Evaluating the Effects of Aquaculture Wastewater Irrigation with Fertilizer Reduction on Greenhouse Tomato Production,Economic Benefits and Soil Nitrogen Characteristics

The utilization of aquaculture wastewater as irrigation is an effective way to recycle and reuse water and nitrogen fertilizer resources because it contains numerous nutrients.However,it is still unclear that the pattern of substituting aquaculture wastewater irrigation for fertilizer supplementing is conducive to improving the soil nitrogen status,fruit yield and water-fertilizer use efficiency for tomato production.In this context,the experiment was intended to establish the appropriate irrigation regime of aquaculture wastewater in tomato production for freshwater replacement and fertilizer reduction to ensure good yields.Pot experiments were conducted with treatments as farmers accustomed to irrigation and fertilization used as control(CK),1.75 L aquaculture wastewater with base fertilizer(W1),2 L aquaculture wastewater with base fertilizer;and 2.25 L aquaculture wastewater with base fertilizer(W3).We examined the effects of aquaculture wastewater irrigation on soil nitrogen distribution,Nrelated hydrolases,tomato yield,and economic benefits.The results showed that the control treatment had the highest N input,about 24.68%higher than the W3 treatment,while the yield was only about 7.81%higher than W3.This indicated that the overuse of chemical fertilizer was present in the current tomato production.Although the reduction of fertilizer in aquaculture wastewater irrigation caused a decrease in tomato production,this economic loss can be compensated by cost savings in the wastewater disposal.Among aquaculture wastewater treatments,the W3 treatment had the highest overall benefit,achieving 62.63%freshwater savings,37.50%fertilizer input reduction,and an economic return of approximately 19,466 Yuan per hectare higher than the control.Additionally,increasing the irrigation volume of aquaculture wastewater could provide more available nutrients to the soil,which were more prevalent in the form of organic nitrogen.The lower soil nitrate reductase activities(NR)under aquaculture wastewater treatments after harvesting also proved that this pattern was beneficial to reduce soil nitrate nitrogen residues.Overall,the results demonstrate that aquaculture wastewater irrigation alleviates the soil nitrate residues,improves nutrient availability,and results in more economic returns with water and fertilizer conservation for the greenhouse production of tomatoes.

Effects of water application intensity of micro-sprinkler irrigation and soil salinity on environment of coastal saline soils

To achieve the greatest leaching efficiency,water movement must occur under unsaturated flow conditions.Accordingly,the water application intensity of irrigation must be chosen carefully.The aim of this study was to evaluate the impact of the water application intensity of micro-sprinkler irrigation on coastal saline soil with different salt contents.To achieve this objective,a laboratory experiment was conducted with three soil salinity treatments(2.26,10.13,and 22.29 dS/m)and three water application intensity treatments(3.05,5.19,and 7.23 mm/h).The results showed that the effect of soil salinity on soil water content,electrical conductivity,and pH was significant,and the effect of the water application intensity was insignificant.High soil water content was present in the 40e60 cm profile in all soil salinity treatments,and the content was higher in the medium and high water application intensity treatments than in the low-intensity treatment.Significant salt leaching occurred in all treatments,and the effect was stronger in the high soil salinity treatment and medium water application intensity treatment.In the medium and high soil salinity treatments,pH exhibited a decreasing trend,with no trend change in the low soil salinity treatment,and the pH value was higher in the medium water application intensity treatment than in the other two treatments.These results indicated that the three intensities evaluated had no statistically different effect on the electrical conductivity of saturated soil-paste extracts(EC)in the upper 20 cm of the soil profile,and it would be better to maintain a lower value of the water application intensity.

