Reduced Nitrogen Supply Research Articles

Soil Microbiome Response to Reduced Nitrogen Supply in an Over-Fertilized Wheat-Maize System

Soil Microbiome Response to Reduced Nitrogen Supply in an Over-Fertilized Wheat-Maize System

Effects of N levels on land productivity and N2O emissions in maize-soybean relay intercropping.

Relay intercropping of maize and soybean can improve land productivity. However, the mechanism behind N2O emissions in this practice remains unclear. A two-factor randomized block field trial was conducted to reveal the mechanism of N2O emissions in a full additive maize-soybean relay intercropping. Factor A was three cropping systems - that is, monoculture maize (Zea mays L.), monoculture soybean (Glycine max L. Merr.) and maize-soybean relay intercropping. Factor B was different N supply, containing no N, reduced N and conventional N. Differences in N2O emissions, soil properties, rhizosphere bacterial communities and yield advantage were evaluated. The land equivalent ratio was 1.55-2.44, and the cumulative N2O emission ( ) was notably lower by 60.2% in intercropping than in monoculture, respectively. Reduced N declined without penalty on the yield advantages. The relay intercropping shifted soil properties - for example, soil organic matter, total N, and protease activity - and improved the soil microorganism community - for example, Proteobacteria and Acidobacteria. Intercropping reduced by directly suppressing nirS- and amoA-regulated N2O generation during soil N cycling, or nirS- and amoA-mediated soil properties shifted to reduce indirectly. Reduced N directly reduced by decreasing soil N content and reducing soil microorganism activities to alleviate N2O produced in soil N cycling. Conducting a full additive maize-soybean relay intercropping with reduced nitrogen supply provides a way to alleviate N2O emissions without the penalty on the yield advantage by changing rhizosphere bacterial communities and soil N cycling. © 2024 Society of Chemical Industry.

Effect of Applying Different Levels of Nitrogen Fertilizer on Growth and Essential Oil of Chamomile (Matricaria chamomilla L.)

High nitrogen input is important to guarantee higher production and essential oil yield. Ecologically, it is necessary to determine whether reduced nitrogen levels have an impact on the medicinal herbs’ productions. In the recent research, the influences of reduced nitrogen supply on the agronomic traits and essential oil productivity of chamomile have been evaluated. The experiment pots were set, and five levels of nitrogen fertilizer Urea (0, 25, 50, 75, and 100 kg N/ha) have been applied to the soil during the growing season. As a result, Chamomile growth, flower, essential oil content and yield were significantly increased when urea was applied as 75 kg N/ha. As a result, this research illustrates that reducing nitrogen supply might be a promising environmentally friendly way and an alternate strategy for improving the essential oil of chamomile and perhaps other medicinal plants, while also helping the environment.

Limnospira fusiformis harbors dinitrogenase reductase (nifH)-like genes, but does not show N2 fixation activity

East African soda lakes (EASLs), some of them world-renowned for their large flocks of flamingos, range amongst the most productive aquatic ecosystems worldwide. The non-heterocytous filamentous cyanobacterium Limnospira fusiformis (formerly Arthrospira fusiformis or Spirulina platensis), forming almost unialgal blooms, is supposed to be a key driver in those ecosystems and is gaining increasing attention because of its nutritional value. Compared to phosphorus and carbon availability, these lakes show reduced nitrogen supply. We studied the possibility of molecular nitrogen (N2) fixation in Limnospira, as contradictory statements have been published, and some closely related taxa were confirmed as N2 fixers (diazotrophs). We cultivated nine isolates originating from various EASLs under nitrate-rich and nitrate-depleted conditions. We detected dinitrogenase reductase (nifH)-like genes in all strains; however, the genes grouped within nifH cluster IV that mostly contains nitrogenases not functioning in N2 fixation. Accordingly, incubations with 15N2 gas did not support N2 fixation activity of the investigated strains. Under laboratory conditions, all strains faded during nitrate-depleted growth after approximately three weeks. Both phycocyanin and chlorophyll-a dropped to a threshold, and chlorophyll fluorescence indicated a severe problem with nitrogen supply. In summary, our data indicate that the investigated Limnospira fusiformis strains are not capable of N2 fixation.

