Nitrogen Fertilizer Application Research Articles

Retrieval of nicotine content in cigar leaves by remote analysis of aerial hyperspectral combining machine learning methods

Cigar leaf is a special type of tobacco plant, which is the raw material for producing high-quality cigars. The content and proportion of nicotine and other composite substances of cigar leaves have a crucial impact on their quality and vary greatly with the time of harvest. Hyperspectral remote sensing technology has been widely used in the field of crop monitoring because of its advantages of large area coverage, fast information acquisition, short cycle turnover, strong real-time performance and high efficiency. Therefore, it is important to accurately monitor nicotine content of field crops in a timely manner in the production of high-quality cigar leaf. To this end, this study set out to measure crop reflectance spectra acquired by UAV drones from tobacco field crops by hyperspectral image acquisition. MSC, SG, and SNV were combined and applied to the raw data. The output of these operations was then further processed by CARS, SPA, and UVE algorithms to determine the nicotine sensitive bands. Three machine learning algorithms were then used to analyze the data: PLS, BP, RF, and the SVM. An inversion model of the content of nicotine was established, and the model was evaluated for accuracy. The main research conclusions are as follows: (1) With the increase in the rate of application of nitrogen fertilizer, the nicotine content of cigar leaves increased; (2) Processing data by the CARS, SPA, and UVE methods reduces the degree of data redundancy and information co-linearity in the screening of the content of nicotine sensitive bands; (3) The MSC-SNV-SG-CARS-BP model has the best predictive accuracy on the nicotine content. The prediction accuracy of the testing set was R2 = 0.797, RMSE = 0.078,RPD = 2.182.

Effects of combined application of nitrogen, phosphorus, and potassium fertilizers on seed yield, seed quality and economic returns of Elymus nutans in alpine region.

The Qinghai-Tibetan Plateau (QTP), one of the most important ecological regions in the world, is experiencing a decline in ecological function as a result of severe grassland degradation. Elymus nutans is one of the ecological grass species for restoring degraded grasslands in QTP. The seed yield and seed quality are often limited by soil nutrients in QTP, so it is very important to optimize the application rates of fertilizer for E. nutans seed production. In this study, a "3414" fertilization experiment (nitrogen: 0 ~ 225kg N ha- 1; phosphorus: 0 ~ 180kg P2O5 ha- 1; potassium: 0 ~ 135kg K2O ha- 1) was established in the third year of planting E. nutans seed field based on the soil nutrient supply situation in the planting area to explore the effects of combined application of N, P and K fertilizers on the seed yield and seed quality of E. nutans. The results showed that the balanced application of N, P and K fertilizers significantly improved the seed yield, seed quality and seed vigour of E. nutans. The seed yield of E. nutans was regulated by the seed yield components. Under different fertilization treatments, the number of fertile tillers and thousand kernel weight had a greater contribution to seed yield, followed by the number of spikelets per panicle. Compared to the no fertilization treatment, the combined application of N, P, and K fertilizers increased the seed yield of E. nutans by 23.05%-90.49%. The seed size, seed nutrient content, germination percentage and seedling growth of E. nutans were positively affected by the combined application of N, P and K fertilizers. The seed vigour of E. nutans increased by 38.23%-89.85% compared to the no fertilizer treatment. Fertilizer application promoted seed nutrient storage and increased seed size thereby promoting seed germination and seedling growth. The crude protein, soluble sugar and starch content of E. nutans seed increased by 9.70%-54.05%, 6.70%-25.70% and 4.31%-35.88%, respectively. Nitrogen fertilizer had a greater effect on seed yield and seed quality of E. nutans than phosphorus and potassium fertilizers. The balanced nitrogen, phosphorus and potassium fertilizers at an application rate of 150kg N ha- 1, 120kg P2O5 ha- 1, 90kg K2O ha- 1 in the planting area of QTP was found to be the optimum fertilization amount for increasing seed yield, seed quality and net income. This study provides theoretical evidence and certain practical suggestions for sustainable forage seed production in alpine regions of QTP.

