Reduced Nitrogen Input Research Articles

Growth, Photosynthesis and Yield Responses of Common Wheat to Foliar Application of Methylobacterium symbioticum under Decreasing Chemical Nitrogen Fertilization

Current agriculture intensifies crop cultivation to meet food demand, leading to unsustainable use of chemical fertilizers. This study investigates a few physiological and agronomic responses of common wheat following the inoculation with plant growth-promoting bacteria to reduce nitrogen inputs. A field trial was conducted in 2022–2023, in Legnago (Verona, Italy) on Triticum aestivum var. LG-Auriga comparing full (180 kg ha−1) and reduced (130 kg ha−1) N doses, both with and without foliar application at end tillering of the N-fixing bacterium Methylobacterium symbioticum. Biofertilization did not improve shoot growth, while it seldom increased the root length density in the arable layer. It delayed leaf senescence, prolonged photosynthetic activity, and amplified stomatal conductance and PSII efficiency under the reduced N dose. Appreciable ACC-deaminase activity of such bacterium disclosed augmented nitrogen retrieval and reduced ethylene production, explaining the ameliorated stay-green. Yield and test weight were unaffected by biofertilization, while both glutenin-to-gliadin and HMW-to-LMW ratios increased together with dough tenacity. It is concluded that Methylobacterium symbioticum can amplify nitrogen metabolism at a reduced nitrogen dose, offering a viable approach to reduce chemical fertilization under suboptimal growing conditions for achieving a more sustainable agriculture. Further research over multiple growing seasons and soil types is necessary to corroborate these preliminary observations.

Dynamic responses of soil microbial communities to seasonal freeze-thaw cycles in a temperate agroecosystem

Soil freeze-thaw cycles (FTCs) are common in temperate agricultural ecosystems during the non-growing season and are progressively influenced by climate change. The impact of these cycles on soil microbial communities, crucial for ecosystem functioning, varies under different agricultural management practices. Here, we investigated the dynamic changes in soil microbial communities in a Mollisol during seasonal FTCs and examined the effects of stover mulching and nitrogen fertilization. We revealed distinct responses between bacterial and fungal communities. The dominant bacterial phyla reacted differently to FTCs: for example, Proteobacteria responded opportunistically, Actinobacteria, Acidobacteria, Choroflexi and Gemmatimonadetes responded sensitively, and Saccharibacteria exhibited a tolerance response. In contrast, the fungal community composition remained relatively stable during FTCs, except for a decline in Glomeromycota. Certain bacterial OTUs acted as sensitive indicators of FTCs, forming keystone modules in the network that are closely linked to soil carbon, nitrogen content and potential functions. Additionally, neither stover mulching nor nitrogen fertilization significantly influenced microbial richness, diversity and potential functions. However, over time, more indicator species specific to these agricultural practices began to emerge within the networks and gradually occupied the central positions. Furthermore, our findings suggest that farming practices, by introducing keystone microbes and changing interspecies interactions (even without changing microbial richness and diversity), can enhance microbial community stability against FTC disturbances. Specifically, higher nitrogen input with stover removal promotes fungal stability during soil freezing, while lower nitrogen levels increase bacterial stability during soil thawing. Considering the fungal tolerance to FTCs, we recommend reducing nitrogen input for manipulating bacterial interactions, thereby enhancing overall microbial resilience to seasonal FTCs. In summary, our research reveals that microbial responses to seasonal FTCs are reshaped through land management to support ecosystem functions under environmental stress amid climate change.

