Conventional Nitrogen Application Research Articles

Efficacy of nano urea in replacing conventional nitrogen application and its effect on fruit quality in strawberry

In a study conducted on strawberry cv. Winter Dawn, the combined application of nano urea and Azotobacter was investigated for its impact on quality and biochemical attributes under protected cultivation. The findings revealed a noteworthy response of strawberry plants to foliar nano applications compared to conventional soil application of urea. Despite the lower nitrogen dosage associated with nanoparticle supplementation, strawberries with nanoparticles exhibited significant improvements in qualitative and biochemical parameters. These results underscore the potential of urea nanoparticles as a viable nitrogen source, advocating for alternative approaches to nitrogen fertilization. By fine-tuning the dosage ratio, this strategy shows promise in fostering a more environmentally friendly, sustainable and modern method for cultivating strawberries. The enhanced quality and biochemical attributes observed in strawberries treated with nano urea highlight the efficacy of this innovative approach in optimizing plant growth and productivity. Furthermore, the utilization of nano urea in combination with Azotobacter demonstrates synergistic effects, potentially enhancing nutrient uptake and utilization efficiency in plants. This holistic approach improves crop quality and reduces the environmental impact associated with traditional fertilization methods. In conclusion, the findings of this study support the adoption of urea nanoparticles as a valuable tool in strawberry cultivation, offering a pathway towards sustainable agricultural practices. Future research efforts should focus on optimizing application protocols and assessing long-term effects to fully exploit the potential of nano-based fertilizers for strawberry.

Effects of Controlled-release Blended Fertilizer on Crop Yield and Greenhouse Gas Emissions in Wheat-maize Rotation System

The increasing use of nitrogen fertilizers exerts extreme pressure on the environment (e.g., greenhouse gas emissions, GHGs) for winter wheat-summer maize rotation systems in the North China Plain. The application of controlled-release fertilizers is considered as an effective measure to improve crop yield and nitrogen fertilizer utilization efficiency. To explore the impact of one-time fertilization of controlled-release blended fertilizer on crop yield and GHGs of a wheat-maize rotation system, field experiments were carried out in Dezhou Modern Agricultural Science and Technology Park from 2020 to 2022. Five treatments were established for both winter wheat and summer maize, including no nitrogen control (CK), farmers' conventional nitrogen application (FFP), optimized nitrogen application (OPT), CRU1 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 5:5 and 3:7, respectively), and CRU2 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 7:3 and 5:5, respectively). The differences in yield, nitrogen fertilizer utilization efficiency, fertilization economic benefits, and GHGs among different treatments were compared and analyzed. The results showed that nitrogen application significantly increased the single season and annual crop yields of the wheat-maize rotation system (P < 0.05). Compared with those of FFP, the CRU1 and CRU2 treatments increased the yields of summer maize by 0.4% to 5.6%, winter wheat by -5.4% to 4.1%, and annual yields by -1.1% to 3.9% (P > 0.05). N recovery efficiency (NRE), N agronomic efficiency (NAE), and N partial factor productivity (NPFP) were increased by -8.6%-43.4%, 2.05-6.24 kg·kg-1, and 4.24-10.13 kg·kg-1, respectively. Annual net income increased by 0.2% to 6.3%. Nitrogen application significantly increased the annual emissions of soil N2O and CO2 in the rotation system (P < 0.05) but had no effect on the annual emissions of CH4 (except for in the FFP treatment in the first year). The annual total N2O emissions under the CRU1 and CRU2 treatments were significantly reduced by 23.4% to 30.2% compared to those under the FFP treatment (P < 0.05). Additionally, nitrogen application significantly increased the annual global warming potential (GWP) of the rotation system (P < 0.05), but the intensity of greenhouse gas emissions was reduced due to the increase in crop yields. Compared with that under FFP, the annual GWP under the CRU1 and CRU2 treatments decreased by 9.6% to 11.5% (P < 0.05), and the annual GHGs decreased by 11.2% to 13.8% (P > 0.05). In summary, the one-time application of controlled-release blended fertilizer had a positive role in improving crop yield and economic benefits, reducing nitrogen fertilizer input and labor costs, and GHGs, which is an effective nitrogen fertilizer management measure to promote cleaner production of food crops in the North China Plain.

Effects of water-nitrogen interactions on NH3 and N2O emissions and yield in winter wheat cropland

