Nitrogen Application Strategies Research Articles

Effect of nano urea on greenhouse gas emissions in transplanted rice (Oryza sativa L.) ecosystems

The application of conventional nitrogen fertilizer (urea) to improve rice crop yield has a significant influence on soil methane (CH4) and nitrous oxide (N2O) emissions. An experiment was conducted at Tamil Nadu Agricultural University, Coimbatore, wetlands farm, during the summer of 2023. A Randomized Block Design (RBD) was used with 8 treatments and 3 replications to evaluate the impact of different nitrogen application strategies on greenhouse gas emissions, specifically methane and nitrous oxide in transplanted rice, including the varying nitrogen levels. The study aimed to improve rice growth and yield through foliar application of nano urea, focusing on the rice variety CO55 with a recommended dose of NPK (150:50:50 NPK kg/ha). The results indicated that applying 75 kg nitrogen/ha (50 % of the recommended dose) as basal through conventional urea, along with 3 nano urea foliar sprays at 20, 40 and 60 days after transplanting (T5), resulted in significantly lower methane and nitrous oxide emissions compared with 100 % of the recommended nitrogen dose i.e. 150 kg nitrogen/ha applied through conventional urea, with 25 % used at basal, active tillering, panicle initiation and heading stage (T1) and 150 kg nitrogen/ha i.e. 100 % recommended dose of nitrogen applied through conventional urea, with 50 % as basal and 2 top dressings of 25 % of the recommended dose of nitrogen (RDN) each at active tillering and panicle initiation (T2).

Highly Efficient Water and Nitrogen Application Strategies for Maintaining Summer Maize Yield in the North China Plain During Future Drought Years

ABSTRACTFuture frequent droughts threaten summer maize production in the North China Plain (NCP). A proper combination of irrigation and nitrogen (N) application can improve water and N use efficiency while maintaining summer maize yield. However, the optimal irrigation and N application strategies (OINASs) for summer maize during future drought years in the NCP require further exploration. This study applied the DSSAT‐CERES‐Maize model to investigate OINASs for summer maize for all drought years during 2021–2050 under three shared socioeconomic pathways (SSP1‐2.6, SSP2‐4.5, and SSP5‐8.5). The performance of the OINASs was subsequently evaluated against no irrigation and N application (CK) condition and a conventional irrigation and N application strategy (CINAS). The results highlight the following: (1) For all drought years under the three SSP scenarios, the base fertilizer rate should be 60 kg/hm2, after that the irrigation and N application are required during the jointing and heading periods. Under the SSP1‐2.6 scenario, the average values of irrigation and N application during each earlier period are 35.5 mm and 22 kg/hm2. Under the SSP2‐4.5 and SSP5‐8.5 scenarios, the average values are (34.5 mm, 23 kg/hm2) and (47.5 mm, 18 kg/hm2). (2) Under all SSP scenarios, the optimal irrigation amounts and N application rates are much lower than those under the CINAS. After applying OINASs for summer maize, an average of 1.16–1.22 billion kg of N and 2.98–5.19 billion m3 of freshwater will be saved per future drought year in the NCP. (3) Under all SSP scenarios, the summer maize yields under the OINASs are slightly and significantly greater than those under the CINAS and CK conditions. Moreover, both water and N use efficiencies improved under the OINASs compared with those under the CINAS, with more significant improvements in N use efficiency. The OINASs provide a practical way to ensure food security and environmental sustainability.

Optimizing maize productivity through split nitrogen application strategies

Optimizing maize productivity through split nitrogen application strategies

Combining Site-Specific Nutrient Allocation Tools Can Decrease Input Demands in No-Till Wheat Farming