Varietal differences in stem assimilate translocation and lodging resistance of rice under reduced nitrogen input

AbstractThe low translocation rate of stem assimilates and lodging under high nitrogen conditions are major factors limiting the realization of the yield potential of rice. The objectives of this study were to (1) determine the characteristics of stem nonstructural carbohydrates (NSCs) translocation and lodging resistance in different types of rice varieties and (2) elucidate the responses of stem NSCs translocation and lodging resistance to reduced nitrogen (RN) input. Field experiments were conducted using four types of rice varieties with two nitrogen levels, including normal nitrogen (NN, namely, farmer's practice, 225 kg N ha−1 for indica conventional and indica hybrid rice and 300 kg N ha−1 for japonica conventional and indica–japonica hybrid rice in Jiangsu Province, China) and 20% RN (180 and 240 kg N ha−1, respectively). The results showed that there were significant differences in the stem NSCs translocation and lodging index of the basal stem among different types of varieties; indica hybrid rice was the highest, followed by indica conventional rice and indica–japonica hybrid rice, while japonica conventional rice was the lowest. The high activities of α‐amylase, β‐amylase, and sucrose phosphate synthase may contribute to high stem NSCs translocation. Correlation analysis revealed that NSCs translocation was significantly positively correlated with 1000‐grain weight, grain yield, and lodging index, while it was significantly negatively correlated with dry weight/length, dry weight/volume, and bending stress of the basal stem. Compared with NN, RN significantly improved NSCs translocation and had no significant effect on the lodging resistance‐related traits of the basal stem or grain yield. Therefore, this research indicates that a 20% reduction in nitrogen input can maintain grain yield by enhancing stem assimilate translocation without lodging resistance reduction and consequently synergizing nitrogen reduction, high yield, and lodging resistance.

Yield, Quality, and Nitrogen Leaching of Open-Field Tomato in Response to Different Nitrogen Application Measures in Northwestern China.

The overuse of fertilizers in open-field tomato leads to soil deterioration through nutrient leaching and increases the risk of agricultural non-point source contamination. Currently, the combined effects of different fertilization methods on soil nitrogen leaching and tomato production are still unclear. Therefore, the most effective fertilization method for open-field tomato should be discovered by examining how different fertilization methods affected tomato yield and quality, nitrogen use efficiency (NUE), and soil nitrogen leaching. Compared with CK (no fertilization), fertilization significantly increased the yield, total sugar (TS), total soluble solids (TSS), and vitamin C (vC) contents of fruits (p < 0.05), and OPT (optimal fertilization, controlled release nitrogen application, 240 kg ha-1) had the largest effect on increasing yield, quality, and net profit. However, when the fertilizer application rate reached 375 kg ha-1, these indices decreased. Nitrogen leaching concentrations, leaching amount, and titratable acids (TAs) increased with increased nitrogen application rates. Compared with other treatments, OPT reduced the total leaching amounts of total nitrogen (TN), nitrate nitrogen (NO3--N), and ammonia nitrogen (NH4+-N) by 30.09-51.79%, 24.89-50.03%, and 30-65%, respectively. Principal component analysis (PCA) showed that OPT achieved the highest overall score in terms of yield, quality, and nitrogen leaching conditions. The partial least squares path modeling (PLS-PM) further reveals that applications of high amounts of nitorigen have a positive effect on soil nitrogen leaching. The amount of nitrogen leaching vegetatively affects tomato yield and quality, while plant uptake of nitrogen positively affects tomato production. These findings confirm the importance of using controlled-release fertilizers and reducing nitrogen inputs to control nitrogen leaching and enhance open-field tomato yields.

Effects of different nitrogen fertilization systems on crop yield and nitrogen use efficiency – Results of a field experiment in southern Germany

The effects of the German Fertilizer Application Ordinance (GFO) on crop yield, nitrogen use efficiency and economical performance are highly controversial in science and practice in Germany. This study presents the results of a multi-year field experiment conducted at an experimental farm in southern Germany, in which the effects of different fertilizer systems on crop yield, protein concentration and nitrogen balance were analyzed.At this study site, relatively low N mineralization from the soil N pool was detected. Wheat (triticum aestivum L.) and barley (hordeum vulgare L.) showed strong yield declines from annual to multi-annual unfertilized plots, for maize (zea mays L.), this yield decrease was not observed. The recommendations according to GFO meets the fertilizer requirement at the trial site well. A 20% reduction of fertilization compared to GFO resulted in a 5% yield reduction and a decrease in protein concentration of wheat and barley.According to the quadratic N response function, the GFO treatment was slightly below the economic optimum nitrogen rate (Nopt) for wheat, and close to Nopt for winter barley on average over the trial years. For maize, a relatively high yield variability has been observed in the trial period so far. Sensor-based fertilization resulted in very high yields with high N use efficiency (up to 85%). This fertilization system can help to reduce nitrogen input and minimize nitrogen surplus.For wheat and barley, N fertilization and N uptake were well balanced, for maize clearly negative N surpluses were calculated. Despite all the discussion and criticism of GFO, the results of the plot trial show that high yields with high N use efficiency can be achieved with fertilization according to GFO.

