Search

Biochar prepared from agricultural waste resource coconut shells was used as the original charcoal, which was oxidatively modified and characterized using batch adsorption tests before and after modification by SEM, FTIR, surface area, and elemental analyses. The removal capacity and adsorption mechanism of the modified biochar for Pb2+ and Cd2+ in water were investigated, and its adsorption kinetics and thermodynamics were discussed. The findings demonstrated that the specific surface area of potassium permanganate and nitric acid-modified coconut shell carbon (MHBC) is 3.02 times than that of the coconut shell carbon (BC). The kinetic data of adsorption of Pb2+ and Cd2+ on MHBC were more in accordance with the pseudo-second order kinetic model, indicating that chemical adsorption played a dominant role, and the adsorption rate gradually tended to balance with a decrease in solution ion concentration. The isothermal thermodynamic data of the adsorption of Pb2+ and Cd2+ by MHBC conformed to the Langmuir model. At pH = 5.5, the maximum adsorption capacities of Pb2+ and Cd2+ were 160.41 mg·g−1 and 47.46 mg·g−1, respectively. Thermodynamic parameter fitting showed that the process of adsorption of Pb2+ and Cd2+ by MHBC is a spontaneous endothermic reaction. The higher the temperature is, the stronger the adsorption capacity is. When the ions coexist, Pb2+ and Cd2+ have obvious competitive adsorption, and Pb2+ has a significant competitive advantage. Among them, MHBC has high adsorption and good reusability for Pb2+ and Cd2+, and has good practical application prospects.

For aquaculture wastewater with low ammonium nitrogen concentration, combining the carrier adsorption and biological nitrogen removal processes can maximize their respective advantages. Functional ceramsite that has excellent ammonium nitrogen adsorption performance and excellent biocompatibility was the key to the moving bed biofilm reactor (MBBR) adsorption—shortcut simultaneous nitrification and denitrification (shortcut SND) process. Our group prepared a high-strength lightweight ceramsite that met those requirements. In this study, we applied functional ceramsite in MBBR to cope with low-concentration ammonium aquaculture wastewater. The findings show that utilizing functional ceramsite as a filler was conducive to the adhesion of microorganisms. The biofilm has a minimal effect on the adsorption capacity of ceramsite due to the existence of pores on its surface. Our study further examined the NH4+-N adsorption mechanism of bio-ceramsite. The Freundlich adsorption isotherm model and the quasi-second-order kinetic model had better fitting effects on the NH4+-N adsorption process. The adsorption of bio-ceramsite to NH4+-N was an endothermic process that included physical and chemical adsorption. Furthermore, the results of adsorption thermodynamics suggested that bio-ceramsite has an affinity for the adsorption of NH4+-N. Consequently, this functional ceramsite can be a promising option for MBBR to improve nitrogen removal from aquaculture wastewater.

Excessive discharge of ammonia nitrogen wastewater from intensive aquaculture has worsened in recent years. Therefore, there is an urgent need to develop an effective and energy-saving denitrification technology. This study intends to adopt a moving bed biofilm reactor (MBBR) to remove ammonia nitrogen through the combination of adsorption and shortcut simultaneous nitrification and denitrification (SND). The research focuses on the operational parameters and regeneration mechanism of the MBBR adsorption-shortcut SND process. The optimal operating parameters in the adsorption stage were a hydraulic retention time of 8 h and an agitation rate of 120 r/min. For the shortcut SND stage, the ideal optimal parameters were two times alkalinity and dissolved oxygen (DO) 1.0 mg/L. Under optimal operating parameters conditions, the SND rate, TN removal rate, NH4+-N removal rate and nitrite accumulation rate were 89.1%, 84.0%, 94.3%, and 86.4%, respectively. The synergetic actions of ion exchange and microorganisms were the main driving force for regenerating ceramsite zeolite components. The synergistic inhibitory effect of high-concentration free ammonia and low-level DO on nitrite-oxidizing bacteria was the key to achieving stable and efficient NO2−-N accumulation. NO2−-N produced in shortcut nitrification entered the ceramsite through complex mass transfer, and denitrifying bacteria can reduce these NO2−-N to N2.

