Nitrogen Fertilizer Application Rates Research Articles

Effects of Time and Rate of Nitrogen Fertilizer Application on Phenology, Growth and Yield of Maize at Jimma, Southwestern Ethiopia

Maize (Zea mays L.) is one of the most important crops in Ethiopia in general and in the Jimma area in particular. However, its productivity is low due to the inadequate management of nitrogen fertilizer rates and inappropriate timing of fertilizer applications. Hence, a field experiment was conducted during the 2020-2022 main cropping seasons to determine the effect of different rates and times of nitrogen applications on phenology, growth, yield, and yield components of maize and to estimate the most economical rate and time of nitrogen fertilizer application. The experiment was laid out in a factorial randomized complete block design with three replications. The experiment consisted of five rates of nitrogen (0, 46, 92,138 and 184kg N ha<sup>-1</sup>) and three times of application (Full at planting, 1/2 at planting +1/2 at the 5-leave stage, and 1/3 at planting+1/3 at 5-leave stage + 1/3 at booting). The result revealed that days to 50% tasseling, days to 90% physiological maturity, plant height, ear height, stem diameter, numbers of ears per plant, grain yield, above-ground dry biomass, and harvest index were significantly affected by either the main effects of N fertilizer rate or time of N application. The interaction of rates and time of nitrogen application affected considerably days to 50% silking. The highest mean grain yield (8355.60 kg ha<sup>-1</sup>) was recorded with applied N in three splits (1/3 at planting, 1/3 at the 5-leave stage, and 1/3 at booting) and the highest grain yield (9213.5 kg ha<sup>-1</sup>) was obtained from 184kg N ha<sup>-1</sup>. Grain yield was positively and /highly/ significantly association with days to maturity (r=35), height (r=0.30), ear height (r=0.24), girth (r=0.55), number of ears per plant (r=0.62), biomass yield (r=0.91), harvest index (r=0.35) while grain yield was negatively and/highly/ significantly association with days to tasseling (r=0.20) and days to silking (r=0.23). Partial budget analysis revealed that N in three split applications and 184kg N ha<sup>-1</sup> rate realized the maximum net benefit of 208,311.10 Birr ha<sup>-1</sup> and 226,380.2 Birr respectively. Therefore, based on the highest net benefit applying N in three splits (1/3 at planting, 1/3 at 5-leave stage, and 1/3 at booting) and 184kg N ha<sup>-1</sup> application an economic yield response and also acceptable for farmers of study areas and similar agroecology.

Logistic and Structural Equation Fitting Analyses of the Effect of Slow-Release Nitrogen Fertilizer Application Rates on the Nitrogen Accumulation and Yield Formation Mechanism in Maize

The purpose of this study is to clarify the differential effects of the application rate of slow-release nitrogen fertilizer (SRFN) on the nitrogen (N) accumulation dynamics, nutrient organ N distribution and transportation, yield, and N utilization efficiency of maize harvested using grain-type machines. This has significant implications for the scientific application of SRFN, as well as for reducing its application rate and improving its efficiency, in the agro-pastoral transitional zone of northern China. In a long-term positioning experiment that began in 2018, five treatments consisting of different SRFN application rates were set up, namely, N120 (120 kg ha−1), N180 (180 kg ha−1), N240 (240 kg ha−1), N300 (300 kg ha−1), and N360 (360 kg ha−1), with no fertilization during the growth period used as control (CK) treatment. To explore the characteristics of nitrogen accumulation dynamics in maize populations and the main factors affecting maize yield formation under the different SRFN application rate treatments, this study adopted a combination of quantitative analyses and model fitting, including logistic models, principal component analysis, and structural equation modeling. The research results show that SRFN application increased the aboveground N accumulation of the maize population, and the fitting effect of the logistic models was significant. The maximum rate of N accumulation in both years showed a trend of first increasing and then decreasing with the increase in the SRFN application rate. Compared with CK, SRFN application reduced the proportion of N distribution in the nutrient organs during the R6 stage, and it increased the N transport from the nutrient organs to the grains after the VT-R1 stage. With the increase in the SRFN application rate, both the economic yield and biological yield showed a single peak curve change and were maximized in the N240 treatment. The economic yield reached 15,342.07 kg ha−1 in 2020 and 16,323.51 kg ha−1 in 2021, increasing by 36.2% and 61.7% compared with CK, respectively. The apparent N fertilizer recovery rate, N uptake efficiency, N agronomic efficiency, and N fertilizer partial productivity all gradually decreased with the increase in the SRFN application rate. In maize populations, an appropriate SRFN application rate can adjust the characteristic parameters during the aboveground N accumulation rapid growth period, increase the N accumulation amount in aboveground parts, promote the transport of N from nutrient organs to grains, and improve yield. An application of 180–240 kg ha−1 SRFN is recommended for maize cultivation in the agro-pastoral transitional zone of northern China, as it is beneficial for stabilizing and increasing maize yield, as well as reducing the rate and improving the efficiency of N fertilizer.

