Regulating Leaf Photosynthesis and Soil Microorganisms through Controlled-Release Nitrogen Fertilizer Can Effectively Alleviate the Stress of Elevated Ambient Ozone on Winter Wheat.

The mitigation mechanisms of a kind of controlled-release nitrogen fertilizer (sulfur-coated controlled-release nitrogen fertilizer, SCNF) in response to O3 stress on a winter wheat (Triticum aestivum L.) variety (Nongmai-88) were studied in crop physiology and soil biology through the ozone-free-air controlled enrichment (O3-FACE) simulation platform and soil microbial metagenomics. The results showed that SCNF could not delay the O3-induced leaf senescence of winter wheat but could enhance the leaf size and photosynthetic function of flag leaves, increase the accumulation of nutrient elements, and lay the foundation for yield by regulating the release rate of nitrogen (N). By regulating the soil environment, SCNF could maintain the diversity and stability of soil bacterial and archaeal communities, but there was no obvious interaction with the soil fungal community. By alleviating the inhibition effects of O3 on N-cycling-related genes (ko00910) of soil microorganisms, SCNF improved the activities of related enzymes and might have great potential in improving soil N retention. The results demonstrated the ability of SCNF to improve leaf photosynthetic function and increase crop yield under O3-polluted conditions in the farmland ecosystem, which may become an effective nitrogen fertilizer management measure to cope with the elevated ambient O3 and achieve sustainable production.

Transcriptomic and Hormonal Changes in Wheat Roots Enhance Growth under Moderate Soil Drying.

Understanding the mechanisms that regulate plant root growth under soil drying is an important challenge in root biology. We observed that moderate soil drying promotes wheat root growth. To understand whether metabolic and hormonic changes are involved in this regulation, we performed transcriptome sequencing on wheat roots under well-watered and moderate soil drying conditions. The genes upregulated in wheat roots under soil drying were mainly involved in starch and sucrose metabolism and benzoxazinoid biosynthesis. Various plant hormone-related genes were differentially expressed during soil drying. Quantification of the plant hormones under these conditions showed that the concentrations of abscisic acid (ABA), cis-zeatin (CZ), and indole-3-acetic acid (IAA) significantly increased during soil drying, whereas the concentrations of salicylic (SA), jasmonic (JA), and glycosylated salicylic (SAG) acids significantly decreased. Correlation analysis of total root length and phytohormones indicated that CZ, ABA, and IAA are positively associated with wheat root length. These results suggest that changes in metabolic pathways and plant hormones caused by moderate soil drying help wheat roots grow into deeper soil layers.

Old pesticide, new use: Smart and safe enantiomer of isocarbophos in locust control.

Locust plagues are still worldwide problems. Selecting active enantiomers from current chiral insecticides is necessary for controlling locusts and mitigating the pesticide pollution in agricultural lands. Herein, two enantiomers of isocarbophos (ICP) were separated and the enantioselectivity in insecticidal activity against the pest Locusta migratoria manilensis (L. migratoria) and mechanisms were investigated. The significant difference of LD50 between (+)-ICP (0.609 mg/kg bw) and (-)-ICP (79.412 mg/kg bw) demonstrated that (+)-ICP was a more effective enantiomer. The enantioselectivity in insecticidal activity of ICP enantiomers could be attributed to the selective affinity to acetylcholinesterase (AChE). Results of in vivo and in vitro assays suggested that AChE was more sensitive to (+)-ICP. In addition, molecular docking showed that the -CDOKER energies of (+)-ICP and (-)-ICP were 25.6652 and 24.4169, respectively, which suggested a stronger affinity between (+)-ICP and AChE. Significant selectivity also occurred in detoxifying enzymes activities (carboxylesterases (CarEs) and glutathione S-transferases (GSTs)) and related gene expressions. Suppression of detoxifying enzymes activities with (+)-ICP treatment suggested that (-)-ICP may induce the detoxifying enzyme-mediated ICP resistance. A more comprehensive understanding of the enantioselectivity of ICP is necessary for improving regulation and risk assessment of ICP.

Nitrogen use efficiency is regulated by interacting proteins relevant to development in wheat.