ABSTRACT Wheat cultivated under conservation agriculture faces challenges in nutrient management due to altered soil dynamics and heavy residue loads. This often necessitates excessive nutrient applications to address the nutritional demands of the crop. Conducted at the Norman E. Borlaug Crop Research Centre during the winter seasons of 2020–21 and 2021–22, this study explored the effects of different nitrogen (N) application strategies on the ‘HD 2967’ wheat cultivar planted amidst rice residues using a super-seeder. The Nutrient Expert® (NE) combined with LCC-based N top dressing (NE+LCC) demonstrated the most optimal nutrient balance, leading to a 5.9% increase in grain yield and a 42.8% increase in dry matter accumulation compared to traditional methods. The composite SSNM treatments like NE+SPAD and NE+LCC recorded 48.9% and 41.9% higher SPAD values, respectively, as compared to RDF. The NE treatments resulted in significant savings, with a reduction of 60% in phosphorus usage and 5% in potassium. Economically, the NE treatment proved superior, showcasing a 12.7% higher net return compared to the RDF approach. The study concludes that site-specific nutrient management, facilitated by advanced tools like LCC and SPAD, when integrated with software-driven strategies, boosts wheat yield and fosters sustainable farming practices. This approach minimizes environmental impacts by optimizing nutrient applications and aligns with the sustainability development goal of responsible consumption and production.

Soil metagenomics reveals the effect of nitrogen on soil microbial communities and nitrogen-cycle functional genes in the rhizosphere of Panax ginseng.

Nitrogen (N) is the primary essential nutrient for ginseng growth, and a reasonable nitrogen application strategy is vital for maintaining the stability of soil microbial functional communities. However, how microbial-mediated functional genes involved in nitrogen cycling in the ginseng rhizosphere respond to nitrogen addition is largely unknown. In this study, metagenomic technology was used to study the effects of different nitrogen additions (N0: 0, N1: 20, N2: 40 N g/m2) on the microbial community and functional nitrogen cycling genes in the rhizosphere soil of ginseng, and soil properties related to the observed changes were evaluated. The results showed that N1 significantly increased the soil nutrient content compared to N0, and the N1 ginseng yield was the highest (29.90% and 38.05% higher than of N0 and N2, respectively). N2 significantly decreased the soil NO3 -N content (17.18 mg/kg lower than N0) and pH. This resulted in a decrease in the diversity of soil microorganisms, a decrease in beneficial bacteria, an increase in the number of pathogenic microorganisms, and an significant increase in the total abundance of denitrification, assimilatory nitrogen reduction, and dissimilatory nitrogen reduction genes, as well as the abundance of nxrA and napA genes (17.70% and 65.25% higher than N0, respectively), which are functional genes involved in nitrification that promote the soil nitrogen cycling process, and reduce the yield of ginseng. The results of the correlation analysis showed that pH was correlated with changes in the soil microbial community, and the contents of soil total nitrogen (TN), ammonium nitrogen (NH4 +-N), and alkaline-hydrolyzed nitrogen (AHN) were the main driving factors affecting the changes in nitrogen cycling functional genes in the rhizosphere soil of ginseng. In summary, nitrogen addition affects ginseng yield through changes in soil chemistry, nitrogen cycling processes, and functional microorganisms.

The effect of nitrogen and phosphorus fertiliser application rate and strategy on herbage production and nitrogen response in spring

Maximising herbage yield while reducing nitrogen (N) fertiliser input, particularly in spring, is essential to ensure environmental and economic sustainability on grassland farms. A plot experiment was conducted over 2 yr, comparing three different spring N application rates of 30 (30N), 60 (60N) and 90 (90N) kg N/ha using three different spring application strategies: 0:100 (S1), 50:50 (S2) or a 33:66 (S3) split across February and March, respectively. Half of the plots also received phosphorus (P) fertiliser with the first application of N at a rate of 13 kg P/ha. Nitrogen fertiliser application for the remainder of the year (April–September) was the same for all plots (23 kg N/ha/application). Both spring and cumulative herbage yields were significantly affected (P < 0.05) by N application rate; 90N had the greatest spring and cumulative herbage yield compared to 30N and 60N (10,925, 9,834 and 10,499 kg DM/ha, respectively); however, N response reduced as N application rate increased. Nitrogen application strategy had a significant effect (P < 0.05) on spring herbage yield, with S1 significantly lower than S2 and S3. Applying 13 kg P/ha in spring increased herbage yield at defoliations 2 (23 April) and 3 (15 May) (+133 and 56 kg DM/ha, respectively), relative to no application of P fertiliser, as well as increasing cumulative herbage yield (+241 kg DM/ha). The results of the current study indicate that N should be applied in early February and the strategic application of N and P during spring can increase spring and cumulative herbage yield.