To investigate the effects of different irrigation and nitrogen application modes on nitrogen gaseous loss in winter wheat farmland, we conducted a field experiment at Changqing Irrigation Experiment Station in Shandong Province, with two irrigation levels (80%-90% θf(I1) and 70%-80% θf(I2)) and three nitrogen application levels (conventional nitrogen application of 240 kg·hm-2(N1), nitrogen reduction of 12.5% (N2), and nitrogen reduction of 25% (N3)). The results showed that ammonia volatilization and nitrous oxide emission rate peak appeared within 2-4 days after fertilization or irrigation. The ammonia volatilization rate during the chasing fertilizer period was significantly higher than that during the basal fertilizer period. Compared with other treatments, the ave-rage ammonia volatilization rate of I2N2 treatment during the chasing fertilizer period was reduced by 10.1%-51.6%, and the average nitrous oxide emission rate over the whole growth period was reduced by 15.4%-52.2%. The ammonia volatilization rate was significantly positively associated with surface soil pH value and ammonium nitrogen content, while the nitrous oxide emission rate was significantly positively associated with nitrate content in topsoil. The accumulation amount of soil ammonia volatilization and nitrous oxide emission ranged from 0.83-1.42 and 0.11-0.33 kg·hm-2, respectively. Moderate reduction of irrigation water and nitrogen input could effectively reduce cumulative amounts of ammonia volatilization and nitrous oxide emission from winter wheat farmland. The cumulative amounts of ammonia volatilization and nitrous oxide emission under I1N3 and I2N2 treatments were signi-ficantly lower than those under other treatments. The highest winter wheat yield (5615.6 kg·hm-2) appeared in I2N2 treatment. The irrigation water utilization efficiency of I2 was significantly higher than that of I1, with the maximum increase rate of 45.2%. Compared with N1 and N3 treatments, the maximum increase rate of nitrogen fertilizer productivity and agricultural utilization efficiency in N2 reached 15.2% and 31.8%, respectively. In conclusion, the treatment with 70%-80% θf irrigation level and 210 kg·hm-2 nitrogen input could effectively improve the utilization efficiency of irrigation water and nitrogen fertilization and reduce gaseous loss from winter wheat farmland.

Effects of different nitrogen application rates and picking batches on the nutritional components of Lycium barbarum L. fruits.

Lycium barbarum L., commonly known as wolfberry, is not only a traditional Chinese medicine but also a highly nutritious food. Its main nutrients include L. barbarum polysaccharide, flavonoid polyphenols, carotenoids, alkaloids, and other compounds, demonstrating its wide application value. This study investigated the effects of nitrogen application on the accumulation of the main nutrients and metabolites in wolfberry fruits under three different nitrogen application rates, namely, N1 (20% nitrogen (N) reduction, 540 kg·ha-2), N2 (medium N, 675 kg·ha-2), and N3 (20% nitrogen increase, 810 kg·ha-2,which is a local conventional nitrogen application amount.). Additionally, due to continuous branching, blossoming, and fruiting of wolfberry plants during the annual growth period, this research also explored the variation in nutritional composition among different harvesting batches. The contents of total sugar and polysaccharide in wolfberry fruit were determined by Fehling reagent method and phenol-sulfuric acid method, respectively;The content of betaine in fruit was determined by high-performance liquid chromatography,and the flavonoids and carotene in the wolfberry fruits were determined by spectrophotometry. Analysis of data over three consecutive years revealed that as nitrogen application increased, the total sugar content in wolfberry fruits initially decreased and then increased. The levels of L. barbarum polysaccharides, total flavonoids, and total carotenoids initially increased and then decreased, while the betaine content consistently increased. Different picking batches significantly impacted the nutrient content of wolfberry fruits. Generally, the first batch of summer wolfberry fruits had greater amounts of total sugar and flavonoids, whereas other nutrients peaked in the third batch. By employing a broadly targeted metabolomics approach, 926 different metabolites were identified. The top 20 differentially abundant metabolites were selected for heatmap generation, revealing that the contents of L-citrulline, 2-methylglutaric acid, and adipic acid increased proportionally to the nitrogen gradient. Conversely, the dibutyl phthalate and 2, 4-dihydroxyquinoline contents significantly decreased under high-nitrogen conditions. The remaining 15 differentially abundant metabolites, kaempferol-3-O-sophorosid-7-O-rhamnoside, trigonelline, and isorhamnosid-3-O-sophoroside, initially increased and then decreased with increasing nitrogen levels. Isofraxidin, a common differentially abundant metabolite across all treatments, is a coumarin that may serve as a potential biomarker for wolfberry fruit response to nitrogen. Differentially abundant metabolites were analyzed for GO pathway involvement, revealing significant enrichment in metabolic pathways and biosynthesis of secondary metabolites under different nitrogen treatments. In conclusion, a nitrogen application of 675 kg·ha-2, 20% less than the local farmers' actual application, was most beneficial for the quality of four-year-old Ningqi 7 wolfberry fruits. Consumers who purchase wolfberry-dried fruit for health benefits should not consider only the first batch of summer wolfberry fruits. These results offer a broader perspective for enhancing the quality and efficiency of the wolfberry industry.

Effect of nitrogen reduction combined with biochar application on soda saline soil and soybean growth in black soil areas.