Effects of Sensor-Based, Site-Specific Nitrogen Fertilizer Application on Crop Yield, Nitrogen Balance, and Nitrogen Efficiency

This study investigates the effects of sensor-based, variable-rate mineral nitrogen (N) application (VRA) in winter wheat (Triticum aestivum L.) on the spatial variability of grain yield, protein content, N uptake, N balance, and N efficiency compared with uniform N application (UA). To analyze the effects of VRA and UA on yield and N balance parameters, on-farm strip trials were conducted on heterogeneous arable fields covering an area of 49 hectares. The trials were carried out over a four-year period, from 2020 to 2023, with crops under both application methods placed in strips side-by-side. The N fertilizer requirements for growth stages (GSs) 32 and 39 were determined using an online map-overlay VRA method. This method integrated the site-specific yield potential and current plant development derived from spectral reflectance measurements using a tractor-mounted sensor system. The results show that the application of N fertilizer can be reduced by up to 38 kg ha−1 yr−1. The N efficiency can be increased by 15% and a significant reduction in variability of N balances can be achieved. However, the effects on yield and N efficiency are highly dependent on the specific application conditions (weather conditions, disease occurrence, and crop development). Not every field trial showed advantages of VRA over UA fertilization. Overall, the VRA system demonstrated encouraging potential, functioning as intended. However, further adjustment and optimization are required to ensure that the VRA fertilization system works robustly and reliably under on-farm conditions.

Subsurface Irrigation With Ceramic Emitters Improved the Water Productivity and Nitrogen Use Efficiency of Greenhouse Melons.

ABSTRACTIncreasing nitrogen use efficiency in agricultural fields is crucial for sustainable agricultural development. In a 2‐year greenhouse study, we compared two methods, subsurface irrigation with ceramic emitters (SICE) and subsurface drip irrigation (SDI), to evaluate their effects on soil moisture and nitrogen distribution, photosynthetic efficiency and plant stoichiometry. The results showed that SICE can reduce the soil nitrate nitrogen content by approximately 20% while maintaining the soil moisture content at 70%–80%, improving the photosynthetic efficiency and melon yield. Under the optimal yield treatment (applying 60.67 kg of nitrogen fertilizer per hectare), compared with SDI, SICE increased yield by 8%, water productivity by 13%, nitrogen absorption efficiency by 4% and nitrogen use efficiency by 3%. In addition, by analysing the stoichiometric characteristics of melon at different nitrogen fertilizer application rates and growth stages under the two irrigation methods, we found that the main reason for the increase in SICE yield was the coupled effect of the increase in plant photosynthetic efficiency and the need for plants to maintain their internal stoichiometric balance.

ЭФФЕКТИВНОСТЬ КОМПЛЕКСНОГО ПРИМЕНЕНИЯ УДОБРЕНИЙ И СРЕДСТВ ЗАЩИТЫ РАСТЕНИЙ ПРИ ВОЗДЕЛЫВАНИИ ЯРОВОГО РАПСА В УСЛОВИЯХ АЛТАЙСКОГО КРАЯ

