Elevated CO2 and Nitrogen Supply Boost N Use Efficiency and Wheat (T. aestivum cv. Yunmai) Growth and Differentiate Soil Microbial Communities Related to Ammonia Oxidization.

Elevated CO2 levels (eCO2) pose challenges to wheat (Triticum aestivum L.) growth, potentially leading to a decline in quality and productivity. This study addresses the effects of two ambient CO2 concentrations (aCO2, daytime/nighttime = 410/450 ± 30 ppm and eCO2, 550/600 ± 30 ppm) and two nitrogen (N) supplements (without N supply-N0 and with 100 mg N supply as urea per kg soil-N100) on wheat (T. aestivum cv. Yunmai) growth, N accumulation, and soil microbial communities related to ammonia oxidization. The data showed that the N supply effectively mitigated the negative impacts of eCO2 on wheat growth by reducing intercellular CO2 concentrations while enhancing photosynthesis parameters. Notably, the N supply significantly increased N concentrations in wheat tissues and biomass production, thereby boosting N accumulation in seeds, shoots, and roots. eCO2 increased the agronomic efficiency of applied N (AEN) and the physiological efficiency of applied N (PEN) under N supply. Plant tissue N concentrations and accumulations are positively related to plant biomass production and soil NO3--N. Additionally, the N supply increased the richness and evenness of the soil microbial community, particularly Nitrososphaeraceae, Nitrosospira, and Nitrosomonas, which responded differently to N availability under both aCO2 and eCO2. These results underscore the importance and complexity of optimizing N supply and eCO2 for enhancing crop tissue N accumulation and yield production as well as activating nitrification-related microbial activities for soil inorganic N availability under future global environment change scenarios.

Shallow groundwater table fluctuations weaken nitrogen accumulation in the thin layer vadose zone of cropland around plateau lakes, Southwest China.

Excessive accumulation of nitrogen (N) in the soil profile in the intensive agricultural region will seriously threaten groundwater quality and safety. However, the impact of shallow groundwater table (SGWT) fluctuations driven by seasonal variations on the N accumulation characterizations in the soil profiles has not been well quantified, particularly in the regions with thin layer vadose zone. Through in-situ monitoring and simulation experiments, the changes in the SGWT and N accumulation of soil profile in intensive cropland around 7 plateau lakes in Yunnan were studied during the rainy season (RS) and dry season (DS), and the N loss in soil profile of cropland driven by SGWT fluctuations was estimated. The results showed that the SGWT and N accumulation in soil profile of cropland around the plateau lakes had obvious seasonal variation characteristics. The proportion of N storage in different forms in 60-100 cm soil layer in the RS was greater than that in the DS, particularly the proportion of NH4+-N storage was as high as 55 %, while N accumulation in surface soil was obvious in the DS. Compared with the DS, due to the rising SGWT in the RS, the maximum storages of TN and NO3--N in the 0-100 cm soil layer decreased by17% and 36 %, respectively. The TN loss intensities from the 0-100 cm soil profiles of cropland around Fuxian Lake, Yilong Lake, Qilu Lake, Dianchi Lake, Yangzong Lake, Erhai Lake, and Xingyun Lake were 74, 54, 127, 105, 93, 72 and 207 kg/ha, respectively. Moreover, if the SGWT was <30 cm, the average TN loss intensity and amount could reach 177 kg/ha and 1250 t, respectively. Therefore, the SGWT regulation was one of the key measures to reducing soil N loss from the thin layer vadose zone of cropland around plateau lakes and improving groundwater quality.

Straw returning and nitrogen reduction: Strategies for sustainable maize production in the dryland.

