Optimum Nitrogen Fertilizer Research Articles

Optimizing nitrogen fertilization rate to achieve high yield and high soil quality in paddy ecosystems with straw incorporation.

Plastic film mulching is a potentially water-saving cultivation strategy, while straw return coupled with nitrogen (N) fertilization can ensure sustainable soil productivity and increased soil organic matter (SOM) sequestration. Nevertheless, a comprehensive understanding of how soil quality and agronomic productivity respond to long-term N fertilization and straw incorporation practices under non-flooded conditions with plastic film mulching remains elusive. Herein, a 15-year field experiment with straw incorporation practices (straw return and no straw return) under various N fertilization rates (N0, N1, N2, N3, and N4: 0, 45, 90, 135, and 180kgN ha-1, respectively) was conducted to explore their long-term effects. Compared with N0, N fertilization significantly improved rice yield (52.2-74.0%) and plant N uptake (50.1-96.8%). Effective panicle density was the primary component affecting rice yield under different N conditions. However, N use efficiency was lowest under 180kgN ha-1. N fertilization primarily impacted rice yield by directly supplying N for rice growth, accounting for 79% of the rice yield variation. The modest enhancement in rice yield resulting from straw return was attributed to its positive effects on soil physicochemical properties. Straw return increased alkali-hydrolyzable nitrogen, Olsen-phosphorus, and NH4OAc-exchangeable potassium by 3.4%, 10.4%, and 38.5%, respectively. N fertilization rates altered the impact of straw return on SOM; SOM increased in N2 and N4 under straw return, whereas no difference was observed between the straw management groups under N0, N1, or N3 fertilization. Moreover, while higher N fertilization rates decreased the soil quality index (SQI), straw return offset this negative effect. Considering rice yield, N use efficiency, and SQI, straw return treatment coupled with N application rate of 135kgha-1 was deemed suitable for sustainable rice production with plastic film mulching.

Basic Characteristics of Ionic Liquid-Gated Graphene FET Sensors for Nitrogen Cycle Monitoring in Agricultural Soil.

Nitrogen-based fertilizers are crucial in agriculture for maintaining soil health and increasing crop yields. Soil microorganisms transform nitrogen from fertilizers into NO3--N, which is absorbed by crops. However, some nitrogen is converted to nitrous oxide (N2O), a greenhouse gas with a warming potential about 300-times greater than carbon dioxide (CO2). Agricultural activities are the main source of N2O emissions. Monitoring N2O can enhance soil health and optimize nitrogen fertilizer use, thereby supporting precision agriculture. To achieve this, we developed ionic liquid-gated graphene field-effect transistor (FET) sensors to measure N2O concentrations in agricultural soil. We first fabricated and tested the electrical characteristics of the sensors. Then, we analyzed their transfer characteristics in our developed N2O evaluation system using different concentrations of N2O and air. The sensors demonstrated a negative shift in transfer characteristic curves when exposed to N2O, with a Dirac point voltage difference of 0.02 V between 1 and 10 ppm N2O diluted with pure air. These results demonstrate that the ionic liquid-gated graphene FET sensor is a promising device for N2O detection for agricultural soil applications.

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.

Morphological and agronomic features of potato cv. Gardena highly resistant to Phytophthora infestans (Mont.) de Bary depending on the nitrogen dose

