Nitrogen Use Efficiency Research Articles

Soil and foliar Si fertilization alters elemental stoichiometry and increases yield of sugarcane cultivars

Silicon (Si) fertilization is widely recognized to improve the development of crops, especially in tropical soils and cultivation under dryland management. Herein, our working hypothesis was that Si stoichiometry favors the efficient use of carbon (C), nitrogen (N), and phosphorus (P) in sugarcane plants. Therefore, a field experiment was carried out using a 3 × 3 factorial scheme consisting of three cultivars (RB92579, RB021754 and RB036066) and three forms of Si application (control without Si; sodium silicate spray at 40 mmol L−1 in soil during planting; sodium silicate spray at 40 mmol L−1 on leaves at 75 days after emergence). All Si fertilizations altered the elemental C and P stoichiometry and sugarcane yield, but silicon-induced responses varied depending on sugarcane cultivar and application method. The most prominent impacts were found in the leaf Si-sprayed RB92579 cultivar, with a significant increase of 7.0% (11 Mg ha−1) in stalk yield, 9.0% (12 Mg ha−1) in total recoverable sugar, and 20% (4 Mg ha−1) in sugar yield compared to the Si-without control. In conclusion, our findings clearly show that silicon soil and foliar fertilization alter C:N:P stoichiometry by enhancing the efficiency of carbon and phosphorus utilization, leading to improved sugarcane production and industrial quality.

Long-term anthropogenic field management enhanced wheat productivity and resource utilization in the Loess Plateau region of China

Low precipitation and poor soil quality are the main factors that limit wheat production in the Loess Plateau region of China. Straw incorporation and/or adding organic fertilizer can enhance wheat productivity by improving the soil water content (SWC) and soil fertility, but systematic long-term research has not yet been conducted. Thus, we conducted a 12-year continuous in-situ experiment in the Loess Plateau by testing four treatments: (1) CK: no fertilization and wheat straw removal; (2) FM: straw removal and application of inorganic fertilizer; (3) SI: straw incorporation and application of inorganic fertilizer; (4) SIOM: straw incorporation and application of inorganic fertilizer, with organic fertilizer added to replace 10% of the inorganic fertilizer. Under CK, the soil chemical properties and enzyme activities tended to decrease over the years. The soil fertility was significantly higher under FM than CK, and higher under SI and SIOM than FM (P < 0.05). SIOM significantly improved the soil nutrients and wheat productivity than other treatments (P < 0.05). Compared with FM, the soil bulk density in the 0–20 cm soil layer under SIOM decreased by 4.5%, while SOC, TN, TP, AN, and Olsen-P increased by 4.5%, 6.1%, 4.9%, and 12.3%, respectively. The DOC, DON, MBC, and MBN contents increased by 18.5%, 26.4%, 15.8%, and 16.2%, respectively. The activities of urease, sucrase, and catalase increased by 12.8%, 13.6%, and 22.8%, and the N uptake, nitrogen use efficiency (NUE), water use efficiency (WUE), water productivity, and wheat yield increased by 17.8%, 43.7%, 38.6%, 33.5%, and 22.4%. SIOM obtained the highest NUE, WUE, yield, and economic benefits of 37.83%, 14.34 kg ha–1 mm–1, 4579.16 kg ha–1, and 7990.39 Yuan ha–1, respectively. Linear mixed effects modeling showed that the year and treatment significantly affected the soil fertility and wheat productivity (P < 0.05). Random forest and structural equation modeling showed that the soil and fertilizer management strategies increased wheat productivity (R2 = 0.50) by improving the soil fertility. Therefore, straw incorporation and applying inorganic/organic fertilizers are effective management strategies for improving soil fertility and wheat productivity in semi-arid areas of Loess Plateau regions.

Rapid Visual Detection of High Nitrogen-Use Efficiency Gene OsGRF4 in Rice (Oryza sativa L.) Using Loop-Mediated Isothermal Amplification Method.