Implementing continue straw returning practices and optimizing nitrogen application can mitigate nitrogen losses and enhance nitrogen use efficiency (NUE) in dryland. 15N-labeled technique offers a robust approach for tracking fertilizer nitrogen fate and assessing nitrogen use efficiency. Based on the continue (>6 yr) experiment, we conducted a two-year experiment (2020 and 2021) to evaluate the effects of straw returning and nitrogen management under plastic film mulching on 15N recovery rates, N2O emissions and maize yield with three treatments: no straw returning with 225 kg N·ha-1 under plastic film mulching (RP-N225), straw returning with 225 kg N·ha-1 under plastic film mulching (RPS-N225), and straw returning with 20% nitrogen reduction (180 kg N·ha-1) under plastic film mulching (RPS-N180). After six years, both continue straw returning with plastic film mulching increased uptake of fertilizer nitrogen, had higher 15N recovery rates than RP-N225, leading to increased 15N accumulation in grain and aboveground biomass, ultimately enhancing yield. The RPS-N225 treatment exhibited the highest spring maize yield and nitrogen harvest index. The RPS-N180 treatment significantly increased maize yield more than RP-N225 and had the highest NUE, partial factor productivity of nitrogen fertilizer, and nitrogen uptake efficiency, with improvements ranging from 1.7 to 2.4%, 19.3-29.6%, and 17.3-27.5%, respectively, compared to the other treatments. Moreover, RPS-N225 resulted in significantly higher cumulative N2O emissions and yield-scaled N2O emissions than the other treatments, whereas the RPS-N180 treatment significantly decreased yield-scaled N2O emissions compared to RP-N225. Hence, combining continue straw returning with appropriate nitrogen reduction can effectively increase maize yield and yield-scaled N2O emissions. By offering insights into optimizing nitrogen fertilizer management after continue maize straw return, this study is contributed to widespread adoption of straw return practices and sustainable agricultural development in semi-arid areas.

Aeration Alleviated the Adverse Effects of Nitrogen Topdressing Reduction on Tomato Root Vigor, Photosynthetic Performance, and Fruit Development.

To explore the compensation effect of aeration on tomato vegetative and reproductive growth in arid and semi-arid areas, a two-year field experiment was conducted with four micro-nano aeration ratios (0%, 5%, 10%, and 15%) and three nitrogen topdressing levels (80, 60, and 40 kg·ha-1) during the tomato growth period in Ningxia, China. The results showed that increasing the aeration ratio in the range of 0-15% was conducive to the enhancement of tomato root vigor (the ability of triphenyltetrazolium chloride to be reduced, 3-104%) and the leaf net photosynthetic rate (14-63%), favorable to the facilitation of plant dry matter accumulation (3-59%) and plant nitrogen accumulation (2-70%), and beneficial to the improvement of tomato yield (12-44%) and fruit quality. Interestingly, since the aeration ratio exceeded 10%, the increase in the aeration ratio showed no significant effects on the single-fruit weight, tomato yield, and fruit quality. Moreover, with aerated underground drip irrigation, properly reducing the traditional nitrogen topdressing level (80 kg·ha-1) by 25% was favorable for enhancing tomato root vigor (5-31%), increasing tomato yield (0.5-9%), and improving fruit soluble solid accumulation (2-5%) and soluble sugar formation (4-9%). Importantly, increasing the aeration ratio by 5% could compensate for the adverse effects of reducing the nitrogen topdressing level by 25% by improving the leaf photosynthetic rate, promoting plant dry matter accumulation, increasing tomato yield, and enhancing the soluble solid and soluble sugar accumulation in tomato fruits. Synthetically considering the decrease in the nitrogen topdressing amount, leading to plant growth promotion, a tomato yield increase, and fruit quality improvement, a favorable nitrogen topdressing level of 60 kg·ha-1 and the corresponding proper aeration ratio of 10% were suggested for tomato underground drip irrigation in the Yinbei Irrigation District of Ningxia.

Piped-slow-release calcium nitrate dosing: A new approach to in-situ sediment odor control in rural areas.

Calcium nitrate addition is economically viable and highly efficient for the in-situ treatment of contaminated sediment and enhancement of surface water quality, particularly in rural areas. However, conventional nitrate addition technologies have disadvantages such as excessive nitrate release, sharp ammonium increase, and weakened sulfide oxidation efficiency owing to rapid nitrate injection into the sediment. To resolve these defects, we propose a piped-slow-release (PSR) calcium nitrate dosing method and investigate its treatment efficiency and underlying mechanisms. The results illustrated that PSR dosing had a longer half-life (t1/2 = 5.08 days) and a lower maximum apparent nitrate escape rate of 1.28 % than conventional nitrate injection and other dosing methods. In addition, the PSR managed the inorganic nitrogen release into the overlying water, and after the treatment, the nitrate, ammonium, and nitrite concentrations of 0 mg/L, 8.60 mg/L, and 0 mg/L on day 28 were close to those of the control group (0 mg/L, 8.76 mg/L, and 0 mg/L, respectively). Moreover, the PSR method maintained a moderate nitrate concentration of approximately 3000 mg/L in sediment interstitial water by its controlled-release design, thus greatly enhancing the sulfide oxidation efficiency by relieving the inhibitory effects of high nitrate concentrations, with 83.0 % sulfide being eradicated within 5 days. Sulfide-ferrous nitrate reduction (denitrification and dissimilatory nitrate reduction to ammonium) genera (e.g., Sulfurimonas, Thiobacillus, and Thioalkalispira) were successively enhanced and dominated the microbial community, and the related functional genes displayed high relative abundances. These results imply that the PSR dosing method for calcium nitrate, characterized by flexible operation, high efficiency, low cost, and controllable processes, is appropriate for remediating black-odorous sediment in rural areas.

Variations in Nitrogen Accumulation and Use Efficiency in Maize Differentiate with Nitrogen and Phosphorus Rates and Contrasting Fertilizer Placement Methodologies.

Balanced nitrogen (N) and phosphorus (P) rates, coupled with rational fertilization methodology, could promote crop N accumulation, N use efficiency, and yield production, particularly in semi-arid and arid regions. To test these characteristics, a two-year (2018 and 2019) pot experiment was performed by growing summer maize in a rain-proof glass greenhouse under nine combined N (112, 150, and 187 kg ha-1, urea) and P (45, 60, and 75 kg ha-1 calcium superphosphate) rates and three contrasting fertilizer placements. The fertilizers were placed by broadcast on the soil surface (Broadcast), a side band on a 4 cm strip of soil surface within 7 cm from the sowing line (Side band), and a deep band on a 4 cm strip below 7 cm soil depth within 7 cm from the sowing line (Deep band). Results from three maize growth stages (eight-leaf, 45 days after sowing, DAS; tasseling, 60 DAS; and harvest, 115 DAS) showed that leaf, stem, root N accumulation, and total soil N were significantly increased under Deep band than under both Side band and Broadcast at N150P60, N187P60, N150P75, and N187P75, but not at N112P45, N150P45, N187P45, N112P60, and N112P75. Significantly greater leaf, stem, and root N accumulations were also displayed at N150 and N187 than at N112 for the same P60 or P75 under the Deep band at 60 DAS and 115 DAS; while for leaf and stem, N accumulations were greater at P75 and P60 than at P45 for the same N150 under Deep band at 45 DAS, 60 DAS, and 115 DAS. Significantly greater agronomy N use efficiency, partial factor productivity, and N use efficiency were exhibited under the Deep band than under the Side band and Broadcast at N150P75 and N187P75, but at N150P60 and N187P60 for NUE only. In addition, leaf, stem, seed, and root N concentrations positively correlated with their own N accumulations or soil N concentrations at the tasseling and harvest stages. Our results demonstrate that a synchronized N150P60, N187P60, N150P75, or N187P75 fertilization rate with Deep band placement can improve soil N availability and root N uptake, and thereby, increase aboveground N accumulation, N use efficiency, and yield production of maize, which is particularly practical for small-holder farmers globally.

Nitrogen loss via runoff and leaching from paddy fields with the proportion of controlled-release urea and conventional urea rates under alternate wetting and drying irrigation.

Alternate wetting and drying irrigation (AWD) can reduce non-point source pollution from paddy fields by mitigating field water depth. However, the influence of compounding modes of polymer-coated urea (PCU) and conventional urea (CU) on nitrogen (N) loss via runoff and leaching from paddy fields under AWD conditions remains unclear. To address this question, in this study, a 2-year field experiment was set up with three N management treatments: (a) 100% CU (N1), (b) 60% PCU + 40% CU (N2), and (c) 100% PCU (N3), at an equivalent N rate of 240 kg ha-1 that was applied to traditional continuously flooded (CI) and AWD systems. The results of this experiment showed a high-risk period of N loss from the paddy fields within 7 d after basal fertilization and 5 days after tillering fertilization. AWD reduced irrigation frequencies by 3.5 times and total input of irrigation water by 38.1%, increasing water utilization from precipitation by 44.4% than CI and reducing the volume of runoff by 46.1% and leaching water by 22.1%. This reduced the total N (TN) loss through runoff and leaching under AWD. In the N2 and N3 treatment groups, N concentration in floodwater decreased from 33.8 to 24.9%, TN loss via runoff decreased by 35.3 to 25.0%, and leaching decreased by 41.7 to 30.3% from the paddy field compared to N1. With the same N mode, AWD showed a higher N uptake (from jointing to maturity stage) and rice yield compared to CI. Besides, N2 and N3 had higher N uptake compared to N1 under the two irrigation regimes. Moreover, the AWDN3 and AWDN2 treatments resulted in the lowest and second-lowest loss of TN via runoff (2.21 to 2.66 kg ha-1) and leaching (8.14 and 10.21 kg ha-1), respectively, from the paddy fields and had the relatively high N uptake in rice in the maturity stage. Remarkably, compared with N3, N2 had a comparable grain yield under CI; however, it showed a higher yield under AWD, suggesting that there is a positive interaction in the rice yield between the AWD and compounding N (PCU + CU) fertilization practice. Thus, AWD coupled with N2 could be recommended as a useful approach to reduce N loss via runoff and leaching from paddy fields, which could increase the grain yield of middle-season rice.

Nano fertilizer synergist effects on nitrogen utilization and related gene expression in wheat.

The application of nano materials is one of the current hot spots in agricultural production. The aim of this work was to evaluate the effects of different nano fertilizer synergists on nitrogen (N) utilization and related gene expression in wheat. The experiments were carried out in pot and field conditions at the West-Coast Economic New Area experimental base and Greenhouse of Qingdao Agricultural University. Seven treatments were set up: CK (compound fertilizer), T1 (compound fertilizer + 0.3% nano carbon synergist), T2 (compound fertilizer + 0.3% nano calcium carbonate synergist), T3 (compound fertilizer + 0.3% composite nano synergist), T4 (70% compound fertilizer + 0.3% nano carbon synergist), T5 (70% compound fertilizer + 0.3% nano calcium carbonate synergist), T6 (70% compound fertilizer + 0.3% composite nano synergist). The results showed that compared with CK, the N accumulation of T1, T2, T3, T4, T5 and T6 increased by 40-50%, 30-40%, 55-65%, 20-30%, 15-20% and 30-40%, respectively; and the N use efficiency increased by 12-19%, 9-18%, 16-22%, 5-17%, 4-16% and 10-20% respectively. And the gene expression levels of TaNRT2.2, TaNRT2.3, TaGS1 and TaGS2 in the treatments with synergistic phosphate fertilizer were significantly higher than those in the CK. The application of nano fertilizer synergist can significantly improve N accumulation, N use efficiency, and promote the expression of genes related to N transport and metabolism.

The effect of changing dialysate bicarbonate concentration on serum bicarbonate, body weight and normalized nitrogen appearance rate.

INTRODUCTION: Most hemodialysis machines deliver a fixed bicarbonate concentration. Higher concentrations may improve acidosis, but risk post-hemodialysis alkalosis, whereas lower concentrations potentially increase acidosis but reduce alkalosis. We reviewed the effects of lowering dialysate bicarbonate. METHODS: We reviewed peri-dialysis chemistries in patients switching to a lower bicarbonate dialysate at 4 time points over 19 months. RESULTS: We studied 126 patients, mean age 63.7 ± 16.3 years, 57.9% males. Post-hemodialysis alkalosis fell from 1.6 to 0.3% sessions, but pre-hemodialysis acidosis increased from 11.9 to 23.8% sessions (p = 0.005) reducing dialysate bicarbonate from 32 to 28 mmol/L. After 3 months, pre-hemodialysis serum bicarbonate fell (21.1 ± 2.3 to 19.8 ± 2.2 mmol/L), and post-hemodialysis (24.9 ± 2.1 to 22.5 ± 2.0 mmol/L, p < 0.001) with a fall in pre-hemodialysis weight from 74.6 ± 20.7 to 71.7 ± 18.2 kg, normalized protein nitrogen accumulation rate 0.8 ± 0.28 to 0.77 ± 0.2 g/kg/day, p < 0.05, and serum albumin 39.7 ± 4.2 to 37.7 ± 4.9 g/L, p < 0.001. Thereafter, apart from pre- and post-hemodialysis serum bicarbonate, weight and normalized protein nitrogen accumulation stabilized, although albumin remained lower (37.6 ± 4.0 g/L, p < 0.001). On multivariate logistic analysis, serum bicarbonate increased more with lower pre-hemodialysis bicarbonate standardized coefficient ß 0.5 (95% confidence interval -0.6 to -0.42), increased normalized protein nitrogen accumulation ß 0.2 (0.96 to 2.38), p < 0.001, and session time ß 0.09, (0.47 to 5.98), p < 0.022, and less with lower dialysate bicarbonate 0.0-0.23 (-1.54 to -0.74), p < 0.001. CONCLUSION: Increases in SE-Bic with hemodialysis, depend on the bicarbonate gradient, session time and nPNA. Lower D-Bic reduces post-hemodialysis alkalosis but increases pre-hemodialysis acidosis and may initially have adverse effects on weight and normalized protein nitrogen accumulation.

[The planting effect of cover crop in Sanjiang Plain, Northeast China]. / 东北三江平原覆盖作物种植效果.