Elucidating the attributes of winter wheat grain quality under reduced nitrogen input through near‐infrared spectroscopy

AbstractBackground and ObjectivesResearch in crop science is usually conducted in studies with a small number of plants and crops. The aim of this project was to investigate whether near‐infrared spectroscopy (NIRS) can contribute to the analysis of such small data sets. For this purpose, NIR spectra of a small sample set of whole‐grain wheat flours of two winter wheat cultivars harvested from greenhouse and field experiments with different fertilization management were analyzed.FindingsPrincipal component analysis (PCA) facilitated the discrimination of samples based on fertilization, baking volume, and growing conditions for each wheat cultivar. In addition, PCA allowed the differentiation of wheat cultivars in a data set containing both cultivars. Spectra–structure relationships were also established. Accurate calibrations with R2 of .98, .98, and .54 were obtained for fertilization, crude protein concentration, and baking volume, respectively, even for a small data set of 10 samples of wheat cultivar Discus.ConclusionThe NIR spectra of whole‐grain wheat flour samples provided high‐resolution information on various parameters such as fertilization, baking volume, wheat cultivar, and growing site. This study demonstrates that NIRS is a valuable and efficient tool for the analysis of small data sets in crop science. This illustrates the effectiveness of the elegant NIRS method.Significance and NoveltyIn this study, small data sets of whole‐grain wheat flour from crop science experiments were analyzed by NIRS. Characteristic changes of the NIR spectra based on applied fertilizer amount, crude protein concentration, baking volume, growing site, and wheat cultivar were revealed. The detection of cause‐and‐effect relationships between spectra and chemical properties of samples contributes to a better understanding of NIR spectra of wheat flours in an interpretative way.

Response of carrot (Daucus carota Linn.) to different doses and sources of nitrogen in Sindhuli, Nepal

As a root crop known for its substantial nitrogen requirements, carrot responds well to both organic and inorganic fertilizers that supply different amounts of nitrogen. This study aimed to assess the efficacy of various proportions of farmyard manure (FYM) and recommended dosages of chemical fertilizers (RDF) in carrot production to address the issues posed by their sole use. A Randomized Complete Block Design (RCBD) was used to plan the field study, which consisted of five treatments and five replications with different nitrogen rates and sources, viz., T1 (100% FYM), T2 (25% RDF+75% FYM), T3 (50% RDF+50% FYM), T4 (75% RDF+25% FYM), and T5 (100% RDF) during December 2019 to April 2020 in the tropical region of Sindhuli, Nepal. Among the treatments, T3 exhibited the earliest germination (7.60 DAS) and the most desirable plant height (42.61 cm), root length (20.41 cm), root diameter (3.01 cm), fresh root weight plant-1 (96.04 g), total root dry matter content (15.01%), root biomass plant-1 (55.44 g), and total biomass plant-1 (85.33 g) at harvest. However, T5 resulted in the highest leaf count plant-1 (8.6) and fresh foliage weight plant-1 (42.96 g) at harvest. Similarly, T3 was significantly higher for quality parameters, such as cortex diameter (1.36 cm), pH (6.72), TSS (12.48 0Brix), TA (0.22 g liter-1), and organoleptic score (7.60). Although there were minimal root disorders in T3 (17%), T1 also had insignificant cases of cracking (8%) and postharvest weight loss (1.63%). Thus, reducing nitrogen input from the recommended dose and adding FYM improves carrot yield, quality, and shelf life. Furthermore, this guarantees higher economic returns with a B:C ratio of 1.65. Despite these positive results, the efficacy of the tested nutrient combinations needs to be analyzed on a larger scale, as well as in different ecological regions.