Optimizing irrigation and nitrogen application strategies to improve sunflower yield and resource use efficiency in a cold and arid oasis region of Northwest China.

In arid regions, water scarcity, land degradation and groundwater pollution caused by excessive fertilization are the main constraints to sustainable agricultural production. Optimizing irrigation and fertilizer management regime is an effective means of improving crop water and fertilizer productivity as well as reducing negative impacts on the ecosystem. In order to investigate the effects of different irrigation and nitrogen (N) fertilizer rates on sunflower growth, yield, and water and N use efficiency, and to determine the optimal water and N management strategy, a two-year (2021 and 2022) field experiment with under-mulched drip irrigation was conducted in the Hexi Oasis area of Northwest China. The experiment design comprised three irrigation levels (W1, 55%-65% FC, where FC represents field water capacity; W2, 65%-75% FC; W3, 75%-85% FC) and three N application levels (N1, 120kg ha-1; N2, 180kg ha-1; N3, 240kg ha-1), resulting in a total of nine treatments. The findings indicated that increasing irrigation and N application rates led to improvements in leaf area index (15.39%-66.14%), dry matter accumulation (11.43%-53.15%), water consumption (ET, 1.63%-42.90%) and sunflower yield (6.85%-36.42%), in comparison to the moderate water deficit and low N application (W1N1) treatment. However, excess water and N inputs did not produce greater yield gains and significantly decreased both water use efficiency (WUE) and nitrogen partial factor productivity (NPFP). Additionally, a multiple regression model was developed with ET and N application as explanatory variables and yield, WUE and NPFP as response variables. The results based on the regression model combined with spatial analysis showed that an ET range of 334.3-348.7 mm and N application rate of 160.9-175.3 kg ha-1 achieved an optimal balance between the multiple production objectives: yield, WUE and NPFP. Among the different irrigation and N management strategies we evaluated, we found that W2N2 (65%-75% FC and 180kg N ha-1) was the most fruitful considering yield, resource use efficiency, etc. This result can serve as a theoretical reference for developing appropriate irrigation and N fertilization regimes for sunflower cultivation in the oasis agricultural area of northwest China.

13 Stockpiling Bahiagrass to Extend the Grazing Season and decrease Winter Supplementation Costs for South Alabama Cattle Producers

Abstract Stockpiling forage is a management practice that can be used to decrease the cost of winter cow supplementation and is defined as the process of accumulating forage late in a growing season for grazing at a later date. The purpose of this study was to explore the effectiveness of bahiagrass as a potential stockpiled forage in lower Alabama by developing a better understanding of its forage accumulation, nutritive value and persistent characteristics during the stockpiling period (6 to 10 weeks). A small-plot stockpiling trial was conducted at three locations in south Alabama (Troy, Headland, and Goodway). Nine, 6.5 m x 2.0 m plots were cut to a 7.5 cm stubble height with a buffer of 0.9 m between plots at each location beginning on September 16, 2021. Nitrogen fertilization strategy was the main plot [0 N fertilizer, split N application (33.6 kg N/ha at initiation and again 30 d later), or 67.2 kg N/ha; 3 replications/treatment; N source = urea (46-0-0)]. Stockpiling period length was the split-plot (6, 8 or 10 weeks of forage accumulation; n = 9 subplots/treatment). Response variables were measured including forage mass and nutritive value at 6, 8 and 10 weeks, and nutritive value of standing forage 30 days after the stockpiling period. Data were analyzed using the PROC MIXED procedure of SAS 9.3. As the accumulation period length increased, average forage mass increased across all treatments with 1,312.6 kg DM/ha at 6 weeks, 1,270.1 kg DM/ha at 8 weeks and 1,585.9 kg DM/ha at 10 weeks. With respect to the fertilization treatments, the split N application (1,621.8 kg DM/ha) and 67.2 kg N/ha fertilization strategies (1,606.1 kg DM/ha) did not differ in forage accumulation but were greater (P < 0.05) than bahiagrass not receiving N fertilizer (1,377.6 kg DM/ha). For nutritive value, nitrogen application strategy impacted bahiagrass crude protein (CP), with both the split N application (14%) and 67.2 kg N/ha (13.8%) treatments having a greater CP (P < 0.05) than the 0 N fertilization approach (11.7%). Average total digestible nutrients across stockpiling periods were 62.5%. Year one results study indicate that bahiagrass may support forage production and nutritive value for cow-calf operations wanting to extend grazing into the fall and early winter months in the Southeast US. Based on year one results for forage mass measured at 6, 8 and 10 weeks, stockpiled bahiagrass could provide an estimated 45 to 55 days of grazing depending on mature cow weight, pasture stocking strategy and accumulation period length.