The planting effect and the planting potential of 12 cover crops (Leguminous: alfalfa, smooth vetch, hairy vetch, red clover, white clover, common vetch; non-leguminous: sudangrass, green radish, Nitro radish, rape, kale, endive) in the Sanjiang Plain of Northeast China were comprehensively evaluated by soil penetration resistance, pre-winter biomass, root characteristics, and plant nitrogen accumulation. The results showed that all the 12 cover crops grew normally during the experimental sowing period. Compared with the control, all the cover crops successfully reduced soil compactness. The planting of green radish, nitro radish, and sudangrass decreased soil penetration resistance by 47.1%, 43.4% and 33.4%, respectively. The pre-winter total fresh biomass of cover crop populations was between 3.38 and 13.98 kg·m-2, and the total dry matter mass was between 0.78 and 2.43 kg·m-2. The biomass of non-leguminous cover crops was significantly higher than that of the leguminous cover crops. The group roots of radish, rape and endive had large volumes. In particular, the nitro radish roots had a vo-lume of 4018.5 cm3·m-2, and the root system of sudangrass extended over the widest horizontal range. The ash content of leguminous cover crops was significantly lower than that of non-leguminous species, which could provide more organic matter with high decomposability. The total nitrogen accumulation of cover crops varied from 18.72 to 53.09 g·m-2. Kale and endive accumulated the highest amount of nitrogen and large biomass, which could facilitate nitrogen fixation and accumulation. According to the type of main crops in Sanjiang Plain and canopy structure, planting leguminous (clover, vetch, and alfalfa) and non-leguminous (radish, kale and sudangrass) cover crops to plant inter-row or in a line mixed cropping pattern could regulate soil structure and promote nutrient cycing, with positive effects on the fertility of black soil in the Sanjiang Plain.

Allometric Characteristics of Rice Seedlings under Different Transplanted Hills and Row Spacing: Impacts on Nitrogen Use Efficiency and Yield.

The number of seedlings per hill and the configuration of plant row spacing are important management measures to improve rice yield. In the present study, we evaluated the impact of various seedlings per hill (1, 3, 6, and 9 seedlings hill-1) under four different rice verities (two conventional rice, two hybrid rice) on allometric characteristics, nitrogen use efficiency (NUE) and yield in 2020 at early and late season. Results showed that compared with nine seedlings per hill (wide row spacing), the number of effective panicles, yield, grain biomass allocation, grain-to-leaf ratio, grain nitrogen accumulation, nitrogen dry matter production efficiency (NDMPE), N harvest index (NHI) of 1 seedling per hill increased by 21.8%, 10.91%, 10.5%, 32.25%, 17.03%, 9.67%, 6.5%, respectively. With the increase of seedlings per hill and the expansion of row spacing, stem biomass (SB) and reproductive biomass (RB) increased with the increase of above-ground biomass, mainly showing the relationship of isometric growth. Leaf biomass (LB) increased with above-ground biomass, mainly showing the relationship of allometric growth. The results suggested that under the same basic seedlings, transplanting 1 seedling per hill and dense planting was the most beneficial to improve rice yield.

Cultivar differences in carbon and nitrogen accumulation, balance, and grain yield in maize.

The balance of carbon (C) and nitrogen (N) metabolism influences plant growth and development as well as yield. A two-year field experiment was conducted in a hilly region in southwest China in 2019-2020 to investigate the correlation between the accumulation and balance of C and N, as well as the grain yield of maize cultivars with contrasting N efficiencies. Using Zhenghong 311 (ZH 311) and Xianyu 508 (XY 508) as research sources, the differences in C and N accumulation and balance in maize cultivars with contrasting N efficiencies were compared to analyze the correlation between the accumulation and balance of C and N with grain yield. According to the results, the ZH 311 cultivar had higher C and N accumulation in each stage and grain yield than the XY 508 cultivar, while the C/N ratio in each stage and organ was significantly lower in ZH 311 than in XY 508, with the greatest difference occurring in the silking stage and leaf, indicating that the N-efficient cultivar ZH 311 had evident advantages in accumulation and balance of C and N and grain yield than the N-inefficient cultivar XY 508. Moreover, the C and N accumulation and grain yield increased significantly with N application, while the C/N ratio in each stage and organ decreased significantly with N application, but the differences between ZH 311 and XY 508 increased first and then decreased with the increase of N level, the optimum N level when obtaining the highest grain yield of ZH 311 (273.21 kg ha-1) was significantly lower than that of XY 508 (355.88 kg ha-1). Furthermore, grain yield was positively correlated with C (R 2 = 0.9251) and N (R 2 = 0.9033) accumulation, affected by pre-anthesis N (R 2 = 0.9198) and post-anthesis C (R 2 = 0.8632) accumulation, and negatively correlated with the C/N ratio (R 2 = 0.7664), with the highest correlation between grain yield and the C/N ratio in silking stage (R 2 = 0.7984) and leaf (R 2 = 0.7616). In conclusion, the N-efficient cultivar ZH 311 could better coordinate the C and N balance of the plant, especially the C and N balance in the silking stage and leaf, promote photosynthetic product storage and transport, prolong the leaf function period, and make the pre-anthesis and post-anthesis C and N accumulation of ZH 311 significantly higher than those of XY 508, allowing higher grain yields.