Evaluation of Nutrient Levels, Optical Sensors and Decision Support Tools for Nitrogen Optimization in Rice during Dry Season

Background: Improving the efficiency of nitrogen utilization in rice is vital for achieving significant crop yields with minimum harm to the environment. To tackle this challenge, various portable optical sensors and decision-support tools have been emerging in recent times. However, there is currently a lack of comprehensive assessment and comparison of these tools with different levels of fertilizer recommendation with and without additional supplementation of nano urea. Methods: The current study was carried out during the dry season of 2021 and 2022 at the P.G. Experimental Farm of Centurion University of Technology and Management. The investigated treatments encompassed the following: T1: Absolute control, T2: 90-45-45 (N-P2O5-K2O kg/ha), T3: 120-60-60 (RDF), T4: 150-75-75, T5: T2+NU @ 2 ml/L at panicle initiation, T6: T3+NU @ 2 ml/L at panicle initiation, T7: N application at LCC d™ 3, T8: N application at LCC d™4, T9: N application at SI less than 90%, T10: Nutrient Expert (TY: 5.5 t/ha), T11: Rice crop manager (TY: 5.5t/ha) which were allocated in randomized block design with three replications. Result: The findings showed that implementing nitrogen (N) application when the sufficiency index (SI) is below 90% led to a significant 16.85% boost to grain yield of rice compared to the application of 120-60-60 at fixed intervals as per the standard recommendation. In the former approach, 150 kg N/ha was applied in four splits. However, N application at a leaf color chart (LCC) value of 4 or less was considered efficient, with maximum agronomic efficiency (18.22 and 19.22 kg grain/kg N applied) and recovery efficiency (43.27% and 50.25%) observed in 2021 and 2022, respectively since, this approach resulted in a comparable yield increase and nitrogen absorption with a reduced nitrogen input.

Growth and Yield of Strawberry Cultivars under Low Nitrogen Supply in Italy

Nitrogen plays a vital role in plants’ biochemical and physiological functions, and it contributes significantly to increasing plant yield and fruit quality. Plants that efficiently absorb and utilize nitrogen enhance the efficiency of fertilizers, reducing their input costs and preventing ecosystem damage. Thus, an adequate nitrogen supply can significantly improve plant growth, fruit quality, and nutritional value. This research focused on evaluating the plant vegetative and productive performance and fruit quality of three short-day strawberry genotypes (“Cristina”, “Romina”, and “Sibilla”) that were fertilized with different amounts of nitrogen, in a crop that was protected under a plastic tunnel. The trial was conducted during two cultivation cycles. The nitrogen rates were 113, 90, and 68 kg/ha for the first year, and 118, 97, and 76 kg/ha for the second. Reduced nitrogen inputs did not significantly affect plant height, indicating that decreased nutritional intake does not harm plant development. The fruit sugar content value remained stable across all nitrogen supplies, as did the fruit titratable acidity. The cultivars maintained a medium fruit firmness at a 60% nitrogen supply, and the Chroma index was not affected. This study found that reducing nitrogen inputs did not have a significant negative impact on the three tested cultivars, making them suitable for cultivation with reduced nitrogen inputs to reduce the environmental impact and save growers’ inputs.

