plant and laboratory. Sampling and analyses were carried out in January 2023, before agricultural field implementation started in February 2023. Methodology: Firstly, Physico-chemical and microbiological analyses, allowed characterization of outlet treated wastewaters. A determination of their suitability for irrigation was then done through Sodium Adsorption Ratio calculation and water classification with Diagram of Richards. An assessment of their fertilizing capacity was finally carried out using these waters for irrigating and fertilizing crop plots (3x2 m), and consisting of determining firstly their biodegradability index, then their nutrient contents (Nitrogen, Phosphorus and potassium), and the influence of their use on crop development and yield. Results: The results show that several parameters meet standards for discharge of treated wastewater except total nitrogen, suspended matters and total phosphorus (67.67 mg/l, 271.33 mg/l and 18.30 mg/l). Sodium Adsorption Ratio (SAR) value=3.78 and C3S1 class indicate that these treated effluents can be used for irrigation without salinization risk. As fertilizer, treated effluents brought to crops respectively 603 kg/ha of nitrogen, 162 kg/ha of phosphorus and 99 kg/ha of potassium for maize; and 368.5 kg/ha of nitrogen, 99 kg/ha of phosphorus and 60.5 kg/ha of potassium respectively for Okra. A yield of 12.2 kg of fresh maize and 3.15 kg of fresh okra was obtained for the plot irrigated by treated effluents, compared with 4.80 kg of fresh maize and 0.36 kg of fresh okra for the plot irrigated by well water. Conclusion: This study has shown that outlet treated wastewater from Korhogo’s wastewater treatment plant is suitable for crops irrigation, contains sufficient nutrients enhancing crops development and yield.

Temporal and spatial analysis of fertilizer application intensity and its environmental risks in China from 1978 to 2022

Fertilizers are an essential input in agriculture as they can enhance crop yields. However, their use also poses significant environmental risks. To thoroughly explore the intensity of fertilizer use and its potential threats to the ecological environment, this study analyzed the environmental risks of fertilizer use from a temporal and spatial perspective based on fertilizer application data in China from 1978 to 2022. Additionally, the contribution of fertilizer application in Chinese farmland to greenhouse gas N2O emissions was quantified using IPCC emission factor methodology. The results indicated that fertilizer application intensity and N2O emissions in China initially increased and then decreased from 1978 to 2022. Despite the implementation of various fertilizer control measures at the policy level, such as the Zero Growth of Fertilizer Action in 2015 and the Efficiency-Increasing Action for Reducing Fertilizer Use in 2022, the intensity of fertilizer application in China still exceeded international safety standards by 1.33-fold in 2022, reaching 298.79 kg/hm2. Furthermore, N2O emissions amounted to 50.17 × 104t, accounting for 16% of China's total agricultural greenhouse gas emissions that year. Correlation and regression analyses demonstrated that with increasing fertilizer application, crop production exhibits an inverted U-shaped growth trend, indicating limited effectiveness of high-intensity fertilizer use in increasing crop yields. These findings highlight the profound greenhouse effect resulting from the use of agricultural nitrogen fertilizer. Therefore, this study proposed technical and policy-level mitigation measures to address the issues caused by excessive fertilizer application, aiming to provide insights for controlling agricultural non-point source pollution and preserving the agroecological environment.

Nitrogen-Fixing Gamma Proteobacteria Azotobacter vinelandii—A Blueprint for Nitrogen-Fixing Plants?

The availability of fixed nitrogen limits overall agricultural crop production worldwide. The so-called modern “green revolution” catalyzed by the widespread application of nitrogenous fertilizer has propelled global population growth. It has led to imbalances in global biogeochemical nitrogen cycling, resulting in a “nitrogen problem” that is growing at a similar trajectory to the “carbon problem”. As a result of the increasing imbalances in nitrogen cycling and additional environmental problems such as soil acidification, there is renewed and increasing interest in increasing the contributions of biological nitrogen fixation to reduce the inputs of nitrogenous fertilizers in agriculture. Interestingly, biological nitrogen fixation, or life’s ability to convert atmospheric dinitrogen to ammonia, is restricted to microbial life and not associated with any known eukaryotes. It is not clear why plants never evolved the ability to fix nitrogen and rather form associations with nitrogen-fixing microorganisms. Perhaps it is because of the large energy demand of the process, the oxygen sensitivity of the enzymatic apparatus, or simply failure to encounter the appropriate selective pressure. Whatever the reason, it is clear that this ability of crop plants, especially cereals, would transform modern agriculture once again. Successfully engineering plants will require creating an oxygen-free niche that can supply ample energy in a tightly regulated manner to minimize energy waste and ensure the ammonia produced is assimilated. Nitrogen-fixing aerobic bacteria can perhaps provide a blueprint for engineering nitrogen-fixing plants. This short review discusses the key features of robust nitrogen fixation in the model nitrogen-fixing aerobe, gamma proteobacteria Azotobacter vinelandii, in the context of the basic requirements for engineering nitrogen-fixing plants.