The purpose of research is to study the influence and interaction of chemical protection agents (herbicides, fungicides, insecticides) and nitrogen fertilizers on the productivity of spring rapeseed. Research was carried out to improve the system for protecting spring rapeseed from a complex of pests at different levels of nitrogen nutrition in 2014–2016. During the growing season of the crop, pests such as rapeseed sawfly, cabbage moth, cruciferous bugs, and rapeseed flower beetle were identified. The EPV was exceeded only in terms of the number of rapeseed flower beetle. The application of nitrogen fertilizers contributed to an increase in the competitiveness of the crop, which is reflected in a decrease in the amount of weed component and its mass and resistance to phytophages. The rapeseed flower beetle prefers less developed and more weedy crops. The biological effectiveness of the insecticide against the background of fertilizers was higher and amounted to 89.6 %, and against the background without fertilizers it was 88.1 %. In the variant without fertilizers and protective agents, there were 234.4 pieces/m2 of weeds; in the variant with fertilizer there were 186.9 pieces/ m2, 20.3 % lower compared to the unfertilized background. The herbicides used on an unfertilized background (“Zellek Super” tank mixture, EC – 0.5 l/ha + “Galera Super 364”, VR – 0.3 l/ha) effectively suppressed the weed component – from 81.2 to 83.4 %. On a fertilized background, the effectiveness of herbicides was higher and varied from 92.4 to 94.3 %. The crops were treated against diseases after the first signs of Alternaria brassicae blight appeared on the lower leaves of the rapeseed. However, during the years of research, no further development of the disease was observed. As a result of the use of modern plant protection products against the background of nitrogen fertilizers, significant increases in the yield of spring rapeseed (0.23–0.58 t/ha) were obtained. Of the studied elements of the agricultural complex, the most significant factor was the application of nitrogen fertilizers, which ensured an increase in yield by 62.8 % without protective equipment. The maximum yield increase of 1.48 t/ha (112 %) was ensured by the use of complex protection against the background of nitrogen fertilizers.

Study on improving yield and antioxidant enzyme activities in millet by rationing molybdenum and nitrogen

The application of appropriate nitrogen and molybdenum fertilizer can improve the growth and development of plants, increase photosynthetic efficiency, regulate active oxygen metabolism in vivo, maintain the oxidation balance required for normal cell growth, enhance the activity of crop antioxidant enzymes and dry matter accumulation, so as to increase crop yield. In order to investigate the effect mechanism of nitrogen fertilizer combined with foliar molybdenum fertilizer on millet yield and antioxidant enzyme activity, two nitrogen application gradients (N0 (0 kg/hm2) and N1 (75 kg/hm2) were set with millet variety Changnong 47 as material. Leaf molybdenum fertilizer Mo0 (0 %), Mo1 (0.1 %), Mo2 (0.2 %), Mo3 (0.3 %) and Mo4 (0.4 %) were sprayed at the joining stage. Photosynthetic parameters, chlorophyll content, antioxidant enzyme activity, dry matter accumulation and yield at the complete ripening stage were measured. After the analysis of significant difference, the results showed that the combined application of molybdenum nitrogen significantly increased the yield of millet, and the maximum yield under the Mo3 treatment was 5869.04 kg/hm2 under the N1 condition, which was 13% higher than that under the no fertilization treatment. The total dry matter accumulation was 36.96 g/ plant, which was 31% higher than that without fertilization. The net photosynthetic rate (Pn) and stomatal conductivity (gs) increased first and then decreased with the increase of molybdenum fertilizer concentration gradient, and reached the maximum values under N1Mo3 condition, which were 24.77 μmol•m-2•s-1 and 391.33 mol•m-2•s-1, respectively. Application of molybdenum fertilizer can improve the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the test samples. In conclusion, under N1 condition, Mo3 (0.3%) treatment can effectively improve millet yield, photosynthetic characteristics and antioxidant enzyme activity. The results of this study provided theoretical basis and data support for the application of nitrogen and molybdenum fertilizer in millet production.

Effect of Application of Nitrogen Fertilizer, Microbial and Humic Substance-Based Biostimulants on Soil Microbiological Properties During Strawberry (Fragaria × ananassa Duch.) Cultivation

Plant biostimulants have been the subject of intense interest in recent years. The aim of this study was to assess, during the years 2021–2022, the effect of mineral nitrogen (N) fertilizer, experimental (PGPB) and commercial (G) microbial biostimulants, and humic substance product (A) on the soil microbial communities, and yield of strawberries, under field conditions. Dehydrogenase activity was significantly affected by nitrogen fertilization, but an increase occurred in the treatment N+G. The treatments N+G, N+G+A, and N+PGPB+A increased FDA hydrolysis, and phosphatase activity. All plant biostimulants increased basal as well as substrate-induced respiration. Culturable bacteria (total counts, dormant forms, actinomycetes) were not clearly affected by treatment. Based on 16S rRNA analysis, bacterial community composition was different in N+PGPB+A and N+G+A treatments. The number of cultivable fungi was significantly lower in N+PGPB and N+PGPB+A treatments. The genus of fungi Pilidium, a potential phytopathogen of strawberries, was present in the second year, but in these treatments, it was absent. In the second year, strawberry yield was shown to be 95% higher in the N+PGPB+A treatment than in the control. Microbial biostimulants in combination with humic substances represent a potential solution in increasing strawberry production.