Soil residual N is a potential factor threatening the environment, but it is also an N fertilizer resource. Few studies have evaluated the fate of soil residual N under agronomic practice. The objective of this study was to investigate the distribution of residual N and its possible influencing factors with different irrigation regimes. Under three N residual situations created by the previous season using the 15N labeled urea, we employed lettuce as the plant material and three lower limits of drip irrigation including 75% (DR1), 65% (DR2), and 55% (DR3) accounting for the field water capacity as experimental treatments. A furrow irrigation treatment (FI) with the same irrigation regime as DR2 was used as control. Results showed that 2.1–4.8% of the residual 15N from the previous season was absorbed by the succeeding lettuce, 78.0–84.4% was still remained in the 0–80 cm soil, and 10.9–20.0% was unaccounted for. After harvest of succeeding lettuces, the soil residual 15N mainly existed in the mineral form. Moreover, the lettuce reuse efficiency for15N was positively correlated with the total residual 15N amount (p < 0.01) and the mineral 15N amount (p < 0.01). The overall results indicated that an appropriate irrigation regime (DR2) was conducive to promoting absorption of residual N by succeeding crop.

The purposes are to monitor the nitrogen utilization efficiency of crops and intelligently evaluate the absorption of nutrients by crops during the production process. The research object is Chinese cabbage. The Chinese cabbage population with different agricultural parameters is constructed through different densities and nitrogen fertilizer application rates based on digital image processing technology, and an estimation NC (Nitrogen Content) model is established. The population is classified through the K-Means Clustering algorithm using the feature extraction method, and the Chinese cabbage population quality BPNN (Backpropagation Neural Network) model is constructed. The nonlinear mapping relationship between different agricultural parameters and population quality, and the contribution rate of each indicator, are studied. The nitrogen utilization of Chinese cabbage is monitored effectively. Results demonstrate that the proposed NC estimation model has correlation coefficients above 0.70 in different growth stages. This model can accurately estimate the NC of the Chinese cabbage population. The results of the Chinese cabbage population quality BPNN model show that the population planting density based on the seedling number is reasonable. The constructed population quality evaluation model has a high R2 value and a comparatively low RMSE (Root Mean Square Error) value for the quality evaluation of Chinese cabbage in different periods, showing that it applies to evaluate the population quality of Chinese cabbage in different growth stages. The constructed nitrogen utilization model and quality evaluation model can monitor the nutrient utilization of crops in different growth stages, ascertain the agricultural characteristics of other yield groups in different growth stages, and clarify the performance of agricultural parameters in different growth stages. The above results can provide some ideas for crop growth intelligent detection.

Drought is a worldwide concerned issue which causes huge losses in agriculture, economic and damages in natural ecosystems. The precise assessment of drought evolution characteristics is essential for agricultural water management and drought resistance, while such work is rarely reported. Thus, eight meteorological stations located within the Southwest Guizhou Autonomous Prefecture (SGAP) were selected, and the Standardized Precipitation Index (SPI) was used to assess the drought evolution characteristics. The results revealed that the drought occurrences number in Pu'an station was the largest (23 droughts), and the average drought duration in Xingren station was the longest (48.75 months). Moreover, the drought characteristics of the eight stations have account for the largest proportion under normal conditions, was more than 60%, the frequency of drought disaster occurring in Xingren is the highest (30.05%), followed by Wangmo (23.73%). The results of this study will provide theoretical guidance for drought resistance and agricultural production in Southwest Guizhou Autonomous Prefecture of China.