Spatiotemporal Variation Characteristics and Source Identification of Nitrogen in the Baiyangdian Lake Water, China

To study the characteristics and sources of nitrogen in the Baiyangdian Lake, this research conducted water quality monitoring during three hydrological periods (normal period, flood period, and dry period), and 165 pieces of routine water quality monitoring data were collected from the three national control sections for Baiyangdian Lake and its inflow rivers. By integrating water chemical analysis with multivariate statistical techniques, the study comprehensively investigated the spatiotemporal variation patterns of nitrogen in Baiyangdian Lake and identified the sources of nitrogen pollution. The results showed that the concentration of total nitrogen (TN) was highest during the dry period, reaching an average of 0.924 mg/L, and 31.3% of the sites exceeded the national Grade III surface water quality standard, reflecting a potential risk of nitrogen pollution. Based on the ion ratio method and principal component analysis (PCA), the main sources of nitrogen pollution in Baiyangdian Lake were identified as manure and domestic sewage, with agricultural fertilizers also having a certain impact on water nitrogen pollution. In addition, the study also compared the nitrogen concentration in Baiyangdian Lake with several important lakes in China. The results showed that the concentrations of TN and ammonium nitrogen (NH4+-N) in Baiyangdian Lake are lower than those in lakes in areas with similar human activity intensity, indicating that the water quality of Baiyangdian is relatively good. This study can provide a scientific basis for water quality management and pollution prevention for Baiyangdian Lake.

Enhancing the sustainability of cowpea production through the integrated use of fish effluents and animal manure

AbstractThe integration of aquaculture and agriculture in arid and semi‐arid environments is crucial for maximizing water and land productivity, especially considering the increasing global water scarcity and the simultaneous use of water for crop and fish production. A greenhouse study was conducted to determine the effects of fish effluent on the growth, yield parameters, and yield of cowpea (Vigna unguiculata). The experiment involved 13 fertilization treatments, including three types of irrigation water (river water—control, Nile tilapia (Oreochromis niloticus), African sharp‐toothed catfish (Clarias gariepinus), four fertilizers (poultry, cattle, and sheep manures at 10 t ha−1), recommended rate of inorganic fertilizer (150 kg ha−1 of NPK 6‐20‐10), and six mixed treatments with fish effluent and 50% of the applied rate of manure alone (5 t ha−1). The combined use of C. gariepinus effluent + 50% poultry manure significantly increased stem diameter, nodules per plant, pods per plant, and seed yield compared to NPK treatments. The shortest days to reach 50% flowering were obtained with the effluent of O. niloticus + 50% sheep manure, C. gariepinus/O. niloticus + 50% poultry manure, and 10 t ha−1 poultry manure. However, fertilization treatments did not significantly influence the number of branches, pod and root length, number of pods per plant, 100‐seed weight, and leaf chlorophyll concentrations. This study suggests that fish effluents, when combined with manure, can improve plant growth and seed yield, providing a cost‐effective alternative to inorganic fertilizers for smallholder farmers.

Role of Organic Fertilizer in the Transfer of Lead to Vegetables Produced in Tropical Mountain Agroecosystems.

Understanding the relationship between the aerobic transformation of organic matter (OM) and the bioavailability of lead to plants may allow the safe application of organic fertilizers (OF) in agriculture. The present study aimed to elucidate the relationship of different OM structures with Pb, revealing the action of OF (poultry litter) on Pb dynamics, presenting the effects of OM transformations on bioavailability and transfer to vegetables produced in tropical mountain agroecosystems (TMA). The association of Pb with hydrophilic structures (CAlk-O and CAlk-di-O) during the aerobic transformation of poultry litter (PL) contributes to the increase in the water-soluble form of this metal (3.17-15.30%). The structural changes promoted by the transformation of OM, in addition to reducing the adsorption capacity of Pb in PL (Kd reduction from 1135.50 to 87.49), favor the formation of outer-sphere complexes. PL that have a more labile structure, i.e., those that are less humified, have greater affinity for Pb. The greater affinity of Pb for labile structures that are preserved in PL during OM transformations contributed to its increase and transport to edible plant parts. Considering the edible parts of vegetables grown in TMA and fertilized with fresh PL, 100% of broccoli, 91.78% of cabbage, 80.00% of tomato, 65.96% of parsley, 49.19% of lettuce, and 32.88% of cauliflower showed Pb contamination that exceeded the permitted level. Therefore, OF contributes to lead contamination of food produced in TMA, representing a risk to human health. Studies are needed to propose additional treatments for this residue before its use.

