Nutrient Limiting Factor and Agronomic Efficiency of Wheat in Fluvo-aquic Soil District in Northwest of Shandong Province

[Objective] This study aimed to provide basis for rational fertilizer application of wheat in fluvo-aquic soil in the northwest of Shandong Province.[Method] In this paper,the treatments of reduced N,P and K were set in order to explore the effects of fertilizer recommendation based on ASI systematic approach on wheat yield,agronomic efficiency and recovery rate of nutrients.[Result] Nitrogen was the main limiting factor for wheat production in that area,followed by phosphorus,and the third was potassium.Compared with the optimum treatment （OPT）,the reduction of N,P and K reduced the grain yield obviously,which came up to 22.4％,14.4％ and 13.4％ respectively.There were no obvious differences in grain yield among Farmer＇s Fertilization Practice （FP）,60％ OPT-N and OPT treatment.[Conclusion] Agronomic efficiency of N,P and K was 6.3,12.9 and 10 kg/kg respectively.The recovery rates of N,P and K in wheat season were 16.41％,17.27％ and 27.27％ respectively.

Atrazine Adsorption Behavior on a Fluvo-Aquic Soil as Influenced by Contact Periods

A batch experiment was performed to investigate nonequilibrium adsorption behavior of atrazine （2-chloro-4-ethylamino-6-isopropylamlno-1,3,5-triazlne） on a fluvo-aquic soil. The amount of atrazine sorbed increased with increasing adsorption contact periods. For a range of initial atrazlne concentrations, the percentage of atrazine sorbed within 24 h ranged from 24% to 77% of the observed total amount sorbed for the longest contact period; when adsorption contact periods were more than 72 h, the deviations in curves fitted using a nonlinear Freundllch equation gradually became less. The opposite trend was observed for the atrazine concentrations in solution. The effect of adsorption contact periods on atrazine adsorption behavior was evaluated by interpreting the temporal variations in linear and nonlinear Freundlich equation parameters obtained from the phase-distribution relationships. As the adsorption contact period increased, the nonlinear Freundlich capacity coefficient kf showed a significant linear increase （r^2 = 0.9063, P 〈 0.001）. However, a significant negative linear correlation was observed for the nonlinear coefficient n, a dimensionless parameter （r^2 = 0.5666, P 〈 0.05）. Furthermore, the linear distribution coefficient kd ranged from 0.38 to 1.44 and exhibited a significant linear correlation to the adsorption contact period （r^2 = 0.72, P 〈 0.01）. The parameters kf and n obtained from a time-dependent isotherm rather than the distribution coefficient kd estimated using the linear Freundlich equation were more appropriate to predict the herbicide residue in the field and thus more meaningful for environmental assessment.

Long-term organic and inorganic fertilizations enhanced basic soil productivity in a fluvo-aquic soil

The improvement of soil productivity depends on a rational input of water and nutrients, optimal field management, and the increase of basic soil productivity（BSP）. In this study, BSP is defined as the productive capacity of a farmland soil with its own physical and chemical properties for a specific crop season under local field management. Based on 19-yr data of the long-term agronomic experiments（1989–2008） on a fluvo-aquic soil in Zhengzhou, Henan Province, China, the decision support system for agrotechnology transfer（DSSAT ver. 4.0） crop growth model was used to simulate yields by BSP of winter wheat（Triticum aestivium L.） and summer maize（Zea mays L.） to examine the relationship between BSP and soil organic carbon（SOC） under long-term fertilization. Five treatments were included：（1） no fertilization（control）,（2） nitrogen, phosphorus and potassium fertilizers（NPK）,（3） NPK plus manure（NPKM）,（4） 1.5 times of NPKM（1.5NPKM）, and（5） NPK plus straw（NPKS）. After 19 yr of treatments, the SOC stock increased 16.7, 44.2, 69.9, and 25.2% under the NPK, NPKM, 1.5NPKM, and NPKS, respectively, compared to the initial value. Among various nutrient factors affecting contribution percentage of BSP to winter wheat and summer maize, SOC was a major affecting factor for BSP in the fluvo-aquic soil. There were significant positive correlations between SOC stock and yields by BSP of winter wheat and summer maize（P〈0.01）, and yields by BSP of winter wheat and summer maize increased 154 and 132 kg ha^（–1） when SOC stock increased 1 t C ha^（–1）. Thus, increased SOC accumulation is a crucial way for increasing BSP in fluvo-aquic soil. The manure or straw combined application with chemical fertilizers significantly enhanced BSP compared to the application of chemical fertilizers alone.