Effects of reduced nitrogen fertilizer application rates on grain yield and rice quality of early- and late-season dual-use rice in South China

Effects of reduced nitrogen fertilizer application rates on grain yield and rice quality of early- and late-season dual-use rice in South China

Effects of nitrogen fertilizer application rate on lodging resistance for rice (Oryza sativa L.) stem

Rice yield could be increased by apply higher level of nitrogen fertilizer, but excessive use of nitrogen fertilizer will cause plant lodging. This study aimed to investigate the effect of nitrogen application rate on lodging resistance of rice stems. Four japonica rice varieties with different lodging resistance were used, and six nitrogen fertilizer levels were set up to analyze the morphological structure, mechanical properties, and chemical components of rice stems under such treatments. The dynamic changes of lodging resistance of rice stems under different nitrogen fertilizer application rates were exanimated. The study provide valuable insights for improving lodging resistance and subsequently increasing rice yield. The results indicated that WYD4 exhibited the highest yield under the N1 treatment, whereas JYJ, JJ 525, and JND 667 achieved the highest yield under the N2 treatment. The lodging index of rice varieties fluctuated at the filling stage, peaking 30 days after heading. Moreover, the lodging index increased progressively with higher nitrogen fertilizer application rates, reaching its maximum under the N5 treatment, which corresponded to an increased lodging risk. Specifically, the lodging index under the N5 treatment increased by 0.63–1.21 times compared to the optimal nitrogen fertilizer level. Concurrently, the fracture bending point (s) and lodging resistance of the rice stem exhibited a gradual decline. Additionally, plant height, internode length, and barycenter height significantly increased with rising nitrogen application rates and were positively correlated with the lodging index. Conversely, the wall thickness of the second basal node decreased and showed a negative correlation with the lodging index. Furthermore, the contents of lignin, cellulose, soluble sugar, and starch in the second internode diminished with increasing nitrogen rates, and were positively correlated with the breaking moment.

Long-Term Intercropping With Nitrogen Management to Improve Soil Quality and Control Crop Diseases.

Long-term positioning experiments have demonstrated significant benefits in agricultural production and environmental protection. Faba bean-wheat intercropping with nitrogen fertiliser can effectively mitigate the occurrence of faba bean wilt disease. Identifying the optimal nitrogen application rate is essential for enhancing the disease control efficacy of intercropping. This study aimed to investigate the long-term effects of varying nitrogen application levels on the physical, chemical, and biological changes in the rhizosphere soil of faba bean under intercropping conditions and to examine their relationship with the incidence of faba bean wilt disease. In a 9-year field experiment, two treatments of faba bean-wheat intercropping for 1 year (IF-1) and 9 years (IF-9) were established to investigate the incidence of faba bean wilt under four nitrogen levels (N0: 0 kg ha-1; N1: 45 kg ha-1; N2: 90 kg ha-1; N3: 135 kg ha-1). Rhizosphere soil from faba bean plants was collected to assess the corresponding physical, chemical, and biological indicators. Long-term intercropping promoted the growth of faba bean plants and effectively controlled faba bean wilt disease by improving soil structure and fertility and soil quality (SQI). Under different nitrogen application levels, certain soil physical properties (moisture content, macroaggregate proportion, MWD, and GMD) and chemical properties (SOM, total carbon, SOC, total nutrients, and available nutrients) peaked under N2 (90 kg ha-1), with SQI showing a similar trend. Additionally, long-term intercropping enhanced enzyme activity in the faba bean rhizosphere, reshaped microbial community composition, maximised the benefits of beneficial microbes, reduced the abundance of the pathogenic fungus Fusarium, and achieved optimal disease control under N2. Under long-term intercropping with nitrogen fertiliser application at N2 (90 kg ha-1), the physical structure of the faba bean rhizosphere soil was significantly improved, soil quality and fertility were enhanced, and the abundance of plant pathogens was reduced by modifying the microbial community composition. This effectively alleviated faba bean disease, promoted healthy plant growth, and maintained soil function.