Antimicrobial resistance in plant endophytes associated with poultry-manure application revealed by selective culture and whole genome sequencing

Poultry manure is widely used as organic fertilizer in agriculture during the cultivation of crops, but the persistent high-level use of antibiotics in poultry production has raised concerns about the selection for reservoirs of antimicrobial resistance genes (ARGs). Previous studies have shown that the addition of poultry manure can increase the abundance of genes associated with resistance to tetracyclines, aminoglycosides, fluoroquinolones, sulfonamides, bacitracin, chloramphenicol, and macrolide-lincosamide-streptogramin in soil and plants. Understanding the microbial populations that harbor these ARGs is important to identify microorganisms that could enter the human food chain. Here, we test the hypothesis that environmental exposure to poultry manure increases the occurrence of antimicrobial resistance (AMR) in plant endophytes using selective culture, phenotypic Antibiotic Susceptibility Testing (AST), phylogenetic analysis, and whole genome sequencing (WGS). Endophytes from poultry manure treated Sorghum bicolor (L.) Moench plant root and stem samples showed increased phenotypic and genotypic resistance against multiple antibiotics compared to untreated controls. Comparison of AMR phenotype-to-genotype relationships highlighted the detection of multi-drug resistant (MDR) plant endophytes, demonstrating the value of genomic surveillance for emerging drug-resistant pathogens. The increased occurrence of ARGs in poultry manure-exposed endophytes highlights the need for responsible antibiotic use in poultry and animal farming to reduce contamination of ecological niches and transgression into endophytic plant microbiome compartments. It also emphasizes the requirement for proper manure management practices and vigilance in monitoring and surveillance efforts to tackle the growing problem of antibiotic resistance and preserve the efficacy of antibiotics for human and veterinary medicine.

Evaluating Belizean Sugarcane Farmers’ Adoption Intentions Regarding Organic Fertilizer

Sugarcane is vital to Belize’s economy, significantly contributing to its Gross Domestic Product and supporting a large portion of the population. It is necessary to address the declining soil health in this nation due to excessive chemical fertilizer use, and Belize aims to promote organic fertilizers, which enhance soil quality and reduce environmental impacts. The primary purpose of this study was to investigate the determinants of adoption intentions regarding organic fertilizers among Belizean sugarcane farmers using the Extended Theory of Reasoned Action. Data were collected from 207 farmers in the Orange Walk and Corozal districts using a non-probability sampling approach via a self-administered questionnaire measuring perceived health risks, environmental concerns, attitudes, subjective norms, and adoption intentions. The results revealed that both perceived health risks and environmental concerns influenced farmers’ attitudes and subjective norms, which, in turn, affected their adoption intentions, as revealed through path analysis; socio-economic factors, years of farming experience, and ownership background partially affected adoption intentions regarding organic fertilizers, as determined via binary logistic regression analysis. The findings suggest that raising farmers’ awareness of health risks and environmental crises, as well as enhancing farmers’ knowledge and their positive attitudes towards the use of organic fertilizers, will contribute to the sustainable development of the sugarcane industry in Belize. Some interventions by policymakers are recommended to support the transition to the use of organic fertilizers in sugarcane farming.

Advances in the Study of NO3− Immobilization by Microbes in Agricultural Soils

The extensive application of nitrogen (N) fertilizers in agriculture has resulted in a considerable accumulation of N in the soil, particularly nitrate (NO3−), which can be easily lost to the surrounding environments through leaching and denitrification. Improving the immobilization of NO3− by soil microorganisms in agriculture is crucial to improve soil N retention capacity and reduce the risk of NO3− loss. In this paper, we reviewed the significance of microbial immobilization of soil NO3− in soil N retention, the techniques to quantify soil gross microbial NO3− immobilization rate, and its influencing factors. Specifically, we discussed the respective contribution of fungi and bacteria in soil NO3− retention, and we clarified that the incorporation of organic materials is of vital importance in enhancing soil microbial NO3− immobilization capacities in agricultural soils. However, there is still a lack of research on the utilization of NO3− by microorganisms of different functional groups in soil due to the limited techniques. In the future, attention should be paid to how to regulate the microbial NO3− immobilization to make soil NO3− supply capacity match better with the crop N demand, thereby improving N use efficiency and reducing NO3− losses.