Characteristics of Magnesium Release from Fluvo-Aquic Soil and Relative Availability of Magnesium to Plants

Experiments including two in laboratory and one in greenhouse were carried out to study non- exchangeable magnesium release from fluvo-aquic soils sampled from Daxing and changping counties located in the suburbs of Beijing and Mg relative availability of the two soils to plants. In a batch experiment in laboratory the soils were incubated under wet conditions and alternation of dry and wet conditions and determined for amount of Mg released at the 4th, 8th and 12th week, respectively, after extraction of exchangeable Mg with 1 mol L-1 NH4Ac. The amount of Mg released from the soil of Daxing was higher than from the soil of Changping, which was in accordance with the fact that the soil of Daxing had higher contents of all forms of Mg than that of Changping. There was little difference in Mg release from soils between wet conditions and alternation of dry and wet conditions. About 1%~2% of the total non-exchangeable Mg might be released within 12 weeks of incubation, restoring about 30%~35% of the original soil exchangeable Mg. Results of the experiment on kinetics of Mg release from the soils through continuous extractions with 0.5 mol L-1 NH4Ac (pH 7.0) on a continuous flow apparatus in laboratory showed that Mg released rapidly in the beginning, decreased sharply with time and kept stable at 60 and 240 min for the soils of Changping and Daxing, respectively. Among the five mathematical models used to describe the kinetics of Mg release, the parabolic diffusion equation best fitted the cumulative Mg release, indicating that diffusion of Mg out of the soils might be the controlling process. The experiment of exhaustive cropping with 1 crop of tomato (Lycopersicon esculentum Mill.) followed by six crops of corn (Zea mays L.) in greenhouse showed that soil exchangeable Mg decreased remarkably with cropping. After three crops, the percentage of the total plant Mg uptake that came from soil non-exchangeable Mg was 29.5% for the soil from Changping and 35% for the soil from Daxing. About 50% of the total Mg uptake by plants in the six crops was believed to come from the soil non-exchangeable Mg form.

Effects of Conservation Tillage on the Content of Carbon, Nitrogen in Fluvo-aquic Soil

In order to verify organic carbon cycle under conservation tillage condition and the promotion mechanism of soil fertility and offer scientific theory support for the popularization and application of conservation tillage technological, the research investigated effects of different tillage treatments on the content of total organic car- bon, total nitrogen and different components of them in fluvo-aquic soil based on a long-term experiment site of conservation tillage. The research revealed effects of conservation tillage on the content of carbon, nitrogen in fluvo-aquic soil by study the distribution of soil total organic carbon, total nitrogen, dissolved organic carbon, dissolved organic nitrogen, microbial biomass carbon, liable carbon in different soil depth under different tillage treatments. The results showed that compared to con- ventional tillage treatment, contents of soil total organic carbon under intermittent tillage （tillage once every 2 or 4 years） and no-tillage treatment improved by 1.81%, 6.43%, 14.04%, respectively and contents of soil total nitrogen went up by 0.80%, 10.04%, 7.93%, respectively. Contents of soil total organic carbon and total nitrogen in 10-20 cm soil layer under no-tillage treatment were significantly lower than the other treatments. Under the condition of straw returned, intermittent tillage and no- tillage could significantly improve the content of soil dissolved organic carbon and ni- trogen in 0-5 cm and 5-10 cm soil. Compared to conventional tillage treatment, content of soil microbial biomass carbon and liable carbon in 0-5 cm soil under in- termittent tillage and no-tillage were improved in varying degrees. Content of soil microbial biomass carbon in 10-20 cm soil layer under no-tillage treatment was sig- nificantly lower than the other treatments. Straw returning had improved the content of soil total organic carbon, total nitrogen, dissolved organic carbon and other com- ponents of active organic carbon in varying degrees. In general, conservation tillage measures could increase carbon and nitrogen storage in 0-5 cm soil layer, the negative effects of ＂nutrients enrichment in surface＂ under no-tillage condition could be ameliorated by intermittent tillage.