Analysis of the Synergistic Effect of Endophytic Bacteria and Metabolites on Yield in Soybean Roots Under Biochar with Nitrogen Fertilization

The appropriate application of nitrogen fertilizers and biochar to the soil is beneficial for soybean growth, and a combination of biochar and nitrogen can improve low-nitrogen fertilizer utilization efficiency. However, the effect of the combination of biochar and nitrogen fertilizer on soybean roots is still unclear. Therefore, in this study, we investigate the changes in endophytic bacterial communities and metabolites in soybean roots under different combinations of biochar and nitrogen fertilizer treatments by setting different fertilization levels and using high-throughput sequencing and non-targeted metabolomics techniques. The results showed that applying 20 t/ha of biochar and 180 kg/ha of nitrogen fertilizer (C2N1) resulted in the highest soybean yield. By studying the endophytic bacterial community in soybean roots, it was observed that the dominant phyla were Proteobacteria, Bacteroidota, and Actinobacteriota, and the dominant genera were Bradyrhizobium, Streptomyces, and Rhizobacter. Moreover, a metabolic pathway analysis revealed that glycosylphosphatidylinositol (GPI)-anchor biosynthesis was the most significant metabolic pathway in the C0N1 vs. C0N0 comparison group, and glycerophospholipid metabolism was the most significant metabolic pathway in the C2N1 vs. C1N1 comparison group; they were both associated with regulatory mechanisms such as plant growth promotion and nutrient cycling. Structural equation modeling indicates that both endophytic bacteria and metabolites have a significant positive impact on yield. Bradyrhizobium and Rhizobium are observable variables with significant positive effects on endophytic bacteria, while Phe-Thr and 7-allyloxycoumarin are observable variables with significant positive effects on metabolites. Endophytic bacteria not only have a direct impact on crop yield, but also indirectly affect crop yield through their effects on metabolites. This study has important scientific value and guiding significance for improving soybean yields.

Component analysis of the nitrogen agronomic efficiency revealed the improved contribution of uptake efficiency in a maize-bean intercropped system

The objective of this study was to determine the share of nitrogen Agronomic Efficiency/Productivity components (recovery/uptake efficiency; RE × physiological/utilization efficiency; PE) in a common intercropping system (maize-bean) which until the current research, there is no information about it. A split plots arrangement based on the randomized complete block design (RCBD) with three replications, was carried out during two successive cropping years. The main plot factor consisted of sole cultivation of maize and bean, row intercropping with ratios including 50%:50% (1 row of maize: 1 row of bean), 67%:33% (2 rows of maize: 1 row of bean), and 33%: 67% (1 row of maize: 2 rows of bean). Application and non-application of nitrogen (N) fertilizer (55 kg ha−1) were assigned to the subplots. In both species, when NUE was calculated based on the seed yield, the N utilization efficiency (NUtE) was higher in all treatments compared with NUtE based on the dry matter yield. Under the conditions of N application, the ratio of 50:50 of bean: maize intercropped had higher N uptake efficiency (NUpE) for both species. Moreover, the ratio of 50:50 had the highest total land equivalent ratio (LER) based on the seed yield (1.10), the NUpE (2.30%), and NUE indices (1.98 kg kg−1 and 2.02 kg kg−1 based on the seed yield and the dry matter yield, respectively). The ratio of 50:50 of bean: maize intercropped having the highest efficiency indices, can be a lasting solution to reduce N application and losses, improving its uptake efficiency. Reducing the excessive use of chemical N fertilizer increases the productivity of this input in agroecosystems and reduces costs and health concerns.

