Effect of hydraulic regime on sulfur-packed bed performance: Denitrification and disproportionation.

Sulfur-packed beds (SPBs) have been increasingly incorporated into constructed wetland systems to overcome limitations in achieving satisfactory nitrate removal efficiency. However, the underlying impact of hydraulic regimes on SPB performance remains understudied. This study investigated the performance of a pilot-scale SPB, encompassing sulfur autotrophic denitrification (SAD) and sulfur disproportionation (SDP) processes, under various horizontal flow (HF) and vertical flow (VF) regimes. The HF regime exhibited superior SAD efficiency, achieving 3.1-4.4 mg-N/L of nitrate removal compared to 0.9-2.8 mg-N/L under VF regimes. However, greater sulfide production of 3.8-5.6 mg/L was observed, in contrast to only 1.5-2.3 mg/L under VF regimes when SDP occurred. Employing current computational fluid dynamics simulations could predict general regimes but lacked precision in detailing sulfur layer dynamics. In contrast, determining the spatial distribution of SAD substrates and SDP products offered a viable solution, revealing stagnate, short-circuit, and back flows. Moreover, the feasibility of an aeration approach to reduce sulfide emissions below 0.5 mg/L in case of accidental SDP occurrence was confirmed. This study offers a method for assessing detailed hydraulic regimes within SPBs. Additionally, it provides guidance on optimizing the packing of sulfur-based materials when implementing SPBs in constructed wetland systems and presents a strategy for mitigating excessive sulfide emissions.

Using HJ-CCD image and PLS algorithm to estimate the yield of field-grown winter wheat.

Remote sensing has been used as an important means of estimating crop production, especially for the estimation of crop yield in the middle and late growth period. In order to further improve the accuracy of estimating winter wheat yield through remote sensing, this study analyzed the quantitative relationship between satellite remote sensing variables obtained from HJ-CCD images and the winter wheat yield, and used the partial least square (PLS) algorithm to construct and validate the multivariate remote sensing models of estimating the yield. The research showed a close relationship between yield and most remote sensing variables. Significant multiple correlations were also recorded between most remote sensing variables. The optimal principal components numbers of PLS models used to estimate yield were 4. Green normalized difference vegetation index (GNDVI), optimized soil-adjusted vegetation index (OSAVI), normalized difference vegetation index (NDVI) and plant senescence reflectance index (PSRI) were sensitive variables for yield remote sensing estimation. Through model development and model validation evaluation, the yield estimation model's coefficients of determination (R2) were 0.81 and 0.74 respectively. The root mean square error (RMSE) were 693.9 kg ha-1 and 786.5 kg ha-1. It showed that the PLS algorithm model estimates the yield better than the linear regression (LR) and principal components analysis (PCA) algorithms. The estimation accuracy was improved by more than 20% than the LR algorithm, and was 13% higher than the PCA algorithm. The results could provide an effective way to improve the estimation accuracy of winter wheat yield by remote sensing, and was conducive to large-area application and promotion.

Quantitative monitoring of leaf area index in wheat of different plant types by integrating NDVI and Beer-Lambert law.

Normalized difference vegetation index (NDVI) is one of the most important vegetation indices in crop remote sensing. It features a simple, fast, and non-destructive method and has been widely used in remote monitoring of crop growing status. Beer-Lambert law is widely used in calculating crop leaf area index (LAI), however, it is time-consuming detection and low in output. Our objective was to improve the accuracy of monitoring LAI through remote sensing by integrating NDVI and Beer-Lambert law. In this study, the Beer-Lambert law was firstly modified to construct a monitoring model with NDVI as the independent variable. Secondly, experimental data of wheat from different years and various plant types (erectophile, planophile and middle types) was used to validate the modified model. The results showed that at 130 DAS (days after sowing), the differences in NDVI, leaf area index (LAI) and extinction coefficient (k) of the three plant types with significantly different leaf orientation values (LOVs) reached the maximum. The NDVI of the planophile-type wheat reached saturation earlier than that of the middle and erectophile types. The undetermined parameters of the model (LAI = -ln (a1 × NDVI + b1)/(a2 × NDVI + b2)) were related to the plant type of wheat. For the erectophile-type cultivars (LOV ≥ 60°), the parameters for the modified model were, a1 = 0.306, a2 = -0.534, b1 = -0.065, and b2 = 0.541. For the middle-type cultivars (30° < LOV < 60°), the parameters were, a1 = 0.392, a2 = -0.881, b1 = 0.028, and b2 = 0.845. And for the planophile-type cultivars (LOV ≤ 30°), those parameters were, a1 = 0.596, a2 = -1.306, b1 = 0.014, and b2 = 1.130. Verification proved that the modified model based on integrating NDVI and Beer-Lambert law was better than Beer-Lambert law model only or NDVI-LAI direct model only. It was feasible to quantitatively monitor the LAI of different plant-type wheat by integrating NDVI and Beer-Lambert law, especially for erectophile-type wheat (R2 = 0.905, RMSE = 0.36, RE = 0.10). The monitoring model proposed in this study can accurately reflect the dynamic changes of plant canopy structure parameters, and provides a novel method for determining plant LAI.