Slow-Release Nitrogen Fertilizer Promotes the Bacterial Diversity to Drive Soil Multifunctionality

The application of slow-release nitrogen fertilizer not only economizes labor input, but also decreases the frequency of use of mechanical intakes, with significant implications in advancing modern intensive agricultural production. Whether slow-release nitrogen fertilizer application can influence the association between microbial diversity and soil multifunctionality remains controversial. This study analyzed the spatial variances of soil environmental factors, soil multifunctionality, and their correlations with bacterial and fungal communities under five nitrogen application rates. The key factors influencing the dominant microbial species and community structures at different spatial locations were determined by the slow-release nitrogen fertilizer application rate, and the driving factors and dominant species of soil multifunctionality were identified. In contrast to the control group, moderate slow-release nitrogen fertilizer application enhanced soil multifunctionality and ameliorated the resilience of microbial diversity loss at diverse spatial locations resulting from irrational nitrogen fertilizer application. The resilience of the fungal community to disturbances caused by fertilization was lower than that of the bacterial community. Bacterial diversity exhibited a significant correlation with soil multifunctionality, and the soil multifunctionality intensity under 240 kg ha−1 treatment increased by 159.01% compared to the CK. The main dominant bacterial communities and the dominant fungal community Ascomycota affected soil multifunctionality through slow-release nitrogen fertilizer application. Structural equation modeling and random forest analysis demonstrated that bacterial community diversity, particularly in bulk soil and the rhizosphere, community composition, and soil nitrogen form are the primary driving factors of soil multifunctionality. Results indicated that the microbial niche alterations induced by slow-release nitrogen fertilizer application positively affect soil multifunctionality.

Optimizing Irrigation and Nitrogen Levels for Enhanced Cabbage Growth in Yobe's Semi-Arid Region

This study investigated the effects of irrigation schedules and nitrogen fertilizer application rates on the growth and productivity of cabbage in Damaturu, Yobe State. Using a Randomized Complete Block Design (RCBD) in a 3x5 factorial arrangement with three replications, we tested three irrigation intervals “3, 6, and 9 days” and five nitrogen fertilizer levels “0, 25, 50, 75, and 100 kg ha⁻¹” on an improved cabbage variety (Datdiku-5m). Results indicated cabbage growth positively responded to optimal irrigation intervals and increasing nitrogen fertilizer rates. The combination of 6-day irrigation intervals and 100 kg ha⁻¹ of nitrogen fertilizer resulted in impressive outcomes: a tallest head height of 18.92 cm, the largest head diameter of 16.95 cm, maximum plant height of 24.92 cm, the largest plant spread of 37.12 cm, a maximum marketable yield of 63.5 t/ha, and the highest total yield of 71.52 t/ha (Table 3). This combination ensures an adequate supply of water and nutrients, promoting robust growth and significant yield in semi-arid region. In contrast, lower irrigation intervals (9 days) and reduced nitrogen levels (0-50 kg ha⁻¹) led to stunted growth and lower productivity metrics, illustrating the critical role of proper water and nutrient management in achieving optimal cabbage yields. Therefore, adopting a 6-day irrigation schedule and applying 100 kg ha⁻¹ of nitrogen fertilizer may effectively increase cabbage yield. Future research should explore different nitrogen fertilizer rates and the combined effects of various nutrients with different irrigation intervals to further assess their impact.