The combination of biochar and nitrogen (N) fertilization in agricultural salt-affected soils is an effective strategy for amending the soil and promoting production. To investigate the effect of nitrogen reduction combined with biochar application on a soda saline soil and soybean growth in black soil areas, a pot experiment was set up with two biochar application levels, 0 (B0) and 4.5 t/hm2 (B1); two biochar application depths, 0-20 cm (H1) and 0-40 cm (H2); and two nitrogen application levels, conventional nitrogen application (N0) and nitrogen reduction of 15% (N1). The results showed that the application of biochar improved the saline soil status and significantly increased soybean yield under lower nitrogen application. Moreover, increasing the depth of biochar application enhanced the effectiveness of biochar in reducing saline soil barriers to crop growth, which promoted soybean growth. Increasing the depth of biochar application increased the K+ and Ca2+ contents, soil nitrogen content, N fertilizer agronomic efficiency, leaf total nitrogen, N use efficiency, AN, Tr, gs, SPAD, leaf water potential, water content and soybean yield and its components. However, the Na+ content, SAR, ESP, Na+/K+, Ci and water use efficiency decreased with increasing biochar depth. Among the treatments with low nitrogen input and biochar, B1H1N1 resulted in the greatest soil improvement in the 0-20 cm soil layer compared with B0N0; for example, K+ content increased by 61.87%, Na+ content decreased by 44.80%, SAR decreased by 46.68%, and nitrate nitrogen increased by 26.61%. However, in the 20-40 cm soil layer, B1H2N1 had the greatest effect on improving the soil physicochemical properties, K+ content increased by 62.54%, Na+ content decreased by 29.76%, SAR decreased by 32.85%, and nitrate nitrogen content increased by 30.77%. In addition, compared with B0N0, total leaf nitrogen increased in B1H2N1 by 25.07%, N use efficiency increased by 6.7%, N fertilizer agronomic efficiency increased by 32.79%, partial factor productivity of nitrogen increased by 28.37%, gs increased by 22.10%, leaf water potential increased by 27.33% and water content increased by 6.44%. In conclusion, B1H2N1 had the greatest effect on improving the condition of saline soil; it not only effectively regulated the distribution of salt in soda saline soil and provided a low-salt environment for crop growth but also activated deep soil resources. Therefore, among all treatments investigated in this study, B1H2N1 was considered most suitable for improving the condition of soda saline soil in black soil areas and enhancing the growth of soybean plants.

Controlled-Release Nitrogen Mixed with Common Nitrogen Fertilizer Can Maintain High Yield of Rapeseed and Improve Nitrogen Utilization Efficiency.

Field experiments were conducted to study the effects of different proportions of controlled-release nitrogen fertilizer mixed with quick-acting nitrogen fertilizer on the yield and nitrogen utilization efficiency of direct-seeding rapeseed. Using a conventional nitrogen application rate of 180 kg ha-1 as a control, a total of 5 types of available nitrogen fertilizers and different proportions of controlled-release nitrogen fertilizers were mixed for fertilizer treatment. The proportion of available nitrogen fertilizer used was 135 kg ha-1, and the addition ratios of the five types of controlled-release nitrogen fertilizers were 0%, 30%, 50%, 70%, and 100%, respectively (i.e., the proportion of controlled-release nitrogen to the total nitrogen application amount). These ratios were represented as N135R0, N135R1, N135R2, N135R3, and N135R4, respectively. The results showed that there was no significant difference in the number of pods per plant, the number of seeds per pod, or the grain yield under the treatment of controlled-release nitrogen fertilizer mixed with quick-acting nitrogen fertilizer for proportions of 30-50% (N135R1~R3) when compared with the control, and a stable yield was achieved. Mixing controlled-release nitrogen fertilizer under reduced nitrogen application can significantly improve the apparent utilization rate of rapeseed nitrogen fertilizer, but it first increases and then decreases with the increase of the controlled-release nitrogen mixing ratio, reaching its highest under the N135R2 treatment. The agronomic utilization efficiency and partial productivity of nitrogen fertilizer first increased and then decreased with the increased proportion of controlled-release nitrogen, and both reached their highest utilization with the N135R2 treatment. The mixed treatment of controlled-release nitrogen did not affect soil urease activity, but significantly increased soil sucrase activity. The mixed treatment of controlled-release nitrogen also increased soil microbial biomass nitrogen and carbon content. Especially in the flowering stage, the soil microbial biomass nitrogen and carbon content was significantly higher under a controlled-release nitrogen mixing ratio of 30-50%. At the same time, it had a similar effect on soil inorganic nitrogen content. Therefore, a controlled-release nitrogen mixing treatment provided sufficient nitrogen for the key growth period of rapeseed. Under the condition of reducing the amount of nitrogen fertilizer by 25% based on the amount of nitrogen fertilizer applied to conventional rapeseed, the application of controlled-release urea mixed with common nitrogen fertilizer mixed at a ratio of 30-50% can be an effective way to maintain grain yield levels and improve nitrogen utilization efficiency.

Increasing Planting Density and Reducing N Application Improves Yield and Grain Filling at Two Sowing Dates in Double-Cropping Rice Systems.

Grain filling plays an important role in achieving high grain yield. Manipulating planting densities is recognized as a viable approach to compensate for the reduced yield caused by nitrogen reduction. Understanding the effects of nitrogen fertilization and planting density on superior and inferior grain filling is crucial to ensure grain security. Hence, double-cropping paddy field trials were conducted to investigate the effect of three nitrogen levels (N1, conventional nitrogen application; N2, 10% nitrogen reduction; N3, 20% nitrogen reduction) and three planting densities (D1, conventional planting density; D2, 20% density increase; D3, 40% density increase) on grain yield, yield formation, and grain-filling characteristics at two sowing dates (S1, a conventional sowing date, and S2, a date postponed by ten days) in 2019-2020. The results revealed that the annual yield of S1 was 8.5-14% higher than that of S2. Reducing nitrogen from N2 to N3 decreased the annual yield by 2.8-7.6%, but increasing planting densities from D1 to D3 significantly improved yield, by 6.2-19.4%. Furthermore, N2D3 had the highest yield, which was 8.7-23.8% higher than the plants that had received the other treatments. The rice yield increase was attributed to higher numbers of panicles per m2 and spikelets per panicle on the primary branches, influenced by superior grain filling. Increasing planting density and reducing nitrogen application significantly affected grain-filling weight, with the 40% density increase significantly facilitating superior and inferior grain filling with the same nitrogen level. Increasing density can improve superior grains while reducing nitrogen will decrease superior grains. These results suggest that N2D3 is an optimal strategy to increase yield and grain filling for double-cropping rice grown under two sowing-date conditions.