Wheat (Triticum aestivum) has low nitrogen use efficiency (NUE). The genetic mechanisms controlling NUE are unknown. Positional cloning of a major quantitative trait locus for N-related agronomic traits showed that the vernalization gene TaVRN-A1 was tightly linked with TaNUE1, the gene shown to influence NUE in wheat. Because of an Ala180 /Val180 substitution, TaVRN-A1a and TaVRN-A1b proteins interact differentially with TaANR1, a protein encoded by a wheat orthologue of Arabidopsis nitrate regulated 1 (ANR1). The transcripts of both TaVRN-A1 and TaANR1 were down-regulated by nitrogen. TaANR1 was functionally characterized in TaANR1::RNAi transgenic wheat, and in a natural mutant with a 23-bp deletion including 10-bp at the 5' end of intron 5 and 13-bp of exon 6 in gDNA sequence in its gDNA sequence, which produced transcript that lacked the full 84-bp exon 6. Both TaANR1 and TaHOX1 bound to the Ala180 /Val180 position of TaVRN-A1. Genetically incorporating favourable alleles from TaVRN-A1, TaANR1 and TaHOX1 increased grain yield from 9.84% to 11.58% in the field. Molecular markers for allelic variation of the genes that regulate nitrogen can be used in breeding programmes aimed at improving NUE and yield in novel wheat cultivars.

Amyloplast is involved in the MIZ1-modulated root hydrotropism.

Roots exhibit hydrotropism in response to moisture gradients, with the hydrotropism-related gene Mizu-kussei1 (MIZ1) playing a role in regulating root hydrotropism in an oblique orientation. However, the mechanisms underlying MIZ1-regulated root hydrotropism are not well understood. In this study, we employed obliquely oriented experimental systems to investigate root hydrotropism in Arabidopsis. We found that the miz1 mutant displays reduced root hydrotropism but increased root gravitropism following hydrostimulation, as compared to wild-type plants. Conversely, overexpression of AtMIZ1 leads to enhanced root hydrotropism but decreased root gravitropism following hydrostimulation, as compared to wild-type plants. Using co-immunoprecipitation followed by mass spectrometry (IP-MS), we explored proteins that interact with AtMIZ1, and we identified PGMC1 co-immunoprecipitated with MIZ1 in vivo. Furthermore, the miz1 mutant exhibited higher expression of the PGMC1 gene and increased phosphoglucomutase (PGM) activity, while AtMIZ1 overexpressors resulted in lower expression of the PGMC1 gene, reduced amyloplast amount, and reduced PGM activity in comparison to wild-type roots. In addition, different Arabidopsis natural accessions having difference in their hydrotropic response demonstrated expression level of PGMC1 was negatively correlated with hydrotropic root curvature and AtMIZ1 expression. Our results provide valuable insights into the role of amyloplast in MIZ1-regulated root hydrotropism.

Treefrog-Inspired Flexible Electrode with High Permeability, Stable Adhesion, and Robust Durability.

Long-term continuous monitoring (LTCM) of physiological electrical signals is an effective means for detecting several cardiovascular diseases. However, the integrated challenges of stable adhesion, low impedance, and robust durability under different skin conditions significantly hinder the application of flexible electrodes in LTCM. This paper proposes a structured electrode inspired by the treefrog web, comprising dispersed pillars at the bottom and asymmetric cone holes at the top. Attachment structures with a dispersed pillar improve the contact stability (adhesion increases 2.79/13.16 times in dry/wet conditions compared to an electrode without structure). Improved permeable duct structure provides high permeability (12 times compared to cotton). Due to high adhesion and permeability, the electrode's durability is 40 times larger than commercial Ag/AgCl electrodes. The treefrog web-like electrode has great advantages in permeability, adhesion, and durability, resulting in prospects for application in physiological electrical signal detection and a new design idea for LTCM wearable dry electrodes.

Optimal N management affects the fate of urea-15N and improves N uptake and utilization of wheat in different rotation systems.

Rice-wheat and maize-wheat rotations are major cropping systems in the middle and lower reaches of Yangtze River in China, where high nitrogen (N) inputs and low N efficiency often exacerbate resource waste and environmental pollution. Due to the changes in factors such as soil properties and moisture content, the N fate and the N utilization characteristics of wheat in different rotations are significantly different. Efficient N management strategies are thus urgently required for promoting maximum wheat yield in different rotation systems while reducing N loss. A 2-year field experiment using isotopic (15N) tracer technique was conducted to evaluate the fate of 15N-labeled urea in wheat fields and the distribution characteristics of N derived from different sources. The wheat yield and N use efficiency under various N rates (180 and 240 kg ha-1, abbreviated as N180 and N240) and preceding crops (rice and maize, abbreviated as R-wheat and M-wheat) were also investigated. The results showed that N240 increased N uptake and grain yield by only 8.77-14.97% and 2.51-4.49% compared with N 180, but decreased N agronomic efficiency (NAE) and N physiological efficiency (NPE) by 14.78-18.79% and 14.06-31.35%. N240 also decreased N recovery in plants by 2.8% on average compared with N180, and increased N residue in soil and N loss to the environment. Compared with that of basal N, the higher proportion of topdressing N was absorbed by wheat rather than lost to the environment. In addition, the accumulation of topdressing N in grain was much higher than that of basal N. Compared with that in R-wheat treatment, plants in M-wheat treatment trended to absorb more 15N and reduce unaccounted N loss, resulting in higher yield potential. Moreover, the M-wheat treatment increased N recovery in 0-20 cm soil but decreased 80-100 cm soil compared with R-wheat treatment, indicating a lower risk of N loss in deeper soil. Collectively, reducing N application rate and increasing the topdressing ratio is an effective way to balance sustainable crop yield for a secure food supply and environmental benefit, which is more urgent in rice-wheat rotation.

Split application of polymer-coated urea combined with common urea improved nitrogen efficiency without sacrificing wheat yield and benefits while saving 20% nitrogen input.

Controlled-release nitrogen fertilizer (CRNF) has been expected to save labor input, reduce environmental pollution, and increase yield in crop production. However, the economic feasibility is still controversial due to its high cost. To clarify the suitable application strategy of CRNF in promoting the yield, nitrogen use efficiency and income on wheat grown in paddy soil, four equal N patterns were designed in 2017-2021 with polymer-coated urea (PCU) and common urea as material, including PCU applied once pre-sowing (M1), PCU applied 60% at pre-sowing and 40% at re-greening (M2), 30% PCU and 30% urea applied at pre-sowing, 20% PCU and 20% urea applied at re-greening (M3), and urea applied at four stage (CK, Basal:tillering:jointing:booting=50%:10%:20%:20%). In addition, M4-M6, which reduced N by 10%, 20% and 30% respectively based on M3, were designed in 2019-2021 to explore their potential for N-saving and efficiency-improving. The results showed that, compared with CK, M1 did not significantly reduce yield, but decreased the average N recovery efficiency (NRE) and benefits by 1.63% and 357.71 CNY ha-1 in the four years, respectively. M2 and M3 promoted tiller-earing, delayed the decrease of leaf area index (LAI) at milk-ripening stage, and increased dry matter accumulation post-anthesis, thereby jointly increasing spike number and grain weight of wheat, which significantly increased yield and NRE compared with CK in 2017-2021. Due to the savings in N fertilizer costs, M3 achieved the highest economic benefits. With the 20% N reduction, M5 increased NRE by 16.95% on average while decreasing yield and net benefit by only 6.39% and 7.40% respectively, compared with M3. Although NRE could continue to increase, but the yield and benefits rapidly decreased after N reduction exceeds 20%. These results demonstrate that twice-split application of PCU combined with urea is conducive to achieving a joint increase in yield, NRE, and benefits. More importantly, it can also significantly improve the NRE without losing yield and benefits while saving 20% N input.

Comparative transcriptomic and metabolomic analysis revealed molecular mechanism of two wheat near-isogenic lines response to nitrogen application.