Changes in Physical Fractions within Soil Aggregates Under Nitrogen Reduction and Film Mulching Measures in Dryland Wheat Field

We studied the changes in various physical fractions within aggregates in the arid plateau of southern Shanxi Province, which has great significance for synergistically improving soil fertility and crop productivity in this region. Bulk soil samples were collected from 0-20 cm layers during a 7-year long-term experiment in Hongtong County, Shanxi Province. Wheat grain yields, SOC concentrations, proportions, and OC contents within soil aggregates were analyzed. OC contents included： unprotected coarse particulate organic carbon within macroaggregate （M-cPOC） and fine particulate organic carbon within macroaggregate （M-fPOC）, physically protected intra-aggregate particulate organic carbon within macroaggregate （M-iPOC）, chemically/biochemically protected mineral organic carbon within macroaggregate （M-MOC）, unprotected fine particulate organic carbon within microaggregate （m-fPOC）, physically protected intra-aggregate particulate organic carbon within microaggregate （m-iPOC）, and chemically/biochemically protected mineral organic carbon within microaggregate （m-MOC）. The treatments were ① farmer fertilization （FP）, ② nitrogen reduction monitoring and control fertilization （MF）, ③ nitrogen reduction monitoring and control fertilization plus ridge film and furrow sowing （RF）, and ④ nitrogen reduction monitoring and control fertilization plus flat film hole sowing （RF）. The results showed that compared with that in the FP treatment, MF reduced SOC concentration while maintaining wheat grain yield, RF and FH synergistically improved soil fertility and crop yield, especially for the FH with SOC concentration, and wheat grain yield increased by 8.44% and 48.86%, respectively. MF significantly reduced the content of M-cPOC, RF significantly increased the content of M-iPOC, and FH significantly increased the contents of M-fPOC, M-iPOC, M-MOC, and m-iPOC by 64.00%, 98.39%, 6.16%, and 17.48%, respectively. In addition, combined with redundancy analysis, we found that the M-iPOC fraction played a major role in increasing SOC concentration and wheat grain yield, with a contribution rate of 61.5%. Therefore, the contribution of macroaggregates to soil fertility and crop productivity was higher than that of microaggregates in the arid plateau area of southern Shanxi, and flat film hole sowing could increase the content of M-iPOC, thereby synergistically increasing SOC sequestration and wheat grain yield, which could promote this cultivation technology in the region and even in the country's arid agricultural areas.

Isolation, Selection, and Biological Evaluation for Bacteria that Fix Nitrogen and Produce Indole-3-Acetic Acid from Paddy Soils in Vietnam

Introduction/Background Acidic soils are limiting the production of crops and indirectly harming the environment due to the use of nitrogen (N) chemical fertilizer. Therefore, the current study aims to isolate a promising N2-fixing candidate to solve this issue in some communes of Phu Luong District, Thai Nguyen Province, Vietnam. Materials and Methods The bacteria were isolated using the Ashby medium. The IAA generation and nitrogen fixation were assessed using spectroscopy. The selected bacteria were tested at temperatures ranging from 28°C to 42°C and pH levels of 4.0 to 9.0. As a result, the Box-Behnken model yielded a growth equation. The API kit test was used to measure the biochemical properties of the selected bacteria. Results The result demonstrated that there were ten nitrogen-fixing bacteria (NFB) isolates with capacities of N2 fixation and IAA production at 2.35–24.61 and 0.00–119.13 µg/ml. Among them, the NL3 strain was the best strain. The optimum condition to grow the NL3 strain was calculated as 5.44 days at pH 7.10 and temperature of 32.18°C to reach a bacterial density of 9.77929×108 CFU/ml. In addition, the NL3 strain was identified as an Azotobacter species. The genomic analysis revealed that the genome of Azotobacter sp. NL3 was nearly 5.4 Mb long and contained 45 N2 fixation-relating genes and 7 IAA production-relating genes. Conclusion Not only can this study provide insight into the features of Azotobacter spp., but it also introduces a potent candidate that can improve soil health and crop yield by fixing N2 and producing IAA in order to limit the use of N chemical fertilizer for a sustainable agriculture. Therefore, the selected bacterial strain should be further tested under the local field conditions and subsequently commercialized as a biofertilizer.