Effects of Long-term Located Fertilization on Evolution of Available Phosphorus and Phosphorus Pool in Shandong Fluvo-aquic Soil

This study was conducted to investigate the effects of long-term located fertilization on soil phosphorus,the changes of soil available phosphorus(OlsenP),the evolution of soil total phosphorus(TP)and the ratio change of Olsen-P to TP(PAC)by 33-year fertilization experiments in winter wheat-summer maize rotation system in Shandong fluvo-aquic soil.Eight treatments were designed as no fertilization(CK),nitrogen fertilizer(N),nitrogen and phosphate fertilizer(NP),nitrogen and potassium fertilizer(NK),phosphate and potassium fertilizer(PK),nitrogen-phosphate-potassium fertilizer(NPK),reduced NPK fertilizer(N(15)PK),and increased NPK fertilizer(N_(25)PK).Meanwhile,eight organic fertilizer-added treatments were designed based on the application of inorganic fertilizer the same as the above ones.The results showed that TP,Olsen-P and PAC of treatments added with organic fertilizer were higher than those without organic fertilizer,and those of the treatments applied with phosphate fertilizer were higher than those of no phosphate fertilizer.With the increase of years,soil P pool decreased due to crop absorption,nutrient loss and morphological transformation and other causes under the treatments of without and only phosphate fertilizer,while remained stable under the treatments added with organic fertilizer.The PAC values were generally lower in fluvo-aquic soil,and it could be improved by the application of organic fertilizer.On the whole,the application of chemical phosphate fertilizer combined with organic fertilizer could improve the phosphorus content in soil and ensure the supply of phosphorus nutrition.This study would provide scientific basis for fertilization management and soil fertility in fluvo-aquic soil.

Research on Effects of Remediation by Fertilization on Off-Balanced Fluvo-aquic Soils in Nutrient

[Objective] The research aimed to study the effects of fertilization on soil remediation.[Method]Pot fertilizer tests were conducted to remedy the soils which had off-balanced in nutrients resulted by long-term unreasonable fertilization.[Result]The results showed that applying NPK fertilizers with manure was the best method to restore the soil nutrients and increase soil fertility and crop yield;NPK and NP fertilizers could balance soil fertility and increase crop yields,the effects were the same and next to MNPK.Phosphate and nitrogen respectively had the similar restoring effect with NPK fertilizers on soil from long-term NK and PK treatments.[Conclusion]Crops in soil with long-term applying NPK fertilizers had strong dependence on fertilizers.The yields of corn and wheat decreased by 78.6% and 52.8% respectively after stopping applying fertilizers.Meanwhile,The yields of corn and wheat increased by 112% and 182% respectively after stopping applying fertilizers in NK treatment as well as 15.1% and 59% in PK treatment.Manure had strong and last effect on increasing yield.

Response of soil Olsen-P to P budget under different long-term fertilization treatments in a fluvo-aquic soil