Effective microorganism treatment, a low-cost and remediation measure that with no secondary pollution, was conducted in aquaculture wastewater. Unfortunately, effective microorganism erosion caused by the momentum of water flow under in situ conditions limits the treatment effect. In the channel test, a floating plant bed coupled with the effective microorganism was used to treat crab-breeding wastewater. This study explored the effect of plant coverage and hydraulic loading on aquaculture wastewater purification in the floating plant bed–effective microorganism coupled system. The results show that the effect of the coupled treatment effect is much better than pure microorganism treatment. The pollutant degradation coefficient has a significantly positive correlation with the length of the floating plant bed. A plant coverage rate of 30% and effluent hydraulic loading of 1.0 m3/m2·day are optimum floating plant bed–effective microorganism test conditions. Once the coverage rate exceeded 30%, the increase in the CODMn removal efficiency was not clear. At the same time, the high plant coverage inhibited the oxygen capacity in the water body, which directly led to a decrease in the degradation ability of organic matter by the plant. The biology–ecology coupled technology proposed in this study overcame the shortcomings of the easy-to-lose effective microorganism during the traditional unfixed process and improved the stability of the processing system. It strengthened the crab-breeding wastewater remediation effect. For an in situ application, the artificial restoration system 1 km in length was efficient, and the discharge met the standard at the end of the river.

This study aimed to determine the effect of irrigation amount and irrigation frequency on drip-irrigated flue-cured tobacco evapotranspiration (ETa), yield, and water use efficiency. Four irrigation treatment levels were imposed: 100% IRT (fully irrigated treatment, no stress), 85% IRT, 70% IRT, RFT (rainfed treatment), and high, medium, and low irrigation frequencies were set. The relationship between irrigation volume and yield is a quadratic curve. The evapotranspiration had a positive relationship with the irrigation amount. The yield of flue-cured tobacco was the highest in 2016 (wet year), and the corresponding ETa was the smallest. The irrigation water use efficiency (IWUE) in the driest year, 2017, was lower than IWUE in the wet years 2015 and 2016, and the crop water use efficiency (CWUE) had similar results for the three years. IWUE increased with irrigation amount. The effect of irrigation frequency on CWUE was not significant. The CWUE had a positive relationship with yield. No significant differences due to irrigation frequency were found for yield.

A reasonable water and nitrogen (N) coupling management should be use to get good quality and high yield of flue-cured tobacco. In this paper, ten water-N coupling treatments were designed to treat tobacco 'Yunyan85' (Nicotiana tabacum L.85) as W1N1, W2N1, W3N1, W1N2, W2N2, W3N2, W1N3, W2N3, W3N3, W2N0 (conducted as check). Wl, W2 and W3 showed water systems as 50%-70%-60% (lower limited water control at ratio of field capacity at rooting stage-vigorous stage-mature stage-nitrogen application), 60%-80%-70% and 70%-90%-80%, respectively. The N applications wereNO at 0, Nl at 4.0 g/plant, N2 at 6.0 g/plant and N3 at 8.0 g/plant. Irrigation amount at the whole or three growing stages were displayed as I or II, 12 and 13, respectively. The evapo-transpiration quantities were showed as ET, ET1, ET2 and ET3. Yield (Y), water use efficiency (WUE), irrigation water use efficiency (IWUE) and unit output value (UOV) were analyzed. Water-N coupling yield models as Jensen model and four polynomial models (Linear, Interaction Function, Pure Quadratic Function, Total Quadratic Function) from MATLAB 2018 were fitted. Results showed that water-N coupling treatment remarkably enhanced productivity efficiency. W1N2 significantly reduced irrigation and evapo-transpira-tion (p<0.05). W3N3 got the obvious largest tobacco yield at 2.92 t/hm2 (p<0.05), while W1N3 received the evident largest WUE (0.58 kg/m3), IWUE (0.44 kg/m3) and UOV (735.8 USD/mm/hm2) (p<0.05), respectively. Projection Pursuit Classification Model (PPC) confirmed 50%-70%-60%-8.0 as the bestmanagement model on production efficiency for Yunyan85' (Nicotiana tabacum L. 85). The Linear equations of Y(ET1, ET2, ET3, N), Y(ET, N), Y(I, N), and total quadratic functioned Y(I1, 12, 13, N)were successfully functioned (p<0.001) at first, which could be used to manage growth of 'Yunyan

The accumulation of lead (Pb) in sediments resulted from substandard discharge of industrial and agricultural sewage hold serious threat to agro-ecology and human health during its recycling process. Electro-kinetic remediation (EKR) is a promising technique for Pb decontamination in porous matrix while pH polarization remains to be the main obstacle for its widespread application. In this study, lab-scale EKR experiments were conducted with enhanced strategies of non-uniform electric intensity (NEI), polarity reversal (PR) and electrolyte conditioning (EC). From the obtained results, all the strategies could alleviate the pH polarization of sediments and increase the removal of Pb by 6.2-37.4%. Operating parameters of electric intensity (El), electrode exchange frequency and electrolyte type were optimized and determined to be 1.0 V/cm, 24 h/time and 0.1 M HAc, respectively. Higher extraction efficiencies of Pb (75-86%) were reached when employed the enhanced EKR and the optimal result was observed when applied the NEI, PR and EC strategies simultaneously. The remediation duration, energy utilization efficiency and energy cost of EKR with optimal enhanced scheme to remove all sediment Pb was evaluated to be in an acceptable value of 178.2 h, 42.3 mg/kWh and $ 0.65/kg, respectively. The methodology and results in this study might provide theoretical foundation to support the designation of EKR in full-scale applications. [ABSTRACT FROM AUTHOR]

Photosynthesis is related to dry matter accumulation in aboveground part of rice plant, which is the direct factor of production. This study carried out research on physiological indicators and the relationship between photosynthesis and dry matter accumulation under different water management in paddy field. In general, the photosynthetic and physiological indicators showed the trend of increasing and then decreasing with the growth stage of rice. Experimental results showed that, chlorophyll content and leaf area index of rice leaves showed a quadratic curve positive correlation. Canopy light transmission reached the maximum at heading-flowering stage, and it had quadratic relationship with leaf area index, while it showed extremely positive correlation under rain-water storage irrigation mode. Photosynthetic rate (Pn) and transpiration rate (Tr) had quadratic curve positive correlation with chlorophyll content. The water condition under rain-water storage was favorable for dry matter accumulation in panicle. After multiple regression and main factor analysis, canopy light transmission, light transmission coefficient and Pn were main factors related to dry matter accumulation. The conclusions in this article were helpful for promoting rice yield in practice. [ABSTRACT FROM AUTHOR]

An appropriate coupling of water fertilizer can improve the quality and yield of tobacco (Nicotiana tabacum L.). However, the optimal scheme of that is still unknown under the condition of effective microorganisms (EM) biochar-based fertilizer application. In this study, 12 treatments were set up, which were divided into four fertilization gradients (0, 100, 300, and 600 g pot-1, represented CK1-K3, T1-T3, T4-T6, and T7-T9, respectively), and each fertilization gradient had three irrigation gradients (40, 80, and 120 L pot-1). Each treatment was set in triplicate. Compared to CK, the nicotine content, reducing sugar, total nitrogen, potassium, chlorine, and yield of flue-cured tobacco increased by 13.22-48.87%, 1.53-13.46%, 7.68-29.23%, 7.73-21.76%, 6.48-34.55%, and 7.93-65.51% after the application of EM biocharbased fertilizer. The quality of flue-cured tobacco was less affected by the amount of irrigation (P > .05), and the yield was positively correlated with the amount of irrigation and EM biochar-based fertilizer (P < .05). The principal component analysis (PCA) was performed on all indexes of flue-cured tobacco quality and established the comprehensive evaluation system. Analytic hierarchy process--entropy weight method (AHP--EWM) and projection pursuit classification (PPC) algorithms were utilized to build the model, and the optimal water--fertilizer coupling scheme was selected according to AHP--EWM score and projection values. In conclusion, 120 L pot-1 irrigation combined with 100 g pot-1 of EM biochar-based fertilizer application treatment was the best water-fertilizer coupling scheme, and the AHP--EWM score and projection value were .632 and 1.169. The results of this study might provide theoretical and practical guidance for the plantation of flue-cured tobacco in production areas. [ABSTRACT FROM AUTHOR]