Reducing Nitrogen Inputs Improves the Production of Maize Grain and Forage

ABSTRACT Aiming to optimize the nitrogen (N) application rate during maize production and to improve the production process, we carried out a 2-year field study included 5 N application rates and five recommended production patterns (maize grain (P1); maize grain and straw (P2); the whole maize plant (WMP) forage (P3); grain, straw and milk (P4); WMP forage and milk (P5)). The results showed that reducing N application rate from 400 to 300 kg N ha−1 maintained the maize yield and the forage quality for different patterns. Compared to 400 kg N ha−1, 300 kg N ha−1 increased the economic profit and the economic efficiency of N fertilizer (EEN) of all patterns. Compared to the optimal N rate with the same pattern, the 75% of optimal N rate caused in a 2% decrease in economic profits, but saved N fertilizer by 25% and increased EEN by 30%; the 75% of optimal N rate saved N fertilizer by 50% and increased EEN by about 40%, but caused in a 8–9% decrease in economic profits. Therefore, the 75% of optimal N rate was optimal in improving maize production. When the economic profits from the five patterns were optimized based on regression equations, ranking the optimal N rates and economic profits in increasing order led to the following result: P1 < P2 < P3 < P4 < P5. The extending maize production chain from P1 to P5 improved economic profits, and increased the optimal N rate, improving the productivity of N fertilizer.

Reduced Nitrogen Input Combined with Nitrogen-Saving japonica Rice Varieties Balances Yield and Nitrogen Use Efficiency in The Lower Reaches of the Yangtze River in China

Maintaining rice yield and reducing nitrogen (N) input are two important targets in sustainable agriculture practices. The adoption of a nitrogen-saving variety (NSV) provides a unique opportunity to achieve this. However, limited options in NSV japonica rice and a lack of information on their responses to N reduction make management decisions difficult. This study aims to explore the responses of yield and nitrogen use efficiency (NUE) in NSV to N reduction. Two newly released NSVs and two popular general varieties (GVs) of japonica rice were field tested in Yangzhou, located at the lower reaches of Yangtze River of China, in two consecutive years. The results showed that for NSVs, with a 40–60% reduction in common practice N rate (300 Kg ha−1), the rice yield could maintain a record average level (p &lt; 0.05), whereas the yield for the GV would drop 20–30% (p &lt; 0.05). This indicates that combining the practices of adoption of NSV and N reduction to 120–180 Kg N ha−1 could balance the yield and N consumption. Moderate N reduction promotes the N accumulation and NUE, and it increases the number of tillers, the productive tiller percentage and the total amount of spikelets in the population, and increases the carbon and N metabolism of the population in the NSV. Compared with GV, NSV showed higher NUE and non-structural carbohydrate re-mobilization in the reduced N rate. The results showed that the practice of N reduction has to adopt NSV at the same time in order to maintain the grain yield level in rice.

A behavioural agent-based modelling approach for the ex-ante assessment of policies supporting precision agriculture

Precision agriculture technologies can help reduce nitrogen losses and the associated negative environmental impacts. As the adoption rate of such technologies in small-scale farming systems is still low, additional policy measures are required to support their broader application. We provide an ex-ante assessment of policy measures (payments for reduced nitrogen, subsidy for the technology or area subsidies) to incentivize the adoption of sensing technologies for site-specific nitrogen fertilization with a specific focus on farmers' behavioural characteristics such as reluctance to change and their individual perception of the policy measures. We combine a bio-economic optimization model with data from a choice experiment, survey, and census data in an agent-based modelling framework. We simulate the impact of the policy measures on farmers' adoption decisions in Swiss wheat production. Simulations suggest that for the same level of nitrogen reduction a results-based payment (paying farmers for reduced nitrogen) is 1.5 times more cost-efficient than area-based subsidies and subsidies for technology use. Our results also suggest that considering how farmers perceive costs and benefits decreases the potential to reduce nitrogen input by ∼20%. We conclude that disregarding behavioural factors such as the perception of the instrument may result in a significant overestimation of the policy effect.

Transcriptomic and Physiological Analyses of Two Rice Restorer Lines under Different Nitrogen Supplies Provide Novel Insights into Hybrid Rice Breeding.