Response of Yield of Shallot (<i>Allium ascalonium</i> L.) to Nitrogen Fertilizer Rates and Spacing Under Irrigation at Mulo, Ethiopia

The shallot (<i>Allium ascalonium</i> L.) is one of the important alliaceous crops cultivated in many tropical countries. It is an important horticultural crop used to flavor the local stew "wot" and a source of income for farmers in Ethiopia. However, the productivity of shallot is low at study area due to various limiting factors such as low soil fertility, plant population and lack of improved agronomic practices. A field experiment was conducted to investigate the effect of intra-row spacing and nitrogen fertilizer levels on growth, yield and quality of shallot at Mulo District, Oromia Regional state, Ethiopia during 2021/22 off season. The treatments consisted of four intra-row spacing (5, 10, 15 and 20) cm and four levels of nitrogen fertilizer (0, 50, 100 and 150) kgNha<sup>-1</sup> tested in a randomized complete block design with three replications. Data on shallot yield was collected. The interaction effect of intra-row spacing and nitrogen fertilizer influenced the marketable yield, unmarketable yield, bulb weight, bulb fresh weight, bulb dry weight, dry matter and total yield. As a result, the treatment combination of 150kgha<sup>-1</sup> nitrogen and 15cm intra-row spacing yielded the highest net benefit of shallot (Eth-Birr 1,012,274), followed by the treatment combination of 150kgha<sup>-1</sup> nitrogen and 20 cm intra-row spacing. In conclusion, the above findings indicated that the combined application of 150kgNha<sup>-1</sup> with 15 cm spacing can improve shallot growth and productivity in the Mulo district area. However, more research needs to be done in different seasons and locations, taking into account the application rate of nitrogen fertilizer and different intra-row spacing, to generate more reliable information.

Improvement of Transplanting Rice Yield and Nitrogen Use Efficiency by Increasing Planting Density in Northeast China Under the Optimal Nitrogen Split-Fertilizer Applications

There are few studies on how nitrogen (N) fertilizer application rates and transplanting densities impact rice yield, root distribution, and N use efficiency in the cold regions of Northeast China. This research involved a two-year field trial utilizing Jinongda 667 as the material. In 2021, three N split-fertilizer applications—T1 (6:3:1), T2 (5:3:2), T3 (4:3:3)—and two transplanting densities—D1 (30 cm × 13.3 cm) and D2 (30 cm × 20 cm)—were compared with the conventional cultivation mode (T0: 175 kg N hm−2, 6:3:1), whereby the N application mode most suitable for increasing density was explored. In 2022, four N application levels—0 (N0), 125 (N1), 150 (N2), and 175 (N3) kg N hm−2—were assessed under the same density treatment to analyze the yield, resource utilization efficiency, and root traits of Jinongda 667. The results indicated that when the transplanting density was 30 cm × 13.3 cm, the application of 5:3:2 fertilizer was more conducive to improving rice yield. Increasing planting density under reduced N input significantly enhanced both rice yield and N use efficiency. In contrast to the conventional cultivation method (D2N3), the treatment of increased planting density (D1N2) under reduced N input led to a 21.2% rise in the number of panicles per square meter and an 8.6% boost in rice yield. Furthermore, increasing planting density under reduced N input significantly enhanced the agronomic efficiency of N fertilizer, the apparent utilization rate, and the N harvest index. It also boosted the SPAD value, photosynthetic rate, and the utilization efficiency of light and N resources in rice. However, it was noted that root enzyme activity decreased. This study demonstrated that increasing planting density, combined with the N application mode of 5:3:2 and an N application rate of 150 kg hm−2, maximized resource utilization efficiency, optimized root absorption capacity, and resulted in higher yields.

Effects of Different Straw Returning Periods and Nitrogen Fertilizer Combinations on Rice Roots and Yield in Saline–Sodic Soil

Straw return is an effective management practice for improving physical and chemical properties of saline–sodic soil in Northeast China. Straw decomposition and nutrient release are deeply influenced by soil and climatic factors. In Northeast China, straw decomposes slowly due to the long winter with low temperatures. Therefore, the season of straw return may be a key issue affecting rice. However, the impact of returning straw in different seasons on rice is disregarded and not commonly researched. We conducted a 2-year field experiment, including two residue management treatments: spring straw return treatment (SR) and autumn straw return treatment (AR), each containing five different N rates (0, 90, 180, 270, and 360 kg ha−1) as sub-treatments. The results reveal that, compared with the spring straw returning treatment, the autumn straw returning treatment significantly improved root morphology and root vigor and increased the number of spikes per unit area, which directly increased rice yield by 4.76% (2020) and 6.62% (2021). In addition, rice yield showed an increasing and then decreasing trend with the increase in N fertilizer application, and it was at its maximum when the N application rate was 270 kg ha−1. Compared to the spring straw return treatment, the autumn straw return treatment was able to reduce 31.46% (2020) and 38.48% (2021) of N fertilizer application without decreasing rice yield. Our findings demonstrate that straw return combined with nitrogen fertilization may be a promising management practice for improving rice root systems and yield in saline–sodic soils, and under the conditions of the autumn straw returning treatment, the best nitrogen fertilizer application rate was 270 kg ha−1.