Effects of nitrogen fertilizer substitution by cow manure on yield, net GHG emissions, carbon and nitrogen footprints in sweet maize farmland in the Pearl River Delta in China

Long-term excessive nitrogen (N) application in sweet maize farmland in the Pearl River Delta in China has caused huge greenhouse gas (GHG) and reactive nitrogen (RN) emissions in the region. This study compared the effects of N fertilizer replaced by cow manure at 20.00% (CD20) and 50.00% (CD50) ratios on crop yield, on-field N2O, CH4 and CO2 emissions, soil organic carbon (SOC) concentration, GHG emission intensity and carbon footprint (CF) and nitrogen footprint (NF) based on field research carried out for four consecutive cropping seasons during 2020–2021. The results showed that, compared with conventional nitrogen application (CK), CD20 could reduce N2O emissions by 6.65% and increase the SOC concentration by 48.08% when ensuring yield, although GHG emissions and intensity were both increased by 36.13%–36.44%. The CD50 lowered the crop yield 8.77% as the GHG emissions and intensity increased by 74.32%–74.58% at the same time compared to the CK, although the SOC concentration in farmland was significantly improved by 295.82% due to the higher substitution ratio of N fertilizer. Moreover, the CFs based on the area and yield of CD20 and CD50 were 23.22%–135.52% lower than CK. The NF of CD20 based on area and yield was 10.81%–16.35% lower than that of CK, but the NF of CD50 based on area and yield was 4.82%–14.90% higher than that of CK. In conclusion, replacing 20% synthetic nitrogen with cow manure in sweet maize farmland in the Pearl River Delta could achieve the synergistic technical effects of maintaining crop yield, improving the soil carbon sink and decreasing GHG and RN emissions at the life cycle level. We suggest the application of this method as an alternative fertilization practice for realizing a sustainable sweet maize cultivation system in South China. This study provided a research basis for developing the sustainable sweet maize farming system in the Pearl River Delta in China. It would also provide valuable information for the development of clean agricultural production in typical subtropical area in East Asia.

Effects of nitrogen application rate on the accumulation of 13C assimilates after flowering and water-nitrogen use efficiency of wheat under supplemental irrigation based on soil moisture.

This study aimed to explore nitrogen fertilizer management measures to synergistically improve wheat yields and water and nitrogen use efficiency under supplemental irrigation based on soil moisture in the Huang Huai winter wheat area. Wheat variety "Yannong 1212" was used as the test material. There were three nitrogen application levels, 150 kg·hm-2 (N1), 210 kg·hm-2 (N2), and 270 kg·hm-2 (the conventional nitrogen application rate in the Huang Huai winter wheat area, N3), with the relative soil water content of 0-40 cm of each treatment was supplemented to 70% at the jointing and flowering stages. We investigated the effects of nitrogen rates on photosynthetic characteristics of flag leaves after flowering, 13C assimilate accumulation and transport, and water and nitrogen use efficiency after flowering of wheat. The results showed that photosynthetic capacity of flag leaves in the N2 and N3 was significantly higher than that in N1 14-35 days after flowering, and that there was no significant diffe-rence between N2 and N3 treatments. The 13C isotope tracing results showed that the translocation amount of 13C assimilates in vegetative organs in N2 was 12.1% and 7.1% higher than that in N1 and N3, respectively. The distribution amount of 13C assimilates in grains at maturity was 10.1% and 5.3% higher than that of N1 and N3, respectively. The amount of nitrogen fertilizer affected water consumption, water consumption proportion, and total water consumption in different growth stages of wheat. Water consumption during the whole growth period showed no difference between N2 and N3 treatments, but both were significantly higher than that for N1. Water consumption and water consumption proportion of N2 were higher from the jointing to maturity stages, water use efficiency of N2 was 7.5% and 4.8%, and grain yield was 4.7% and 10.9% higher than that of N3 and N1 treatments, respectively. The partial productivity of nitrogen fertilizer was 34.6% higher in the N2 than that of N3. Considering wheat grain yield and water and nitrogen use efficiency, 210 kg·hm-2 nitrogen application was the best rate under water-saving condition of supplementary irrigation after soil moisture measurement in the study area.

Modelling soil emissions and precision agriculture in fertilization life cycle assessment - A case study of wheat production in Austria

The environmental assessment of using optical crop sensors for variable rate nitrogen application (VRNA) has been limited by the lack of a robust method to quantify site- and technology-specific impacts. This study aimed to (1) present a comparative life cycle assessment (LCA) of a conventional winter wheat production system with and without using a crop sensor for VRNA applied to an Austrian case study. Special emphasis was placed on simulating site-specific field emissions with the DeNitrification-DeComposition (DNDC) biogeochemical soil model; (2) assess the environmental impacts of only the fertilization process; and (3) compare soil emissions simulated by the DNDC with soil emissions coming from a benchmark ecoinvent wheat production process. Three nitrogen fertilization schemes – one conventional and two VRNA – were modeled. Two functional units were used – 1 ha of cultivated winter wheat and 1 kg of winter wheat produced. The system boundary includes tillage, seeding, plant protection, nitrogen fertilization, and harvesting processes. Information communication technologies (ICT) – manufacturing of the sensor, internet and computer manufacturing and usage – were also included within the boundary. Local and global environmental impacts attributed to nitrogen emissions due to fertilization were evaluated in this LCA, including climate change (CC), fine particulate matter formation (FPMF), freshwater eutrophication (FE), freshwater ecotoxicity (FET), terrestrial acidification (TA), marine eutrophication (ME), and human noncarcinogenic toxicity (HTnc). The CC of the fertilization process was 1,662.8 kg CO2 eq./ha with conventional nitrogen application versus 1,518.8 kg CO2 eq./ha as the lower of the two VRNA results, an 8.6% reduction due to less fertilizer applied. Fertilization was found to be responsible for more than 80% of the total emissions that impact CC, 55% of the FET, 44% of the HTnc, 96% of the FE and 96% of the TA. The largest greenhouse gas (GHG) emitters were soil N emissions as simulated by the DNDC, followed by the fertilizer manufacturing process in all of the impacts, except for FET and HTnc, where fertilizer production was the highest contributor. ICT components contributed less than 1% to all of the impacts assessed. The amount of applied N fertilizer has a greater influence on NH3 and NO3 indirect soil emissions than on direct N2O emissions. This study demonstrates that using optical crop sensors for VRNA could have a limited but positive environmental impact and highlights the importance of applying site-specific soil models to estimate field emissions.

Gas Emissions and Environmental Benefits of Wheat Cultivated under Different Fertilization Managements in Mollisols

The NH3, N2O and CO2 emissions from farmland soil pose a great threat to the environment, and the application of organic fertilizer and other reasonable fertilization measures can reduce soil gas emissions. However, research into greenhouse gas emissions and environmental benefits under the combined measures of partial substitution of organic fertilizer and phased application of chemical fertilizer is limited. Herein, a field experiment involving soil gas emission monitoring was conducted to study the effects of chemical fertilizer application in stages on Mollisols’ gas emissions and environmental benefits based on the partial replacement of chemical fertilizer with organic fertilizer. Five treatments were set up, including conventional nitrogen application (CF); no nitrogen application (N0); and one-stage (N1), two-stage (N2) and three-stage (N3) application of chemical nitrogen based on 25% of chemical nitrogen being replaced with organic fertilizer. The results showed that N1 had the best emission reduction. Compared with CF, N1 reduced NH3 volatilization and N2O and CO2 emission accumulation by 27.64%, 12.09% and 15.48%, respectively. Compared with N2 and N3, N1 could better reduce the soil urease, nitrate reductase, catalase and β-glucosidase activities, reduce the rate of the conversion of urea and organic carbon, increase the content of NH4+-N in the soil and reduce the NH3 volatilization rate and N2O and CO2 emission rates. A comprehensive analysis showed that N1 showed the best effects in reducing the soil gas emission rate, and environmental cost.

Reducing and Delaying Nitrogen Recommended by Leaf Critical SPAD Value Was More Suitable for Nitrogen Utilization of Spring Wheat under a New Type of Drip-Irrigated System

Timely and accurate judgment of the nitrogen nutritional status of crops is the key to develop an optimal nitrogen application strategy. However, the evaluation criteria of nitrogen nutrition and nitrogen application strategies at each growth stage of wheat are not clear for the new type of drip-irrigated spring wheat system, TR6S (where one drip tube serves six rows of wheat, with a row spacing (RS) of 10 cm, inter-block space (IBS) of 25 cm and the lateral spacing (LS) of 80 cm, which achieved a lower drip-tube input and higher profit compared with the traditional planting system in Xinjiang). Therefore, we studied the recommendation mechanism of nitrogen fertilizer in different growth stages of wheat based on the critical SPAD values of leaves under TR6S. We set four nitrogen treatments (N1 (300 kg ha−1), N2 (270 kg ha−1), N3 (240 kg ha−1) and N4 (0 kg ha−1)) during two spring wheat growth seasons. The results revealed that the correlation coefficient (r2) between SPAD (soil plant analysis development) value and plant nitrogen content in the middle of first top leaf (L1-M) of wheat was higher than that in other leaf types and leaf positions under TR6S. A quadratic function relationship existed between a SPAD value of L1-M and grain yield. The critical SPAD values at the jointing, booting, anthesis, early milk, and late milk stages were 37.34, 39.40, 42.25, 45.57, and 35.91, respectively. In addition, through the establishment of the nitrogen application recommendation model for various wheat growth stages based on the critical SPAD value, the recommended optimal nitrogen application rates at jointing, booting, anthesis, early milk, and late milk stages were observed to be 69.4, 80.0, 90.8, 44.0, and 6.0 kg ha−1, respectively. This recommended nitrogen application strategy exhibited a better parallel relationship with the nitrogen nutrition index (NNI) of each growth period than the conventional nitrogen application strategy. Therefore, it was more in line with the actual absorption and utilization of nitrogen in wheat of TR6S. In conclusion, the SPAD values of L1-M could be relatively more accurate to evaluate the nitrogen nutrition status of wheat. Compared to traditional nitrogen application strategy, reducing and delaying nitrogen application, recommended based on the leaf SPAD model, was more suitable for nitrogen utilization under TR6S. The results can be applied in other arid and semiarid regions.

Effect of Film Mulching, Straw Retention, and Nitrogen Fertilization on the N2O and N2 Emission in a Winter Wheat Field

In order to explore the characteristics of N2O emissions from winter wheat fields in the Loess Plateau under different farming methods and nitrogen levels, the dynamic changes in N2O emissions from rain-fed winter wheat fields were quantified using static box-gas chromatography. Winter wheat 'Xiaoyan22' was used as the material, and a two-factor split area design was adopted. The conventional tillage (CT), straw incorporated into soil (SM), and flat film mulching (FM) were assigned as the main plot, and three nitrogen fertilizer rates (no nitrogen fertilization, 20% nitrogen reduction (144 kg·hm-2), and conventional nitrogen application (180 kg·hm-2)) were assigned as a split plot. Taking CT as a control, the effects of FM and SM on soil N2O emissions under different nitrogen rates were assessed. Furthermore, the correlation between relevant environmental factors and N2O emission flux were analyzed, and N2 emissions were estimated using empirical formulas. The results showed the following:the N2O emissions from the soil of each nitrogen treatment occurred within 20 days, and N2O emission flux peaked within two weeks post-fertilization. The average N2O flux, the total N2O emissions, and the global warming potential of N2O were 1.92-22.75 μg·(m2·h)-1, 0.10-0.46 kg·hm-2, and 26.72-122.15 kg·hm-2, respectively. The N2O emission coefficient of fertilizer nitrogen was 0.05%-0.28%. The total N2 emissions ranged from 0.70-1.82 kg·hm-2. The N fertilization and film mulching significantly increased the N2O emission flux (P<0.05) and the cumulative N2O emissions (P<0.05); however, SM marginally reduced the total N2O emissions. The N2O emission coefficient and global warming potential of fertilizer nitrogen under FM were significantly higher than those under CT and SM (P<0.05). The N2O emissions without nitrogen treatment were only significantly positively correlated with soil water-filled pore spaces (WFPS) (P<0.05); the N2O emissions in the N fertilization condition were significantly positively correlated with WFPS, ω(NO3--N), ω(NH4+-N), and 0-5 cm soil layer temperature (P<0.05). Overall, under the condition of no fertilization, water was the main factor to control the nitrogen transformation and soil N2O emission; nevertheless, under the N fertilization condition, both nitrification and denitrification contributed to the N2O emissions in the rain-fed winter wheat fields. Film mulching practice and nitrogen application markedly increased the N2O emissions, fertilizer nitrogen emission coefficient, and global warming potential in the rain-fed winter wheat fields. Nonetheless, straw incorporated into the soil resulted in a marginal reduction in N2O emissions.

Effects of different amounts of straw return and nitrogen fertilizer application on soil CO2 emission from maize fields.

Understanding the effects of different amounts of straw returning and nitrogen fertilizer application on soil CO2 emission from maize field can provide theoretical support for carbon sequestration and CO2 emission reduction and the implementation of black soil region conservation plan. Three rates of straw returning were set up in the semi-arid area of northwest Liaoning Province, China, i.e. 3000 (S1), 6000 (S2) and 9000 kg·hm-2(S3, full amount of straw returned to the field); crossed with three nitrogen fertilizer application rates in the sub-region, respectively, i.e. 105 (N1), 210 (N2, conventional nitrogen application rate) and 420 kg N·hm-2(N3). In addition, there was a control treatment (CK) without nitrogen fertilizer and straw returning. Soil samples were collected after 4 years field experiment with maize plantation. The influence of different treatments on maize field soil CO2 emission and the relationship between CO2 emission and soil dissolved organic carbon (DOC) and microbial biomass carbon (MBC) were investigated in an incubation experiment. The results showed that both of straw returning and nitrogen fertilizer application promoted soil CO2 emission in maize field, which were increased significantly with the increases of straw returning amount and nitrogen application amount. Nitrogen fertilizer application was the most important factor promoting soil CO2 emission in maize field. Straw returning combined with nitrogen fertilizer promoted soil CO2 emission by increasing microbial biomass and increasing DOC consumption. MBC and DOC stimulated soil CO2 emission significantly in maize field, and were mainly affected by their contents in the early stage of incubation. From the perspective of ensuring the fertilization of straw return to the field while reducing CO2 emissions, results from our experiment showed that 210 kg N·hm-2 conventional nitrogen application in combination with 6000 kg N·hm-2 straw returning (N2S2) was the most promising mode in the semi-arid area of northwest Liaoning Province.

Nitrogen and density treatment to improve resource utilization and yield in late sowing &amp;lt;italic&amp;gt;japonica&amp;lt;/italic&amp;gt; rice