Assessment of Fv/Fm absorbed by wheat canopies employing in-situ hyperspectral vegetation indexes.

Chlorophyll fluorescence parameter of Fv/Fm, as an important index for evaluating crop yields and biomass, is key to guide crop management. However, the shortage of good hyperspectral data can hinder the accurate assessment of wheat Fv/Fm. In this research, the relationships between wheat canopy Fv/Fm and in-situ hyperspectral vegetation indexes were explored to develop a strategy for accurate Fv/Fm assessment. Fv/Fm had the highest coefficients with normalized pigments chlorophyll ratio index (NPCI) and the medium terrestrial chlorophyll index (MTCI). Both NPCI and MTCI were increased with the increase in Fv/Fm. However, NPCI value ceased to increase as Fv/Fm reached 0.61. MTCI had a descending trend when Fv/Fm value was higher than 0.61. A piecewise Fv/Fm assessment model with NPCI and MTCI regression variables was established when Fv/Fm value was ≤0.61 and >0.61, respectively. The model increased the accuracy of assessment by up to 16% as compared with the Fv/Fm assessment model based on a single vegetation index. Our study indicated that it was feasible to apply NPCI and MTCI to assess wheat Fv/Fm and to establish a piecewise Fv/Fm assessment model that can overcome the limitations from vegetation index saturation under high Fv/Fm value.

[Difference in nitrogen accumulation and translocation between semi-winterness and springness wheat.] / æ˜¥æ€§å’ŒåŠå†¬æ€§å°éº¦æ¤æ ªæ°®ç´ ç§¯ç´¯ä¸Žè¿è½¬ç‰¹å¾å·®å¼‚.

Nitrogen accumulation, translocation and allocation were investigated in a field experiment to find out the difference between six semi-winterness wheat cultivars and nine springness wheat cultivars that are mainly grown in Jiangsu. Results indicated that the average nitrogen accumulation amount (NAA) in the semi-winterness wheat cultivars was lower from the beginning of wintering to jointing stage, but higher from booting to maturity stage, compared with the springness wheat cultivars tested under the same rate of nitrogen fertilization. The amount of nitrogen accumulated between the beginning of wintering and jointing stage showed no significant difference between the two types of wheat cultivars, but that accumulated between anthesis and maturity in the semi-winterness wheat cultivars was higher than that in the springness wheat cultivars. The total N translocation amount (TNTA) and N accumulation amount to grains after anthesis (NAAA) were significantly higher in the semi-winterness wheat cultivars than those in the springness wheat cultivars, but the total N translocation efficiency (NTE), the contribution proportion of accumulated N (ANCP), and the contribution proportion of translocated N (TNCP) did not show significant difference between the two types of wheat cultivars. In leaves, the semi-winterness wheat cultivars showed lower TNTA, NTE and TNCP than the springness wheat cultivars, but in stem and sheath these N indexes were higher in the semi-winterness wheat cultivars, with a significant level for TNTA. These were significant differences in NAA, NAAA, TNTA and TNCP among cultivars with the same spring type or semi-winter type. According to the differences in nitrogen absorption, utilization and translocation among different wheat cultivars, nitrogen utilization efficiency could be improved by using approp-riate amount and reasonable proportion of nitrogen fertilizers at different developmental stages of wheat.

[Changes of endogenous hormone contents and antioxidative enzyme activities in wheat leaves under low temperature stress at jointing stage].

Low temperature stresses (-3 and -5 °C) were simulated using artificial temperature-controlled phytotrons to study the freezing rate, the contents of endogenous hormones, and the activities of antioxidative enzymes in the leaves of wheat plants of Yangmai 16 (YM 16) and Xumai 30 (XM 30) at jointing stage. The grade and index of freezing injury increased with lower temperature and longer stress. The freezing rate was at the 5th level and the main stems and tillers of both cultivars were finally dead under -5 °C lasting for 72 h. On the last day of stress initiation, the contents of abscisic acid (ABA) and zeatin riboside (ZR), and the activities of superoxide dismutase (SOD), peroxide dismutase (POD), and catalase (CAT) in leaves increased at the beginning and then declined as low temperature progressed. On the 3rd day after stress, the contents of ABA and ZR and the activities of antioxidative enzymes were higher than those on the last day of cold stress, and then reduced to the level of the control on the 6th day after stress. The content of gibberellins (GA3) was lowered by cold stress. For YM 16, GA3 content increased from the 3rd day to the 6th day after cold stress, whereas, for XM 30, it increased first and then decreased. For the treatment of -5 °C lasting for 72 h, the contents of hormones and the activities of antioxidative enzymes were significantly lower than those of the other treatments. Correlation analyses showed that higher ABA and ZR contents, and higher SOD, POD and CAT activities as well as lower GA3 content could alleviate the low-temperature injury in wheat plants under low temperature stress.

Assessment of the AquaCrop model for use in simulation of irrigated winter wheat canopy cover, biomass, and grain yield in the North China Plain.

Improving winter wheat water use efficiency in the North China Plain (NCP), China is essential in light of current irrigation water shortages. In this study, the AquaCrop model was used to calibrate, and validate winter wheat crop performance under various planting dates and irrigation application rates. All experiments were conducted at the Xiaotangshan experimental site in Beijing, China, during seasons of 2008/2009, 2009/2010, 2010/2011 and 2011/2012. This model was first calibrated using data from 2008/2009 and 2009/2010, and subsequently validated using data from 2010/2011 and 2011/2012. The results showed that the simulated canopy cover (CC), biomass yield (BY) and grain yield (GY) were consistent with the measured CC, BY and GY, with corresponding coefficients of determination (R(2)) of 0.93, 0.91 and 0.93, respectively. In addition, relationships between BY, GY and transpiration (T), (R(2) = 0.57 and 0.71, respectively) was observed. These results suggest that frequent irrigation with a small amount of water significantly improved BY and GY. Collectively, these results indicate that the AquaCrop model can be used in the evaluation of various winter wheat irrigation strategies. The AquaCrop model predicted winter wheat CC, BY and GY with acceptable accuracy. Therefore, we concluded that AquaCrop is a useful decision-making tool for use in efforts to optimize wheat winter planting dates, and irrigation strategies.

[Effects of elevated atmospheric ozone concentration on flag leaf photosynthetic pigment contents of wheat].

By using a free-air controlled enrichment (FACE) system, this paper studied the effects of elevated atmospheric ozone (O3) concentration (150% of ambient O3) on the flag leaf photosynthetic pigment contents of wheat varieties Yannong 19, Yangmai 16, Jiaxin 002, Yangmai 15, and Yangfumai 2. For the test varieties, no significant differences were observed in the flag leaf chlorophyll a, chlorophyll b, chlorophyll (a+b), and carotenoid contents between treatments elevated O3 concentration and ambient O3 at booting and anthesis stages, but the photosynthetic pigment contents in treatment elevated O3 concentration all decreased after anthesis, with a significant decrease of chlorophyll a, chlorophyll b, and chlorophyll (a+b) contents, which indicated that elevated O3 had minor effects on the synthesis of photosynthetic pigments but accelerated their decline process. Different wheat varieties had genetic difference in the responses of flag leaf photosynthetic pigment contents to elevated O3, among which, Yangmai 15 and Jiaxin 002 had better tolerance to ozone stress. The flag leaf chlorophyll a, chlorophyll b, and chlorophyll (a+b) contents at grain-filling stage (about 21 days after anthesis) had a significant positive correlation with the 1000-grain mass.

[Impacts of elevated atmospheric ozone concentration on flag leaf microscopic structure of wheat: a field study with FACE system].