Impact of Foliar Supplementation of Nitrogenous Fertilizer on Yield Attributes and Yield of Wheat (Triticum aestivum L.)

Foliar application of nitrogenous fertilizers has become a key factor in improving nitrogen use efficiency, boosting crop yields, and reducing farming costs. Liquid fertilizers are essential for precise nutrient management, ensuring crops receive the necessary nutrients throughout their growth cycle, thereby enhancing yield potential. A field experiment was conducted in the Rabi seasons of 2022-23 and 2023-24 to examine the impact of soil and foliar nitrogen supplementation on wheat growth. The experiment followed a Split Plot Design with three main plots and five subplots, each repeated thrice. The main plots included various nitrogen doses: M1 (100% recommended dose of nitrogen, RDN), M2 (75% RDN), and M3 (50% RDN). The subplots tested different foliar treatments: S1 (one spray of nano urea at the tillering stage), S2 (two sprays of nano urea at the tillering and jointing stages), S3 (two sprays of 5% urea at the tillering and jointing stages), S4 (one spray of NPK 19:19:19 at the tillering stage), and S5 (no spraying, control). The results showed that the full recommended nitrogen dose significantly improved wheat yield and related characteristics. The 100% RDN increased grain yield (4309 kg/ha), straw yield (6307 kg/ha), biological yield (10616 kg/ha), harvest index (40.58%), number of ear heads per square meter (324.39), ear head length (10.11 cm), number of grains per ear head (47.93), and 1000-grain weight (42.49 g) compared to the 75% and 50% RDN treatments. Moreover, foliar nitrogen application enhanced grain and straw yields. The highest ear head number (320.69), ear head length (9.89 cm), grains per ear head (47.44), 1000-grain weight (42.03 g), grain yield (4229 kg/ha), straw yield (6301 kg/ha), biological yield (10530 kg/ha), and harvest index (40.69%) were observed with two sprays of 5% urea at the tillering and jointing stages. This treatment performed similarly to two sprays of nano urea. Therefore, two spray of urea (5%) at tillering (45 DAS) and jointing (65 DAS) stage of wheat along with RDF would improve the performance of Wheat.

Assessment of the Health Impacts of Sewage Water Irrigation on Agricultural Workers

Wastewater can be explored as an alternative water resource for irrigation in arid and semi-arid areas. In addition to conserving surface and subsurface water resources, the safe use of treated sewage water can increase crop yields. Despite numerous studies on wastewater irrigation, relatively limited research has been undertaken on the health impacts of wastewater irrigation on agricultural workers was undertaken. Many regions lack robust health monitoring systems for agricultural workers, making it difficult to assess the long-term health impacts of wastewater exposure. There is an urgent need to explore impacts of wastewater irrigation on farmworkers’ health. It is of an utmost importance to consider advantages as well as the risks of wastewater irrigation to public health and the environment. With this objective, experiments focusing on sewage water reuse for the irrigation of Wheat and Green gram crops were conducted at the Campus of Nirma University, Ahmedabad. The study design took into account several treatments based on the use of sewage water, groundwater, and surface water in various blending ratios. The design of the studies also takes into account different treatments based on the application of nitrogenous fertilizer to soils. A total of three replications were performed for all experiments for wheat & green gram crops. The methodology involves assessing the health impacts on agricultural workers as a result of their exposure to pathogens associated with wastewater. The impacts on public health under said treatments are analyzed and discussed in the paper. Lead levels, Total Bilirubin, Conjugated Bilirubin, Unconjugated Bilirubin, SGPT, Polymorphs, Lymphocytes, Eosinophils, Monocytes and Basophils were found to be within the normal range in agricultural workers associated with sewage water irrigation for wheat and green gram crops.

Effect of Organic Fertilizer Replacing Nitrogen Fertilizer on Major Grain Yield in China

To comprehensively assess the changing pattern of organic fertilizer substitution with nitrogen fertilizer on the yield of major grains in China, with 102 literature as the research object, through Meta-analysis we quantitatively explored the impacts of soil physicochemical properties, climatic conditions, and different nitrogen fertilizer replacement rates and supplemental application amounts. The results showed that the replacement of nitrogen fertilizer by organic fertilizer could increase crop yields compared with those from the application of nitrogen fertilizer alone, and soil quick-acting potassium content, pH, and annual average temperature had the most significant effects on the yields of the three major grains. When the nitrogen fertilizer replacement rate and the amount of supplemental nitrogen fertilizer applied were 31.06% and 241.78 kg·hm-2, 26.52% and 173.31 kg·hm-2, and 39.23% and 149.17 kg·hm-2, the optimum yield increase ratios of 3.31%, 3.32%, and 1.08% were achieved for maize, wheat, and rice, respectively. Thus, the results of this study can provide a reference basis for rational fertilizer application in future crop production and help promote green agriculture.

Effect of Different Nitrogen Levels on Growth, Yield, and Nitrogen Use Efficiency (NUE) of Hardinath Hybrid Dhan-1 in Madhesh Province, Nepal

Determining the optimum dose of nitrogen fertilizer application for hybrid rice is vital for boosting production and productivity of rice. Therefore, this study examines the effect of different nitrogen levels on the growth, yield, and nitrogen use efficiency (NUE) of Hardinath Hybrid Dhan-1 in Madhesh Province, Nepal. A field experiment conducted in 2020 at the National Rice Research Program, Hardinath, Dhanusha tested six nitrogen levels (0, 75, 100, 125, 150, and 175 kg ha-1) with four replications under Randomized Complete Block Design during rainy season (June-September). The results showed that nitrogen application significantly improved plant growth and yield, with the highest grain yield (4.99 t ha-1) achieved at 150 kg N ha-1. Increasing nitrogen beyond this level did not further boost yield, indicating that excessive nitrogen does not improve productivity. Nitrogen use and agronomic efficiency were also highest at 150 kg N ha-1, marking it as the ideal rate for optimal rice performance. Soil health, in terms of organic matter and nutrient availability, improved with higher nitrogen levels, while the highest nitrogen uptake occurred at 175 kg N ha-1. In conclusion, 150 kg N ha-1 is recommended as the optimal nitrogen level to enhance hybrid rice yield and NUE, promoting sustainable rice production in the region. These findings highlight the need for optimal nitrogen management to improve crop yield and soil properties while minimizing environmental impact.

A meta-analysis of the effects of nitrogen fertilizer application on maize (Zea mays L.) yield in Northwest China.

Nitrogen fertilizer application is an important method for the production of high-quality maize. However, nitrogen fertilizer addition patterns vary according to regional climate, field management practices, and soil conditions. In this study, a meta-analysis was used to quantify the yield effects of nitrogen addition on maize, and meta-regression analysis and a random forest model were used to study the main factors affecting the yield effects of nitrogen addition on maize. The results showed that nitrogen addition significantly increased maize yield by 50.26%-55.72%, and a fluctuating increasing trend was observed with the advancement of the experimental year. The increase in maize yield upon nitrogen addition was the highest in Gansu Province, and showed a decreasing trend with the rise in average annual temperature, but did not change significantly with the average annual precipitation. Among the field management factors, the increase in maize yield was better with the variety Qiangsheng 51, topdressing at the jointing and tasseling stages (JS, TS), nitrogen application rate of 175-225 kg·ha-1, and controlled release of nitrogen fertilizer and urea (CRNFU) or the application of a combination of organic and inorganic nitrogen (OIF). Moreover, the positive effects of nitrogen fertilizer application on maize yield improved with soil pH, organic matter, available potassium, available phosphorus, and total nitrogen content; decreased with soil carbon and nitrogen ratio and available nitrogen (AN) content; and were enhanced in chestnut soil, clay, and at a bulk density of 1.2-1.4 g·cm-3. Random forest model and multifactorial optimization revealed that the effects of nitrogen addition on maize yield in Northwest China were primarily influenced by experimental year, variety, soil type, AN, and soil pH.