Despite the observed a warming climate, observations across many regions show that the rate of evaporation at a regional scale has been decreasing over the past 50 years, the changes of evaporation have attracted widespread attention due to it is important for understanding the global hydrological cycle and agricultural production. It is necessary to explain the spatio-temporal variation of evaporation due to the Southwest Guizhou Plateau strongly influences climatic and environmental changes in China. In this paper, we present an analysis of changes in the spatio-temporal variation and the abrupt changes of evaporation with a warming climate based on time series data from 1961 to 2015. The results showed that the mean annual evaporation decreased from 1961 to 2015 with the linear trend of-1.86 mm/year, the seasonal evaporation is estimated to decrease - 1.26, -1.09, -0.27, and -0.24 mm/year for spring, summer, and autumn. The annual evaporation was largest in the south and southwest, while significantly lower in the north and northeast. The evaporation of annual and seasonal have abrupt change with a decreasing trend despite under a warming climate, and the annual, spring, and summer evaporation all exceeds the confidence level of 99%. Incontrovertible, Southwest Guizhou Plateau has occurred a pan evaporation paradox, which was thought to be affected by global warming and climate change and this effect will continue. Evaporation should be continuously measured and monitoring programs should be established to help further understand the regional responses of agricultural production and sustainable use and management of water resources. [ABSTRACT FROM AUTHOR]

Effective microorganism biochar-based fertilizer (EMBF) can improve the physiological properties of tobacco (Nicotiana tabacum L.) In this study, the irrigation and EMBF rates were applied as factors that influence the photosynthetic characteristics and chlorophyll content of tobacco. The experiment involved 12 treatments: CK1-CK3, T1-T3, T4-T6, and T7-T9; these four groups represented 0, 100, 300, and 600 g EMBF pot-1, respectively. Each group was irrigated at rates of 40, 80, and 120 L pot-1. When comparing with the control treatment CK, results showed that net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), and soil plant analysis development (SPAD) increased by 8.21%-107.03%, 18.78%-118.27%, 18.78%-118.27%, 7.24%-104.15%, and 3.47%- 69.09%, respectively, after EMBF application. The Pn, gs, Ci, and Tr at the growth and maturity stages were highly significant (P < 0.01) and positively correlated with EMBF application. The Pn, gs, and Tr were significant (P < 0.05) and positively correlated with irrigation, and Ci was less affected by irrigation (P > 0.05). The SPAD value of flue-cured tobacco at three growing stages was highly significant (P < 0.01) and positively correlated with the irrigation and fertilization rates. The SPAD values at the growth and maturity stages were higher than those at the rooting stage by 46.73%-79.2% and 2.21%- 46.17%, respectively. Furthermore, the 80 L pot-1 irrigation rate combined with 300 g EMBF pot-1 is the best water and fertilizer combination. The results of this study might provide theoretical and practical guidance for growing flue-cured tobacco in production areas. [ABSTRACT FROM AUTHOR]

Soil water and fertilizer had interacted effects on plant growth, evaporation, transpiration, water production efficiency. In this study, three soil water control treatments were set as 50%-70%-60% (W1, ratios of field moisture capacity at rooting period-vigorous growing period-mature period), 60%-80%-70% (W2), 70%-90%-80% (w3). Each water control interacted with four potassium (K) usages (K1: 0 g/plant, K2:10.0 g/plant, K3:15.0 g/plant, K4:20.0 g/plant) to plant flue-cured tobacco Yunyan85 (Nicotiana tabacum L. 85). Soil water content (SW), air temperature (T), relative humidity (RH), some photosynthetic indexes (Pn, Gs, Tr, LWUE), biomass yield (Y), water use efficiency (WUE), irrigation water use efficiency (IWUE), unit output value (UOV), conditions of evaportranspiration were analyzed to study wa-ter-K coupling effects. Results showed that tobacco soil moisture content fluctuated and gradually reduced as tobacco growing. An significant influence presented between SW and soil evaporation (p<0.05). T was the greatest factor leading to soil evaporation, while RH and SW decreased water lose. T and RH obviously effected soil evaporation especially at the vigorous and mature growth stages. K application to some extend adjusted water demand for tobacco growth. Wa-ter-K coupling treatments significantly advanced tobacco photosynthesis (p<0.05). The reasonable usage of water and K fertilizer would reduce irrigation quantity and crop water requirement, augmenting WUE, IWUE, Pn, Gs, Tr, Ci, LWUE, Y and UOV (p<0.05) at each growing stage. To sum up, water-K treatment of W3K4 at 70%-90%-80%-20.0 would be the best water and potassium interacting management for Yunyan 85 production. [ABSTRACT FROM AUTHOR]