Combination of nitrogen and organic fertilizers reduce N2O emissions while increasing winter wheat grain yields and quality in China

Wheat grain yields, quality, and nitrous oxide (N2O) emissions were controlled through the type and application rate of nitrogen (N) fertilizer. Here, we investigated the optimal management of N fertilization by examining the combined effects of organic and N fertilizers on wheat yields, quality, and N2O emissions. Field trials under six treatments were located on campus farms at Anhui Science and Technology University, including farmer’s common practice (270 kg N ha-1, N270), 2/3 reduction in N270 (90 kg N ha-1, N90), organic fertilizer with equal N270 (OF270), 2/3 reduction in OF270 (OF90), 4/5 reduction OF270 + 1/5 reduction N270 (20% OF270 + 80% N270), and 4/5 reduction OF90 + 1/5 reduction N90 (20% OF90 + 80% N90) were applied to winter wheat. The plots were arranged in a randomized complete block experimental design. The N2O emissions were quantified under different fertilization measures in the peak wheat growing season during sowing, jointing, and grain filling stages, respectively. Compared with N270 and N90 treatments, N2O emissions were significantly decreased by 18.6% and 27.2%, respectively, under 20% OF270 + 80% N270% and 20% OF90 + 80% N90 (p < 0.05). Further, N2O emissions in N270 were increased by 50.8% relative to N90. Wheat yields increased significantly under 20% OF90 + 80% N90 by 27.6% (N270) and 16.4% (N90), and were considerably enhanced under 20% OF270 + 80% N270 by 40.6% (N270) and 12.7% (N90) in contrast to OF270 and N270 (p < 0.05). Compared with N90, the content of wet gluten, protein and starch under 20% OF90 + 80% N90 treatment significantly increased by 7.7%, 13.8% and 7.9%, and enhanced by 7.6%, 4.8%, 8.0% relative to OF90, respectively (p < 0.05). The starch content increased significantly by 2.0%, whereas the settlement value decreased considerably by 2.9% under 20% OF270 + 80% N270 (p < 0.05), and there was no notable difference in the wet gluten and protein contents (p > 0.05). Our findings indicated that organic fertilizer mixed with N fertilizer can effectively reduce N2O emissions, increase both the grain yields and quality in wheat field compared with N fertilizer alone.

Effect of Irrigation Depth and Nitrogen Fertilizer Rates on Pepper (Capsicum annum L.) Yield and Water Use Efficiency in Tselemty District, Tigray, Ethiopia

Optimizing agricultural crop production involves utilizing proper irrigation and fertilization techniques. A two-year experiment conducted in the Tselemty district during the off seasons of 2019 and 2020 aimed to assess the impact of varying irrigation levels and nitrogen fertilizer application rates on the growth, yield, and crop water productivity of pepper. The study included three irrigation levels (75%, 100%, and 125% of the required irrigation) and three nitrogen fertilizer application rates (75%, 100%, and 125% of the recommended amount). Analysis of the results using Gen-Stat software revealed that most pepper yield attributes were not significantly affected by the different irrigation and fertilizer levels. However, the marketable yield showed significant variation based on the combined application rates. The research indicates that, under ideal circumstances, the optimal approach for pepper growers is a combination of meeting 100% of the irrigation requirement and applying 100% of the recommended nitrogen fertilizer rate. Nevertheless, in scenarios where water resources are limited and fertilizer expenses are high, a reduced irrigation level of 75% of the requirement coupled with 75% of the recommended nitrogen fertilizer rate could be a viable alternative that does not lead to a substantial decrease in yield.