Nitrogen (N) is an essential nutrient element required for plant growth, and the development of wheat varieties with high nitrogen use efficiency (NUE) is an urgent need for sustainable crop production. However, the molecular mechanism of NUE between diverse wheat varieties in response to N application remains unclear. To reveal the possible molecular mechanisms underlying this complex phenomenon, we investigated the transcriptional and metabolic changes of flag leaves of two wheat near-isogenic lines (NILs) differing in NUE under two N fertilizer treatments. Comparative transcriptome analysis indicated that the expression levels of the genes responsible for carbon and nitrogen metabolism were significantly higher in high-NUE wheat. The metabolome comparison revealed that the activity of the tricarboxylic acid (TCA) cycle was enhanced in high-NUE wheat, while reduced in low-NUE wheat after the N fertilizer application. Additionally, amino acid metabolism increased in both wheat NILs but more increased in high-NUE wheat. In summary, more upregulated transcripts and metabolites were identified in high-NUE wheat, and this study provides valuable new insights for improving NUE in wheat.

The fate of nitrogen from different sources in a rice-wheat rotation system - A 15N labeling study.

High loss and low nitrogen (N) efficiency in agricultural production is severe. Also, ammonia volatilization and N leaching aggravated environmental pollution. The eutrophication of surface water and the emissions of N2O increased, hence green fertilization management urgently needs to be rationalized. Coordinating N supply from different sources has been shown to reduce environmental pollution. Therefore, this study was dedicated to clarifying the transport of N sources in the rice-wheat rotation system. The stable isotope tracer technology was used to label fertilizer (F), soil (T), and straw (J) with 15N, respectively. The utilization of N by crops (the N ratio in organs), as well as the residual N in soil and loss status, were measured. According to the potential of response to N, all the wheat cultivars were divided into groups with high (HNV) and low efficiency (LNV). The N contribution ratio showed that 43.28%~45.70% of total N accumulation was from T, while 30.11%~41.73% and 13.82%~24.19% came from F and J. The trend in soil N residue (T > F > J) was consistent with the above, while it was the opposite in N loss (T< F< J). The seasonal effectiveness showed that T achieved the highest N utilization efficiency (31.83%~44.69%), followed by F (21.05%~39.18%) and J (11.02%~16.91%). The post-season sustainability showed that T decreased the most in soil N residue (2.08%~12.53%), and F decreased the most in N accumulation (9.64%~18.13%). However, J showed an increase in N recovery rate (2.87%~5.89%). N translocation and distribution showed that N from different sources in grains was significantly higher than that in stems, glumes, and leaves. The ratio of HNV (75.14%~79.62%) was higher than that of LNV (71.90%~74.59%) in grain, while it was the opposite in other organs. Plant N accumulation, soil N supply, and straw N transformation were determined jointly by the three N sources, thus reducing N loss and N2O production. Therefore, the results will highlight the insights for constructing local N and emission reduction models.

[Hyperspectral estimation of leaf water content for winter wheat based on grey relational analysis (GRA)].

The objective of the present study was to compare two methods for the precision of estimating leaf water content (LWC) in winter wheat by combining stepwise regression method and partial least squares (SRM-PLS) or PLS based on the relational degree of grey relational analysis (GRA) between water vegetation indexes (WVIs) and LWC. Firstly, data utilized to analyze the grey relationships between LWC and the selected typical WVIs were used to determine the sensitivity of different WVIs to LWC. Secondly, the two methods of estimating LWC in winter wheat were compared, one was to directly use PLS and the other was to combine SRM and PLS, and then the method with the highest determination coefficient (R2) and lowest root mean square error (RMSE) was selected to estimate LWC in winter wheat. The results showed that the relationships between the first five WVI and LWC were stable by using GRA, and then LWC was estimated by using PLS and SRM-PLS at the whole stages with the R2 and RMSEs being 0.605 and 0.575, 4.75% and 7.35%, respectively. The results indicated that the estimation accuracy of LWC could be improved by using GRA firstly and then by using PLS and SRM-PLS.

Evaluating and Screening of Agro-Physiological Indices for Salinity Stress Tolerance in Wheat at the Seedling Stage.