The concentration of soil Olsen-P is rapidly increasing in many parts of China, where P budget(P input minus P output) is the main factor influencing soil Olsen-P. Understanding the relationship between soil Olsen-P and P budget is useful in estimating soil Olsen-P content and conducting P management strategies. To address this, a long-term experiment(1991–2011) was performed on a fluvo-aquic soil in Beijing, China, where seven fertilization treatments were used to study the response of soil Olsen-P to P budget. The results showed that the relationship between the decrease in soil Olsen-P and P deficit could be simulated by a simple linear model. In treatments without P fertilization(CK, N, and NK), soil Olsen-P decreased by 2.4, 1.9, and 1.4 mg kg^(–1) for every 100 kg ha^(–1) of P deficit, respectively. Under conditions of P addition, the relationship between the increase in soil Olsen-P and P surplus could be divided into two stages. When P surplus was lower than the range of 729–884 kg ha^(–1), soil Olsen-P fluctuated over the course of the experimental period with chemical fertilizers(NP and NPK), and increased by 5.0 and 2.0 mg kg^(–1), respectively, when treated with chemical fertilizers combined with manure(NPKM and 1.5 NPKM) for every 100 kg ha^(–1) of P surplus. When P surplus was higher than the range of 729–884 kg ha^(–1), soil Olsen-P increased by 49.0 and 37.0 mg kg^(–1) in NPKM and 1.5 NPKM treatments, respectively, for every 100 kg ha^(–1) P surplus. The relationship between the increase in soil Olsen-P and P surplus could be simulated by two-segment linear models. The cumulative P budget at the turning point was defined as the "storage threshold" of a fluvo-aquic soil in Beijing, and the storage thresholds under NPKM and 1.5 NPKM were 729 and 884 kg ha^(–1)P for more adsorption sites. According to the critical soil P values(CPVs) and the relationship between soil Olsen-P and P budget, the quantity of P fertilizers for winter wheat could be increased and that of summer maize could be decreased based on the results of treatments in chemical fertilization. Additionally, when chemical fertilizers are combined with manures(NPKM and 1.5 NPKM), it could take approximately 9–11 years for soil Olsen-P to decrease to the critical soil P values of crops grown in the absence of P fertilizer.

Effect of Continuous Vegetable Cultivation on Phosphorus Levels of Fluvo-Aquic Soils

Soil P status, inorganic P fractions, and P sorption properties were studiedusing sandy fluvo-aquic horticultural soils, which are high in organic matter content for vegetableproduction in comparison with a soil used for grain crop production in Zhengzhou, Henan Province,China P fractions, Olsen-P, and OM were determined at different depths in the soil profile andsorption isotherm experiments were performed Most P in excess of plant requirements accumulated inthe topsoil and decreased with soildepth. Total P, inorganic P, and OM concentrations increased withcontinued horticultural use Olsen-P concentrations in the 0-20 cm depth of horticultural soils were9 to 25 times higher than those of the grain crop soil. A linear transformation of the Langmuirequation showed that the P adsorption maximum (491.3 mg P kg^(-1)) and the maximum phosphatebuffering capacity (162.1 L kg^(-1)) for 80--100 cm were greater in the grain crop soil than thehorticultural soils. Thus, the most immediate concern with excess P were in areas where heavy Pfertilizer was used for vegetable crops and where soil P sorption capacities were low due to sandysoils and high organic matter content.

Effects of straw addition on increased greenhouse vegetable yield and reduced antibiotic residue in fluvo-aquic soil

Organic manure application is an important measure for high yield and good quality vegetable production, whereas organic manure is also a main source of residual antibiotic in soils. A 3-yr experiment was conducted on a fluvo-aguic soil in Tianjin of northern China. The objective of this study was to investigate the effects of different fertilization patterns on yield of six-sea- son vegetables with celery and tomato rotation, and dynamic change of tetracyclines residues in the soil during the sixth growing season （tomato season）. The field experiment comprised six treatments depending on the proportion of nitrogen of each type of fertilizer： 4/4 CN （CN, nitrogen in chemical fertilizer）, 3/4 CN＋1/4 MN （MN, nitrogen in pig manure）, 2/4 CN＋2/4 MN, 1/4 CN＋3/4 MN, 2/4 CN＋1/4 MN＋I/4 SN （SN, nitrogen in corn straw）, and CF （conventional fertilization, the amounts of nitrogen application were 943 and 912 kg N ha-1 for celery and tomato season, respectively）. In addition to CF treatment, the amount of nitrogen application in other treatments was greatly reduced and equal （450 and 450 kg N ha-1 for celery and tomato season, respectively）. Results showed that the combined application of 3/4 CN＋1/4 MN achieved the highest yield and economic benefit in the first four seasons, but addition of straw （2/4 CN＋1/4 MN＋I/4 SN treatment） performed better in the subsequent two seasons, and the average yields of 2/4 CN＋1/4 MN＋I/4 SN treatment were respectively higher by 9.9 and 12.8% than those of 4/4 CN treatment, and by 5.6 and 10.5% than those of CF treatment. The residual chlortet- racycline （CTC） in manure-amended soil for three consecutive years increased along with the increase of applied amount of pig manure. Under the same amount of pig manure application, content of CTC in straw-amended soil was obviously decreased compared with no straw-amended soil （3/4 CN＋1/4 MN treatment）, and averagely decreased by 41.9% for four sampling periods in the sixth season. Addition of crop straw facilitated the degradation of CTC in manure-amended soil. As a whole, the conventional fertilization was not the desirable pattern based on yield, economic benefit and environment, the optimal fertilization pattern with the highest yield and profit and the least soil chlortetracycline residue was the treatment of 2/4 CN＋1/4 MN＋I/4 SN under this experimental condition.