Precipitation is one of the most important meteorological variables which can impact the occurrence of drought. Analyze the spatio-temporal variation of precipitation and drought is very important for drought resistance and the agricultural production, while such work are rare reported in Southwest Guizhou Autonomous Prefecture (SGAP). Thus, eight meteorological stations located within the SGAP were selected, and the integrated approach (linear regression analysis, moving average, geostatistical analyst and Mann-Kendall trend detection test) was used to assess the spatiotemporal variation of precipitation and drought. The results revealed that the precipitation in Wangmo (WM) and Xingren (XR) stations showed an increasing trend with values of 8.269 and 20.29 mm/year. While Anlong (AL), Ceheng (CH), Pu'an (PA), Qinglong (QL), Xingyi (XY), and Zhenfeng (ZF) stations showed decreasing trends of -2.419, - 1.848, -3.681, -3.779, -1.815, and -1.758 mm/year. The spring precipitation in the central and southwest was significantly lower on the spatial scale. The spring drought in SGAP has occurred frequently due to the precipitation decline year by year and the uneven spatial and temporal distribution, which impacted the regional drought and agricultural production. The results of this study will provide theoretical guidance for drought resistance and agricultural production in SGAP of China. [ABSTRACT FROM AUTHOR]

Nitrogen-water system is one of the main growth management for flue-cured tobacco. With unhealthy growth under unreasonable nitrogen application and irrigation, a suitable Nitrogen-water treatment availably promote tobacco growth, saving water and fertilizer. In this text, nitrogen treatments for flue-cured tobacco were designed at 4.0, 5.5 and 7.0 g per plant. Each N treatment coupled with irrigation treatments at root extending period (50%, 60%), vigorous growth period (70%, 80%, 90%), harvesting period (60%, 70%), of which above ratios were proportion of saturation moisture capacity. Tobacco biological yield, water evaporation were investigated. The results showed that irrigation system with 90%, 70% in last growing period, could obviously enhance tobacco leaves, while the root extending water was 50% or 60%. Water-nitrogen coupling production function was best fitted at full quadratic curve equation (R2=0.669, P<0.001), which can be to same extend used to direct water and nitrogen system for flue-cured tobacco. [ABSTRACT FROM AUTHOR]

The endogenous release of nitrogen and phosphorus from aquaculture sediment can continuously pollute the water quality in aquaculture ponds. In this study, an integrated bioremediation approach that combined effective microorganisms (EM) with aeration techniques was designed to restore contaminated aquaculture sediment. Initially, a set of laboratory-scale experiments was designed to evaluate the feasibility of the technology for the bioremediation of nitrogen and phosphorus. The removal and transformation efficiency indexes of both the overlying water and sediment were measured. From the obtained results, the combination of sediment aeration and immobilized EM significantly improved the nitrogen and phosphorus removal rate from the overlying water and sediment when compared to other methods. Subsequently, a series of field-scale experiments was further implemented to assess the integrated technique in practical applications. In field experiments, the variation in the comprehensive trophic level index (TLI) and sediment biodegradation activities (G value) was used to assess the effect of sediment bioremediation. In pond II which promotes sediment biodegradation, the values of TLI varied from 70.13 to 54.16, and the classification level changed from Hypereutrophic to a Light eutrophic. In addition, the G value increased from 0.98 kg/(kg·h) to 2.12 kg/(kg·h). The organic matter (OM) and sediment thickness (ST) decreased by 17.4 g/kg and 2.3 cm, respectively. The obtained results indicated that the combination of EM and sediment aeration might be feasible and effective for the remediation of nitrogen- and phosphorus-polluted aquaculture sediment. [ABSTRACT FROM AUTHOR]