The GROWTH-REGULATING FACTOR4 (OsGRF4) allele is an important target for the development of new high nitrogen-use efficiency (NUE) rice lines that would require less fertilizers. Detection of OsGRF4 through PCR (polymerase chain reaction)-based assay is cumbersome and needs advanced laboratory skills and facilities. Hence, a method for conveniently and rapidly detecting OsGRF4 on-field is a key requirement for further research and applications. In this study, we employed cleaved amplified polymorphic sequences (CAPs) and loop-mediated isothermal amplification (LAMP) techniques to develop a convenient visual detection method for high NUE gene OsGRF4NM73 (OsGRF4 from the rice line NM73). The TC→AA mutation at 1187-1188 bp loci was selected as the target sequence for the OsGRF4NM73 allele. We further employed this method of identification in 10 rice varieties that carried the OsGRF4 gene and results revealed that one variety (NM73) carries the target OsGRF4NM73 allele, while other varieties did not possess the osgrf4 genotype. The optimal LAMP reaction using hydroxynaphthol blue (HNB), a chromogenic indicator, was carried out at 65 °C for 60 min, and the presence of OsGRF4NM73 allele was confirmed by color changes from violet to sky blue. The results of this study showed that the LAMP method can be conveniently and accurately used to detect the OsGRF4NM73 gene in rice.

Nitrogen transport and assimilation in tea plant (Camellia sinensis): a review.

Nitrogen is one of the most important nutrients for tea plants, as it contributes significantly to tea yield and serves as the component of amino acids, which in turn affects the quality of tea produced. To achieve higher yields, excessive amounts of N fertilizers mainly in the form of urea have been applied in tea plantations where N fertilizer is prone to convert to nitrate and be lost by leaching in the acid soils. This usually results in elevated costs and environmental pollution. A comprehensive understanding of N metabolism in tea plants and the underlying mechanisms is necessary to identify the key regulators, characterize the functional phenotypes, and finally improve nitrogen use efficiency (NUE). Tea plants absorb and utilize ammonium as the preferred N source, thus a large amount of nitrate remains activated in soils. The improvement of nitrate utilization by tea plants is going to be an alternative aspect for NUE with great potentiality. In the process of N assimilation, nitrate is reduced to ammonium and subsequently derived to the GS-GOGAT pathway, involving the participation of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH). Additionally, theanine, a unique amino acid responsible for umami taste, is biosynthesized by the catalysis of theanine synthetase (TS). In this review, we summarize what is known about the regulation and functioning of the enzymes and transporters implicated in N acquisition and metabolism in tea plants and the current methods for assessing NUE in this species. The challenges and prospects to expand our knowledge on N metabolism and related molecular mechanisms in tea plants which could be a model for woody perennial plant used for vegetative harvest are also discussed to provide the theoretical basis for future research to assess NUE traits more precisely among the vast germplasm resources, thus achieving NUE improvement.

Silicon application mitigated the adverse effects of salt stress and deficit irrigation on drip-irrigated greenhouse tomato

Tomato (Solanum lycopersicum L.) is an important vegetable crop around the world, and water scarcity and soil salinization are two major unfavorable factors limiting the fruit yield and quality of greenhouse tomato in arid and semi-arid regions. The application of exogenous silicon has been reported to enhance tomato yield under salt or drought stress, but its effect under combined salt-drought stress remains unclear. A two-season (autumn 2021 and spring 2022) experiment was conducted with three irrigation levels (I1, 90%−100% θf, where θf is the field capacity; I2, 70%−80% θf; I3, 50%−60% θf), two soil salinity levels (S0, 0.1%, g/g; S1, 0.4%, g/g) and two silicon application rates (T0, 0 mM; T1, 2.4 mM) to explore their combined effects on leaf silicon content, photosynthetic parameters, fruit yield, nutrient yield, crop water productivity (WP), nitrogen uptake and utilization, nutrient water productivity (NWP) and economic benefit of drip-irrigated greenhouse tomato. The results showed that deficit irrigation and salt stress exerted significant inhibiting effects on leaf silicon content, photosynthetic parameters, tomato yield, and water-nitrogen productivity, but the inhibition was alleviated by silicon application, which increased leaf silicon content by 67.0%, net photosynthetic rate (Pn) by 25.3%, fruit yield by 12.3%, WP by 11.9%, nutrient yield by 10.0% (titratable acids) - 27.4% (soluble sugars) and NWP by 9.2% (titratable acids) - 26.1% (soluble sugars) on average. The average fruit yield over the two growing seasons was 66.01, 54.29 and 44.31 t ha−1 under I1, I2 and I3, and the silicon application increased average leaf silicon content by 71.9%, 65.2% and 63.0%, Pn by 11.1%, 12.9% and 7.6%, and fruit yield by 12.8%, 16.2%, and 8.1% at the three irrigation levels, respectively. Plant nitrogen uptake (NU) and nitrogen partial factor productivity (NPFP) increased but nitrogen use efficiency (NUE) tended to decrease with the increasing irrigation level, while silicon application improved NUE by 3.9% and 2.2% and NPFP by 13.8% and 11.7% in the two growing seasons, respectively. Silicon application significantly increased net profit by 24.3% and 17.7% in autumn 2021 and spring 2022, respectively. According to the principal component analysis, I1T1S0 ranked first in both growing seasons. The correlation matrix showed that fruit yield was positively correlated with leaf silicon content, Pn, stomatal conductance, WP, NU, NUE, NPFP, nutrient yield and net profit, while it had negative correlation with NWP. In conclusion, exogenous silicon application can improve the fruit yield and nutrient yield of drip-irrigated greenhouse tomato by enhancing leaf silicon content and photosynthetic capability under drought-stressed and salt-affected conditions.

Finding Balance in Adversity: Nitrate Signaling as the Key to Plant Growth, Resilience, and Stress Response.

To effectively adapt to changing environments, plants must maintain a delicate balance between growth and resistance or tolerance to various stresses. Nitrate, a significant inorganic nitrogen source in soils, not only acts as an essential nutrient but also functions as a critical signaling molecule that regulates multiple aspects of plant growth and development. In recent years, substantial advancements have been made in understanding nitrate sensing, calcium-dependent nitrate signal transmission, and nitrate-induced transcriptional cascades. Mounting evidence suggests that the primary response to nitrate is influenced by environmental conditions, while nitrate availability plays a pivotal role in stress tolerance responses. Therefore, this review aims to provide an overview of the transcriptional and post-transcriptional regulation of key components in the nitrate signaling pathway, namely, NRT1.1, NLP7, and CIPK23, under abiotic stresses. Additionally, we discuss the specificity of nitrate sensing and signaling as well as the involvement of epigenetic regulators. A comprehensive understanding of the integration between nitrate signaling transduction and abiotic stress responses is crucial for developing future crops with enhanced nitrogen-use efficiency and heightened resilience.

Layered-Strip Fertilization Improves Nitrogen Use Efficiency by Enhancing Absorption and Suppressing Loss of Urea Nitrogen

Appropriate deep application of fertilizer is the key basis for improving nitrogen use efficiency (NUE). However, the effects of different deep application methods and fertilizer types on nutrient migration, NUE and biomass in wheat season are unclear. Therefore, in this study, a barrel planting test with multilayer fertilization (15N labeled urea (U) and coated urea (CU)) was conducted in a long-term positioning trial of winter wheat in the North China Plain (NCP). We quantified the migration of fertilizer N (Ndff) in soil–plant–atmosphere and its effects on wheat biomass and NUE based on surface (Usur, CUsur), layered-strip (Ustr, CUstr) and layered-mix fertilization (Umix, CUmix) of U and CU. Compared with surface fertilization, the concentration of mineral N in root zone (0–40 cm) was increased by Ustr and Umix (8.6–50.3%), and the concentration of ammonium N was decreased by CUstr and CUmix (49.6–76.0%), but there was no change in the nitrate N. The biomass and total N absorption of wheat tissues (straw and root) were increased by 12.3–38.9% under Ustr and CUstr. Meanwhile, the distribution of Ndff in the 0–10 cm soil was decreased under Ustr and CUstr, but it was increased in the 10–30 cm soil, thereby promoting the absorption of Ndff in wheat tissues by 12.3–28.7%. The rates of absorption and loss of Ndff were the highest (57.6–58.5%) and the lowest (4.5%) under Ustr and CUstr, respectively, compared with other treatments. Consequently, layered-strip fertilization optimized the migration and utilization of Ndff within the soil–plant–atmosphere system. This approach equalized distribution, enhanced absorption and minimized losses of Ndff, resulting in an increase in NUE by 9.6–16.7%. Under the same treatment, CU was more suitable for crop nutrient requirements than U, which was more conducive to the improvement of NUE. Our findings will provide a scientific basis for the precise directional fertilization of winter wheat in the NCP.

Genetic Parameter and Hyper-Parameter Estimation Underlie Nitrogen Use Efficiency in Bread Wheat.