K^+ Adsorption Kinetics of Fluvo-Aquic and Cinnamon Soil Under Different Temperature

The K+ adsorption kinetics of fluvo-aquic soil and cinnamon soil under different temperatureswere studied. The results showed: 1) The first order equations were the most suitable forfitting the adsorption under various temperature levels with constant K+ concentration indisplacing fluid. With temperature increasing, the fitness of Elovich equation increased,while those of power equation and parabolic diffusion equation decreased; 2)the apparentadsorption rate constant ka and the product of ka multiplied by the apparent equilibriumadsorption qincreased when temperature increased, while the apparent equilibrium adsorptionqreduced; 3)temperature influenced hardly the reaction order, the order of concentrationand adsorpton site were always 1 under various temperatures, if they were taken intoaccount simultaneously, the adsorption should be a two-order reaction process; 4)theGibbs free energy change △G of potassium adsorption were negative, ranged from -4444.56to -2450.63Jmol-1,and increased with temperature increasing, while enthalpy change △H,entropy change △S, apparent adsorption activation Ea, adsorption activation energy E1and desorption activation energy E2 were temperature-independent; 5)the adsorption wasspontaneous process with heat releasing and entropy dropping, fluvo-aquic soil releasedmore heat than cinnamon soil.

Microscale heterogeneity of soil bacterial communities under long-term fertilizations in fluvo-aquic soils

Differently sized soil aggregates,with non-uniform distribution of space and nutrients,provide spatially heterogeneous microenvironments for microorganisms and are important for controlling microbial community ecology and biogeochemistry in soils.Here,we investigated the prokaryotic communities within different aggregate-size fractions:macroaggregate(>0.25 mm),microaggre-gate(0.053–0.25 mm)and silt+clay(<0.053 mm).These were isolated from fluvo-aquic soils under 39-year fertilization strategies:no fertilizer(CK),chemical fertilizer(NPK),manure fertilizer(M),and combination of manure and chemical fertilizers(MNPK).The results showed that the proportion of macroaggregate,soil aggregate-associated organic carbon(SOC)content and aggregate stability were all significantly increased by both manure and chemical fertilizations.Organic fertilizations(M and MNPK)more effectively boosted formation and stability of macroaggregates and enhanced SOC concentration than NPK.The distribution patterns of microorganisms in aggregates were primarily shaped by fertilization and aggregate size.They explained 76.9%of the variance in bacterial community compositions.Fertilizations,especially with organic fertilizers primarily transitioned bacterial communities from slow-growing oligotrophic groups(e.g.,Chloroflexi)dominance to fast-growing copiotrophic groups(e.g.,Proteobacteria and Bacteroidetes)dominance across all aggregate sizes.Macroaggregates possessed a more stable bacterial community and efficiency of resource transfer,while smaller aggregates increased antagonism and weakened mutualism among bacterial communities.Overall,combination of manure and chemical fertilizers was crucial for increasing SOC content and aggregation,leading to a clear shift in bacterial community structures at aggregate scale.