Agro-Techniques for Enhancing Wheat Productivity under Dry-land Conditions; An Overview

Wheat, being a most important stable food crop of the world and second most important food crop after rice in India, played vital role in food security of the country. Wheat is grown in India in 6 wheat growing zones, both under irrigated and dry land conditions with a lot of variation in yield. Agronomic practices such as planting pattern, seeding rate, nitrogen (N) application strategy as well as cultivars influences the pattern of use of soil water [1]. Despite sizeable area under dry land condition, production is very low mainly due to lack of proper adaptation of agro-technology. Although, there is sufficient scope to increase the dry land wheat productivity by treating seed with 1% Potassium salts, sowing drought tolerant varieties on or before 20th November in moist zone that gives more yield as compared to delayed sowing. Fertilizer application in the moist zone @ 50, 45 and 30 Kg N, P2O5, K2O ha-1, and one foliar application @ 2 % urea performed best under dry-land condition. Intercropping of dry land wheat with legume and oilseed (4:1) give more wheat equivalent yield over sole wheat. Weed management during (30-45 DAS) critical period of crop-weed competition increase wheat productivity.

Profitable, low-emission nitrogen application strategies in Western Australian dryland cropping

Context Australian grain producers may need to report their farm greenhouse emissions. Accordingly, nitrogen fertiliser application strategies will need to include consideration of their environmental as well as economic impacts. Aims We aim to identify the nitrogen application strategies suited to dryland cropping in Western Australia that are highly profitable and that generate lower emissions. Methods Simulation modelling is used to examine the gross margins and emissions associated with four broadly different nitrogen strategies at 14 locations in the grainbelt of Western Australia for different frequencies of cropping. Key results Strategies that generate high gross margins and moderate emissions often focus on maximising the gross margin of crop production, and apply a decile 5 view of unfolding seasonal conditions. A similarly useful strategy applies nitrogen in a fixed ratio where a tonne of expected cereal receives 45 units of nitrogen from various sources, and a tonne of expected canola receives 70 units of nitrogen from various sources. Where a farmer prefers to apply a constant rate of nitrogen, then exceedingly high or low rates of application should mostly be avoided, either for economic or for environmental reasons, with the better option at many locations being to apply 50 or 75 kg N/crop ha. Conclusions A few preferred nitrogen application strategies are suggested to be applicable to dryland cropping in the study region. The strategies achieve high profits and generate moderate or low emissions. Implications Selection of highly profitable and lower emission nitrogen application strategies across the study region can deliver sizeable economic and environmental benefits.

A process simulation-based framework for resource, food, and ecology trade-off by optimizing irrigation and N management

Improving food production and resource utilization efficiency and mitigating the functional degradation of agroecosystems are major challenges worldwide. However, few studies have reconciled the conflicts among resources, food, and ecology (RFE) in agricultural production. This study develops a water–carbon–nitrogen process simulation-based framework for RFE trade-off by coupling the agro-hydrological model, i.e., AHC (Agro-Hydrological & chemical and Crop systems simulator) with the ecosystem service value (ESV) assessment method and decision-making method, i.e., VIKOR (VlseKriterijuska Optimizacija I Komoromisno Resenje). The framework is capable of (1) quantifying farmland ESVs; (2) reconciling conflicts among resource utilization, food production and ecosystem development by optimizing farmland irrigation and nitrogen (N) application strategies (FINS). The framework was used to analyze the FINS, and then to obtain the compromise decision focusing on a lower negative ESV and the maximizing group utility decision focusing on a higher yield and positive ESV for spring wheat farmland in Northwest China. Results indicated that under the local FINS, i.e., 450 mm irrigation and 340 kg ha−1 N application, the total ESV generated by spring wheat farmland per season was [4.76, 4.87] × 104 CNY ha−1. Among these ESVs, every 1 CNY ha−1 positive ESV generation was accompanied by approximately 0.11 CNY ha−1 negative ESV. Compared with the local FINS, the compromise decision, i.e., the FINS with 210 mm irrigation and 200 kg ha−1N application, significantly reduced negative ESV but caused slight losses in yield and positive ESV, while the maximizing group utility decision, i.e., the FINS with 210 mm irrigation and 260 kg ha−1N application, increased yield and positive ESV but resulted in a small negative ESV mitigation. Moreover, both FINSs could save irrigation water and N fertilizer resources, and improve water and N productivity to various degrees. This framework has excellent performance in reconciling conflicts among RFE systems and generating coordinated solutions and has potential to achieve sustainable development goals in agricultural RFE systems.