Quantitative assessment of the effects of rising temperature on the grain protein of winter wheat in china and its adaptive strategies

With advancements in genetics and technology, wheat yields have continuously increased, but grain quality has remained stagnant or even decreased in recent decades. The effects of temperature on the future grain quality of winter wheat in China are unknown. This study used an improved WheatGrow model, along with two future temperature scenarios, to quantify the regional impacts of temperature increases on grain protein in China and aimed to find effective strategies to adapt to the impact of temperature increases on quality. Compared with those in the baseline period, the protein concentration of wheat grains in the main winter wheat production region of China increased by 0.27% and 0.41% under the 1.5 ℃ and 2.0 ℃ temperature increase scenarios, respectively. However, the grain protein concentrations in the Sichuan Basin of Medium and Weak Gluten Wheat Subregion (Ⅴ) decreased. The temperature rise was estimated to increase the proportion of strong gluten-type wheat but reduce the proportion of medium gluten-type wheat, with the proportion of weak gluten-type wheat changing slightly. Advanced planting date was projected to increase the grain protein concentration in the Northern Strong Gluten Wheat Subregion (Ⅰ), the Northern of Huang-Huai Strong and Medium Gluten Wheat Subregion (Ⅱ), the Southern of Huang-Huai Medium Gluten Wheat Subregion (Ⅲ) and the Yangzi River of Medium and Weak Gluten Wheat Subregion (Ⅳ), whereas a delayed planting date reduced the protein concentration in subregions Ⅰ, Ⅱ, and Ⅲ. In addition, the grain protein concentration was not significantly affected in the higher high-temperature threshold varieties in the southern winter wheat production region under the global warming scenarios. However, if more strong gluten-type wheat is required in the northern China in the future, varieties with lower high-temperature thresholds can be selected without considering wheat yields. Moreover, increasing the nitrogen fertilizer application rate could further increase the wheat protein concentration under future warming scenarios, and the protein concentration of wheat was more sensitive to the nitrogen fertilizer application rate in the northern winter wheat production region than in the southern region. These findings are crucial for improving grain quality across different wheat production regions of China in the future.

Nitrogen fertiliser application rate to temperate mid-season grass: Digestion, nitrogen balance and rumen microbiota in beef cattle, and rumen fermentation and methane production in vitro

Nitrogen (N) excretion by cattle, particularly urinary N, can have detrimental environmental impacts on air and water quality, and contributes to greenhouse gas emissions. The effects of increasing the application rate of inorganic N fertiliser from 15 (N15) to 80 (N80) kg/ha per cut to Lolium perenne dominant swards in summer, on intake, rumen fermentation, rumen microbial populations, apparent total-tract digestibility and N-balance in beef cattle, and in vitro fermentation and methane output, were studied. Sixteen suckler-bred Charolais steers, used in a randomised block design experiment, were offered fresh grass mechanically harvested 21-d after N fertiliser application. Similar grass was incubated in an eight-vessel in vitro RUSITEC system. Grass crude protein concentration was 50 g/kg dry matter (DM) higher for N80 compared to N15. There was no difference in grass DM intake between treatments. Rumen fermentation variables did not differ between treatments, except for the molar proportion of propionate, which was greater for N80 than N15. Gross microbial community structure in the rumen was not significantly altered by inorganic N fertiliser application rate. The relative abundance of individual genera Lachnospiraceae_NK3A320_group and Ruminococcaceae_NK4A214_group, and Acetitomaculum were significantly lower at the higher N application rate. Mean plasma urea concentration was greater for N80 compared to N15. In vivo digestibility of DM, organic matter, neutral detergent fibre and acid detergent fibre was unaffected by fertiliser N application rate. Nitrogen intake was 75 g/d greater, and urinary and faecal N excretion were 20 and 5 g/d greater, respectively, for N80 than N15. The quantity of N retained and N use efficiency was greater for N80 compared to N15. In vitro NH3 concentration was greater for N80 than N15, whereas other rumen fermentation variables, and in vitro methane and total gas output, did not differ between treatments. Reducing the inorganic N fertiliser rate applied to mid-season temperate grass reduced N excretion from beef cattle, which is environmentally beneficial, with no effect on in vitro methane production.

Long-term integrated agronomic optimization maximizes soil quality and synergistically improves wheat yield and nitrogen use efficiency

Integrated agronomic optimization (IAO) adopts suitable crop varieties, sowing dates, planting density and advanced nutrient management to redesign the entire production system according to the local environment, which can achieve synergistic improvements in crop yields and resource utilization. However, the intensity and magnitude of the impacts of IAO on soil quality under long-term intensive production and high nitrogen use efficiency (NUE) require further clarification. Based on a 13-year field experiment conducted in Dawenkou, Tai'an, China, we investigated the effects of four cultivation modes on the grain yield, NUE, soil aggregate structure, as well as the fraction of organic matter (SOM) and soil quality, reflected by integrated fertility index (IFI) during the winter wheat maturation period in 2020–2022. The four cultivation modes were traditional local farming (T1), farmer-based improvement (T2), increased yield regardless of production cost (T3), and integrated soil–crop system management (T4). As IAO modes, T2 and T4 were characterized by denser planting, reduced nitrogen (N) fertilizer application rates, and delayed sowing compared to T1 and T3, respectively. In this long-term experiment, IAO was found to maintain aggregate stability, increase SOM content (by increasing organic carbon and total nitrogen of the light fraction (LF) and the particulate organic matter fraction (POM)), and improve SOM quality by increasing the proportions of LF and POM and the ratio of organic carbon to total nitrogen in SOM. Compared to T1, the IFI of T2, T3, and T4 increased by 10.91, 23.38, 25.55%, and by 17.78, 6.41, 28.94% in the 0–20 and 20–40 cm soil layers, respectively. The grain yield of T4 was 22.52% higher than that of T1, reaching 95.98% of that in T3. Furthermore, NUE of T4 was 35.61% higher than that of T1 and T3. In conclusion, our results suggest that T4 synergistically increases grain yield and NUE in winter wheat, while maximizing soil quality.

Variable-Rate Fertilization for Summer Maize Using Combined Proximal Sensing Technology and the Nitrogen Balance Principle

Soil is a heterogeneous medium that exhibits considerable variability in both spatial and temporal dimensions. Proper management of field variability using variable-rate fertilization (VRF) techniques is essential to maximize crop input–output ratios and resource utilization. Implementing VRF technology on a localized scale is recommended to increase crop yield, decrease input costs, and reduce the negative impact on the surrounding environment. This study assessed the agronomic and environmental viability of implementing VRF during the cultivation of summer maize using an on-the-go detector of soil total nitrogen (STN) to detect STN content in the test fields. A spatial delineation approach was then applied to divide the experimental field into multiple management zones. The amount of fertilizer applied in each zone was determined based on the sensor-detected STN. The analysis of the final yield and economic benefits indicates that plots that adopted VRF treatments attained an average summer maize grain yield of 7275 kg ha−1, outperforming plots that employed uniform-rate fertilization (URF) treatments, which yielded 6713 kg ha−1. Through one-way ANOVA, the yield p values of the two fertilization methods were 6.406 × 10−15, 5.202 × 10−15, 2.497 × 10−15, and 3.199 × 10−15, respectively, indicating that the yield differences between the two fertilization methods were noticeable. This led to an average yield increase of 8.37% ha−1 and a gross profit margin of USD 153 ha−1. In plots in which VRF techniques are utilized, the average nitrogen (N) fertilizer application rate is 627 kg ha−1. In contrast, in plots employing URF methods, the N fertilizer application rate is 750 kg ha−1. The use of N fertilizer was reduced by 16.4%. As a result, there is a reduction in production costs of USD 37.5 ha−1, achieving increased yield while decreasing the amount of applied fertilizer. Moreover, in plots where the VRF method was applied, STN was balanced despite the reduced N application. This observation can be deduced from the variance in summer maize grain yield through various fertilization treatments in a comparative experiment. Future research endeavors should prioritize the resolution of particular constraints by incorporating supplementary soil data, such as phosphorus, potassium, organic matter, and other pertinent variables, to advance and optimize fertilization methodologies.

Effects of Straw and Fertilizer Managements on Nitrogen Loss in Rice Cultivation in Taihu Lake Basin

Nitrogen loss from rice systems is an important source of agricultural non-point source pollution. Many studies revolve around reducing the rate of nitrogen fertilizer application. However, studies examining the characteristics of nitrogen loss in multiple loss paths （runoff, leaching, and lateral seepage） under different straw and fertilizer managements are lacking. Therefore, a study was carried out based on a rice field planted for more than 20 years with straw continuously returned to the field for more than 5 years in Taihu lake basin. The effects of straw and fertilizer managements on nitrogen loss in different paths during the whole growth period of rice were studied. Moreover, straw and fertilizer managements were evaluated by their production suitability and environmental friendliness based on crop yield, nitrogen use efficiency, and nitrogen loss. The results showed that straw removal from the field increased the response sensitivity of nitrogen accumulation in plant tissue to nitrogen application. The nitrogen loss in the rice season was 9-17 kg·hm-2, accounting for 5%-7% of the nitrogen application rate. Straw removal increased the risk of nitrogen loss when soaking water discharged. Straw returning could decrease the nitrogen loss by more than 15%, though the effect of straw on nitrogen loss via lateral seepage was not clear. Furthermore, the suitable substitution of organic fertilizer （30% in this study） could respectively reduce the amount of nitrogen loss via runoff, leaching, and lateral seepage by 16%, 26%, and 37% compared with the fertilizer application under the same nitrogen gradient. In conclusion, the implementation of straw returning and fertilizer type optimization measures effectively reduced the nitrogen loss for unit weight of rice production and realized the balance between agricultural production and environmental protection.

Effect of nitrogen fertilizer on the quality traits of Indica rice with different amylose contents.

Nitrogen is a key factor affecting the quality of rice. Studying the impact of nitrogen fertilizer on the taste, physicochemical properties, and starch structure of Indica rice with different amylose contents is of great significance for scientifically fertilizing and cultivating high-quality rice varieties for consumption. The results indicate that increasing nitrogen fertilizer application reduces the amylose content and increases the protein content, resulting in a decrease in taste quality. Simultaneously, it reduces the intergranular porosity of starch particles, improving the appearance and milling quality of rice. Compared to the N1 treatment (nitrogen fertilizer application rate of 90 kg ha-1), the taste of low-amylose rice (Yixiangyou 2115) and high-amylose rice (Byou 268) decreased by 14.24% and 19.79%, respectively, under N4 treatment (nitrogen fertilizer application rate of 270 kg ha-1). The effect of nitrogen fertilizer on low-amylose rice is mainly reflected in increased rice hardness, enthalpy value, and setback viscosity, resulting in a decline in taste. The effect of nitrogen fertilizer on high-amylose rice is mainly reflected in a decrease in peak viscosity, an increase in gelatinization temperature, and crystallinity under high nitrogen levels. Increasing nitrogen fertilizer application can improve the appearance and milling quality of rice, but it also leads to an increase in protein content, hardness, gelatinization enthalpy, decrease in breakdown value, and a decline in palatability. In practical production, different production measures should be taken according to different production goals. © 2024 Society of Chemical Industry.

Optimal Nitrogen Fertilizer Rates for Soybean Cultivation

The soybean (Glycine max. L. Merr) can satisfy a large portion of its requirement for nitrogen (N) by living in symbiosis with symbiotic bacteria. However, this source of N may be inadequate in varieties with high yield potential. To fully exploit this potential, soybeans should additionally utilize mineral forms of nitrogen present in the soil. The aim of this study was to determine the effect of varied nitrogen fertilizer application rates on the dry weight of the separated parts of soybean plants and the whole plant, including the number and weight of root nodules, the potential to reduce atmospheric nitrogen (N2), and the content and uptake of nitrogen. Four levels of pre-sowing nitrogen fertilizer supply were tested: 0, 60, 120, and 180 kg N·ha−1. Measurements of the tested parameters were taken during the flowering stage and the fully ripe stage. During the flowering stage, a reduction in the number of root nodules was observed following the application of 120 and 180 kg N·ha−1. In the fully ripe stage, each increase in nitrogen application caused a systematic decrease in the number of nodules on the roots. Increasing the level of nitrogen application therefore reduced the N2 fixation potential of soybeans, regardless of the developmental stage. The use of high doses of nitrogen in soybean cultivation did not increase seed yield or the weight of the entire plant. With high doses of nitrogen, the content and accumulation of nitrogen in soybean seeds and total mass did not increase. Therefore, the content and yield of crude protein did not increase. The main organ of nitrogen accumulation in the soybean flowering stage was the leaves (58.6–64.8% of total N uptake), however, in the fully ripe stage, it was the seeds (66.8–74.2% of total N uptake).