Soil salinity is a worldwide issue that affects wheat production. A comprehensive understanding of salt-tolerance mechanisms and the selection of reliable screening indices are crucial for breeding salt-tolerant wheat cultivars. In this study, 30 wheat genotypes (obtained from a rapid selection of 96 original varieties) were chosen to investigate the existing screening methods and clarify the salinity tolerance mechanisms in wheat. Ten-day-old seedlings were treated with 150 mM NaCl. Eighteen agronomic and physiological parameters were measured. The results indicated that the effects of salinity on the agronomic and physiological traits were significant. Salinity stress significantly decreased K+ content and K+/Na+ ratio in the whole plant, while the leaf K+/Na+ ratio was the strongest determinant of salinity tolerance and had a significantly positive correlation with salt tolerance. In contrast, salinity stress significantly increased Na+ concentration and relative gene expression (TaHKT1;5, TaSOS1, and TaAKT1-like). The Na+ transporter gene (TaHKT1;5) showed a significantly greater increase in expression than the K+ transporter gene (TaAKT1-like). We concluded that Na+ exclusion rather than K+ retention contributed to an optimal leaf K+/Na+ ratio. Furthermore, the present exploration revealed that, under salt stress, tolerant accessions had higher shoot water content, shoot dry weight and lower stomatal density, leaf sap osmolality, and a significantly negative correlation was observed between salt tolerance and stomatal density. This indicated that changes in stomata density may represent a fundamental mechanism by which a plant may optimize water productivity and maintain growth under saline conditions. Taken together, the leaf K+/Na+ ratio and stomatal density can be used as reliable screening indices for salt tolerance in wheat at the seedling stage.

Transcriptome Analysis Reveals Different Responsive Patterns to Nitrogen Deficiency in Two Wheat Near-Isogenic Lines Contrasting for Nitrogen Use Efficiency.

The development of crop cultivars with high nitrogen use efficiency (NUE) under low-N fertilizer inputs is imperative for sustainable agriculture. However, there has been little research on the molecular mechanisms underlying enhanced resilience to low N in high-NUE plants. The comparison of the transcriptional responses of genotypes contrasting for NUE will facilitate an understanding of the key molecular mechanism of wheat resilience to low-N stress. In the current study, the RNA sequencing (RNA-seq) technique was employed to investigate the genotypic difference in response to N deficiency between two wheat NILs (1Y, high-NUE, and 1W, low-NUE). In our research, high- and low-NUE wheat NILs showed different patterns of gene expression under N-deficient conditions, and these N-responsive genes were classified into two major classes, including "frontloaded genes" and "relatively upregulated genes". In total, 103 and 45 genes were identified as frontloaded genes in high-NUE and low-NUE wheat, respectively. In summary, our study might provide potential directions for further understanding the molecular mechanism of high-NUE genotypes adapting to low-N stress.

Transcriptome Analysis of Two Near-Isogenic Lines with Different NUE under Normal Nitrogen Conditions in Wheat.

Nitrogen (N) is an essential nutrient element for crop productivity. Unfortunately, the nitrogen use efficiency (NUE) of crop plants gradually decreases with the increase of the N application rate. Nevertheless, little has been known about the molecular mechanisms of differences in NUE among genotypes of wheat. In this study, we used RNA-Sequencing (RNA-Seq) to compare the transcriptome profiling of flag leaves at the stage of anthesis in wheat NILs (1Y, high-NUE, and 1W, low-NUE) under normal nitrogen conditions (300 kg N ha-1, corresponding to 1.6 g N pot-1). We identified 7023 DEGs (4738 upregulated and 2285 downregulated) in the comparison between lines 1Y and 1W. The responses of 1Y and 1W to normal N differed in the transcriptional regulatory mechanisms. Several genes belonging to the GS and GOGAT gene families were upregulated in 1Y compared with 1W, and the enhanced carbon metabolism might lead 1Y to produce more C skeletons, metabolic energy, and reductants for nitrogen metabolism. A subset of transcription factors (TFs) family members, such as ERF, WRKY, NAC, and MYB, were also identified. Collectively, these identified candidate genes provided new information for a further understanding of the genotypic difference in NUE.

Tillage and seeding strategies for wheat optimizing production in harvested rice fields with high soil moisture.

Suitable tillage and seeding strategies for wheat can be used to combat excessive residues and poor soil conditions in harvested rice fields. This study investigated the effects of different tillage (zero tillage and rotary tillage) and seeding methods on wheat growth, grain yield, nitrogen (N) uptake and utilization, and economic benefit when the soil moisture was high during the tillage and seeding practices. In 2016-2017, three seeders were tested: SM1-1, SM2, and SM3; in 2017-2018, four seeders were tested: SM1-2, SM2, SM3, and SM4. Although the soil moisture was different between years, zero tillage could be used to reduce the sowing depth, which facilitated early-phase wheat growth and N uptake compared with rotary tillage, resulting in higher grain yield, NUpE, and net return. In 2016-2017 (high wet soil), a small-size seeder (SM1-1) with sowing near the soil surface facilitated higher grain yield, NUpE, and net returns compared with the other seeders; in 2017-2018 (low wet soil), medium-size seeders (SM3 and SM4) were more suitable than small-size seeders (SM1-2 and SM2). In both years, the seeders that performed the best mainly improved the spike numbers while increasing N uptake, especially after anthesis. Zero tillage lowered input costs, but small-size seeders did not reduce costs due to the higher labor costs associated with their low working efficiency. Improving net returns depends largely on increasing yield. In conclusion, zero tillage is recommended for wheat production in harvested rice fields with a high soil moisture content, but the suitable seeding method needs to be confirmed according to the soil moisture content.

A single-nucleotide polymorphism that accounts for allelic variation in the Lr34 gene and leaf rust reaction in hard winter wheat.

Leaf rust, caused by Puccinia triticina Eriks, is one of the most common and persistent wheat diseases in the US Great Plains. We report that the Lr34 gene was mapped in the center of a QTL for leaf rust reaction and explained 18-35% of the total phenotypic variation in disease severity of adult plants in a Jagger x 2174 population of recombinant inbred lines (RILs) field-tested for 3 years. The sequence of the complete Lr34 gene was determined for the susceptible Jagger allele and for the resistant 2174 allele. The two alleles had exactly the same sequence as the resistant allele reported previously in Chinese Spring at three polymorphic sites in intron 4, exon 11, and exon 12. A G/T polymorphism was found in exon 22, where a premature stop codon was found in the susceptible Jagger allele (Lr34E22s), confirming a previous report, due to a point mutation compared with the resistant 2174 allele (Lr34E22r). We have experimentally demonstrated a tight association between the point mutation at exon 22 of Lr34 and leaf rust susceptibility in a segregating biparental population. A PCR marker was developed to distinguish between the Lr34E22r and Lr34E22s alleles. A survey of 33 local hard winter wheat cultivars indicated that 7 cultivars carry the Lr34E22s allele and 26 cultivars carry the Lr34E22r allele. This study significantly improves our genetic understanding of allelic variation in the Lr34 gene and provides a functional molecular tool to improve leaf rust resistance in a major US wheat gene pool.

Structure and physicochemical properties of two waxy wheat starches.

The objective of this study was to determine the primary influences of amylopectin (AP) on starch properties using two waxy wheat starches with different pasting properties. Compared with Yang Nuo Mai 1 (YNM1) starch, Ning Nuo Mai 1 (NNM1) starch had a greater average granule diameter, hot water solubility, gelatinization enthalpy, higher pasting viscosity, but lower retrogradation enthalpy. NNM1 starch had a greater proportion of AP long chains, and lower proportion of AP short chains. Therefore, NNM1 starch had a greater degree of crystallinity as well as stronger resonance intensities at the C1, C2, C3, C5, and C6 by solid-state 13C CP/MAS NMR. These results suggested that the proportion of long AP chains (DP ≥ 37) is the main influencing factor in determining waxy starch physicochemical properties. In addition, the proportion of short AP chains (DP 13-24) plays a role in promoting retrogradation of waxy wheat starch.

Does cyclic water stress damage wheat yield more than a single stress?