The formulation of irrigation and nitrogen application strategies under multi-dimensional soil fertility targets based on preference neural network

With the aim of improving soil fertility, it is of great significance to put forward optimal irrigation and nitrogen fertilizer application strategies for improving land productivity and alleviating non-point source pollution effects. To overcome this task, a 6-hidden layer neural network with a preference mechanism, namely Preference Neural network (PNN), has been developed in this study based on the field data from 2018 to 2020. PNN takes soil total nitrogen, organic matter, total salt, pH, irrigation time and target soil depth as input, and irrigation amount and nitrogen application rate (N rate) as output, and the prior preference matrix was used to adjust the learning of weight matrix of each layer. The outcomes indicated that the predictive accuracy of PNN for irrigation amount were (R2 = 0.913, MAE = 0.018, RMSE = 0.022), and for N rate were (R2 = 0.943, MAE = 0.009, RMSE = 0.011). The R2 predicted by PNN at the irrigation amount and N rate were 40.03% to more than 99% and 40.33% to more than 99% higher than those obtained using support vector regression (SVR), linear regression (LR), logistic regression (LOR) and traditional back propagation neural network (BPNN), respectively. In addition, compared with the neural network (Reverse Multilayer Perceptron, RMLP) with the same structure but no preference structure, the R2 of the predicted irrigation amount and N rate by PNN increased by 25.81% and 27.99%, respectively. The results showed that, through the irrigation of 93 to 102, 92 to 98 and 92 to 98 mm, along with nitrogen applications of 65 to 71, 64 to 73 and 72 to 81 kg/hm2 at 17, 59 and 87 days after sowing, respectively, the organic matter, total nitrogen, total salt content and pH of the soil would reach high fertility levels simultaneously.

Improving yield and nitrogen use efficiency of hybrid indica rice through optimizing nitrogen application strategies in the rice season under different rotation patterns

Improving yield and nitrogen use efficiency of hybrid indica rice through optimizing nitrogen application strategies in the rice season under different rotation patterns

Effects of Nitrogen Application Strategy on Nitrogen Enzyme Activities and Protein Content in Spring Wheat Grain

The aim of this study was to determine the regulatory effect of different nitrogen (N) fertilizer application rates on the grain N metabolism enzymes and protein content of drip-irrigated spring wheat under the climatic conditions in Xinjiang, China. A split plot experiment was conducted with strong gluten wheat Xinchun 38 (XC 38) and medium gluten wheat Xinchun 49 (XC 49) as experimental materials. We set up seven nitrogen treatments, in amounts of 300 (Nck), 285 (N5), 270 (N10), 255 (N15), 240 (N20), 225 (N25) and 0 (N0) kg hm−2. The effects of N application rate on nitrate reductase (NR), glutamine synthetase (GS), glutamate-pyruvate aminotransferase (GPT), protein content, protein composition, and yield of wheat grain were studied. The results showed that NR, GS, GPT, protein content, albumin, globulin, glutenin, gliadin, and yield first increased and then decreased with the decrease in N application. Furthermore, different responses to different applications between different wheat varieties was also observed. The indexes of XC 38 reached the maximum in the N15 treatment, and the yield increased 2.99~81.45%. XC 49 showed the best indicators under the N25 treatment and the yield increased 0.37~71.29%. Under the same N level, all indicators of XC 38 were better than XC 49. Correlation analysis showed that the yield and protein yield were significantly positively correlated with NR, GS, and GPT. The interaction of N fertilizer and variety had significant effects on NR, GS, GPT, protein content, components, and yield. These results show that the protein content and yield of wheat grain can be improved by reasonably adjusting the N fertilizer application strategy.