Nitrogen use efficiency, rhizosphere bacterial community, and root metabolome reprogramming due to maize seed treatment with microbial biostimulants

Seed inoculation with beneficial microorganisms has gained importance as it has been proven to show biostimulant activity in plants, especially in terms of abiotic/biotic stress tolerance and plant growth promotion, representing a sustainable way to ensure yield stability under low input sustainable agriculture. Nevertheless, limited knowledge is available concerning the molecular and physiological processes underlying the root‐inoculant symbiosis or plant response at the root system level. Our work aimed to integrate the interrelationship between agronomic traits, rhizosphere microbial population and metabolic processes in roots, following seed treatment with either arbuscular mycorrhizal fungi (AMF) or Plant Growth‐Promoting Rhizobacteria (PGPR). To this aim, maize was grown under open field conditions with either optimal or reduced nitrogen availability. Both seed treatments increased nitrogen uptake efficiency under reduced nitrogen supply revealed some microbial community changes among treatments at root microbiome level and limited yield increases, while significant changes could be observed at metabolome level. Amino acid, lipid, flavone, lignan, and phenylpropanoid concentrations were mostly modulated. Integrative analysis of multi‐omics datasets (Multiple Co‐Inertia Analysis) highlighted a strong correlation between the metagenomics and the untargeted metabolomics datasets, suggesting a coordinate modulation of root physiological traits.

Wheat Growth, Yield, and Quality Under Water Deficit and Reduced Nitrogen Supply. A Review

Wheat Growth, Yield, and Quality Under Water Deficit and Reduced Nitrogen Supply. A Review

Opportunities of Reduced Nitrogen Supply for Productivity, Taste, Valuable Compounds and Storage Life of Cocktail Tomato

Vegetable production requires high nutrient input for ensuring high quality and high yield. As this is ecologically disadvantageous, it is necessary to determine if nitrogen (N) fertilization can be reduced without negative effects on productivity. For quality reasons, the effects of reduced N supply on taste, valuable compounds and storage life must be elucidated in parallel. This study examines whether reducing the N supply of cocktail tomatoes by 50% to recommendations affects the yield and quality of tomato fruits. Three varieties with different skin colors, yellow-orange (‘Apresa’), red (‘Delioso’) and brown (‘Bombonera’), were grown in soil in a greenhouse and harvested at the red-ripen stage. Quality parameters were assessed at harvest and after eight-day storage. Total yield decreased exclusively with ‘Bombonera’ due to reduced fruit weight. Firmness of the fruit pulp, concentrations of minerals, soluble solid contents, total acidity, total phenolics and liposoluble pigments of fruits were not influenced. However, storage affected chemical compositions positively, as shown by increased antioxidants. Descriptive sensory analyses revealed no impact of reduced N supply. From the perspective of the yield, quality and shelf life of fruits, reducing the N supply by 50% offers opportunities for the three cocktail tomato varieties in soil cultivation.

Atmospheric CO2 and VPD alter the diel oscillation of leaf elongation in perennial ryegrass: compensation of hydraulic limitation by stored-growth.