The occurrence of water stress during wheat growth is more frequent due to climate change. Three experiments (cyclic drought, cyclic waterlogging, and cyclic drought plus waterlogging) were conducted to investigate the effects of mild and severe cyclic/single water stress at elongation and heading stages on winter wheat (Triticum aestivum L.) yield. The effect of either mild drought at elongation or mild waterlogging at heading on wheat yield was not significant; however, significance did occur under other single water stresses. As the stress becomes more severe, the yield loss significantly increases. Extreme drought/waterlogging treatment at elongation caused a greater yield penalty than stress at heading stage. Except the combination of mild drought and mild waterlogging treatment, cyclic water stress significantly decreased wheat yields. The decrease in wheat yield under cyclic severe drought and waterlogging was significantly higher than any other treatment, with percentage decreases of 71.52 and 73.51%, respectively. In general, a yield reduction from mild cyclic water stress did not indicate more severe damage than single treatments; in contrast, grain yield suffered more when water stress occurred again after severe drought and waterlogging. Drought during elongation significantly decreased kernel number, whereas drought at heading/waterlogging during elongation and heading decreased the spike weight, which might be the main reason for the yield penalty. Furthermore, water stress caused variation in the decrease of total biomass and/or harvest index. The present study indicates comprehensive understanding of the types, degree, and stages of water stress are essential for assessing the impact of multiple water stresses on wheat yield.

Estimating the responses of winter wheat yields to moisture variations in the past 35 years in Jiangsu Province of China.

Jiangsu is an important agricultural province in China. Winter wheat, as the second major grain crop in the province, is greatly affected by moisture variations. The objective of this study was to investigate whether there were significant trends in changes in the moisture conditions during wheat growing seasons over the past decades and how the wheat yields responded to different moisture levels by means of a popular drought index, the Standardized Precipitation Evapotranspiration Index (SPEI). The study started with a trend analysis and quantification of the moisture conditions with the Mann-Kendall test and Sen's Slope method, respectively. Then, correlation analysis was carried out to determine the relationship between de-trended wheat yields and multi-scalar SPEI. Finally, a multivariate panel regression model was established to reveal the quantitative yield responses to moisture variations. The results showed that the moisture conditions in Jiangsu were generally at a normal level, but this century appeared slightly drier in because of the relatively high temperatures. There was a significant correlation between short time scale SPEI values and wheat yields. Among the three critical stages of wheat development, the SPEI values in the late growth stage (April-June) had a closer linkage to the yields than in the seedling stage (October-November) and the over-wintering stage (December-February). Moreover, the yield responses displayed an asymmetric characteristic, namely, moisture excess led to higher yield losses compared to moisture deficit in this region. The maximum yield increment could be obtained under the moisture level of slight drought according to the 3-month SPEI at the late growth stage, while extreme wetting resulted in the most severe yield losses. The moisture conditions in the first 15 years of the 21st century were more favorable than in the last 20 years of the 20th century for wheat production in Jiangsu.

Is there a nitrogen fertilizer threshold emitting less N2O with the prerequisite of high wheat production?

Excessive use of synthetic nitrogen (N) fertilizer and lower nitrogen use efficiency (NUE) are threatening the wheat production in the middle and lower reaches of Yangtze River. Excess input of N fertilizers also results in severe environmental pollution, climate change and biodiversity loss. However, the study on reasonable nitrogen application and NUE improvement with the prerequisite of stable and high yield remains unexplored. In our study, the four different levels of nitrogen were applied to find out the nitrogen threshold which could be both friendly to environment and promise the stable and high yield. The experiment was carried out in Yangzhou University (Yangzhou, China). The wheat cultivar Yangmai 23 was selected as the research material. The four nitrogen levels were as follows: 0, 189, 229.5, and 270 kg ha-1. The results showed that the grain yield under the application of 229.5 kg ha-1 N was as high as that under 270 kg ha-1 N level, with the observation of 20.3% increase in agronomic efficiency. The N2O emission of 229.5 kg ha-1 N application was as low as that of 189 kg ha-1 N, but the grain yield and agronomic efficiency were significantly higher (11.9%) under 229.5 kg ha-1 treatment than the lower one. Taken together, this indicated the nitrogen level at 229.5 kg ha-1 could be identified as the fertilizer threshold, which will be beneficial for the future fieldwork.