Effect of Progressive Substitution of Cement and Lime by Powdered Shells Used as a Curing Agent for Dredged Soil in a Port Area

This study aimed to address the challenges of solid waste utilization,cost reduction,and carbon reduction in the treatment of deep-dredged soil at Xuwei Port in Lianyungang city of China.Past research in this area was limited.Therefore,a curing agent made from powdered shells was used to solidify the dredged soil in situ.We employed laboratory orthogonal tests to investigate the physical and mechanical properties of the powdered shell-based curing agent.Data was collected by conducting experiments to assess the role of powdered shells in the curing process and to determine the optimal ratios of powdered shells to solidified soil for different purposes.The development of strength in solidified soil was studied in both seawater and pure water conditions.The study revealed that the strength of the solidified soil was influenced by the substitution rate of powdered shells and their interaction with cement.Higher cement content had a positive effect on strength.For high-strength solidified soil,the recommended ratio of wet soil:cement:lime:powdered shells were 100:16:4:4,while for low-strength solidified soil,the recommended ratio was 100:5.4:2.4:0.6.Seawater,under appropriate conditions,improved short-term strength by promoting the formation of expansive ettringite minerals that contributed to cementation and precipitation.These findings suggest that the combination of cement and powdered shells is synergistic,positively affecting the strength of solidified soil.The recommended ratios provide practical guidance for achieving desired strength levels while considering factors such as cost and carbon emissions.The role of seawater in enhancing short-term strength through crystal formation is noteworthy and can be advantageous for certain applications.In conclusion,this research demonstrates the potential of using a powdered shell-based curing agent for solidifying dredged soil in an environmentally friendly and cost-effective manner.The recommended ratios for different strength requirements offer valuable insights for practical applications in the field of soil treatment,contributing to sustainable and efficient solutions for soil management.

The competition between Bidens pilosa and Setaria viridis alters soil microbial composition and soil ecological function

Bidens pilosa is recognized as one of the major invasive plants in China.Its invasion has been associated with significant losses in agriculture,forestry,husbandry,and biodiversity.Soil ecosystems play an important role in alien plant invasion.Microorganisms within the soil act as intermediaries between plants and soil ecological functions,playing a role in regulating soil enzyme activities and nutrient dynamics.Understanding the interactions between invasive plants,soil microorganisms,and soil ecological processes is vital for managing and mitigating the impacts of invasive species on the environment.In this study,we conducted a systematic analysis focusing on B.pilosa and Setaria viridis,a common native companion plant in the invaded area.To simulate the invasion process of B.pilosa,we constructed homogeneous plots consisting of B.pilosa and S.viridis grown separately as monocultures,as well as in mixtures.The rhizosphere and bulk soils were collected from the alien plant B.pilosa and the native plant S.viridis.In order to focus on the soil ecological functional mechanisms that contribute to the successful invasion of B.pilosa,we analyzed the effects of B.pilosa on the composition of soil microbial communities and soil ecological functions.The results showed that the biomass of B.pilosa increased by 27.51% and that of S.viridis was significantly reduced by 66.56%.The organic matter contents in the bulk and rhizosphere soils of B.pilosa were approximately 1.30 times those in the native plant soils.The TN and NO_(3)^(-)contents in the rhizosphere soil of B.pilosa were 1.30 to 2.71 times those in the native plant soils.The activities of acid phosphatase,alkaline phosphatase,and urease in the rhizosphere soil of B.pilosa were 1.98-2.25 times higher than in the native plant soils.Using high-throughput sequencing of the16S rRNA gene,we found that B.pilosa altered the composition of the soil microbial community.Specifically,many genera in Actinobacteria and Proteobacteria were enriched in B.pilosa soils.Further correlation analyses verified that these genera had significantly positive relationships with soil nutrients and enzyme activities.Plant biomass,soil p H,and the contents of organic matter,TN,NO_(3)^(-),TP,AP,TK,and AK were the main factors affecting soil microbial communities.This study showed that the invasion of B.pilosa led to significant alterations in the composition of the soil microbial communities.These changes were closely linked to modifications in plant traits as well as soil physical and chemical properties.Some microbial species related to C,N and P cycling were enriched in the soil invaded by B.pilosa.These findings provide additional support for the hypothesis of soil-microbe feedback in the successful invasion of alien plants.They also offer insights into the ecological mechanism by which soil microbes contribute to the successful invasion of B.pilosa.Overall,our research contributes to a better understanding of the complex interactions between invasive plants,soil microbial communities,and ecosystem dynamics.