Effects of Different Nitrogen Fertilizer Application Rates on Soil Microbial Structure in Paddy Soil When Combined with Rice Straw Return.

Metagenomic sequencing of the microbial soil community was used to assess the effect of various nitrogen fertilizer treatments in combination with constant rice straw return to the soil in the tiller layer of Northeast China's black paddy soil used for rice production. Here, we investigated changes in the composition, diversity, and structure of soil microbial communities in the soil treated with four amounts of nitrogen fertilizers (53, 93, 133, and 173 kg/ha) applied to the soil under a constant straw return of 7500 kg/ha, with a control not receiving N. The relationships between soil microbial community structure and soil physical and chemical properties were determined. The results showed that the available K content of the soil significantly (p < 0.05) increased in soil receiving the lowest N-fertilizer dose. When applied at high amounts, N-fertilizer changed the Chao1 and ACE indices of the soil microorganisms (p < 0.05), and the treatments resulted in significant differences in the β-diversity of the soil microorganisms. By NMDS analysis it was demonstrated that the treatment significantly affected the structure of the soil microbial communities. Redundancy analysis showed that the main physicochemical drivers behind these differences were total nitrogen, total potassium, ammonium nitrogen, total phosphorus, and available potassium. The soil microbial communities in the control treatment were negatively correlated with nitrate and ammonium nitrogen; the lowest N-fertilizer treatment produced positive correlations with total nitrogen, total potassium, and total phosphorus and negative correlations with ammonium nitrogen; the highest dose negatively correlated with total nitrogen, available potassium, available phosphorus, total phosphorus, and pH. This study showed that moderate N fertilizer application is an effective way to increase soil microbial diversity and improve soil quality. This experiment provides technical support for the application of the alternative fertilizer technology of straw return to the field and provides a theoretical basis for rational fertilization of paddy fields in a cold climate.

Nitrogen fertilizer application for improving the biomass, quality, and nitrogen fixation of alfalfa (Medicago sativa L.) at different growth stages in a saline‒alkali soil.

The application of nitrogen (N) fertilizer to alfalfa (Medicago sativa L.) has received little attention due to the ability of this plant to fix N. However, N deficiency stress is often observed in marginal lands of China, especially in saline-alkali soils. Thus, this study aimed to assess the response of alfalfa yield, quality, N fixation, and soil N concentration to N fertilizer application at different stages in saline-alkali soil of Inner Mongolia. A 2-year (2020 and 2021) field experiment with five N fertilizer application rates, namely, 0 (N0), 20 (N20), 60 (N60), 120 (N120) and 180 (N180) kg N ha-1, was conducted in Inner Mongolia. The results showed that N fertilizer application of 180 kg ha-1 significantly increased the total alfalfa yield by 29%-32% by improving the stem‒leaf ratio; however, it didn't lead to a further increase in alfalfa quality. N fertilizer applications of 60 and 120 kg ha-1 significantly improved the crude protein by 10.6%-22.7% and reduced the acid or neutral detergent fiber by 10.0%-18.7% in vegetative and bud stages, respectively, by improving the leaf N concentration. Furthermore, the fraction of N derived from the atmosphere reached 68.6%, with a significant increase in the corresponding amount of N fixed in N60. Soil NO3 --N concentrations significantly increased by 24.1%-33.3%, and NH4 +-N concentrations increased by 1 to 3 times when N fertilizer application exceeded 120 kg N ha-1 compared with that in N0. Overall, this study revealed the essential role of N fertilizer application at low rates in alfalfa production, as this practice not only increases alfalfa yield but also improves N fixation in saline‒alkali soil. However, it did not result in further improvement in alfalfa quality at the early flowering stage. The findings provides valuable guidance for N fertilizer application in alfalfa production on saline‒alkali soils.

Presentation of the PRIMA project: new low cost strategies of crop based on biodiversity and remote sensing to reduce the application of nitrogen fertilizers in the Mediterranean area

Presentation of the PRIMA project: new low cost strategies of crop based on biodiversity and remote sensing to reduce the application of nitrogen fertilizers in the Mediterranean area