<p id="C3">Recently, the phenomenon of late sowing and late transplanting in rice is becoming more and more common in central Jiangsu, a rice and wheat double cropping system area, which is caused by climate change and the expanding of comprehensive rice-and-shrimp planting model. It will lead to the mismatch of rice growth period with light and temperature resources, restricting the stable high yield of rice. This study was conducted under the condition of late sowing and late transplanting (sowing date was June 12th, transplanting date was June 30th) and the seedling was transplanted by machine. Four nitrogen application rates (N₀: 0 kg hm^-2; N₂₄₀: 240 kg hm^-2; N₃₀₀: 300 kg hm^-2; N₃₆₀: 360 kg hm^-2) and three density treatments (D₃: 3 seedlings per hole; D₄: 4 seedlings per hole; D₅: 5 seedlings per hole) were arranged, and the suitable sowing period (May 29), conventional nitrogen application rate, and the seedling number per hole (N₃₀₀D₄) were taken as the controls. Our goal is to explore the effects of nitrogen fertilizer and seedling number per hole on the growth and yield formation in late-sown <italic>japonica</italic> rice, and to provide theoretical basis for improving yield potential and resource use efficiency in late sowing and late transplanting <italic>japonica</italic> rice in central Jiangsu province. The results showed that compared with CK, the yield of each treatment decreased, mainly because of the significantly reduced spikelet number under the late sowing and late transplanting condition. The highest spikelet numbers were 11.94% and 8.12% lower than those of CK in the two years. In addition, the utilization rate of temperature and light resources, nitrogen uptake, and nitrogen utilization rate decreased under late sowing and late transplanting treatment, leading to a decrease in dry matter accumulation and yield. The yield increased with the increase of nitrogen application rate and seedling number per hole under the late sowing and late transplanting condition, while there was no consistent with the trend under N₃₆₀D₅ treatment. We assumed that it was mainly due to the increased spikelet number, larger leaf area index at heading stage, the larger proportion of efficient leaf, and the extended growth period. In summary, the utilization of temperature and light resources and the dry matter accumulation at maturity stage was improved, and the decline in yield was alleviated. Nitrogen use efficiency increased first and then decreased with the increase of nitrogen rate, and N₃₀₀D₅ treatment reached the maximum. In general, under the late sowing and late transplanting condition, in order to alleviate the yield loss and reduce nitrogen fertilizer waste, we should increase the seedling number per hole and then increase the amount of nitrogen fertilizer.

淮北地区麦茬机插优质食味粳稻氮肥减量的精确运筹

<p id="C3">At present, “nitrogen reduction” has become one of the planting measures for good eating quality<italic> japonica</italic> rice, but the scientific management plan of nitrogen fertilizer after nitrogen reduction is unclear and further studies are needed. From 2018 to 2019, good eating quality<italic> japonica</italic> rice varieties including Nanjing 505 and Nanjing 2728 were planted as materials, and four ratios of basic and tillering to panicle fertilizer including 5:5, 6:4, 7:3, and 8:2 were arranged with nitrogen application 20% less than conventional nitrogen application (CK) for mechanical transplanting rice under wheat straw returning. Yield, rice quality, and nitrogen utilization were investigated to determine the effects under nitrogen reduction for good eating quality<italic> japonica</italic> rice. The results were as follows: With the increase of the proportion of the basic and tillering fertilizer in the total nitrogen application, the yield increased first and then decreased. The 7:3 treatment had the highest yield, reaching 11,134.80-11,280.19 kg hm ^-2 for two years. Compared with CK, the yield increased by 1.23%-2.54% and there was no significant difference. The 7:3 treatment group could obtain sufficient population spikelet, higher seed-setting rate, and 1000-grain weight. With the increase of the proportion of nitrogen application in the previous period, the dry matter weight of the population at (N-n) stage and jointing stage displayed an increasing trend, while the dry matter weight at heading stage and maturity stage, the dry matter accumulation from heading to maturity, the final nitrogen accumulation and the nitrogen efficiency increased first and then decreased, and reached a peak in the 7:3 treatment. Compared with CK, nitrogen reduction treatment could ensure higher dry matter accumulation of the population at the later stage by increasing the proportion of nitrogen fertilizer application (7:3) at the early stage, which significantly improved nitrogen absorption and nitrogen use efficiency of the population by 14.10%-15.48%, and significantly higher than CK. For eating quality of<italic> japonica</italic> rice under nitrogen reduction, the processing quality deteriorated with the increase proportion of basic and tillering nitrogen, the appearance quality became better, the cooking and eating quality improved, and rice RVA profile was optimized. Under the condition of the whole wheat straw to the field, nitrogen was reduced by 20% compared with conventional fertilization. To achieve the comprehensive planting goal of high-yield, high-quality, and high-efficiency for good eating quality rice to a certain extent, nitrogen application with the ratio of basic and tillering fertilizer to panicle fertilizer 7:3 could stabilize or slightly increase the yield of good eating quality<italic> japonica</italic> rice, greatly increase nitrogen use efficiency, and improve the appearance and taste quality in rice.

Evaluation on soil fertility quality under biochar combined with nitrogen reduction

A two-year consecutive field experiment was conducted in purple soil in southwest China, to clarify the effects of biochar (0, 10, 20 and 40 t ha−1, namely, B0, B10, B20 and B40) combined with nitrogen reduction (100%, 80% and 60% of conventional nitrogen application rate, namely, N100, N80 and N60) on soil fertility. The performance of thirty-four indices related to soil chemical, physical and biological properties was evaluated by gray correlation analysis, principal component analysis and cluster analysis to determine the most appropriate mode for soil fertilization, and to identify the main soil environmental factors affecting rapeseed yield under the biochar combined with nitrogen reduction. The results indicated that available phosphorus, geometric mean diameter of water stability, fungi number, and the utilization of sugars, amino acids, polymers and carboxylic acids by microorganisms could be used as the main soil factors affecting rapeseed yield. The highest score of soil quality was observed in N100B10 treatment, followed by N80B10 and N100B20 treatments, which were almost in line with the results of rapeseed yields. Cluster analysis classified 12 treatments into 5 main groups on the basis of the measured parameters, which was mostly consistent with the result of soil quality scores. Considering both economic and environmental benefits, 10 t ha−1 biochar combined with 144 kg ha−1 nitrogen was the best combination to restore crop productivity and soil quality, and to achieve nitrogen decreasing and benefit increasing. This study provided scientific basis for the rational fertilization and scientific management of biochar combined with nitrogen fertilizer in purple soil area of southwest China.