Improving plant nitrogen-use efficiency (NUE) has great significance for various crops, particularly in hybrid breeding. Reducing nitrogen inputs is key to achieving sustainable rice production and mitigating environmental problems. In this study, we analyzed the transcriptomic and physiological changes in two indica restorer lines (Nanhui511 [NH511] and Minghui23 [MH23]) under high nitrogen (HN) and low nitrogen (LN) conditions. Compared to MH23, NH511 was more sensitive to different nitrogen supplies and exhibited higher nitrogen uptake and NUE under HN conditions by increasing lateral root and tiller numbers in the seedling and maturation stages, respectively. NH511 also exhibited a lower survival rate than MH23 when planted in a chlorate-containing hydroponic solution, indicating its HN uptake ability under different nitrogen-supply conditions. Transcriptomic analysis showed that NH511 has 2456 differentially expressed genes, whereas MH23 had only 266. Furthermore, these genes related to nitrogen utilization showed differential expression in NH511 under HN conditions, while the opposite was observed in MH23. Our findings revealed that NH511 could be regarded as elite rice and used for breeding high-NUE restorer lines by regulating and integrating nitrogen-utilization genes, which provides novel insights for the cultivation of high-NUE hybrid rice.

Genome-wide identification of nitrate-responsive microRNAs by small RNA sequencing in the rice restorer cultivar Nanhui 511.

Rice productivity relies heavily on nitrogen fertilization, and improving nitrogen use efficiency (NUE) is important for hybrid rice breeding. Reducing nitrogen inputs is the key to achieving sustainable rice production and reducing environmental problems. Here, we analyzed the genome-wide transcriptomic changes in microRNAs (miRNAs) in the indica rice restorer cultivar Nanhui 511 (NH511) under high (HN) and low nitrogen (LN) conditions. The results showed that NH511 is sensitive to nitrogen supplies and HN conditions promoted the growth its lateral roots at the seedling stage. Furthermore, we identified 483 known miRNAs and 128 novel miRNAs by small RNA sequencing in response to nitrogen in NH511. We also detected 100 differentially expressed genes (DEGs), including 75 upregulated and 25 downregulated DEGs, under HN conditions. Among these DEGs, 43 miRNAs that exhibited a 2-fold change in their expression were identified in response to HN conditions, including 28 upregulated and 15 downregulated genes. Additionally, some differentially expressed miRNAs were further validated by qPCR analysis, which showed that miR443, miR1861b, and miR166k-3p were upregulated, whereas miR395v and miR444b.1 were downregulated under HN conditions. Moreover, the degradomes of possible target genes for miR166k-3p and miR444b.1 and expression variations were analyzed by qPCR at different time points under HN conditions. Our findings revealed comprehensive expression profiles of miRNAs responsive to HN treatments in an indica rice restorer cultivar, which advances our understanding of the regulation of nitrogen signaling mediated by miRNAs and provides novel data for high-NUE hybrid rice cultivation.

Managing plant density and nitrogen fertilizer to reduce nitrogen input without yield reduction of late-sown cotton after wheat by improving light interception and sink nitrogen partitioning in a double cropping system

Managing plant density and nitrogen fertilizer to reduce nitrogen input without yield reduction of late-sown cotton after wheat by improving light interception and sink nitrogen partitioning in a double cropping system

Biochar and biofertilizer reduced nitrogen input and increased soybean yield in the maize soybean relay strip intercropping system

Applying Biochar (BC) or biofertilizers (BF) are potential approaches to reduce the nitrogen input and mitigate soil degradation in the maize soybean relay strip intercropping system (IS). In 2019 and 2020, a two-factor experiment was carried out to examine the effects of BC and BF on soil productivity and yield production in IS. 4 N input levels (8.4, 22.5, 45 kg, and 67.5 kg ha − 1) referred to as N0, N1, N2, and N3 were paired with various organic treatments, including BC (150 kg ha − 1), BF (300 kg ha − 1), and without organic amendments (CK). The results demonstrated that, despite BF decreasing the biomass and N distribution into grains, BF performed better on improved soybean yield (5.2–8.5%) by increasing the accumulation of soybean biomass (7.2 ~ 11.6%) and N (7.7%). Even though BC and BF have a detrimental effect on soybean nitrogen fixation by reducing nodule number and weight, the values of soybean nitrogenase activity and nitrogen fixation potential in BF were higher than those in BC. Additionally, BF performs better at boosting the soil’s nitrogen content and nitrate reductase and urease activity. BF increased the concentration of total N, soil organic matter, Olsen-phosphorus, and alkaline hydrolyzable N in the soil by 13.0, 17.1, 22.0, and 7.4%, respectively, compared to CK. Above all, applying BF combination with N2 (45 kg ha − 1 N) is a feasible strategy to raise crop grain output and keep soil productivity over the long term in IS.