We explored the effects of atmospheric CO2 concentration (Ca ) and vapor pressure deficit (VPD) on putative mechanisms controlling leaf elongation in perennial ryegrass. Plants were grown in stands at a Ca of 200, 400 or 800μmolmol-1 combined with high (1.17kPa) or low (0.59kPa) VPD during the 16h-day in well-watered conditions with reduced nitrogen supply. We measured day:night-variation of leaf elongation rate (LERday :LERnight ), final leaf length and width, epidermal cell number and length, stomatal conductance, transpiration, leaf water potential and water-soluble carbohydrates and osmotic potential in the leaf growth-and-differentiation zone (LGDZ). Daily mean LER or morphometric parameters did not differ between treatments, but LERnight strongly exceeded LERday , particularly at low Ca and high VPD. Across treatments LERday was negatively related to transpiration (R2 =0.75) and leaf water potential (R2 =0.81), while LERnight was independent of leaf water potential or turgor. Enhancement of LERnight over LERday was proportional to the turgor-change between day and night (R2 =0.93). LGDZ sugar concentration was high throughout diel cycles, providing no evidence of source limitation in any treatment. Our data indicate a mechanism of diel cycling between daytime hydraulic and night-time stored-growth controls of LER, buffering Ca and daytime VPD effects on leaf elongation.

Perspective on oil flax yield and dry biomass with reduced nitrogen supply

Field experiment was arranged in a randomized complete block design to determine effects of nitrogen (N) application levels (J0: 150 ​kg/hm2, J1: 120 ​kg/hm2, J2: 90 ​kg/hm2, J3: 60 ​kg/hm2) on regulating dry biomass accumulation, allocation and translocation, and grain yield of oil flax during 2018 cropping season. Significant promotion was observed in dry matter during accumulation stage of oil flax, when N rate was reduced by 40% (from 150 to 90 ​kg/hm2). Under J2 treatment, translocation of dry matter from vegetative organs to pod increased by 38.46% and 61.54% respectively, when compared with J1 and J0 treatment. Dry matter distribution proportion of pod at maturity increased 4.47%–7.61%, contribution rate of leaf to grain upgraded 5.09%–8.77%, and number of effective pods and grains per pod increased by 27.16%–45.38% and 6.49%–26.59% respectively compared to other treatments. As a result, seed yield of oil flax under J2 treatment was 2.23%–18.21% higher than those of other treatments. Our study recommended 90 ​kg/hm2 as the best N fertilizer level to improve seed yield of oil flax.

Split application enhances sweetpotato starch production by regulating the conversion of sucrose to starch under reduced nitrogen supply

Split application could improve nitrogen (N) uptake and increase sweetpotato yields under reduced N supply; however, little is known about how it affects the process of starch production in storage roots. An experiment was conducted to determine the effects of three N management strategies [conventional basal N management; 80% of the conventional N rate applied as a basal fertilizer; 80% of the conventional N rate equally split at transplanting and 35 days after transplanting] on starch accumulation, enzyme activity and genes expression in the conversion of sucrose to starch and the relationships among them. The results showed that, compared with conventional basal N management, split application decreased sucrose accumulation by 11.78%, but increased starch accumulation by 11.12% through improving the starch accumulation rate under reduced N supply. The ratio of sucrose synthetase to sucrose phosphate synthase, the enzymatic activity of ADP-glucose pyrophosphorylase (AGPP), starch synthase, and the expression of their corresponding genes were promoted by split application under reduced N supply and were positively correlated with starch accumulation rate. AGPP is the rate-limiting enzyme in starch synthesis in storage roots under different N management strategies. These results indicate that starch accumulation was enhanced by split application through regulating the activity and gene expression of key enzymes involved in the conversion of sucrose to starch under reduced N supply.

Alteration of Phenolic Composition in Lettuce (Lactuca sativa L.) by Reducing Nitrogen Supply Enhances its Anti-Proliferative Effects on Colorectal Cancer Cells.