In a 2-year field study, the impact of mineral nitrogen fertilization on the productivity of a new potato cultivar, promising due to the highest resistance to potato late blight among the registered ones, was compared to the proven, widely cultivated Denar cultivar. The study determined morphological features (size and weight of organs), physiological indicators (cover of soil by leaves – LAI. leaf greenness – SPAD) of potato plants during the growing season, yield and quality characteristics of tubers and optimal level of nitrogen fertilization. Tuber quality was assessed based on the share of tuber size and external defects in the yield structure. Optimal mineral nitrogen fertilization was determined based on the relationship between the increase in tuber yield and the increasing dose of this ingredient. The research took into account two factors: nitrogen dose (0, 50 kg‧ha–1, 100 kg‧ha–1, 150 kg‧ha–1) and cultivar (Gardena and Denar). The increase in the dose of mineral nitrogen fertilization to 150 kg‧ha–1 resulted in a significant increase in plant height, the weight of the root system, stems, leaves and the share of large tubers in the yield. It was shown that the Gardena cultivar was characterized by greater requirements for mineral nitrogen fertilization, low effectiveness of its use, a higher share of large tubers (diameter above 60 mm) and lower tuber yield than the Denar cultivar. In a year characterized by excess rainfall, plants produced a greater mass of the root system and the mass of the above-ground part, and in a year with an amount of rainfall close to optimal the final yield of tubers and the share of large tubers in the yield were higher.

Effects of NPS Fertilizer Rate on Yield and Yield Components of Bread Wheat Production in Degem District, North Shewa Zone, Oromia, Ethiopia

Productivity of wheat was low due to depleted soil fertility and the blanket use of fertilizers. Fertilizer is the most vital input, contributing significantly to final wheat yields although wheat yields have long been low due to a lack of soil test-based site-specific fertilizer recommendations. This study aimed to determine an economically appropriate rate of NPS fertilizer based on calibrated Phosphorus for bread wheat production in the Degem district. The experiments laid out in randomized complete block design (RCBD) with three replications. The treatments were based on already determined Phosphorous critical and requirement factors and consisted of 100% Pc from TSP fertilizer, 25%, 50%, 75%, and 100% Pc from NPS fertilizer and control (without fertilizer). The phosphorus requirement factor (Pf) (5.85), phosphorus critical (Pc) (22 ppm), and optimum nitrogen optimum nitrogen (92 kg ha<sup>-1</sup>) were used from previous studies. Improved bread wheat variety senete was used at 150 kg/ ha seeds rate. The results of a statistical analysis of variance demonstrated that NPS fertilizer rates based on calibrated phosphorus had significant effects on bread wheat production. Partial budget analysis shows the maximum net benefit (101,570.65 Birr ha<sup>-1</sup>) with an acceptable marginal rate of return (MRR) (932’52 %) through the application of 75% of Pc from NPS with optimum nitrogen fertilizer use. Consequently, 75% Pc from NPS should be used in the Degem district for bread wheat production, with the optimum nitrogen. Thus, further scaled-up and demonstration of the technologies for bread wheat production in the Degem district.

Optimizing nitrogen fertilizer for improved root growth, nitrogen utilization, and yield of cotton under mulched drip irrigation in southern Xinjiang, China

The root system plays a crucial role in water and nutrient absorption, making it a significant factor affected by nitrogen (N) availability in the soil. However, the intricate dynamics and distribution patterns of cotton (Gossypium hirsutum L.) root density and N nutrient under varying N supplies in Southern Xinjiang, China, have not been thoroughly understood. A two-year experiment (2021 and 2022) was conducted to determine the effects of five N rates (0, 150, 225, 300, and 450 kg N ha−1) on the root system, shoot growth, N uptake and distribution, and cotton yield. Compared to the N0 treatment (0 kg N ha−1), the application of N fertilizer at a rate of 300 kg N ha−1 resulted in consistent and higher seed cotton yields of 5875 kg ha−1 and 6815 kg ha−1 in 2021 and 2022, respectively. This N fertilization also led to a significant improvement in dry matter weight and N uptake by 32.4% and 53.7%, respectively. Furthermore, applying N fertilizer at a rate of 225 kg N ha−1 significantly increased root length density (RLD), root surface density (RSD), and root volume density (RVD) by 49.6–113.3%, 29.1–95.1%, and 42.2–64.4%, respectively, compared to the treatment without N fertilization (0 kg N ha−1). Notably, the roots in the 0–20 cm soil layers exhibited a stronger response to N fertilization compared to the roots distributed in the 20–40 cm soil layers. The root morphology parameters (RLD, RSD, and RVD) at specific soil depths (0–10 cm in the seedling stage, 10–25 cm in the bud stage, and 20–40 cm in the peak boll stage) were significantly associated with N uptake and seed cotton yield. Optimizing nitrogen fertilizer supply within the range of 225–300 kg N ha−1 can enhance root foraging, thereby promoting the interaction between roots and shoots and ultimately improving cotton production in arid areas.

Greenhouse gas emissions and mitigation potential of crop production in Northeast China

Agricultural management practices that reduce greenhouse gas (GHG) emissions have been identified as effective mitigation strategies. However, research on carbon emissions from major crops in Northeast China focuses on national and provincial data, overlooking city-scale variability and uncertainties, which prevents fine-scale assessment of crop emissions reduction potential. To address this, a life cycle assessment (LCA) combined with the Monte Carlo method was conducted to estimate the carbon footprint of rice, maize, and soybean production for different cities in Northeast China from 1991 to 2020. The results showed that the top one-third of cities with the highest total carbon emissions (TCE) account for approximately 40 % of the region's TCE. Nitrogen losses and production processes related to nitrogen fertilizer application were identified as the primary contributors to TCE from crop production, accounting for 29.6–62.5 % of the total, with a relative importance of 58.5–78.2 %. Scenario analysis indicated that optimizing nitrogen fertilizer management and reducing active nitrogen losses are the most effective strategies for reducing TCE from major crop production, offering a reduction potential of 34.5–60.6 %. Recommended strategies include phased application of nitrogen fertilizer, the addition of nitrification inhibitors, or using slow-release nitrogen fertilizers, combined with appropriate increases in crop planting density, straw return decomposition technologies and water-saving irrigation methods to reduce GHG emissions. These strategies aim to achieve low-carbon sustainable grain production and provide a foundation for exploring the emissions reduction potential of agricultural inputs and optimizing regional crop layouts, offering new insights for developing more effective GHG reduction strategies.

Optimizing nitrogen fertilization in maize: the impact of nitrification inhibitors, phosphorus application, and microbial interactions on enhancing nutrient efficiency and crop performance.

Despite the essential role of nitrogen fertilizers in achieving high crop yields, current application practices often exhibit low efficiency. Optimizing nitrogen (N) fertilization in agriculture is, therefore, critical for enhancing crop productivity while ensuring sustainable food production. This study investigates the effects of nitrification inhibitors (Nis) such as Dimethyl Pyrazole Phosphate (DMPP) and Dimethyl Pyrazole Fulvic Acid (DMPFA), plant growth-promoting bacteria inoculation, and phosphorus (P) application on the soil-plant-microbe system in maize. DMPFA is an organic nitrification inhibitor that combines DMP and fulvic acid for the benefits of both compounds as a chelator. A comprehensive rhizobox experiment was conducted, employing varying levels of P, inoculant types, and Nis, to analyze the influence of these factors on various soil properties, maize fitness, and phenotypic traits, including root architecture and exudate profile. Additionally, the experiment examined the effects of treatments on the bacterial and fungal communities within the rhizosphere and maize roots. Our results showed that the use of Nis improved plant nutrition and biomass. For example, the use of DMPFA as a nitrification inhibitor significantly improved phosphorus use efficiency by up to 29%, increased P content to 37%, and raised P concentration in the shoot by 26%, compared to traditional ammonium treatments. The microbial communities inhabiting maize rhizosphere and roots were also highly influenced by the different treatments. Among them, the N treatment was the major driver in shaping bacterial and fungal communities in both plant compartments. Notably, Nis reduced significantly the abundance of bacterial groups involved in the nitrification process. Moreover, we observed that each experimental treatment employed in this investigation could select, promote, or reduce specific groups of beneficial or detrimental soil microorganisms. Overall, our results highlight the intricate interplay between soil amendments, microbial communities, and plant nutrient dynamics, suggesting that Nis, particularly DMPFA, could be pivotal in bolstering agricultural sustainability by optimizing nutrient utilization.

Optimizing Nitrogen Fertilization to Maximize Yield and Bioactive Compounds in Ziziphora clinopodioides

Optimizing Nitrogen Fertilization to Maximize Yield and Bioactive Compounds in Ziziphora clinopodioides

Optimizing Nitrogen Fertilizer Application for Synergistic Enhancement of Economic and Ecological Benefits in Rice–Crab Co-Culture Systems

The rice–crab co-culture (RC) system is a multidimensional integrated farming model with significant potential for balancing ecological and economic benefits in paddy fields. However, improper nitrogen (N) fertilizer application exacerbates greenhouse gas (GHG) emissions, degrades water quality, and disrupts the balance of the RC ecosystem. Therefore, optimizing and improving N management strategies for the RC system is crucial to maximize its ecological and economic benefits. This study conducted a two-year field experiment to assess the impact of optimizing N application on the productivity, sustainability, and economic benefits in RC systems. Comparisons were made to compare rice and crab productions, GHG emissions, and net ecosystem economic benefit (NEEB) between the RC and rice monoculture (RM) systems under different N application rates (0, 150, 210, and 270 kg ha−1) with the aim of identifying the optimal N application rate for the RC system. The results showed that the N application rate of 210 kg ha−1 in the RC system improved the agronomic traits and N use efficiency, leading to a 0.4% increase in rice yield (7603.1 kg ha−1) compared to the maximum rice yield in the RM system at 270 kg ha−1. At this application rate, surface water quality was optimal for crabs, resulting in the highest crab yields (370.1 kg ha−1) and average weights (81.1 g). The lower N application reduced the greenhouse gas intensity (GHGI) of the RC system by 13.7% compared to the RM system. The NEEB at the optimal N application rate of 210 kg ha−1 in the RC system reached 8597.5 CNY ha−1, which was 1265.7% higher than that of the RM system at 270 kg ha−1. In summary, optimizing N application in the RC system conserves N fertilizer resources, increases rice and crab yields, and reduces GHG emissions, thereby synergistically enhancing both economic and ecological benefits. Optimizing the N application rate has greater potential in other innovative RC models, and the productivity, sustainability, and economic efficiency should be further investigated.

Evaluation of the PROMET model for yield estimation and N fertilization in on-farm research

IntroductionSatellite-sourced data have become a valuable resource for precision agriculture because they provide crucial insights into various parameters that are essential for effective crop management. An array of practical agricultural tools provides comprehensive data for assessing crop biomass, soil conditions, and plant stress symptoms, predicting yields, and performing other functions. Satellite data, when combined with in situ data from different sources, can significantly enhance biomass and yield estimations.Material and MethodsThe ability of the “PROcesses of radiation, Mass and Energy Transfer” (PROMET) model to predict crop biomass and grain yield and to optimize nitrogen fertilization during the vegetation period was investigated. Field trials were conducted to assess the accuracy and limitations of biomass and yield predictions.Results and ConclusionThe predicted yields were sufficiently accurate on a whole-field basis, and site-specific values showed strong correlations. In additional field trials with different fertilization strategies, the highest yield and nitrogen efficiency were observed for the PROMET-based strategy. Additional experiments with different crops and greater durations are needed to draw a more reliable conclusion.

Metabolomics Uncovers the Mechanisms of Nitrogen Response to Anthocyanins Synthesis and Grain Quality of Colored Grain Wheat (Triticum aestivum L.).

Nitrogen (N) is a key factor for plant growth and affects anthocyanin synthesis. This study aimed to clarify the potential mechanisms of N levels (LN, 0 kg·ha-1; MN, 150 kg·ha-1; HN, 225 kg·ha-1) in anthocyanin synthesis and grain quality of colored grain wheat. HN increased the yield component traits and grain morphology traits in colored grain wheat while decreasing the processing and nutrient quality traits. Most quality traits were significantly negatively correlated with the yield composition and morphological traits. Anthocyanin was more accumulated under LN conditions, but other related yield and morphological traits of colored grain wheat declined. The anthocyanin content was the highest in blue wheat, followed by that in purple wheat. Cyanidin-3-O-(6-O-malonyl-β-d-glucoside) and cyanidin-3-O-rutinoside were the predominant anthocyanins in blue and purple wheat. The identified anthocyanin-related metabolites were associated with flavonoid biosynthesis, anthocyanin biosynthesis, and secondary metabolite biosynthesis. Therefore, the study provided information for optimizing nitrogen fertilizer management in producing high quality colored wheat and verified the close relationship between anthocyanin and low N condition.

Optimizing nitrogen fertilization and planting density management enhances lodging resistance and wheat yield by promoting carbohydrate accumulation and single spike development

AbstractNitrogen fertilizer application and increasing planting density have been recognized as essential measures to achieve higher wheat (Triticum aestivum L.) yields. However, inadequate management practices often lead to poor culm quality and lodging. We hypothesized that optimizing culm characteristics could be a feasible approach to improving both lodging resistance and yield. In this study, field experiments involved five nitrogen levels (0, 180, 240, 300, and 360 kg ha−1) and three planting densities (225, 375, and 525 × 104 ha−1). Two wheat cultivars with different lodging resistance were selected and their culm morphological characteristics, biochemical components, field lodging rate, and yield in different treatments were measured. We found that field lodging rate in wheat was negatively correlated with yield, and there was a contradiction between increasing spike number and lodging resistance. Culm carbohydrate accumulation affected field lodging rate by regulating culm quality rather than the center of gravity height. Compared with Xinmai 26, Xinhuamai 818 had higher culm carbohydrate accumulation, which increased the breaking strength and yield by 14.2% and 17.0%. Nitrogen application and planting density had significant effects on yield and lodging resistance. Compared with N0 treatment, increasing nitrogen application rate improved yield of 67.2%–83.2% by increasing spike number and grain number per spike, and the N2 treatment showed the largest increase. Planting density had little effect on yield. Reducing planting density can increase the culm carbohydrate accumulation and enhance lodging resistance. Compared with D3 treatment, the culm breaking strength was increased by 27.6% under the D1 treatment. This study determined that the optimal combination of nitrogen and density for improving wheat lodging resistance and yield is 240 kg ha−1 and 225 × 104 ha−1. This combination enhances culm breaking strength by increasing carbohydrate accumulation and achieves high yield by increasing grain number per spike, 1000‐grain weight, and stabilizing spike number.

Balancing Yield and Environmental Impact: Nitrogen Management and Planting Density for Rice in Southwest China

With growing concerns about global warming, it is crucial to adopt agronomic practices that enhance rice yields from paddy fields while reducing greenhouse gas (GHG) emissions for sustainable agriculture. An optimal nitrogen (N) fertilization rate and planting density are vital to ensure high rice yields, minimize GHG emissions, and understand emission behavior for better field management. We hypothesized that optimizing N application rates and planting density to improve nitrogen use efficiency (NUE) in rice cultivation would reduce resource losses and GHG emissions. To test this hypothesis, we implemented five treatments with a rice straw return cultural system: two planting densities (16 hills m−2 (traditional density, D1) and 20 hills m−2 (25% higher density, D2)) and three N application rates (no N fertilizer (N0), 180 kg N ha−1 (N1), and 144 kg N ha−1 (N2)). The control treatment (CK) was traditional planting density with no N fertilizer. The four new cropping modes were N1D1, N1D2, N2D1, and N2D2. We investigated the effects of N application rates and planting density on rice grain yield, NUE, and GHG emissions in multiple rice-growing seasons. The N1D2 treatment exhibited the highest grain yield over the three years, with a value of 10,452 kg ha−1, representing an increase of 12.2% compared to CK. Moreover, N uptake in N1D2 was the highest, averaging 39.2% (p < 0.05) higher than CK, and 8.5%, 3.5%, and 2.8% (p < 0.05) higher than N1D1, N2D1 and N2D2, respectively. N2D2 exhibited the highest NUE, with a value of 58.99 kg kg−1, surpassing all other treatments over the three years. GHG emissions, global warming potential (GWP), and greenhouse gas intensity (GHGI) in N2D2 were lower than in N1D1, N1D2, and N2D1. Additionally, reducing N application (comparing N1D1 to N2D1) and increasing plant density (comparing N1D1 to N1D2) improved N agronomic efficiency (NAE) and N partial productivity (PFPN). The negative correlation between the NAE and PFPN with GWP and GHG emissions further supports the potential for optimized N management and denser planting density to reduce environmental impact. These findings have important implications for sustainable rice cultivation practices in Southwest China and similar agroecosystems, emphasizing the need for integrated nutrient management strategies to achieve food security and climate change mitigation goals.

Assessing the Fates of Water and Nitrogen on an Open-Field Intensive Vegetable System under an Expert-N System with EU-Rotate_N Model in North China Plain.

Nitrate leaching, greenhouse gas emissions, and water loss are caused by conventional water and fertilizer management in vegetable fields. The Expert-N system is a useful tool for recommending the optimal nitrogen (N) fertilizer for vegetable cultivation. To clarify the fates of water and N in vegetable fields, an open-field vegetable cultivation experiment was conducted in Dongbeiwang, Beijing. This experiment tested two irrigation treatments (W1: conventional and W2: optimal) and three fertilizer treatments (N1: conventional, N2: optimal N rate by Expert-N system, and N3: 80% optimal N rate) on cauliflower (Brassica oleracea L.), amaranth (Amaranthus tricolor L.), and spinach (Spinacia oleracea L.). The EU-Rotate_N model was used to simulate the fates of water and N in the soil. The results indicated that the yields of amaranth and spinach showed no significant differences among all the treatments in 2000 and 2001. However, cauliflower yield under the W1N2 and W1N3 treatments obviously reduced in 2001. Compared with the W1 treatment, W2 reduced irrigation amount by 27.9-29.8%, water drainage by over 76%, increased water use efficiency by 5-17%, and irrigation water use efficiency by 29-45%. Nitrate leaching was one of the main pathways in this study, accounting for 8.4% of the total N input; compared to N1, the input of fertilizer N under the N2 and N3 treatments decreased by over 66.5%, consequently reducing gaseous N by 48-72% and increasing nitrogen use efficiency (NUE) by 17-37%. Additionally, compared with the W1 treatments, gaseous N loss under the W2 treatments was reduced by 18-26% and annual average NUEs increased by 22-29%. The highest annual average NUEs were under W2N3 (169.6 kg kg-1) in 2000 and W2N2 (188.0 kg kg-1) in 2001, respectively. We found that optimizing fertilizer management allowed subsequent crops to utilize residual N in the soil. Therefore, we suggest that the W2N3 management should be recommended to farmers to reduce water and N loss in vegetable production systems.

Straw returning and nitrogen reduction: Strategies for sustainable maize production in the dryland

Implementing continue straw returning practices and optimizing nitrogen application can mitigate nitrogen losses and enhance nitrogen use efficiency (NUE) in dryland. 15N-labeled technique offers a robust approach for tracking fertilizer nitrogen fate and assessing nitrogen use efficiency. Based on the continue (>6 yr) experiment, we conducted a two-year experiment (2020 and 2021) to evaluate the effects of straw returning and nitrogen management under plastic film mulching on 15N recovery rates, N2O emissions and maize yield with three treatments: no straw returning with 225 kg N·ha−1 under plastic film mulching (RP-N225), straw returning with 225 kg N·ha−1 under plastic film mulching (RPS-N225), and straw returning with 20% nitrogen reduction (180 kg N·ha−1) under plastic film mulching (RPS-N180). After six years, both continue straw returning with plastic film mulching increased uptake of fertilizer nitrogen, had higher 15N recovery rates than RP-N225, leading to increased 15N accumulation in grain and aboveground biomass, ultimately enhancing yield. The RPS-N225 treatment exhibited the highest spring maize yield and nitrogen harvest index. The RPS-N180 treatment significantly increased maize yield more than RP-N225 and had the highest NUE, partial factor productivity of nitrogen fertilizer, and nitrogen uptake efficiency, with improvements ranging from 1.7 to 2.4%, 19.3–29.6%, and 17.3–27.5%, respectively, compared to the other treatments. Moreover, RPS-N225 resulted in significantly higher cumulative N2O emissions and yield-scaled N2O emissions than the other treatments, whereas the RPS-N180 treatment significantly decreased yield-scaled N2O emissions compared to RP-N225. Hence, combining continue straw returning with appropriate nitrogen reduction can effectively increase maize yield and yield-scaled N2O emissions. By offering insights into optimizing nitrogen fertilizer management after continue maize straw return, this study is contributed to widespread adoption of straw return practices and sustainable agricultural development in semi-arid areas.

Effects of Planting Density and Nitrogen Management on Light and Nitrogen Resource Utilization Efficiency and Yield of Summer Maize in the Sichuan Hilly Region

The low efficiency of light and nitrogen resources, poor yield and profit, and environmental pollution of maize production are main problems in many areas of China. We hypothesized that optimizing nitrogen fertilizer density management strategies could alleviate the above issues. To address this, a 3-year on-site experiment with three planting densities and four nitrogen rates was conducted in the Sichuan Hilly Region. The results indicated that increasing the planting density could increase the extinction coefficient and solar radiation interception of maize populations as well as enhance the utilization efficiency of light and nitrogen resources and yield. For every 100 kg ha−1 increase in nitrogen fertilizer, RUE increased by 0.16%, NUE decreased by 25.0%, and soil apparent nitrogen loss quantity increased by 67.8 kg ha−1. There was a certain interaction between planting density and nitrogen rate. The appropriate planting density and nitrogen rate combination was 67,500 plants ha−1 with 180 kg N ha−1 under the experimental condition. Excessive close planting in weak-light areas and excessive nitrogen reduction after densification are not advisable. This study indicated that nitrogen–density strategies should be matched with the local natural resources such as sunlight. The results provide a theoretical for high-yield and high-quality maize production in these areas.

Optimizing Nitrogen Fertilization for Enhanced Rice Straw Degradation and Oilseed Rape Yield in Challenging Winter Conditions: Insights from Southwest China

The crop straw returning to the field is a widely accepted method to utilize and remediate huge agricultural waste in a short period. However, the low temperatures and dry conditions of the winter season in Southwest China can be challenging for the biodegradation of crop straw in the field. With a similar aim, we designed a short-term study where rice straw was applied to the field with different concentrations of nitrogen (N) fertilizer while keeping phosphorus (P) constant; CK, (N0P0); T1, (N0P90); T2, (N60P90); T3, (N120P90); and T4, (N180P90) were added to evaluate its impact on straw degradation during cold weather. We found that high fertilization (T4) significantly improved crop yield, organic matter, and lignocellulose degradation under cold temperatures (21.5–3.2 °C). It also significantly improved soil nitrogen agronomic efficiency, nitrogen use efficiency, and nitrogen physiological efficiency. The yield was highest in T4 (1690 and 1399 kg/ha), while T3 acted positively on soil lignocellulolytic enzyme activity, which in turn resulted in higher degradation of OM and lignocellulosic material. Pearson’s correlation analysis revealed that total nitrogen, total phosphorus, available nitrogen, and available phosphorus were important variables that had a significant impact on soil EC, bulk density, water holding capacity, and soil enzymes. We found that nitrogen application significantly changed the soil bacterial community by increasing the richness and evenness of lignocellulolytic bacteria, which aided the degradation of straw in a short duration. This study’s finding indicates that the decomposition of crop straw in the field under cold weather stress was dependent on nutrient input, and N, in an appropriate amount (N120-180), was suitable to achieve higher yield and higher decomposition of straw in such an environment.

Evaluating the effects of the CERES-Rice model to simulate upland rice (Oryza sativa L.) yield under different plant density and nitrogen management strategies in Fogera Plain, Northwest Ethiopia

This study assessed the optimal nitrogen (N) fertilizer rate and planting density for the well-adapted upland rice cultivar NERICA_4 on the Fogera Plain. The primary objective was to evaluate the effects of varied planting densities and N-fertilizer rates on upland rice yield and other agronomic parameters. A two-year field study (2020 and 2021) was conducted at the Fogera Rice Research Field Station, testing nine plant densities (75, 87, and 98; 72, 82, and 91; 70, 79, and 89 plants per m2 and two N rates (115 and 138 kg N ha−1). The Crop Simulation Model Crop Environment Resource Synthesis (CSM-CERES-Rice) within the Decision Support System for Agrotechnology Transfer (DSSAT) framework was calibrated and validated using site-specific weather, soil, crop, and agronomic management data from the experiment. Results on the subsequent RMSE, RMSEn, and d index values during the calibration phase were 0.074 t ha−1, 1.82 %, and 0.86 of grain yield; 0.307 t ha−1, 3.36 %, and 0.87 of by-product yield; 0.489 t ha−1, 3.74 %, and 0.79 of top dry biomass yield; and 0.28, 8.24 %, and 0.63 of leaf area index values, respectively. Whereas results on the corresponding RMSE, RMSEn, and d index values during the evaluation phase were: 0.58 t ha−1, 1.33 %, and 0.90 of grain yield; 0.69 t ha−1, 0.58 %, and 0.99 of by-product yield; 0.678 t ha−1, 4.36 %, and 0.67 of top dry biomass yield; and 0.75, 13.92 %, and 0.74 of leaf area index, respectively. The findings of the long-term simulation showed that a 23 % increase in grain yield was achieved with 138 kg N ha−1 and 87 plants per m2 of planting density, as compared to 115 kg N ha−1 and 75 plants per m2 of plant density. The recommended optimum plant density and N fertilizer rate were 138 kg N ha−1 with PD2 of plant density for upland rice production in the Fogera Plain.

Optimizing fertilization depth to promote yield performance and economic benefit in maize for hybrid seed production

Fertilization depth adjustment is a well-known strategy for increasing crop yields. However, the precise mechanism associated with this strategy remains unclear, particularly regarding increased nutrient absorption and utilization, and maize seed production. Thus, we examined the effects of different nitrogen fertilization depths [0 cm (L0), 5 cm (L5), 15 cm (L15), and 25 cm (L25)] on maize crop growth, nutrient uptake and distribution, fertilizer use efficiency, grain yield, and economic benefits in a field study conducted for two years (2021–2022) in Hexi Oasis Irrigation Area, northwest China. The optimal nitrogen fertilization depth was crucial for enhancing growth, dry matter production, and the grain yield. In particular, compared with L15 and L5, L25 significantly (P < 0.05) increased the average plant height by 5.00 % and 10.36 %, respectively, and dry matter accumulation by 2.65 % and 3.39 %. Furthermore, compared with L5 and L15, the total nutrient uptake was 19.17 % (P < 0.05) and 7.11 % higher under L25, respectively, and the average grain nutrient uptake was 23.33 % higher (P < 0.05). Moreover, L25 significantly increased the N, P, and K fertilizer utilization efficiency compared with L5 and L15, and the highest dry matter to grain translocation occurred under L25. Structural equation modeling confirmed that deep nitrogen fertilization promoted growth, dry matter translocation to grain, and the uptake and distribution of nutrients in maize plants to significantly improve the fertilizer use efficiency and yield. These findings are important for guiding fertilization management practices to increase maize seed production in regions with similar climate conditions.