Effects of chicken manure substitution for mineral nitrogen fertilizer on crop yield and soil fertility in a reduced nitrogen input regime of North-Central China.

Organic manure has been proposed to substitute part of the chemical fertilizers. However, past research was usually conducted in regimes with excessive nitrogen (N) fertilization, which was not conducive to the current national goal of green and sustainable development. Therefore, exploring the potential of organic fertilizer substitution for mineral N fertilizer under regimes with reduced N inputs is important to further utilize organic fertilizer resources and establish sustainable nutrient management recommendations in the winter wheat (Triticum aestivum L.) - summer maize (Zea mays L.) rotation system in North-central China. In this study, a 4-year field experiment was conducted to investigate the effects of different chicken manure substitution ratios on crop yield, N recovery efficiency (REN), soil N and soil organic matter contents, to clarify the optimal organic substitution ratio of N fertilizer under reduced N application (from 540kg N ha-1 year-1 to 400kg N ha-1 year-1). Six substitution ratios were assessed: 0%, 20%, 40%, 60%, 80% and 100% under 200kg N ha-1 per crop season, respectively, plus a control with no N application from chemical fertilizer or chicken manure. Results showed that the highest yield was achieved under the 20% substitution ratio treatment, with 1.1% and 2.3% higher yield than chemical N alone in wheat season and maize seasons, respectively. At the chicken manure substitution ratios of 20% in wheat season and 20%-40% in maize season, the highest REN reached to 31.2% and 26.1%, respectively. Chicken manure application reduced soil residual inorganic N with increasing substitution ratio. All organic substitution treatments increased soil organic matter and total N content. Implementing 20% organic substitution in wheat season and 20%-40% in maize season under the reduced N application regime in the North-central China is therefore recommended in order to achieve high crop yields and REN, improve soil fertility and enhance livestock manure resource utilization.

Zinc- and magnesium-doped hydroxyapatite-urea nanohybrids enhance wheat growth and nitrogen uptake

The ongoing and unrestrained application of nitrogen fertilizer to agricultural lands has been directly linked to climate change and reductions in biodiversity. The agricultural sector needs a technological upgrade to adopt sustainable methods for maintaining high yield. We report synthesis of zinc and magnesium doped and undoped hydroxyapatite nanoparticles, and their urea nanohybrids, to sustainably deliver nitrogen to wheat. The urea nanohybrids loaded with up to 42% nitrogen were used as a new source of nitrogen and compared with a conventional urea-based fertilizer for efficient and sufficient nitrogen delivery to pot-grown wheat. Doping with zinc and magnesium manipulated the hydroxyapatite crystallinity for smaller size and higher nitrogen loading capacity. Interestingly, 50% and 25% doses of urea nanohybrids significantly boosted the wheat growth and yield compared with 100% doses of urea fertilizer. In addition, the nutritional elements uptake and grain protein and phospholipid levels were significantly enhanced in wheat treated with nanohybrids. These results demonstrate the potential of the multi-nutrient complexes, the zinc and magnesium doped and undoped hydroxyapatite-urea nanoparticles, as nitrogen delivery agents that reduce nitrogen inputs by at least 50% while maintaining wheat plant growth and nitrogen uptake to the same level as full-dose urea treatments.