Consumption of vegetables rich in phenolic compounds has become a useful method to reduce the risk of developing several types of cancer. This study investigated the potential relationship between the alteration of phenolic compounds in lettuce induced by reduced nitrogen supply and its anti-proliferative effects on Caco-2 colorectal cancer cells. Our results showed that phenolic extracts from lettuce grown under low nitrogen conditions (LP) exhibited better anti-proliferative effects against Caco-2 cells, in part, by interfering with the cell cycle and inducing apoptosis, compared with those from lettuce supplied with adequate nitrogen. High performance liquid chromatography (HPLC) analysis and correlation analysis indicated that the better anticancer activity of LP may be not only related to the increased phenolic content, but also associated with the increased percentage contribution of quercetin to total phenolics. Taken together, alteration of phenolic composition by reduced nitrogen supply can be an effectively strategy for the development of healthy vegetables as anticancer products.

Reduced nitrogen supply enhances the cellular antioxidant potential of phenolic extracts through alteration of the phenolic composition in lettuce (Lactuca sativa L.).

Nitrogen availability is an important environmental factor that determines the production of phenolic compounds in vegetables, but the relationship between low nitrogen-induced alterations of phenolic compounds in vegetable crops and the cellular antioxidant activities of these compounds remains unclear. This study investigated the effect of reduced nitrogen supply (0.05 mmol L-1 nitrate) on phenolic metabolism in lettuce and the protective role of phenolic extracts against H2 O2 -induced oxidative stress in Caco-2 cells by determining cell damage, reactive oxygen species (ROS) content and antioxidant enzyme activities. Reduced nitrogen supply significantly improved the accumulation of phenolic compounds in lettuce, which was partially correlated with the upregulation of genes related to the phenolic synthesis pathway. Phenolic extracts from lettuce cultivated in low-nitrogen medium exhibited a better protective effect against H2 O2 -induced oxidative damage in Caco-2 cells than those from lettuce cultivated with adequate nitrogen. These extracts act by increasing the activities of antioxidant enzymes and, subsequently, by inhibiting ROS overproduction, which leads to a decrease in mitochondrial membrane and DNA damage. The results of HPLC and correlation analyses implied that the improvement in the protective capacity of lettuce extracts after low-nitrogen treatment may be related, not only to the increased content of phenolic compounds, but also to the increased percentage contribution of chlorogenic acid and quercetin derivatives to the total phenolic content. Reduction in nitrogen supply can be a powerful strategy to modify phenolic metabolism and composition in lettuce and, consequently, to improve their antioxidant capacity. © 2019 Society of Chemical Industry.

Enhancement of the carbohydrate content in Spirulina by applying CO2, thermoelectric fly ashes and reduced nitrogen supply

This study focused on evaluating whether the injection of CO2, which is associated with the use of thermoelectric fly ashes and a reduced supply of nitrogen, affects the production of intracellular carbohydrates from Spirulina. For this purpose, the addition of 0.25 g L−1 of NaNO3, along with a 10% (v v−1) of CO2 injection, a flow rate of 0.3 vvm for 1 or 5 min, as well as 0, 120 and 160 ppm of fly ashes, was studied. The assays with 120 ppm of fly ashes presented the best kinetic parameters and CO2 biofixation rate, regardless of the CO2 injection time. Meanwhile, the experiments with 120 and 160 ppm of fly ash and CO2 injection for 1 min presented 63.3 and 61.0% (w w−1) of carbohydrates, respectively. Thus, this study represents an important strategy to increase the accumulation of carbohydrates in Spirulina, with potential application in the production of bioethanol.

Impact of different rhizobial strains and reduced nitrogen supply on growth, yield and nutrient uptake in cowpea grown hydroponically