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.

Decreased panicle N application alleviates the negative effects of shading on rice grain yield and grain quality

Light deficiency is a growing abiotic stress in rice production. However, few studies focus on shading effects on grain yield and quality of rice in East China. It is also essential to investigate proper nitrogen (N) application strategies that can effectively alleviate the negative impacts of light deficiency on grain yield and quality in rice. A two-year field experiment was conducted to explore the effects of shading (non-shading and shading from heading to maturity) and panicle N application (NDP, decreased panicle N rate; NMP, medium panicle N rate; NIP, increased panicle N rate) treatments on rice yield- and quality-related characteristics. Compared with non-shading, shading resulted in a 9.5–14.8% yield loss (P<0.05), mainly due to lower filled-grain percentage and grain weight. NMP and NIP had higher (P<0.05) grain yield than NDP under non-shading, and no significant difference was observed in rice grain yield among NDP, NMP, and NIP under shading. Compared with NMP and NIP, NDP achieved less yield loss under shading because of the increased filled-grain percentage and grain weight. Shading reduced leaf photosynthetic rate after heading, as well as shoot biomass weight at maturity, shoot biomass accumulation from heading to maturity, and nonstructural carbohydrate (NSC) content in the stem at maturity (P<0.05). The harvest index and NSC remobilization reserve of NDP were increased under shading. Shading decreased (P<0.05) percentages of brown rice, milled rice, head rice, and amylose content while increasing (P<0.05) chalky rice percentage, chalky area, chalky degree, and grain protein. NMP demonstrated a better milling quality under non-shading, while NDP demonstrated under shading. NDP exhibited both lower chalky rice percentage, chalky area, and chalky degree under non-shading and shading, compared with NMP and NIP. NDP under shading decreased amylose content and breakdown but increased grain protein content and setback, contributing to similar overall palatability to non-shading. Our results suggested severe grain yield and quality penalty of rice when subjected to shading after heading. NDP improved NSC remobilization, harvest index, and sink-filling efficiency and alleviated yield loss under shading. Besides, NDP would maintain rice’s milling, appearance, and cooking and eating qualities under shading. Proper N management with a decreased panicle N rate could be adopted to mitigate the negative effects of shading on rice grain yield and quality.

Appropriate Irrigation and Fertilization Regime Restrain Indigenous Soil Key Ammonia-Oxidizing Archaeal and Bacterial Consortia to Mitigate Greenhouse Gas Emissions

Harnessing an ammonia-oxidizing microbiome has become an increasingly attractive form of management for mitigating greenhouse gas emissions in rice paddies; however, the relationship between greenhouse gas emissions and ammonia-oxidizing microbiomes, using a nitrogen application and irrigation regime, has not been well investigated. To decipher which of (and how) the specific mmonia-oxidizing bacterial species drive the greenhouse gas CH4 and N2O emissions, a field experiment with varying nitrogen application and irrigation regimes was initiated to investigate the succession of key bacterial consortia associated with GHG emissions. The results showed that water-saving irrigation (AWD) significantly increased NO3-N and NH4+-N concentrations, compared with conventional irrigation (FDF), whereas (total nitrogen) TN was little higher in FDF (1.38 g kg−1) compared with the AWD (1.36 g kg−1). During the rice-growing season, CH4 emissions ascended speedily, and emissions peaked at maximum values of 3.32 and 4.41 ug mg−2 h−1 on day 5 in FDF and AWD irrigation regimes, respectively, and then they rapidly decreased during the midseason period, maintaining a relatively low emission rate until the rice was harvested. The patterns of N2O emission fluxes had the same tendencies with N fertilization. Putative key taxa, such as Flavobacterium, Massilia, Arenimonas, Novosphingobium, Pseudomonas, exhibited significant positive relationships with higher GHG emissions, suggesting that they make particularly obvious contributions to N2O emissions. These putative taxa should be considered when designing a high nitrogen application and irrigation strategy. As such, the nitrogen application of N180, and the irrigation regimes of water-saving irrigation, are recommended methods for N conservation and the mitigation of greenhouse gas emissions in rice paddies.