Wheat Straw Burial Improves Physiological Traits, Yield and Grain Quality of Rice by Regulating Antioxidant System and Nitrogen Assimilation Enzymes under Alternate Wetting and Drying Irrigation

Wheat straw burial has great potential to sustain rice production under alternate wetting and drying(AWD)irrigation.A field experiment was conducted with three wheat straw burial treatments,including without straw burial(NSB),with light straw burial of 300 kg/hm^(2)(LSB)and dense straw burial of 800 kg/hm^(2)(DSB),as well as three AWD regimes:alternate wetting/moderate drying(AWMD),alternate wetting/severe drying(AWSD)and alternate wetting/critical drying(AWCD).The rice growth and grain quality were higher in LSB and NSB than those in NSB under the same AWD regime.The AWMD×DSB treatment resulted in the highest yield,brown rice rate,milled rice rate,amylose content and protein content.Conversely,the AWCD×NSB treatment led to the lowest yield,brown rice rate,milled rice rate,amylose content and protein content.The active absorption area and nitrate reductase activity of roots were higher in the AWMD×DSB treatment than those in the AWCD×NSB treatment,as the former increased organic carbon and nitrogen contents in the rhizosphere,whereas the latter reduced their availability.Total soluble protein content and glutamine synthetase activity were greater in the AWMD×DSB treatment than those in the AWCD×NSB treatment.The activities of superoxide dismutase and catalase were higher in the AWMD×DSB treatment compared with the AWCD×NSB treatment,leading to the amelioration of oxidative cell injury,as shown by a lower malonaldehyde level.This study suggested that farmers should implement AWMD irrigation after leaving the straw residues in the field,followed by deep tillage to improve soil quality and mitigate the drought stress cycles of AWD.This approach can improve rice growth and grain quality and alleviate the problems of disposal of straw residues and water scarcity for sustainable rice production.

Effects of muddy water irrigation with different sediment gradations on nitrogen transformation in agricultural soil of Yellow River Basin

Muddy water irrigation has been widely practiced in the Yellow River Basin for agricultural production and is an important method of economical and intensive utilization of water resources.In this study,the effects of sediment gradation,sand content,and soil moisture content on nitrogen(N)transformation were studied through a series of experimental tests.The results indicated that muddy water irrigation significantly affected agricultural soil physical and biological properties as well as N transformation.Soil bulk density,total porosity,pH,and microbial enzyme activities significantly correlated with N transformation as affected by the interaction between sediment and soil moisture.Sediment addition generally increased the soil bulk density and reduced the soil porosity and pH significantly,and the optimum moisture for promotion of the N transformation rate was 80%of the water-filled pore space.Therefore,muddy water irrigation has a potentially long-term influence on agricultural N cycles in semi-arid regions of northwestern China.This could provide a theoretical basis for scientific and rational use of muddy water for irrigation.

Approach of water-salt regulation using micro-sprinkler irrigation in two coastal saline soils

This study aimed to investigate whether saline silt and sandy loam coastal soils could be reclaimed by micro-sprinkler irrigation.The experiments were run using moderately salt-tolerant tall fescue grass.Micro-sprinkler irrigation in three stages was used to regulate soil matric potential at a 20-cm soil depth.Continued regulation of soil water and salt through micro-sprinkler irrigation consistently resulted in an increasingly large low-salinity region.The application of the three stages of soil wateresalt regulation resulted in an absence of salt accumulation throughout the soil profile and the conversion of highly saline soils into moderately saline soils.There were increases in the plant height,leaf width,leaf length,and tiller numbers of tall fescue throughout the leaching process.The results showed that micro-sprinkler irrigation in three soil water and salt regulation stages can be used to successfully cultivate tall festuca in highly saline coastal soil.This approach achieved better effects in sandy loam soil than in silt soil.Tall fescue showed greater survival rates in sandy loam soil due to the rapid reclamation process,whereas plant growth was higher in silt soil because of effective water conservation.In sandy loam,soil moisture should be maintained during soil reclamation,and in silt soil,soil root-zone environments optimal for the emergence of plants should be quickly established.Micro-sprinkler irrigation can be successfully applied to the cultivation of tall fescue in coastal heavy saline soils under a three-stage soil wateresalt regulation regime.

钙铝层状双氢氧化物(CaAl-LDH)对铅镉砷污染废水的吸附性能及机制研究

重金属污染普遍存在且日趋严重,解决阳离子和阴离子重金属共存的复合污染问题依然是一个严峻的挑战。本研究采用简便的原位共沉淀法制备了钙铝层状双氢氧化物(CaAl-LDH),用于去除水中的重金属离子。通过XRD、SEM、FTIR和XPS等表征方法研究CaAl-LDH的制备及其对重金属离子的吸附机理。采用批吸附实验研究CaAl-LDH对Pb(Ⅱ)、Cd(Ⅱ)和As(Ⅴ)三种金属离子的吸附能力。结果表明,准一级动力学模型可以很好地拟合CaAl-LDH对三种重金属的吸附。吸附等温线结果表明,与Freundlich模型(R^(2)<0.67)相比,Cd的吸附过程更符合Langmuir模型(R^(2)>0.92)。Langmuir和Freundlich模型都能有效拟合Pb和As的吸附(R^(2)>0.90)。CaAl-LDH对Pb(Ⅱ)、Cd(Ⅱ)和As(Ⅴ)的最大吸附量分别为786.6、437.2和72.9 mg/g,并且在10 min内能够达到吸附平衡,反应快速高效。CaAl-LDH对铅、镉、砷的吸附机理各异。铅的吸附可能通过表面沉淀实现,而镉的吸附机理为同晶置换。至于As的吸附,可能涉及LDH层间的离子交换。该实验提供了一种对阴、阳离子重金属都具有高效吸附性能的LDH材料,并在重金属复合污染废水治理中显示出一定的应用潜力。

Nitrogen Deep Placement Combined with Straw Mulch Cultivation Enhances Physiological Traits,Grain Yield and Nitrogen Use Efficiency in Mechanical Pot-Seedling Transplanting Rice

To assess the effects of straw return coupled with deep nitrogen(N)fertilization on grain yield and N use efficiency(NUE)in mechanical pot-seedling transplanting(MPST)rice,the seedlings of two rice cultivars,i.e.,Yuxiangyouzhan and Wufengyou 615 transplanted by MPST were applied with N fertilizer at 150 kg/hm2 and straw return at 6 t/hm2 in early seasons of 2019 and 2020.The experiment comprised of following treatments:CK(no fertilizer and no straw return),MDS(deep N fertilization and straw return),MBS(broadcasting fertilizer and straw return),MD(deep N fertilization without straw return),MB(broadcasting fertilizer without straw return).Results depicted that the MDS treatment significantly increased the rice yield by 41.69%-72.22%due to total above-ground biomass,leaf area index and photosynthesis increased by 54.70%-55.80%,38.52%-52.17%and 17.89%-28.40%,respectively,compared to the MB treatment.In addition,the MDS treatment enhanced the total N accumulation by 37.74%-43.69%,N recovery efficiency by 141.45%-164.65%,N agronomic efficiency by 121.76%-134.19%,nitrate reductase by 46.46%-60.86%and glutamine synthetase by 23.56%-31.02%,compared to the MB treatment.The average grain yield and NUE in both years for Yuxiangyouzhan were higher in the MDS treatment than in the MD treatment.Hence,deep N fertilization combined with straw return can be an innovative technique with improved grain yield and NUE in MPST in South China.

Effects of maize straw biochar application on soil physical properties, morph-physiological attributes, yield and water use efficiency of greenhouse tomato

Tomato(Solanum lycopersicum L.)production was threatened by the inefficiency of fertilizers,contributing to the deterioration of the soil environment under greenhouse conditions in southern China.Biochar application could ameliorate the physical properties of soil and enhance the growth and productivity of tomatoes.In this study,a pot experiment was conducted with four biochar addition rates of 0%(BA0),1%(BA1),3%(BA3),and 5%(BA5).Results showed that the soil physical properties,morph-physiological indicators,yield,and water use efficiency(WUE)of tomatoes with biochar addition were significantly higher than those of tomatoes without biochar addition.Among the different treatments,BA5 provided the highest total porosity(53.09%),field capacity(40.73%),plant height(72.5 cm),net photosynthetic rate(16.04 mmol/m^(2)·s),total dry matter(184.65 g/plant),yield(54.9 t/hm^(2)),and WUE(38.5 kg/m^(3)).The yield and WUE increased from 44.5 t/hm^(2) and 31.2 kg/m^(3) under BA0,respectively,to 54.9 t/hm^(2) and 38.5 kg/m^(3) under BA5,respectively.The results suggest that BA5 can maximize improvements in soil physical properties to augment plant growth,thereby increasing the yield and WUE of tomatoes.However,the effects of BA3 and BA5 on WUE were not significantly different.Thus,from the perspective of economic investment,BA3 is recommended.

Effects of urea-N and CO_(2) coupling fertilization on the growth,photosynthesis,yield and anthocyanin content of hydroponic purple cabbage Brassica campestris ssp.chinensis

Water and fertilizer coupling is a high-efficiency technology for the development of facility agriculture.However,the interaction effect of nitrogen(N)and air carbon dioxide(CO_(2))on hydroponic purple cabbage,especially on its leaf anthocyanins under hydroponic solution systems,remains unexplored.In this study,six treatments were set as C0N0,C0N2,C0N4,C1N0,C1N2 and C1N4,with N0,N2 and N4 being 0.0 g/L,0.2 g/L and 0.4 g/L exogenous urea-N to hydroponic solution dilution,respectively.C0 and C1 were set as with and without CO_(2)fertilizer(i.e.,800 g CO_(2)agent added one week after transplanting and 600 g CO_(2)agent added when the plant reached 15 cm in height),respectively.Pot experiments were conducted to investigate the interaction effect of N and air CO_(2)(N×CO_(2))on the growth,photosynthesis,yield and anthocyanin content of hydroponic purple cabbage Brassica campestris ssp.chinensis.The results showed N×CO_(2)extremely significantly influenced plant height(H),net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular oxidation concentration(Ci),transpiration rate(Tr),leaf water use efficiency(LWUE)and yield.The C1N0 treatment had the largest yield at 262.5 g/plant,with higher values for root length,root weight,plant height and leaf number than the other treatments.The Pn,Ci and Tr of C1N4 were the highest at 3.05μmol CO_(2)/m2·s,352.8μmol CO_(2)/m2·s and 2.31 mmol H2O/m2·s,respectively.The C1N2 treatment received the largest Gs value of 0.70 mol H2O/m2·s and the largest Tr of 2.31 mmol H2O/m2·s.There was the highest LWUE for C0N2(1.41)and the highest anthocyanin content for C1N2(1.35 mg/kg).There was a significant negative correlation between leaf number and anthocyanin(r=-0.414,p<0.05).The findings demonstrated that adding CO_(2)fertilizer and 0.2 g/L exogenous urea-N to hydroponic solution dilution is a potential N×CO_(2)coupling strategy to increase anthocyanin and the yield of purple cabbage.

Promotion effects of salt-alkali on ammonia volatilization in a coastal soil

Coastal ecosystems are highly susceptible to salt-related problems due to their formation process and geographical location. As such ecosystems are the most accessible land resources on Earth, clarifying and quantifying the effects of salt-alkali conditions on N concentration and ammonia(NH_(3)) volatilization are pivotal for promoting coastal agricultural productivity. The challenge in establishing this effect is to determine how salt-alkali conditions impact NH_(3) volatilization through direct or indirect interactions. An incubation experiment using a coastal soil from a paddy farmland, combined with the structural equation modeling(SEM) method, was conducted to reveal the net effects of salt-alkali on NH_(3) volatilization and the role of environmental and microbial factors in mutual interaction networks. The specific experimental design consisted of four salt treatments(S1, S2, S3, and S4: 1‰, 3‰, 8‰, and 15‰ NaCl by mass of soil, respectively), four alkaline treatments(A1, A2, A3, and A4: 0.5‰, 1‰, 3‰, and 8‰ NaHCO_(3)by mass of soil, respectively) and a control without NaCl or NaHCO_(3) addition(CK), and each treatment had three urea concentrations(N1, N2, and N3: 0.05, 0.10, and 0.15 g N kg^(-1) soil,respectively) and three replicates. At the N1, N2, and N3 levels, NH_(3)volatilization increased by 9.31%–34.98%, 3.07%–26.92%, and 2.99%–43.61% as the NaCl concentration increased from 1‰ to 15‰, respectively, compared with CK. With an increase in the NaHCO_(3)concentration from 0.5‰ to 8‰, NH_(3) volatilization increased by 8.36%–56.46%, 5.49%–30.10%, and 30.72%–73.18% at the N1, N2, and N3 levels, respectively, compared with CK. According to the SEM method, salinity and alkalinity had positive direct effects on NH_(3)volatilization, with standardized path coefficients of 0.40 and 0.19, respectively.Considering the total effects(net positive and negative effects) in the SEM results, alkalinity had a greater influence than salinity(total standardized coefficient0.104 > 0.086). Nitrogen concentrations in the incubation system showed a direct positive effect on NH_(3) volatilization(standardized path coefficient = 0.78),with an obvious decrease under elevated salinity and alkalinity levels. Additionally, gene abundances of nitrogen-transforming microbes indirectly increased NH_(3) volatilization(total indirect standardized coefficient = 0.31). Our results indicated that potential NH_(3) emissions from coastal saline areas could be enhanced more by soil alkalization than by salinization.

Effects of excessive nitrogen fertilizer and soil moisture deficiency on antioxidant enzyme system and osmotic adjustment in tomato seedlings

Long-term excessive application of nitrogen fertilizer induces secondary salinization of soil,which results in inhibiting plant growth.In addition,soil moisture deficiency also affects plant growth.To investigate the effects of excessive nitrogen fertilizer and soil moisture deficiency on the antioxidant enzyme system,plant water relations analyzed through pressure-volume(P-V)curve,and photosynthetic light response parameters in tomato(Solanum lycopersicum L.Myoko)seedlings,an indoor experiment of about 50 d was conducted using two irrigation water amounts based on field capacity(soil moisture deficiency:50%-80%;adequate water:70%-80%),two nitrogen fertilizer rates(moderate nitrogen;excessive nitrogen fertilizer:0.585 g/pot)and two types of irrigation water(tap water and microbial diluent).The results showed that excessive nitrogen fertilizer(N)and soil moisture deficiency(W)reduced the biomass of tomato seedlings.In comparison to CK(combination of adequate water and tap water quality),microbial dilution(EM)increased plant biomass by 5.2%.Also,the nitrogen application increased chlorophyll relative contents(SPAD).The maximum net photosynthetic rate(Pc)decreased with nitrogen application and increased with EM application and irrigation amount.Excessive nitrogen application increased the plant nitrate reductase activity(NR).The plant NR in the N treatment showed a 13.0%increase compared to CK,and the plant NR in the treatment of nitrogen application with water deficiency(WN)increased 34.0%compared to water deficiency(W).After applying excessive nitrogen,N,EM-N,WN,EM-WN respectively increased the plant nitrate reductase activity by 13.0%,22.9%,34.0%,and 28.6%,compared with the corresponding treatment with moderate nitrogen(i.e.,CK,EM,W and EM-W).In addition,the activities of antioxidant enzymes[superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)]in four treatments of nitrogen application(N,EM-N,WN,EM-WN)also increased significantly.Both soil moisture and nitrogen fertilizer significantly affect the parameters of osmotic adjustment,which is manifested in the reduction of osmotic potential(π_(FT)),and the increase in the osmotic concentration(C_(osm))and concentration difference(ΔC_(osm)).But the decrease in the relative water content of apoplast(ζ_(ap))indicated that water deficiency and excessive nitrogen reduced the water absorption and water retention capacity of tomatoes to a certain extent.In conclusion,excessive nitrogen application and soil moisture deficiency inhibit plant growth significantly in this experiment.Meanwhile,microbial dilution can alleviate excessive nitrogen fertilizer and water stress to some extent,but the effect was not significant.

Osmotic adjustment and up-regulation expression of stress-responsive genes in tomato induced by soil salinity resulted from nitrate fertilization

Concerns about the soil salinity caused by excessive fertilization have prompted scientists to clarify the detailed mechanisms and find techniques to alleviate the damage caused by this kind of soil salinity.Aims of this study were to elucidate the effect of soil salinity caused by nitrate fertilization and the differences in salinity effect between nitrate salts and NaCl salt with analyses at various levels of crop physiology and molecular biology.A microbial inoculation was also tried to verify whether it could alleviate the salinity-induced loss and damages.In three experiments(Exp I,II and III),nitrate salts(NS)of Ca(NO_(3))_(2) and KNO_(3) were applied to potted tomato plants to simulate the soil salinity caused by fertilization and a microbial inoculant(MI)was applied.Photosynthesis was measured using Li-6400.Osmotic adjustment was analyzed using the mathematically modeled pressure-volume curve;O_(2)-concentration and activity of SOD and nitrate reductase were measured.Expression of nitrate reductase gene and the stress-responsive gene DREB2 was analyzed using the real-time PCR method.In Exp I and II,where the applied NS amount was moderate,NS application at low concentration induced increases in O_(2)-and MDA concentrations and plants acclimated to the soil salinity as the treatment prolonged for weeks.The acclimation was contributed by osmotic adjustment,activation of SOD and re-compartmentation of cell water between symplasm and apoplasm.These adjustments might be ultimately attributed to up-regulation of stress-responsive genes such as DREB2 as well as the nitrate reductase(NR)gene.However,in Exp III,applications of NaCl and NS at high concentration could not show positive effects as NS did.Application of MI synergistically increased the xerophytophysiological regulation caused by NS and alleviated the salinity damage in addition to its own positive effects on the tomato plants.Different from NaCl,nitrate salts at low application rate increased the total biomass and fruit yield of tomato and induced up-regulation expression of stress-responsive genes and the consequent active osmotic adjustment.However,nitrate application at high level negatively affected tomato plants irrespective of the gene up-regulations.Application of MI alleviated the salinity damage and synergistically increased the xerophytophysiological regulation caused by the soil salinity in addition to its positive effects on the tomato crop but the detailed mechanisms needed to be clarified in future further studies.

Migration and transformation of Sb are affected by Mn(Ⅲ/Ⅳ)associated with lepidocrocite originating from Fe(Ⅱ)oxidation

Antimony(Sb)is a recognized priority pollutant with toxicity that is influenced by its mi-gration and transformation processes.Oxidation of Fe(Ⅱ)to Fe(Ⅲ)oxides,which is a com-mon phenomenon in the environment,is often accompanied by the formation of Mn(Ⅲ/Ⅳ)and might affect the fate of Sb.In this study,incorporated Mn(Ⅲ)and sorbed/precipitated Mn(Ⅲ/Ⅳ)associated with lepidocrocite were prepared by adding Mn(Ⅱ)during and after Fe(Ⅱ)oxidation,respectively,and the effects of these Mn species on Sb fate were inves-tigated.Our results indicated that the association of these Mn species with lepidocrocite obviously enhanced Sb(Ⅲ)oxidation to Sb(V),while concomitantly inhibiting Sb sorption due to the lower sorption capacity of lepidocrocite for Sb(V)than Sb(Ⅲ).Additionally,Mn oxide equivalents increased in the presence of Sb,indicating that Sb oxidation by Mn(Ⅲ/Ⅳ)associated with lepidocrocite was a continuous recycling process in which Mn(Ⅱ)released from Mn(Ⅲ/Ⅳ)reduction by Sb(Ⅲ)could be oxidized to Mn(Ⅲ/Ⅳ)again.This recycling pro-cess was favorable for effective Sb(Ⅲ)oxidation.Moreover,Sb(Ⅴ)generated from Sb(Ⅲ)ox-idation by Mn(Ⅲ/Ⅳ)enhanced Mn(Ⅱ)sorption at the beginning of the process,and thus favored Mn(Ⅲ/Ⅳ)formation,which could further promote Sb(Ⅲ)oxidation to Sb(V).Over-all,this study elucidated the effects of Mn(Ⅲ/Ⅳ)associated with lepidocrocite arisen from Fe(Ⅱ)oxidation on Sb migration and transformation and revealed the underlying reaction mechanisms,contributing to a better understanding of the geochemical dynamics of Sb.

Effects of organic amendments on soil properties and growth characteristics of Melon(Cucumis melo L.)under saline irrigation

Establishing strategies of organic amendments application to mitigate the adverse effects of saline irrigation are essential for the sustainable agriculture.A two-year pot experiment was conducted using combinations of organic amendments including effective microorganisms(EM),biochar(BC)and digestate(Di)to investigate their effects on soil and melon(Cucumis melo L.)compared with the recommended NPK fertilizer and Control(CK)under two levels of irrigation water salinity(SL0:0.25 dS/m,SL1:2.0 dS/m).Results showed combined applications of organic amendments could significantly(p<0.05)increase soil pH and organic matter(OM)compared to NPK and CK.Application of organic amendments containing BC evidently increased the sodium adsorptive capacity(SAC)under saline water solution.The combined application of EM,BC and Di(EM+BC+Di)could significantly(p<0.05)improve soil available water retention under SL0 and SL1 compared with other treatments.Results also showed organic amendments application can significantly(p<0.05)enhance the photosynthetic rate(Pr)and reduce sodium ion(Na+)content in melon leaves.EM+BC+Di could significantly(p<0.05)increase water use efficiency(WUE)and fruit yield of melon under SL0 and SL1 in comparison to other treatments.It proved that EM+BC+Di had a positive effect on soil improvement,melon growth,WUE and fruit yield.Moreover,EM+BC+Di could be used as an alternative strategy for mineral NPK fertilization of melon at reasonable dosages and frequencies under saline irrigation.

Effects of the buried straw layer on soil water and nitrogen distribution under different irrigation limits

At present,water and fertilizer use efficiency is low in many cultivation areas in southern China.Studies show that the buried straw layer can effectively conserve water and fertilizer.To investigate the optimal irrigation upper limit above the straw barrier and its effect on soil moisture and nitrogen distribution,an indoor soil column experiment was conducted.Six treatments were designed consisting of two levels of straw layer i.e.,(with and without buried straw layer at 25 cm depth),and three irrigation water upper limits i.e.,(saturated moisture content(s),field water holding capacity(f),and 80%of field water holding capacity(0.8f)as the upper limit of irrigation).The result revealed that the buried straw layer can inhibit water infiltration and significantly increase the water storage capacity and water storage efficiency of 0-25 cm soil depth.Under the condition of no evaporation,when the upper limit of irrigation water does not exceed the field water holding capacity,the storage efficiency of 0-25 cm soil water reaches 89%-91%after 6 d.Moreover,a buried straw layer can inhibit the deep percolation of nitrate nitrogen and increase the amount of nitrate-nitrogen in 0-25 cm soil.The 80%field water holding capacity irrigation upper limit combined with straw interlayer treatment had a higher nitrate-nitrogen content in the 0-25 cm soil layer than other treatments.Therefore,80%of field water holding capacity as the upper limit of irrigation combined with buried straw layer is the optimal strategy to conserve soil water and nitrogen in the upper soil profile.

Development and application of a new random walk model to simulate the transport of degradable pollutants

To simulate the pollutant transport with seif-purification in inland waters,the widely used random walk model(RWM)is modified to include a source term for the degradation and to consider the impact of land boundaries.The source term for the degradation is derived from the assumption of the first-order reaction kinetics.Parameters for the new model are determined by a comparison to the analytical results.The proposed model is then applied to simulate and analyze the transport of a test pollutant and its spatial distribution in a large reservoir in northeast China.Reasonable results are obtained,and the effects of the runoff,the flow structure,and the wind on the pollutant transport are analyzed.The results may help the risk assessment and the management of the water pollution in inland waters.

Wheat Breeding Strategies under Climate Change based on CERES-Wheat Model

Climate change has inevitably had a negative impact on agricultural production and food security.Crop breeding improvement is an efficient option to adapt to future climate and increase grain production.To study the potential to provide valuable advice for breeding under climate change condition,the crop growth model was used as basis to investigate,the effects of the cultivar genotype parameters of the crop estimation through resource and environment synthesis-wheat(CERES-Wheat)model on yield under different climate scenarios.In this study,solar radiation had a positive effect on the yield of winter wheat,while the effects of daily temperature change conditions on yield were vague,particularly under a change in daily maximum temperature.For the seven cultivar genotype parameters in the CERES-Wheat model,the yield had an approximately linear increasing relationship with kernel number(G1)and kernel size(G2).Vernalization days(P1V)had a fluctuating effect on winter yield without an evident unidirectional tendency.The yield of winter wheat increased with an increase in photoperiodic response(P1D)when P1D values varied from 64.81 to 79.81.Phyllochron interval(PHINT)had a positive impact on the yield of winter wheat.This study presented the potential benefits of the crop growth model to provide directional suggestions for crop breeding.

Effects of surface roughness on overflow discharge of embankment weirs

A numerical study was performed on the embankment weir overflows with various surface roughness and tailwater submergence, to better understand the effects of weir roughness on discharge performances under the free and submerged conditions. The variation of flow regime is captured, from the free overflow, submerged hydraulic jump, to surface flow with increasing tailwater depth. A roughness factor is introduced to reflect the reduction in discharge caused by weir roughness. The roughness factor decreases with the roughness height, and it also depends on the tailwater depth, highlighting various relations of the roughness factor with the roughness height between different flow regimes, which is linear for the free overflow and submerged hydraulic jump while exponential for the surface flow. Accordingly, the effects of weir roughness on overflow discharge appear nonnegligible for the significant roughness height and the surface flow regime occurring under considerable tailwater submergence. The established empirical expressions of discharge coefficient and submergence and roughness factors make it possible to predict the discharge over embankment weirs considering both tailwater submergence and surface roughness.

Bacillus amyloliquefaciens (IAE635) and their metabolites could purify pollutants, Vibrio spp. and coliformbacteria in coastal aquaculture wastewater

High-density aquaculture often causes the emission of polluted water to the marine environment in the coastal areas of China.To solve the aquaculture-related water quality problems,it is appropriate to adapt eco-friendly methods,such as using microbes and their metabolic products to purify polluted water.In this study,the purifying effects ofBacillus amyloliquefaciens(IAE635)metabolites(poly-γ-glutamic acid;PP)and IAE635 combined with their metabolites(MP)on turbidity,COD,NO3--N,NH4+-N,Vibrio spp.andcoliform bacteria in coastal aquaculture wastewater were conducted in the lab and in situ ponds.The results showed that the removal ofturbidity,COD,NH4+-Nand NO3--Nwith PP and MP was more significant(p<0.05).Compared to Control treatment(Co),the turbidity,COD,NH4+-Nand NO3--N concentrations at 24thhour were evidently reduced by 86.6%,87.5%,83.3%and 58.0%for PP,87.9%,93.5%,86.5%and 78.0%for MP,respectively.The populations of water pathogens under PP and MP were also significantly(p<0.05)removed compared with those of Co;at 24thhour,the Vibriospp.and coliform bacteria were decreased by 68.7%and 66.3%forPP,75.0%and 67.1%for MP,respectively.The water purifying effect of MP was slightly better than that of PP.In situ pond purification test demonstrated that MP significantly lowered the concentrations of turbidity,COD,NH4+-N,NO3--N and NO2--N,which was more effective than EM.A significantly higher(p<0.05)γ-PGA concentration and the total bacterial population for MP compared to PP indicatedthatMPpurifies the coastal aquaculture wastewaterby both flocculation and microbial decomposition.The application of MP will benefit the aquaculture industry by providing a novel method for the removal of chemical pollutants and pathogens.

Simulating advance distance in border irrigation systems based on the improved method of characteristics

Improving the simulation accuracy of the advance distance based on the method of characteristics is essential to develop numerical solutions for simulating surface irrigation.Instead of volume balance in the traditional method of characteristics(T-MC),the position of critical flow is determined to simulate the advance distance in the improved method of characteristics(I-MC),which is used in border irrigation systems with rapid variation in inflow discharge in the current research.Specifically,the zones of both subcritical and supercritical flow were firstly distinguished to determine the position of the critical flow point,which was also the upstream boundary of the wetting front region,and then the advance distance was calculated by applying the diffusive wave equation in the wetting front region.The results showed that the I-MC accurately simulated the advance distance with high determination coefficients(0.984-0.998)and low errors(root mean square error of 0.35-1.56 min and coefficient of residual mass of 0.01-0.06),which performed much better than the T-MC.The I-MC provided a suitable and simple numerical simulation tool to improve the establishment of numerical surface irrigation models.