One of the strategies that contributes to more sustainable crop production in greenhouses is the reduction of nitrogen input without compromising yield. In legume crops, this goal can be achieved by using efficient rhizobial strains capable of biologically fixing atmospheric nitrogen to inoculate the seeds or the young seedlings. In soilless culture, inoculation of legumes with rhizobia can considerably reduce the input of inorganic nitrogen when preparing nutrient solutions. However, the practical application of this approach faces some difficulties. On the one hand, the supply of plant-available nitrogen is important at the early growth stage, when the rhizobia are still not functional in terms of N(2) fixation. On the other hand, inorganic nitrogen and especially nitrate N inhibits rhizobium colonization. To cope with these two contrasting needs, fine tuning of the nitrogen supply is needed, whereby legumes grown in soilless culture are inoculated with relevant rhizobial strains. In the present study, two different indigenous rhizobia, Bradyrhizobium sp. VULI1.1 and Ensifer sp. VUKA2, and a mixture of them were used to inoculate cowpea [Vigna unguiculata (L.) Walp.] grown in Perlite and supplied with different nitrogen levels to test their inoculation and nitrogen-fixation ability. Plants were supplied with either full-N (total-N 11.2 mM) or 60% of full-N until the flowering stage. Afterwards, the nitrogen supply was reduced to either 30 or 0% until the end of the cultivation period. Nodule number and weight per plant were also estimated. The reduction of nitrogen supply to 60% of the full requirements during the vegetative stage and 0% during the reproductive stage led to increased nodule weight but decreased number of nodules per plant, which resulted in reduced growth and yield. However, supplying 60% of the full nitrogen requirements up to the flowering stage and 30% thereafter increased both nodulation and yield in rhizobium-inoculated cowpea plants in comparison with 100% nitrogen supply without rhizobium inoculation throughout the cropping period. These results indicate that applying different rates of inorganic nitrogen before and after the formation of N(2)-fixing nodules could be considered an effective strategy to reduce nitrogen fertilizer supply in hydroponic cowpea crops without compromising yield.

Perspective on Wheat Yield and Quality with Reduced Nitrogen Supply.

Wheat is an important cereal crop with a high demand for nitrogen (N) fertilizer to enable the grain protein accumulation that is necessary for baking and processing quality. Here, perspectives for the development of improved wheat genotypes with higher yield stability, better grain quality, and improved N use efficiency to lower environmental impacts are discussed. The development of improved wheat genotypes, for example, genotypes that lack storage proteins that do not contribute to baking quality (e.g., by genome editing), in combination with appropriate N fertilizer management to prevent N losses into the environment underpins a novel approach to improving N use efficiency. This approach may be particularly applicable to wheats grown for animal feed, which have lower quality and functionality requirements.

Do Extended Cultivation Periods and Reduced Nitrogen Supply Increase Root Yield and Anthocyanin Content of Purple Carrots?

Purple carrots are rich in anthocyanins which are interesting as natural dyes in food and beverages. It is, thus, relevant to increase the concentration of anthocyanins by agricultural practices. We tested whether the combination of reduced nitrogen (N) supply and extended harvesting periods maximized the anthocyanin concentration of purple carrot roots, ideally without reducing their yield. The carrot variety ‘Deep Purple’ was grown with total N supplies of 220 kg N ha−1 (controls) and 73 kg N ha−1 (reduced N), respectively. Upon harvests in September, October and November, root yield and quality were assessed. Concentrations of chlorophylls (leaves) and anthocyanins (roots and leaves) were determined by spectroscopic and chemical analyses, and carbon and N content were quantified. Reduced N supply neither affected leaf or root biomass nor their chemical composition. Later harvests did not impact the yield of roots, but increased their diameter by 8.5–20%. Additionally, the anthocyanin concentrations of the roots increased by 40–50% in the controls, but not in N-limited plants, at late harvests. Consequently, extending the harvesting period might increase the anthocyanin concentration in roots of ‘Deep Purple’. Moreover, N supply might be reduced for this carrot variety without negative effects on root yield.