Maize and peanut intercropping improves the nitrogen accumulation and yield per plant of maize by promoting the secretion of flavonoids and abundance of Bradyrhizobium in rhizosphere.

Belowground interactions mediated by root exudates are critical for the productivity and efficiency of intercropping systems. Herein, we investigated the process of microbial community assembly in maize, peanuts, and shared rhizosphere soil as well as their regulatory mechanisms on root exudates under different planting patterns by combining metabolomic and metagenomic analyses. The results showed that the yield of intercropped maize increased significantly by 21.05% (2020) and 52.81% (2021), while the yield of intercropped peanut significantly decreased by 39.51% (2020) and 32.58% (2021). The nitrogen accumulation was significantly higher in the roots of the intercropped maize than in those of sole maize at 120 days after sowing, it increased by 129.16% (2020) and 151.93% (2021), respectively. The stems and leaves of intercropped peanut significantly decreased by 5.13 and 22.23% (2020) and 14.45 and 24.54% (2021), respectively. The root interaction had a significant effect on the content of ammonium nitrogen (NH4 +-N) as well as the activities of urease (UE), nitrate reductase (NR), protease (Pro), and dehydrogenase (DHO) in the rhizosphere soil. A combined network analysis showed that the content of NH4 +-N as well as the enzyme activities of UE, NR and Pro increased in the rhizosphere soil, resulting in cyanidin 3-sambubioside 5-glucoside and cyanidin 3-O-(6-Op-coumaroyl) glucoside-5-O-glucoside; shisonin were significantly up-regulated in the shared soil of intercropped maize and peanut, reshaped the bacterial community composition, and increased the relative abundance of Bradyrhizobium. These results indicate that interspecific root interactions improved the soil microenvironment, regulated the absorption and utilization of nitrogen nutrients, and provided a theoretical basis for high yield and sustainable development in the intercropping of maize and peanut.

Monitoring Leaf Nitrogen Accumulation With Optimized Spectral Index in Winter Wheat Under Different Irrigation Regimes.

Rapid and non-destructive estimation of leaf nitrogen accumulation (LNA) is essential to field nitrogen management. Currently, many vegetation indices have been used for indicating nitrogen status. Few studies systematically analyzed the performance of vegetation indices of winter wheat in estimating LNA under different irrigation regimes. This study aimed to develop a new spectral index for LNA estimation. In this study, 2 years of field experiments with different irrigation regimes were conducted from 2015 to 2017. The original reflectance (OR) and three transformed spectra [e.g., the first derivative reflectance (FDR), logarithm of the reciprocal of the spectra (Log(1/R)), and continuum removal (CR)] were used to calculate two- and three-band spectral indices. Correlation analyses and univariate linear and non-linear regression between transformed-based spectral indices and LNA were performed. The performance of the optimal spectral index was evaluated with classical vegetation index. The results showed that FDR was the most stable transformation method, which can effectively enhance the relationships to LNA and improve prediction performance. With a linear relationship with LNA, FDR-based three-band spectral index 1 (FDR-TBI1) (451, 706, 688) generated the best performance with coefficient of determination (R 2) of 0.73 and 0.79, the root mean square error (RMSE) of 1.267 and 1.266 g/m2, and the ratio of performance to interquartile distance (RPIQ) of 2.84 and 2.71 in calibration and validation datasets, respectively. The optimized spectral index [FDR-TBI1 (451, 706, 688)] is more effective and might be recommended as an indicator for estimating winter wheat LNA under different irrigation regimes.

Nitrogen Accumulation in Oyster (Crassostrea gigas) Slurry Exposed to Virucidal Cold Atmospheric Plasma Treatment.

Viral contamination of edible bivalves is a major food safety issue. We studied the virucidal effect of a cold atmospheric plasma (CAP) source on two virologically different surrogate viruses [a double-stranded DNA virus (Equid alphaherpesvirus 1, EHV-1), and a single-stranded RNA virus (Bovine coronavirus, BCoV)] suspended in Dulbecco's Modified Eagle's Medium (DMEM). A 15 min exposure effectuated a statistically significant immediate reduction in intact BCoV viruses by 2.8 (ozone-dominated plasma, "low power") or 2.3 log cycles (nitrate-dominated, "high power") of the initial viral load. The immediate effect of CAP on EHV-1 was less pronounced, with "low power" CAP yielding a 1.4 and "high power" a 1.0 log reduction. We observed a decline in glucose contents in DMEM, which was most probably caused by a Maillard reaction with the amino acids in DMEM. With respect to the application of the virucidal CAP treatment in oyster production, we investigated whether salt water could be sanitized. CAP treatment entailed a significant decline in pH, below the limits acceptable for holding oysters. In oyster slurry (a surrogate for live oysters), CAP exposure resulted in an increase in total nitrogen, and, to a lower extent, in nitrate and nitrite; this was most probably caused by absorption of nitrate from the plasma gas cloud. We could not observe a change in colour, indicative for binding of NOx to haemocyanin, although this would be a reasonable assumption. Further studies are necessary to explore in which form this additional nitrogen is deposited in oyster flesh.

Human-caused increases in reactive nitrogen burial in sediment of global lakes.

Human activities have increased reactive nitrogen (Nr) input to terrestrial ecosystems compared with the pre-industrial era. However, the fate of such Nr input remains uncertain, leading to missing sink of the global nitrogen budget. By synthesizing records of Nr burial in sediments from 303 lakes worldwide, here we show that 9.6 ± 1.1 Tg N year-1 (Tg = 1012 g) accumulated in inland water sediments from 2000 to 2010, accounting for 3%-5% of global Nr input to the land from combined natural and anthropogenic pathways. The recent Nr burial flux doubles pre-industrial estimates, and Nr burial rate significantly increases with global increases in human population and air temperature. Sediment ratios of C:N decrease after 1950 while N:P ratios increase over time due to increasingly elevated Nr burial and other related processes in lakes. These findings imply that Nr burial in lakes is overlooked as an important global sink of Nr input to terrestrial ecosystems.

Photosynthesis, Chlorophyll Fluorescence, and Yield of Peanut in Response to Biochar Application.

The effect of biochar application on photosynthetic traits and yield in peanut (Arachis hypogaea L.) is not well understood. A 2-year field experiment was conducted in Northwest Liaoning, China to evaluate the effect of biochar application [0, 10, 20, and 40 t ha-1 (B0, B10, B20, and B40)] on leaf gas exchange parameters, chlorophyll fluorescence parameters, and yield of peanut. B10 improved photochemical quenching at flowering and pod set and reduced non-photochemical quenching at pod set, relative to B0. B10 and B20 increased actual photochemical efficiency and decreased regulated energy dissipated at pod set, relative to B0. B10 significantly increased net photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency at flowering and pod set, relative to B0. Compared with B0, B10 significantly improved peanut yield (14.6 and 13.7%) and kernel yield (20.2 and 14.4%). Biochar application increased leaf nitrogen content. B10 and B20 significantly increased plant nitrogen accumulation, as compared to B0. The net photosynthetic rate of peanut leaves had a linear correlation with plant nitrogen accumulation and peanut yield. The application of 10 t ha-1 biochar produced the highest peanut yield by enhancing leaf photosynthetic capacity, and is thus a promising strategy for peanut production in Northwest Liaoning, China.

Smash ridge tillage strongly influence soil functionality, physiology and rice yield.

The practice of smash-ridging on dry land crop cultivation has shown much promise. However, the mechanism how does soil functionality and root traits can affect rice yield under smash ridge tillage with reduced nitrogen fertilization have not yet been explored. To fill this knowledge gap, we used three tillage methods-smash-ridging 40 cm (S40), smash-ridging 20 cm (S20), and traditional turn-over plowing 20 cm (T)-and two rice varieties (hybrid rice and conventional rice) and measured soil quality, root traits, rice yield and their correlation analysis at different growth stages. Soil physical and chemical properties were significantly improved by smash-ridging, including improvements in root morphological and physiological traits during three growth stages compared with T. S40 had the highest leaf area index (LAI), plant height (PH), and biomass accumulation (BA). Increment in biomass and panicle number (PN) resulted in higher grain yield (GY) of 6.9-9.4% compared with T. Correlation analysis revealed that root total absorption area (RTAA), root active absorption area (RAA), and root area ratio (RAR) were strongly correlated with soil quality. Root injury flow (RIF) and root biomass accumulation (RBA) were strongly correlated with LAI and above-ground plant biomass accumulation (AGBA). Conclusively, S40 is a promising option for improving soil quality, root traits, and consequently GY.