Evaluation of coastal farming under salinization and optimized fertilization strategies in China

Nitrogen (N) application and salinity are key factors influencing crop yield and net economic benefit in coastal saline-alkali soils. Integrated analysis and optimization of the benefits of wheat-corn cropping under different nitrogen applications in saline soils could provide lay the scientific basis for sustainable development of agriculture in coastal farmlands. A total of 571 pair-reviewed literature data on two-factor cross-over trials, involving soil salinity and nitrogen application, were integratively analyzed. Based on multi-objective optimization of crop yield, agronomic and net economic benefits, and soil nitrate residue in coastal saline-alkali soils, area-specific nitrogen application strategies were developed. The results showed that increasing the N application rate under 1.8–2.9‰ salinity can increase crop yield and economic benefits. The net economic benefit of crops was negative under 3.5‰ salinity. Above that threshold of 3.5‰, it is not suitable for planting food crops. Consequently, it is necessary to strengthen the management of saline-alkali soils. While the application rate of 2.78 × 108 kg N in winter wheat/summer corn cropping ensured environmental protection, farmers preferred 3.08 × 108 kg of nitrogen dose. These were respectively 40.4% and 33.9% lower than the traditional dose and with relatively higher benefits too.

A recommended nitrogen application strategy for high crop yield and low environmental pollution at a basin scale

Mitigating environmental pollution and sustaining grain production have been foundational issues in sustainable development, however, ascertaining the optimal balance remains poorly investigated. This study used the Soil and Water Assessment Tool (SWAT) model to simulate crop growth and nitrogen loss, established the mapping relationship between nitrogen input to yield and water quality, and proposed a general method to determine a nitrogen application strategy for high yield and low pollution at a basin scale. Lake Xiaoxingkai basin, which is the primary maize producing area in China as well as an internationally important wetland distribution area, was used as a case study. First, we designed application scenarios for 10 base fertilizers (B1–B10) and 10 topdressing fertilizers (T1–T10) and evaluated their combined effects of maize growth to identify the critical nitrogen fertilizer rates determined under fixed and dynamic base/topdressing ratios. Then, the critical base and topdressing fertilizer rates were determined. Based on the mapping relationship between nitrogen fertilizer rate and nitrogen loss, we then revealed water quality at the basin outlet under the critical base and topdressing fertilizer rates. Finally, we proposed alternative nitrogen application strategies for high yield and low pollution while considering the different preferences of decision-makers for the economy, agriculture, and environment. We found that adjusting the ratio of base to topdressing fertilizer may create a win-win situation for agriculture and the environment, which will provide a scientific basis for sustainable development.

Effects of nitrogen application strategy and planting density optimization on sorghum yield and quality

AbstractNitrogen and planting density are two key factors affecting sorghum [Sorghum bicolor (L.) Moench] yield. In this study, two dwarf sorghum cultivars were used to analyze the effects of nitrogen and planting density on the yield and quality of sorghum in northern China. The experiment adopted a two‐factor, split‐zone design with the main plots assigned to three nitrogen application strategies, including all nitrogen applied at the sowing stage (N1), one‐third nitrogen applied at the sowing stage and two‐thirds nitrogen applied at the jointing stage (N2), and all nitrogen applied at the jointing stage (N3). The subplots were assigned to four planting densities of 20 × 104 (D1), 25 × 104 (D2), 30 × 104 (D3), and 35 × 104 plants ha−1 (D4). The results showed that N2 improved significantly the leaf area index, chlorophyll content, and net photosynthetic rate, and the number of grains per panicle and yield were significantly higher than that of the N1 and N3 treatments. Under the same density, the N2 and N3 increased the plant height. Under the same nitrogen, D3 significantly increased the yield. The combination of density and nitrogen was significantly correlated with grain number per panicle and yield. The protein content increased, and the starch content decreased by applying N3 at the jointing stage. The grain yields and grain number per plant were significantly affected by nitrogen application strategy, planting density, and their interaction. The N2D3 was the recommended planting density and nitrogen combination.