Erratum to: Nutritional and Structural Response of Potato Plants to Reduced Nitrogen Supply in Nutrient Solution

Erratum to: Nutritional and Structural Response of Potato Plants to Reduced Nitrogen Supply in Nutrient Solution

Nutritional and Structural Response of Potato Plants to Reduced Nitrogen Supply in Nutrient Solution

Seasonal experiments, spring studies in 2008 and 2014, and autumn studies in 2008 and 2013, were conducted to investigate the nutritional and structural response of potato leaves to reduced nitrogen (N) supply in the nutrient solution. Tissue culture plantlets of cultivars Atlantic and Superior were transplanted into a recirculating aeroponic system and grown at N concentration of 7.2 meq L−1 (6.5 meq L−1 NO3–N and 0.7 meq L−1 NH4–N). The N concentration was reduced to 3.5 meq L−1 for 4, 8, and 16 days at 30 days after transplanting (DAT), and compared with control plants which were grown under a constant concentration (7.2 meq L−1) of N. Plants that underwent reduced N brought back to normal N concentration of 7.2 meq L−1. Potato shoots grown under reduced N supply exhibited suppression of total N, calcium (Ca) and magnesium (Mg) uptake, and enhancement of phosphorus (P) uptake. The suppression of N uptake decreased shoot growth and leaf mesophyll development with inhibited chlorophyll accumulation. Photosynthesis decreased significantly with 16 days of N reduction in two seasons in 2008, but did not differ in 2013 and 2014. During spring, days to tuberization for Atlantic were shorter with the reduced N supply, whereas no difference was observed in autumn. Tuberization of Superior was delayed for two days in plants grown for 16 days with a reduced N supply. Although the number and weight of tubers harvested were significantly different in only one of the four experimental seasons, these values appeared to decline with 16 days of N reduction. The cultivar Atlantic was more susceptible to N reduction because differences in nutrient uptake, chlorophyll synthesis, tuberization, and tuber growth in response to N reduction were greater than in Superior. Response to the N reduction was greater in spring than autumn. The data indicated that careful control of N concentration is necessary to minimize possible decrease in tuberization and tuber growth, especially for the cultivar Atlantic and during the spring season.

Is it possible to enhance the concentrations of valuable compounds by reduced nitrogen supply in several vegetable species?

Is it possible to enhance the concentrations of valuable compounds by reduced nitrogen supply in several vegetable species?

Modulation of intestinal glucose transport in response to reduced nitrogen supply in young goats1

The reduction of dietary protein is a common approach in ruminants to decrease the excretion of N because ruminants are able to recycle N efficiently by the rumino-hepatic circulation. In nonruminant species an impact on other metabolic pathways such as glucose metabolism was observed when dietary protein intake was reduced. However, an impact of dietary N reduction in goats on glucose metabolism especially on intestinal glucose absorption is questionable because ruminants have very efficient endogenous recycling mechanisms. Therefore, the aim of the present study was to characterize the intestinal absorption of glucose in growing goats kept on different N supply under isoenergetic conditions. The different CP concentrations (20, 16, 10, 9, and 7% CP) of the experimental diets were adjusted by adding urea to the rations. Intestinal flux rates of glucose were determined by Ussing chamber experiments. For a more mechanistic approach, the Na(+)-dependent uptake of glucose into intestinal brush-border membrane vesicles (BBMV) and the expression patterns of the Na(+)-dependent glucose transporter SGLT1 and the glucose transporter 2 (GLUT2) were determined. Reduced N intake resulted in a decrease of plasma glucose (P < 0.001) and insulin (P = 0.004) concentrations whereas the intestinal flux rates of glucose were elevated (P < 0.001), which were inhibited by phlorizin. However, the uptake of glucose into intestinal BBMV was not changed whereas the expression of SGLT1 on mRNA (P < 0.05) and protein abundance (P = 0.03) was decreased in response to a reduced N intake. The mRNA expression of GLUT2 was not affected. From these data, it can be concluded that the intestinal absorption of glucose was modulated by changes in dietary N intake. It is suggested that intracellular metabolism or basolateral transport systems or both might be activated during this feeding regimen because the apical located SGLT1 might not be involved. Therefore, an impact of dietary N reduction on glucose metabolism in growing goats occurred as in monogastric animals.