Nitric Oxide Emissions from Chinese Upland Cropping Systems and Mitigation Strategies: A Meta-analysis

Agroecosystems are a significant source of nitric oxide (NO), a potent atmospheric pollutant. It has been well documented that the NO emissions from upland cropping systems and their emission factors are large relative to those from paddy fields. However, a clear understanding of their uncertainty and regulating factors is still lacking. To date, various field experiments have been conducted to investigate NO emissions and mitigation, providing an opportunity for a Meta-analysis. The aims of this study were to 1 investigate the uncertainty and regulating factors of NO emissions and emission factors from maize-winter wheat rotations, non-waterlogging period in rice-winter wheat rotations, vegetable fields, tea plantations, and fruit orchards across China by extracting data from peer-reviewed publications, and 2 quantify the mitigation potential of management practices, such as reducing nitrogen fertilizer input, organic substitution with chemical fertilizers, and application of enhanced-efficiency nitrogen fertilizers or biochar by performing a pairwise Meta-analysis. A total of 49 references (published from 2006 to 2021) were collected. The results showed that annual NO emissions from the maize-winter wheat rotations, tea plantations, and fruit orchards averaged 1.44, 7.45, and 0.92 kg·hm-2, respectively, with significant differences among the three cropping systems (P<0.05). The seasonal NO emissions from the non-waterlogging period in rice-winter wheat rotations and vegetable fields within a single growth period averaged 2.13 kg·hm-2 and 2.09 kg·hm-2, respectively. The NO emissions positively related to nitrogen inputs in the maize-winter wheat rotations, non-waterlogging period in rice-winter wheat rotations, and tea plantations (P<0.01) but not in the vegetable fields and fruit orchards. The emission factors averaged 0.31%, 0.71%, 0.96%, 1.74%, and 0.13% in the maize-winter wheat rotations, non-waterlogging period in rice-winter wheat rotations, vegetable fields, tea plantations, and fruit orchards, respectively, with significant differences among the cropping systems (P<0.01), except between the maize-winter wheat rotations and non-waterlogging period in rice-winter wheat rotations or vegetable fields (P>0.05). Considering the substantial differences in emission factors among the cropping systems, a specific emission factor for each system should be applied when estimating an agricultural NO budget at a regional or national scale. Reducing nitrogen input only mitigated NO emissions (by 36%) at a reducing nitrogen ratio above 25% but did not impact emission factors. An optimal reducing nitrogen ratio has to be further evaluated without crop productivity penalties. Organic substitution in soils with organic carbon content<15 g·kg-1 or pH<7 and application of enhanced-efficiency fertilizers in the maize-winter wheat rotation simultaneously mitigated NO emissions (by -46%- -38%) and emission factors (by -62%- -45%). By contrast, biochar amendment had no significant effects on either NO emissions or emission factors. These findings highlight a possibility of choosing an effective NO mitigation strategy under specific field conditions.

Eutrophication decreases Halophila beccarii plant organic carbon contribution to sequestration potential

Seagrass ecosystems rank among the most effective blue carbon sinks in climate change mitigation and greenhouse gas removal. Nutrient pollution has emerged as a leading threat to seagrass decline and has diminished the carbon sequestration potential in recent decades. Changes in the nutrient regime can also impact the organic carbon compositions (labile and refractory organic carbon compositions) of seagrass tissues, with important implications for determining the quantity and quality of carbon sequestration. However, there is still little information about the impact of nutrient loading on seagrass plant refractory organic carbon composition (ROC), which hinders our ability to reveal the driving mechanisms of anthropogenic factors that decrease seagrass organic carbon sequestration capability. Here, a multidisciplinary approach was employed to investigate the organic carbon variations of Halophila beccarii at five seagrass meadows with contrasting nutrient loading levels. The results showed that H. beccarii plant nitrogen (N) content ranged from 2.21% to 5.65%, which well reflected the external nutrient loading levels. High nutrient loading elevated labile organic carbon content, like free amino acids and soluble sugars. Nevertheless, ROC content (cellulose-associated organic matter) decreased with increasing nutrient loading, which presented a significant negative linear correlation with plant N content. These results provide evidence that eutrophic conditions enhance H. beccarii plant quality (high N and labile organic carbon) and consequently decrease plant ROC sequestration potential. This suggests that reducing nitrogen input to seagrass meadows would aid in increasing seagrass carbon storage.