Effects of Nitrogen Fertilizer and Straw Returning Methods on N2O Emissions in Wheat-Maize Rotational Soils

In order to explore the impacts of nitrogen fertilizer and straw returning methods on N2O emissions, a two-factor split-zone design was adopted for experimentation under the winter wheat-summer maize rotation model in the Guanzhong area of Shanxi, China. The main areas of interest were conventional nitrogen (G) and reduced nitrogen (70% G); the sub-areas were straw no return (N), straw return (S), and straw return + biochar (SB); we analyzed their impacts on N2O emissions and crop yield, and the relationships with related impact factors. The results showed that the N2O emissions peaks appeared in the wheat season and maize season treatments within 5-16 days after fertilization, and also appeared after rainfall. The N2O flux was significantly and positively correlated with soil temperature and NH4+-N content. Regardless of the wheat season, maize season, or annual total N2O emissions, the 70% GSB treatment was the lowest and the GS treatment was the highest. At the same level of nitrogen application, S treatment increased N2O emissions, SB treatment could reduce N2O emissions, both S and SB treatments could significantly increase crop yields, and SB production increased more; 70%G-level annual N2O emissions, when compared with the G level, had been reduced by 40% to 48%, while the yield has not decreased significantly. Through comprehensive consideration, a reduction of nitrogen by 30% was achieved through the combination of straw + biochar on the basis of conventional nitrogen application, while ensuring high crop yields and the best N2O emissions reduction.

Effects of biochar application combined with nitrogen fertilizer on soil physicochemical pro-perties and winter wheat yield in the typical ancient region of Yellow River, China

The aims of this study were to reveal the effects of biochar application combined with nitrogen fertilizer on soil physicochemical properties and crop yield in the typical ancient region of Yellow River, and to clarify the dynamics of carbon and nitrogen content and soil physicochemical properties with different treatments of biochar and nitrogen, which could provide scientific basis for reasonable fertilization of soil, quality improvement of cultivated land, and yield increase of winter wheat. A two-year field experiment was conducted with different biochar applications (0, 15, 30 t·hm-2) combined with different nitrogen levels (N 270, 330 kg·hm-2) to investigate their effects on soil physicochemical property in the typical ancient of Yellow River. After 2-yr biochar application, the generalized soil structure index (GSSI) was increased and three-phase structure distance index of soil (STPSD) was decreased, and three-phase ratio was significantly improved. The most ideal state of three-phase ratio was in the condition of 30 t·hm-2 biochar application. Soil compactness and bulk density was decreased, total porosity and capillary porosity was increased, water holding capacity was improved, water and gas permeability was enhanced, and soil hardening was relieved. The composition of soil aggregate was also changed. Soil aggregate >0.25 mm particle size was increased by 70.6%-94.4%, and mean weight diameter (MWD) was improved by 24.0%-48.0%. Biochar application significantly increased organic carbon content by 15.8%-67.0%, adjusted soil C/N, reduced nitrogen release intensity, improved utilization rate of nitrogen fertili-zer, and enhanced soil fertility. However, it didn't increase soil pH. Soil pH showed a significant downward in 10-20 cm layer. With the same amount of nitrogen application, biochar application significantly increased average yield of winter wheat by 9.6%-25.6% in two years. With the same amount of biochar application, average yield of winter wheat with high nitrogen application was 2.5%-4.4% higher than that with conventional nitrogen application. In summary, combined biochar and nitrogen application could improve soil micro-environment, soil fertility and crop yield. Comprehensively considering soil modification, crop yield improvement and input cost, the optimum amount of fertilization was biochar application (30 t·hm-2) combined with nitrogen fertilizer (330 kg·hm-2).

Response of yield and nitrogen use efficiency to aerated irrigation and N application rate in greenhouse cucumber

Excessive irrigation and fertilization in greenhouse cultivation have a major negative impact, causing economic and environmental problems. Efficient water and fertilizer management methods to increase water use efficiency (WUE) and nitrogen use efficiency (NUE) have been studied often in greenhouses where vegetables are cultivated. However, optimizing the application of nitrogen under certain water conditions does not continue to increase yield. This may be due to oxygen deficiency caused by water saturation in the root zone after irrigation. Aerated irrigation (AI) may be an effective management measure to further reduce the application of nitrogen fertilizer and increase the yield. In order to determine the interaction among irrigation water aeration and N application, a greenhouse study was conducted in Yangling, China, setting up two irrigation methods(AI and drip irrigation)and three N application rates (0, 240, 360 kg ha−1). In this study, AI significantly improved the nitrogen use efficiency (NUE) and yield of cucumber (Qiande 777, p < 0.05). As compared to drip irrigation, the partial factor productivity of applied N (PFP) under AI increased 28.95 % and 18.53 % at 240 and 360 kg N ha-1 nitrogen levels, respectively; cucumber yield under AI was 17.50 % higher than that with drip irrigation condition. AI and N application significantly improved crop yield: the highest yield obtained at AI and nitrogen reduction treatment (I1N2) was 72.3 t ha−1, which was 1.19 and 1.29 times higher than that of non-aerated nitrogen reduction (I0N2) and conventional nitrogen application (I0N3) (p < 0.05). Therefore, AI along with nitrogen application of 240 kg ha−1 is recommended for greenhouse cultivation of cucumber.