By using FACE (Free-Air Controlled Environment)-ozone system, a field plot experiment was conducted in 2008-2009 to study the effects of elevated ozone (O3) concentration on the flag leaf microscopic structure, chlorophyll content, and grain weight of wheat. Two treatments were installed, i. e., ambient O3 and 150% of ambient O3, and four winter varieties, i. e., Yannong 19, Yangmai 16, Jiaxin 002, and Yangfumai 2, were taken as the test materials. At anthesis, elevated O3 concentration had a slight damage to the flag leaf microscopic structure. The mesophyll cell and chloroplast structure began destroying, and the grana lamellae started breaking and loosing. Twenty-one days after anthesis, the differences in the leaf microscopic structure between the two treatments became significant. Under elevated O3, the flag leaf senescence was accelerated, with the endomembrane system disintegrated, grana lamella disappeared, and corpus adiposum inside chloroplast broken down, resulting in a significant decrease of the chlorophyll content, photosynthesis rate, and grain weight at maturing stage. Significant difference was observed among the test varieties in their responses to elevated O3. Jiaxin 002 was tolerant, while Yangfumai 2 was sensitive to the ozone stress.

[Monitoring the chlorophyll fluorescence parameter Fv/Fm in compact corn based on different hyperspectral vegetation indices].

In order to further assess the feasibility of monitoring the chlorophyll fluorescence parameter Fv/Fm in compact corn by hyperspectral remote sensing data, in the present study, hyperspectral vegetation indices from in-situ remote sensing measurements were utilized to monitor the chlorophyll fluorescence parameter Fv/Fm measured in the compact corn experiment. The relationships were analyzed between hyperspectral vegetation indices and Fv/Fm, and the monitoring models were established for Fv/Fm in the whole growth stages of compact corn. The results indicated that Fv/Fm was significantly correlated to the hyperspectral vegetation indices. Among them, structure-sensitive pigment index (SIPI) was the most sensitive remote sensing variable for monitoring Fv/Fm with correlation coefficient (r) of 0.88. The monitoring model of Fv/Fm was established on the base of SIPI, and the determination coefficients (r2) and the root mean square errors (RMSE) were 0.8126 and 0.082 respectively. The overall results suggest that hyperspectral vegetation indices can be potential indicators to monitor Fv/Fm during growth stages of compact corn.

[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.

[Effects of water supply tension on photosynthetic characteristics and root activity of greenhouse cucumber].

To study the effects of soil water content on the photosynthesis, fluorescence parameters, and root growth of greenhouse cucumber (Cucumis sativus L.), a pot experiment was conducted, using a negative pressure water supplying and controlling device to control soil moisture regime. Seven levels of water supply tension (WST), i. e., 1, 3, 5, 7, 9, 11, and 13 kPa, were designed. The WST was inversely proportional to soil water content, and the gravimetric soil water content was maintained in the range of 14.23%-42.32%. With increasing WST, the leaf net photosynthetic rate (P(n)) in different growth periods showed a parabolic trend, being higher when the WST was 7-11 kPa at initial flowering stage, and was 3-5 kPa at fruiting stage. The reason for the decreased P(n) at 9-13 kPa WST was stomatal limitation. Under 1-5 kPa WST, the actual photochemical efficiency (phi(PS II) had a high value, and the possibility of photo inhibition was small. Both the leaf transpiration rate and the chlorophyll content were positively correlated with leaf P(n) in different growth periods. Root growth and activity also had a parabolic trend with increasing WST. The maximum root dry mass and root activity happened at 7 kPa and 5 kPa WST, respectively. Our results indicated that a WST of 3-7 kPa was more profitable for the leaf photosynthesis and root growth of greenhouse cucumber.

[Effects of elevated ozone concentration on wheat grain protein components with FACE system].

In 2006-2009, a Free-Air Controlled Enrichment (FACE) system was applied to study the effects of elevated ozone concentration ([O3]) on the grain protein components and their dynamics of four winter wheat varieties Yannong 19, Yangmai 16, Yangmai 15, and Yangfumai 2. Two levels of [O3] were installed, i. e., ambient level (CK-O3) and 50% higher than the ambient level (E-O3). With the increase of [O3], the grain protein content of the varieties increased, with the increment being 7.55% - 16.37% (2006 - 2007), 4.93% - 22.63% (2007 - 2008), and 2.29% - 17.65% (2008 - 2009) in the three years, respectively, and the differences between treatments, varieties, and years being all significant. Adversely, the grain protein yield was decreased significantly by 1.83% - 11.64% (2006 - 2007), - 0.41% - 24.22% (2007 - 2008), and -1.90% - 15.81% (2008 - 2009), respectively in the three years. The contents of four grain protein components (albumin, globulin, gliadin, and glutenin) were significantly higher under E-O3 than under CK-O3, and the differences between treatments, varieties, and years were significant, except the albumin and glutenin contents between treatments.