Effects of nitrogen fertilization on the fate of high-risk antibiotic resistance genes in reclaimed water-irrigated soil and plants

High-risk antibiotic resistance genes (ARGs) in reclaimed water-irrigated soil pose a potential threat to ecosystem and human health. Inorganic fertilization – including with nitrogen, a key ingredient in agricultural production – may affect the ARG profile in soil. However, little is known about nitrogen fertilization's influence on ARGs profiles in the soil–plant system. This study investigated the effects of different nitrogen fertilizer types (CO(NH2)2, NO3–-N (NaNO3) and NH4+-N (NH4HCO3)) and different nitrogen fertilizer application rates (low, medium, high) on the distribution of high-risk ARGs in reclaimed water-irrigated soil and plants using quantitative PCR, high-throughput sequencing and metagenomic sequencing. Soil microcosms results revealed that nitrogen fertilization significantly affected the pattern of high-risk ARGs in soil, and also affected high-risk ARGs abundance and transfer capacity in plants. Compared with nitrogen fertilizer application rate, nitrogen fertilizer types significantly contributed to enhancing the soil resistome, with the order of CO(NH2)2 > NO3–-N ≈ NH4+-N. The medium application of NO3–-N and NH4+-N significantly reduced high-risk ARGs abundance in the leaf endophyte. Bacterial community mainly drove the variation of ARGs in nitrogen-fertilized soil–plant system, and class I integron and metal resistance genes (MRGs) also had direct effects on these high-risk ARGs. A similar high-risk ARGs pattern was also found in field plot experiments, and several dangerous pathogens were observed as the main high-risk ARGs potential hosts in nitrogen-fertilized soil. Based on an economic assessment, application of NH4+-N (NH4HCO3) could reduce costs by $1,312.83 ha−1 compared with NO3–-N (NaNO3). These results showed that the more important role of nitrogen type might be an effective and economical way to control high-risk ARGs spread in soil–plant system under reclaimed water irrigation.

Rate and time of nitrogen fertilizer application for winter camelina

AbstractWinter camelina [Camelina sativa (L.) Crantz] is a potential third crop to diversify maize (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations in the upper Midwest. Although generally considered a low‐input crop, empirical evidence suggests that it responds to added nitrogen (N) fertilization. However, optimum agronomic N rates have not been extensively studied in the region. A study was conducted from fall 2018 to fall 2020 at three locations to assess the effects of N fertilizer application time (all N‐rate applied in spring and N‐rate split applied in fall and spring) and rates on biomass and seed yield, and quality of winter camelina. Nitrogen application time did not affect yields. Both biomass and seed yields were greatly affected by N rates at all locations. Nitrogen had minimal effects on the oil and protein content of seeds, although greater N rates were associated with a slight decrease in oil content and a slight increase in protein content. The number of branches and silicles per plant varied significantly with N rates in all locations. The seed‐to‐silicle ratio showed significant differences in two out of three locations. Residual soil N increased with increasing N rates. A fertilization rate of 67 kg ha−1 provided the highest camelina seed yield. While this study has determined the agronomic maximum rate for applied N, further economic analysis could provide comprehensive decision‐making for farmers.

Prediction Model of Nitrogen, Phosphorus, and Potassium Fertilizer Application Rate for Greenhouse Tomatoes under Different Soil Fertility Conditions

To reach the target yield of crops, nutrient management is essential. Selecting the appropriate prediction model and adjusting the nutrient supply based on the actual situation can effectively improve the nutrient utilization efficiency, crop yield, and product quality. Therefore, a prediction model of the NPK fertilizer application rate for greenhouse tomatoes under the target yield was studied in this study. Under low, medium, and high soil fertility conditions, a neural network prediction model based on the sparrow search algorithm (SSA-NN), a neural network prediction model based on the improved sparrow search algorithm (ISSA-NN), and a neural network prediction model based on the hybrid algorithm (HA-NN) were used to predict the NPK fertilizer application rate for greenhouse tomatoes. The experimental results indicated that the evaluation indexes (i.e., the mean square error (MSE), explained variance score (EVS), and coefficient of determination (R2)) of the HA-NN prediction model proposed in this study were superior than the SSA-NN and ISSA-NN prediction models under three different soil fertility conditions. Under high soil fertility, compared with the SSA-NN prediction model, the MSE of the ISSA-NN and HA-NN prediction models decreased to 0.007 and 0.005, respectively; the EVS increased to 0.871 and 0.908, respectively; and the R2 increased to 0.862 and 0.899, respectively. This study showed that the HA–NN prediction model was superior in predicting the NPK fertilizer application rate for greenhouse tomatoes under three different soil fertility conditions. Due to the significance of NPK fertilizer application rate prediction for greenhouse tomatoes, this technique is expected to bring benefits to agricultural production management and decision support.

Agronomic performance of maize of contrasting maturities at varying rates of nitrogen fertilizer application in a tropical rainforest agroecology

Agronomic performance of maize of contrasting maturities at varying rates of nitrogen fertilizer application in a tropical rainforest agroecology