Estimation and prediction play a key role in breeding programs. Currently, phenotyping of complex traits such as nitrogen use efficiency (NUE) in wheat is still expensive, requires high-throughput technologies and is very time consuming compared to genotyping. Therefore, researchers are trying to predict phenotypes based on marker information. Genetic parameters such as population structure, genomic relationship matrix, marker density and sample size are major factors that increase the performance and accuracy of a model. However, they play an important role in adjusting the statistically significant false discovery rate (FDR) threshold in estimation. In parallel, there are many genetic hyper-parameters that are hidden and not represented in the given genomic selection (GS) model but have significant effects on the results, such as panel size, number of markers, minor allele frequency, number of call rates for each marker, number of cross validations and batch size in the training set of the genomic file. The main challenge is to ensure the reliability and accuracy of predicted breeding values (BVs) as results. Our study has confirmed the results of bias-variance tradeoff and adaptive prediction error for the ensemble-learning-based model STACK, which has the highest performance when estimating genetic parameters and hyper-parameters in a given GS model compared to other models.

QTL mapping and transcriptome analysis identify candidate genes influencing water–nitrogen interaction in maize

Water and nitrogen fertilization are the key factors limiting maize productivity. The genetic basis of interactions between maize genotype, water, and nitrogen is unclear. A recombinant inbred line (RIL) maize population was evaluated for seven yield and five agronomic traits under four water and nitrogen conditions: water stress and low nitrogen, water stress and high nitrogen, well-watered and low nitrogen, and well-watered and high nitrogen. Respectively eight, six, and six traits varied in response to genotype–water interactions, genotype–nitrogen interactions, and genotype–water–nitrogen interactions. Using a linkage map consisting of 896 single-nucleotide polymorphism markers and multiple-environmental quantitative-trait locus (QTL) mapping, we identified 31 QTL, including 12 for genotype–water–nitrogen interaction, across the four treatments. A set of 8060 genes were differentially expressed among treatments. Integrating genetic analysis, gene co-expression, and functional annotation revealed two candidate genes controlling genotype–water–nitrogen interactions, affecting both leaf width and grain yield. Genes involved in abscisic acid biosynthesis and bZIP, NAC, and WRKY transcription factors participated in maize response to water and nitrogen conditions. These results represent a step toward understanding the genetic regulatory network of maize that responds to water and nitrogen stress and provide a theoretical basis for the genetic improvement of both water- and nitrogen-use efficiency.

Long-term nitrogen fertilizer management for enhancing use efficiency and sustainable cotton (Gossypium hirsutum L.).

Optimal management of nitrogen fertilizer profoundly impacts sustainable development by influencing nitrogen use efficiency (NUE) and seed cotton yield. However, the effect of long-term gradient nitrogen application on the sandy loam soil is unclear. Therefore, we conducted an 8-year field study (2014-2021) using six nitrogen levels: 0 kg/hm2 (N0), 75 kg/hm2 (N1), 150 kg/hm2 (N2), 225 kg/hm2 (N3), 300 kg/hm2 (N4), and 375 kg/hm2 (N5). The experiment showed that 1) Although nitrogen application had insignificantly affected basic soil fertility, the soil total nitrogen (STN) content had decreased by 5.71%-19.67%, 6.67%-16.98%, and 13.64%-21.74% at 0-cm-20-cm, 20-cm-40-cm, and 40-cm-60-cm soil layers, respectively. 2) The reproductive organs of N3 plants showed the highest nitrogen accumulation and dry matter accumulation in both years. Increasing the nitrogen application rate gradually decreased the dry matter allocation ratio to the reproductive organs. 3) The boll number per unit area of N3 was the largest among all treatments in both years. On sandy loam, the most optional nitrogen rate was 190 kg/hm2-270 kg/hm2 for high seed cotton yield with minimal nitrogen loss and reduced soil environment pollution.

The effect of long-term controlled-release urea application on the relative abundances of plant growth-promoting microorganisms

Controlled-release urea (CRUs), including polymer-coated urea (PCU), sulfur-coated urea (SCU), and polymer/sulfur dual layer-coated urea (PSCU), have been demonstrated to increase crop yield and nitrogen use efficiency (NUE). However, the effects of long-term application of CRUs on soil microbial community and function remain unclear. In this study, a 12-year (2009–2021) 24-season wheat -maize rotation lysimeter experiment was studied to investigate the effects of PCU, SCU, and PSCU on soil microbial community composition and function. Wheat was grown, soil chemical properties were analyzed, and soil biological properties including enzyme activities and microbial community structure and function at the wheat filling stage were determined in 2021. The results showed that soil organic matter (SOM) contents were markedly increased by 3.1∼5.0% under the CRUs compared to conventional urea. Meanwhile, some carbon, nitrogen, and sulfur cycle enzyme activities, including cellulase (CE), urease and arylsulfatase (AS), were significantly enhanced by 23.4∼32.4%, 6.6∼32.1%, and 2.5∼3.7% under the CRUs compared to conventional urea, respectively. Redundancy analysis indicated that changes in bacterial and fungal communities were driven by SOM. Co-occurrence network analysis showed that wheat growth promotion by the CRUs was strongly linked to the high relative abundance (Z-score) of bacterial and fungal module 1, which included such plant growth-promoting microorganisms (PGPMs) as Arthrobacter, Bryobacter, Bradyrhizobium, Microscypha, and Marasmius. Compared with PCU, SCU and PSCU showed a better effect in increasing the relative abundances of PGPMs while inhibiting the growth of nitrobacteria, denitrifying bacteria, and plant pathogens, thereby better promoting wheat yields and reducing N loss and plant disease. Of the three CRUs, SCU and PSCU have significantly increased SOM, which provided sufficient substrate for the growth of PGPMs, thus increasing wheat yield. This study provides a support for long-term CRUs application and sustainable agriculture.

Balanced nitrogen–iron sufficiency boosts grain yield and nitrogen use efficiency by promoting tillering

Crop yield plays a critical role in global food security. For optimal plant growth and maximal crop yields, nutrients must be balanced. However, the potential significance of balanced nitrogen–iron (N–Fe) for improving crop yield and nitrogen use efficiency (NUE) has not previously been addressed. Here, we show that balanced N–Fe sufficiency significantly increases tiller number and boosts yield and NUE in rice and wheat. NIN-like protein 4 (OsNLP4) plays a pivotal role in maintaining the N–Fe balance by coordinately regulating the expression of multiple genes involved in N and Fe metabolism and signaling. OsNLP4 also suppresses OsD3 expression and strigolactone (SL) signaling, thereby promoting tillering. Balanced N–Fe sufficiency promotes the nuclear localization of OsNLP4 by reducing H2O2 levels, reinforcing the functions of OsNLP4. Interestingly, we found that OsNLP4 upregulates the expression of a set of H2O2-scavenging genes to promote its own accumulation in the nucleus. Furthermore, we demonstrated that foliar spraying of balanced N–Fe fertilizer at the tillering stage can effectively increase tiller number, yield, and NUE of both rice and wheat in the field. Collectively, these findings reveal the previously unrecognized effects of N–Fe balance on grain yield and NUE as well as the molecular mechanism by which the OsNLP4–OsD3 module integrates N–Fe nutrient signals to downregulate SL signaling and thereby promote rice tillering. Our study sheds light on how N–Fe nutrient signals modulate rice tillering and provide potential innovative approaches that improve crop yield with reduced N fertilizer input for benefitting sustainable agriculture worldwide.

Insect Frass as a Novel Organic Soil Fertilizer for the Cultivation of Spinach (Spinacia oleracea): Effects on Soil Properties, Plant Physiological Parameters, and Nutrient Status

Soils naturally low in organic matter need to be amended with recycled organic materials that would boost soil health. In this work, we tested insect frass, the excrements of the yellow mealworm, Tenebrio molitor, as a novel organic soil amendment in a spinach cultivation. In a 60-day pot experiment with spinach (Spinacia oleracea), we added frass at rates of 0, 0.25, 0.5, and 1%, as well as an inorganic nitrogen-phosphorus-potassium (NPK) fertilizer as a positive control. We found that organic matter increased significantly from 2.7% in the unamended control to 3.2% in the treatment of 1% frass, showing that frass has a valuable role in boosting soil carbon (C). Also with increasing frass rates, N uptake by plant was enhanced, due to the fact that nitrogen use efficiency (NUE) remained unchanged. These findings exhibit the fact that added N was utilized satisfactorily. However, frass effectiveness was not successful in the case of added P and K: the likely reason is the already very high P and K available contents in the unamended soil. Spinach growth was significantly favored by the amendment of frass in a rate-dependent manner: the higher biomass accumulation was found under 1% frass—six-fold higher than NC, while even at 0.25% the yield was significantly higher. Plants at this treatment had the highest chlorophyll a + b content throughout the course of the experiment and also exhibited the highest photosynthetic efficiency and performance of the plant photosynthetic apparatus under frass treatments. The index of total photosynthetic efficiency (PItotal) also fared better in the frass-added treatments upwards from 0.25%. We conclude that frass is a highly valuable soil conditioner, given the amble organic C and N that adds to soil, resulting in boosted growth of spinach. As this report is a preliminary study, we suggest that future works should expand frass testing to (a) more plants, where a series of important plant physiology features must be evaluated, and (b) the role of frass in trace element availability.

English

Overuse of nitrogenous fertilizers and low productivity of cropping systems produce the lowest nitrogen use efficiencies (NUE) in Pakistan. The surplus nitrogen (N) causes environmental degradation and reduces farm profitability. There is a lack of consideration of NUE while setting yield targets and nitrogen fertilization rates. The NUE is an essential indicator for sustainable crop production. The NUE can be improved with optimum nitrogen application without compromising crop yields. To find out an optimum nitrogen level for high NUE in wheat under agro-climatic conditions of Multan, an RCBD experiment comprising six nitrogen fertilizer doses (0, 50, 100, 150, 200, and 250 kg ha-1) was conducted during 2017-18 and 2018-19. Increasing levels of N increased the growth and yield attributes, while the maximum cost-benefit ratio was recorded at 150 kg N ha-1. Higher N doses (200 and 250 kg N ha-1) increased the biological yield but did not translate into grain yield, reducing the harvest index and cost-benefit ratio. Several N use efficiency indices were established, showing that 100 kg N ha-1 recorded the maximum nitrogen use efficiency. Partial factor productivity, internal efficiency, and physiological efficiency were maximum at a lower dose (50 kg N ha-1). In contrast, agronomic efficiency, partial nitrogen balance, recovery efficiency, and NUE were maximum at 100 kg N ha-1. Higher N doses (150-250 kg N ha-1) reduced all the N use efficiency indices. It is concluded that with a yield objective of about 5 t ha-1 under the agro-climatic conditions of Multan, a nitrogen application of 100-150 kg N ha-1 will be the most economical and will produce the maximum nitrogen use efficiency for wheat

Spatial variation in actual and required nitrogen use efficiency and the potential to close the gap by management practices

To boost crop production, China uses almost a third of the world's nitrogen (N) fertilizer. However, N losses due to enhanced application of N fertilizers has led to surface water and groundwater pollution. A reduction in N losses without reducing crop yields is possible by increasing nitrogen use efficiency (NUE), which is important for the effective management of local crop production and water quality. This study used two representative agricultural counties in China (Quzhou and Qiyang) to assess if it is possible to achieve N loss thresholds in surface and groundwater by optimizing N management measures while maintaining actual crop production. We used a spatially explicit N balance model to assess the spatial variation in actual N inputs to soil and N losses to water, and in critical N losses and associated agricultural N inputs. We also used this model to calculate the spatial variation in actual NUEs and the required NUE to align actual crop production with N thresholds. We then assessed the feasibility of achieving the necessary NUE changes through optimizing agricultural N management strategies. It was found that actual N input exceeded critical N input in 95 and 83 % of the agricultural area in Quzhou and Qiyang, respectively. To meet actual crop production without exceeding N loss thresholds, the NUE needs to increase with 11 to 15 % whereas the total N input needs to be reduced by 37 %. NUE gaps can be closed by reducing N rates, enhancing organic manure recycling, and using efficiency-enhancing fertilizers, with optimal combinations being dependent on site conditions.

Optimization of Nitrogen Dose through Fertigation in Cauliflower under Drip Irrigation

Proper management of nitrogenous fertilizers is of paramount importance for economical crop production and sustainable soil-water-atmosphere ecosystem. The present study was conducted to examine the effect of different nitrogen fertigation levels on cauliflower crop through drip irrigation. The nitrogen fertilizer (urea) was applied in 35 equal doses with irrigation water applied at alternate day through drip irrigation system. Soil moisture in the soil profile of different treatments was recorded at fortnight interval. The observed moisture content tended to decrease with increase in radial distance from the drip lateral at all soil depths. The soil moisture tended to decrease with increase in soil depth at all radial distances, throughout the soil profile, during whole crop period, in all the treatments. The cauliflower yield with N-fertigation of 90 kg ha-1 (75% of Recommended dose of N), 120 kg ha-1 (100% RDN) and 150 kg ha-1 (125% RDN) was found to be 221 q ha-1, 231 q ha-1 and 234 q ha-1 respectively. The water use efficiency (WUE) was calculated to be 80.7 kg m-3, 84.2 kg m-3 and 85.4 kg m-3 under 75% RDN, 100% RDN and 125 % RDN respectively. The nitrogen use efficiency (NUE) was found to be 245.6 kg kg-1, 192.2 kg kg-1 and 156 kg kg-1 under 75% RDN, 100% RDN and 125% RDN respectively. The increased N-fertigation level did not improve the cauliflower yield and WUE much but reduced the NUE to a great extent.

Effects of the Annual Nitrogen Fertilization Rate on Vine Performance and Grape Quality for Winemaking: Insights from a Meta-Analysis

Sustainability in grapevine cultivation requires the precise use of water and fertilizers, particularly nitrogen (N), to produce grapes of the highest quality for winemaking, while simultaneously avoiding harm to the surrounding waters and atmosphere by reducing NO3− losses and N2O and NH3 emissions from the vineyards. To address the challenge of optimizing N use in viticulture, many N fertilization trials have been carried out over the last decades, and a compilation and analysis of worldwide trials was therefore needed. The present study tackled this challenge through a meta-analysis of published research, which included 374 fertilization trials. From the compiled data, six vine production parameters and eight grape quality traits were extracted and normalized to enable comparisons between experiments. The Mitscherlich law of diminishing returns was able to satisfactorily describe the set of vine production parameters against nitrogen application rate, and the same occurred with the yeast assimilable nitrogen (YAN). In vines, both reproductive and vegetative growth similarly responded to the N application rate. In general, the nitrogen requirements for 95% of the maximum grape yield amounted to rates between 30 and 40 kg·N·ha−1, which increased nitrogen use efficiency (NUE) to values between 0.27 and 0.36 t·kg·N−1. Although several grape quality traits could not be described against the N rate in terms of any mathematical relationship, an N rate between 20 and 25 kg·N·ha−1 could be considered as maximizing grape quality for winemaking. Such N fertilization range increases NUE up to values between 0.41 and 0.47 t·kg·N−1, thus almost doubling the known NUE standards when grape quality is targeted instead of yield, although soil fertility could be exhausted in the mid-to-long term. Whatever the case, anthocyanins and polyphenols are well preserved in red grapes at such low N rates, although YAN is not. The results of this work will be useful for guiding new vine N nutrition research and N nutrition management in vineyards, thus increasing wine growing sustainability.

Nitrogen fertilization promoted microbial growth and N2O emissions by increasing the abundance of nirS and nosZ denitrifiers in semiarid maize field.

Nitrous oxide (N2O) emissions are a major source of gaseous nitrogen loss, causing environmental pollution. The low organic content in the Loess Plateau region, coupled with the high fertilizer demand of maize, further exacerbates these N losses. N fertilizers play a primary role in N2O emissions by influencing soil denitrifying bacteria, however, the underlying microbial mechanisms that contribute to N2O emissions have not been fully explored. Therefore, the research aimed to gain insights into the intricate relationships between N fertilization, soil denitrification, N2O emissions, potential denitrification activity (PDA), and maize nitrogen use efficiency (NUE) in semi-arid regions. Four nitrogen (N) fertilizer rates, namely N0, N1, N2, and N3 (representing 0, 100, 200, and 300 kg ha-1 yr.-1, respectively) were applied to maize field. The cumulative N2O emissions were 32 and 33% higher under N2 and 37 and 39% higher under N3 in the 2020 and 2021, respectively, than the N0 treatment. N fertilization rates impacted the abundance, composition, and network of soil denitrifying communities (nirS and nosZ) in the bulk and rhizosphere soil. Additionally, within the nirS community, the genera Cupriavidus and Rhodanobacter were associated with N2O emissions. Conversely, in the nosZ denitrifier, the genera Azospirillum, Mesorhizobium, and Microvirga in the bulk and rhizosphere soil reduced N2O emissions. Further analysis using both random forest and structural equation model (SEM) revealed that specific soil properties (pH, NO3--N, SOC, SWC, and DON), and the presence of nirS-harboring denitrification, were positively associated with PDA activities, respectively, and exhibited a significant association to N2O emissions and PDA activities but expressed a negative effect on maize NUE. However, nosZ-harboring denitrification showed an opposite trend, suggesting different effects on these variables. Our findings suggest that N fertilization promoted microbial growth and N2O emissions by increasing the abundance of nirS and nosZ denitrifiers and altering the composition of their communities. This study provides new insights into the relationships among soil microbiome, maize productivity, NUE, and soil N2O emissions in semi-arid regions.

Optimal fertilizer rates towards the improvement of nitrogen use efficiency and reduction of nitrogen export in paddy rice-wheat intensive farming

Introduction: Fertilizer application above plant nitrogen (N) requirements, leading to N use inefficiency, has become the primary source of N surplus, posing nonpoint pollution threats. Chao Lake has received N loadings, primarily from the agroecosystem that surrounds it. Based on 10 years of field monitoring and experiment, this study used optimum fertilizer rates (30% N reduction) to evaluate nitrogen use efficiency (NUE) and N export in the Chao Lake watershed of paddy rice-wheat rotational farming.Methods: Five treatments were tested, namely, the Blank Treatment (CK), Conventional Fertilization Treatment (CFT), High Fertilization Treatment (HFT), Reduced Fertilization Treatment (CFT), Reduced Fertilization Treatment plus Straw addition (RFTS). The parameters employed to measure NUE were 1) by calculating NUE indicators; Agronomic efficiency (kg kg-1), recovery efficiency (%), and partial factor productivity (kg kg-1) 2) using the European Union NUE framework as a comparison tool. N export was measured using N export parameters, namely, nitrogen loading (kg ha-1yr-1), nitrogen runoff loss ratio (%), and net nitrogen runoff loss ratio (%).Results and discussion: Results revealed that optimum N fertilizer input levels maintained high crop and biomass yields. The empirical model of y = y0 + a * exp (−0.5 * (x-x0)/b2) explains the relationships between input N fertilizer and corresponding yield returns. Low yield responses to increased N input beyond certain limits were observed, which may lead to N accumulations. N export was much lower from the reduced fertilization treatments than other treatments. N export increased in 10 years for both paddy rice and wheat seasons. Runoff volume influenced N export more than any other environmental factor studied.Conclusion: Overall, optimal fertilizer levels produced high NUE, maintained high economic yield, and produced lesser N exports; NUE was in the order of reduced &amp;gt; high &amp;gt; conventional fertilization treatments, while it decreased in 10 years (2008–2018) across all treatments. Such strategies that further reduce fertilizer levels by accounting for excess supplies are vital for consolidating effective N control measures.

Optimizing Fertilizer Management Practices in Summer Maize Fields in the Yellow River Basin

This study aims to examine the impact of combined irrigation and fertilizer control on the summer maize yield, nitrogen use efficiency (NE), and nitrogen leaching (NL) in the Yellow River Basin. Based on the measured data from the field summer maize experiment in 2021 and 2022, a water-nitrogen movement model was constructed for ‘Zhengdan 958’ maize under two irrigation methods (wide furrow irrigation (G) and border irrigation (Q)), three fertilizer rates (120 kg/ha (N1), 220 kg/ha (N2), and 320 kg/ha (N3)), and three fertilizer frequencies (1 (T1), 2 (T2), and 3 (T3)), yielding 18 total treatments. Calculation of nitrogen leaching was based on water nitrogen transport modeling. The study then analyzed the factors and their combined effects. A multi-objective optimization genetic algorithm (NSGA-II) was established to evaluate maize yield, nitrogen use efficiency, and nitrogen leaching. The results indicate that the determination coefficients between simulated and measured water, nitrogen values exceeded 0.74. The rate optimized HYDRUS model effectively simulated the soil solute movement. The interaction of the irrigation method, fertilizer rate, and fertilizer application frequency did not significantly affect yield and nitrogen leaching, but did significantly impact nitrogen use efficiency (p &lt; 0.05). Nitrogen leaching increased gradually as nitrogen application increased. The yield under wide furrow irrigation was 6.26% higher than that under border irrigation. The optimal coupling scheme of water and fertilizer was obtained using the genetic algorithm multi-objective optimization method, where the combined GN2T2 treatment was the optimal management model, the summer maize yield reached 14,077 kg/ha, nitrogen use efficiency and nitrogen leaching were reduced to 30.21 kg·kg−1 and 17.64 kg/ha, respectively. These findings can guide summer maize cultivation in the Yellow River Basin and assist in reducing nitrogen surface source pollution.