Biochar Decreases Soil Cadmium(Cd) Availability and Regulates Expression Levels of Cd Uptake/Transport-Related Genes to Reduce Cd Translocation in Rice

Biochar has been used as a soil amendment for heavy metal-contaminated soils, and it has the potential to mitigate Cd accumulation in plants. In this study, we used rice straw biochar(RSB) and kitchen waste biochar(KWB) to clarify the effect of biochar on Cd-contaminated neutral soil, the physiological responses to biochar application, and the gene regulatory networks in a rice genotype.

Subsoil tillage enhances wheat productivity,soil organic carbon and available nutrient status in dryland fields

Tillage practices during the fallow period benefit water storage and yield in dryland wheat crops.However,there is currently no clarity on the responses of soil organic carbon(SOC),total nitrogen(TN),and available nutrients to tillage practices within the growing season.This study evaluated the effects of three tillage practices(NT,no tillage;SS,subsoil tillage;DT,deep tillage)over five years on soil physicochemical properties.Soil samples at harvest stage from the fifth year were analyzed to determine the soil aggregate and aggregate-associated C and N fractions.The results indicated that SS and DT improved grain yield,straw biomass and straw carbon return of wheat compared with NT.In contrast to DT and NT,SS favored SOC and TN concentrations and stocks by increasing the soil organic carbon sequestration rate(SOCSR)and soil nitrogen sequestration rate(TNSR)in the 0-40 cm layer.Higher SOC levels under SS and NT were associated with greater aggregate-associated C fractions,while TN was positively associated with soluble organic nitrogen(SON).Compared with DT,the NT and SS treatments improved soil available nutrients in the 0-20 cm layer.These findings suggest that SS is an excellent practice for increasing soil carbon,nitrogen and nutrient availability in dryland wheat fields in North China.

A dynamic soil freezing characteristic curve model for frozen soil

The soil freezing characteristic curve(SFCC)plays a fundamental role in comprehending thermohydraulic behavior and numerical simulation of frozen soil.This study proposes a dynamic model to uniformly express SFCCs amidst varying total water contents throughout the freezing-thawing process.Firstly,a general model is proposed,wherein the unfrozen water content at arbitrary temperature is determined as the lesser of the current total water content and the reference value derived from saturated SFCC.The dynamic performance of this model is verified through test data.Subsequently,in accordance with electric double layer(EDL)theory,the theoretical residual and minimum temperatures in SFCC are calculated to be-14.5℃to-20℃for clay particles and-260℃,respectively.To ensure that the SFCC curve ends at minimum temperature,a correction function is introduced into the general model.Furthermore,a simplified dynamic model is proposed and investigated,necessitating only three parameters inherited from the general model.Additionally,both general and simplified models are evaluated based on a test database and proven to fit the test data exactly across the entire temperature range.Typical recommended parameter values for various types of soils are summarized.Overall,this study provides not only a theoretical basis for most empirical equations but also proposes a new and more general equation to describe the SFCC.

Straw return increases crop production by improving soil organic carbon sequestration and soil aggregation in a long-term wheat-cotton cropping system