The effect of different sowing dates on dry matter and nitrogen dynamics for winter wheat: an experimental simulation study.

BACKGROUND: Timely sowing is an important agronomic measure to ensure the normal germination, stable seedling establishment, and yield formation for winter wheat (Triticum aestivum L.). Delayed sowing frequently occurs in the current multi-cropping system and mechanized production of this crop. However, the ways in which different sowing dates affect yield and its potential mechanism is still unknown in the middle-lower Yangtze River Basin. We sought to provide a theoretical basis for these mechanisms to improve regional wheat production. METHODS: We investigated the wheat's yield differences in a two-year field study under different sowing dates and took into account related growth characteristics including meteorological conditions, growth period, tillers, dry matter accumulation (DMA), and nitrogen accumulation (NA). We used the logistic curve model to simulate DMA and NA dynamics of single stem wheat under different sowing dates. We then analyzed and compared wheat accumulation for different sowing dates. RESULTS: Our results showed that grain yield declined by 0.97 ± 0.22% with each one-day change (either early or delayed) in sowing beyond the normal sowing date. The yield loss could be explained by the inhibition of crop growth, yield components, biomass and nitrogen (N) production. The negative effects of delayed sowing were caused by environmental limitations including adverse weather factors such as low temperature during vegetative growth, shortened duration of various phases of crop development, and increased temperature during the grain-filling period. The grain yield gap decreased between the late and normal sowing periods owing to a compensatory effect between the highest average rates (Vt ) and the rapid accumulation period (T) of DMA and NA for single stem wheat. The grain yield was maintained at 6,000 kg ha-1 or more when the ratio of DMA at the mature-to-jointing stage (MD/JD) and the ratio of NA at the mature-to-jointing stage (MN/JN) was 4.06 (P < 0.01) and 2.49 (P < 0.05), respectively. The compensatory effect did not prevent the impact caused by delayed sowing, which caused biomass and N production to decrease. Physiological development reached a maximal accumulation rate (Tm ) of NA earlier than DMA.

Recent Nitrogen Storage and Accumulation Rates in Mangrove Soils Exceed Historic Rates in the Urbanized San Juan Bay Estuary (Puerto Rico, United States).

Tropical mangrove forests have been described as "coastal kidneys," promoting sediment deposition and filtering contaminants, including excess nutrients. Coastal areas throughout the world are experiencing increased human activities, resulting in altered geomorphology, hydrology, and nutrient inputs. To effectively manage and sustain coastal mangroves, it is important to understand nitrogen (N) storage and accumulation in systems where human activities are causing rapid changes in N inputs and cycling. We examined N storage and accumulation rates in recent (1970 - 2016) and historic (1930 - 1970) decades in the context of urbanization in the San Juan Bay Estuary (SJBE, Puerto Rico), using mangrove soil cores that were radiometrically dated. Local anthropogenic stressors can alter N storage rates in peri-urban mangrove systems either directly by increasing N soil fertility or indirectly by altering hydrology (e.g., dredging, filling, and canalization). Nitrogen accumulation rates were greater in recent decades than historic decades at Piñones Forest and Martin Peña East. Martin Peña East was characterized by high urbanization, and Piñones, by the least urbanization in the SJBE. The mangrove forest at Martin Peña East fringed a poorly drained canal and often received raw sewage inputs, with N accumulation rates ranging from 17.7 to 37.9 g -2 y-1 in recent decades. The Piñones Forest was isolated and had low flushing, possibly exacerbated by river damming, with N accumulation rates ranging from 18.6 to 24.2 g -2 y-1 in recent decades. Nearly all (96.3%) of the estuary-wide mangrove N (9.4 Mg ha-1) was stored in the soils with 7.1 Mg ha-1 sequestered during 1970-2017 (0-18 cm) and 2.3 Mg ha-1 during 1930-1970 (19-28 cm). Estuary-wide mangrove soil N accumulation rates were over twice as great in recent decades (0.18 ± 0.002 Mg ha-1y-1) than historically (0.08 ± 0.001 Mg ha-1y-1). Nitrogen accumulation rates in SJBE mangrove soils in recent times were twofold larger than the rate of human-consumed food N that is exported as wastewater (0.08 Mg ha-1 y-1), suggesting the potential for mangroves to sequester human-derived N. Conservation and effective management of mangrove forests and their surrounding watersheds in the Anthropocene are important for maintaining water quality in coastal communities throughout tropical regions.