Straw return is a promising strategy for managing soil organic carbon(SOC)and improving yield stability.However,the optimal straw return strategy for sustainable crop production in the wheat(Triticum aestivum L.)-cotton(Gossypium hirsutum L.)cropping system remains uncertain.The objective of this study was to quantify the long-term(10 years)impact of carbon(C)input on SOC sequestration,soil aggregation and crop yields in a wheat-cotton cropping system in the Yangtze River Valley,China.Five treatments were arranged with a single-factor randomized design as follows:no straw return(Control),return of wheat straw only(Wt),return of cotton straw only(Ct),return of 50%wheat and 50%cotton straw(Wh-Ch)and return of 100%wheat and 100%cotton straw(Wt-Ct).In comparison to the Control,the SOC content increased by 8.4 to 20.2%under straw return.A significant linear positive correlation between SOC sequestration and C input(1.42-7.19 Mg ha^(−1)yr^(−1))(P<0.05)was detected.The percentages of aggregates of sizes>2 and 1-2 mm at the 0-20 cm soil depth were also significantly elevated under straw return,with the greatest increase of the aggregate stability in the Wt-Ct treatment(28.1%).The average wheat yields increased by 12.4-36.0%and cotton yields increased by 29.4-73.7%,and significantly linear positive correlations were also detected between C input and the yields of wheat and cotton.The average sustainable yield index(SYI)reached a maximum value of 0.69 when the C input was 7.08 Mg ha^(−1)yr^(−1),which was close to the maximum value(SYI of 0.69,C input of 7.19 Mg ha^(−1)yr^(-1))in the Wt-Ct treatment.Overall,the return of both wheat and cotton straw was the best strategy for improving SOC sequestration,soil aggregation,yields and their sustainability in the wheat-cotton rotation system.

Assessment of soil erosion in the Irga watershed on the eastern edge of the Chota Nagpur Plateau,India

Human activities to improve the quality of life have accelerated the natural rate of soil erosion.In turn,these natural disasters have taken a great impact on humans.Human activities,particularly the conversion of vegetated land into agricultural land and built-up area,stand out as primary contributors to soil erosion.The present study investigated the risk of soil erosion in the Irga watershed located on the eastern fringe of the Chota Nagpur Plateau in Jharkhand,India,which is dominated by sandy loam and sandy clay loam soil with low soil organic carbon(SOC)content.The study used the Revised Universal Soil Loss Equation(RUSLE)and Geographical Information System(GIS)technique to determine the rate of soil erosion.The five parameters(rainfall-runoff erosivity(R)factor,soil erodibility(K)factor,slope length and steepness(LS)factor,cover-management(C)factor,and support practice(P)factor)of the RUSLE were applied to present a more accurate distribution characteristic of soil erosion in the Irga watershed.The result shows that the R factor is positively correlated with rainfall and follows the same distribution pattern as the rainfall.The K factor values in the northern part of the study area are relatively low,while they are relatively high in the southern part.The mean value of the LS factor is 2.74,which is low due to the flat terrain of the Irga watershed.There is a negative linear correlation between Normalized Difference Vegetation Index(NDVI)and the C factor,and the high values of the C factor are observed in places with low NDVI.The mean value of the P factor is 0.210,with a range from 0.000 to 1.000.After calculating all parameters,we obtained the average soil erosion rate of 1.43 t/(hm^(2)•a),with the highest rate reaching as high as 32.71 t/(hm^(2)•a).Therefore,the study area faces a low risk of soil erosion.However,preventative measures are essential to avoid future damage to productive and constructive activities caused by soil erosion.This study also identifies the spatial distribution of soil erosion rate,which will help policy-makers to implement targeted soil erosion control measures.

Three-year field study on grass growth and soil hydrological properties in biochar-amended soil

Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three years.Three 10 m5 m grassed plots were constructed in completely decomposed granitic soil.Two of them were amended,respectively,with 5%and 10%biochar contents(m^(3)/m^(3))for grass growth,while the third was without biochar amendment.During the threeyear monitoring,plant characteristics,saturated water permeability(k_(s))of grassed soil and soil suction were measured.The monitored results show that the grass leaf area index(LAI)and root length density(RLD)with biochar amendment were improved by 38%and 200%,respectively.In the grassed plot without biochar,a threshold RLD existed with a value of 1.7 cm/cm^(3),beyond which k_(s) raised pronouncedly.The threshold RLD increased by 52%when biochar content increased from 0%to 10%.This implies that biochar may restrict the increase in k_(s) of grassed soil due to the rise in the threshold RLD.The presence of biochar and grass can retain over 100%higher suction after heavy rainfalls,while 54%lower peak suction under evapotranspiration(ET)compared with the non-amended plot.Biochar can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss.A 5%peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures.