mlsa-iai-msu-lab/ru_sci_bench_zho_cite_reranking huggingface dataset:
Effect of Limited Single Irrigation on Yield of Winter Wheat and Spring Maize Relay Intercropping

A field experiment was conducted during the 2002/2003 cropping season of winter wheat (Triticum aestivum) and spring maize (Zea mays) to evaluate the effect of limited single drip irrigation on the yield and water use of both crops under relay intercropping in a semi-arid area of northwestern China.A controlled 35 mm single irrigation,either early or late,was applied to each crop at a certain growth stage.Soil water,leaf area,final grain yield and yield components such as the thousand-grain weight,length of spike, fertile spikelet number,number of grains per spike,and grain weight per spike were measured,and water use efficiency and leaf area index were calculated for the irrigated and non-irrigated relay intercropping treatments and sole cropping controls.The results showed that yield,yield components,water use efficiency,and leaf area index in the relay intercropping treatments were affected by limited single drip irrigation during various growth stages of wheat and maize.The total yields in the relay intercropping treatment irrigated during the heading stage of wheat and the heading and anthesis stage of maize were the highest among all the treatments,followed by that irrigated during the anthesis stage of wheat and silking stage of maize;so was the water use efficiency.Significant differences occurred in most yield components between the irrigated and non-irrigated relay-intercropping treatments. The dynamics of the leaf area index in the relay-intercropped or solely cropped wheat and maize showed a type of single-peak pattern,whereas that of the relay intercropping treatments showed a type of double-peak pattern.Appropriately,limited single irrigation and controlled soil water content level could result in higher total yield, water use efficiency,and leaf area index,and improved yield components in relay intercropping.This practice saved the amount of water used for irrigation and also increased the yield.Therefore,heading stage of wheat and heading and anthesis stage of maize were suggested to be the optimum limited single irrigation time for relay-intercropped wheat and maize in the semi-arid area.
Methane Emission from Natural Wetlands in China: Summary of Years 1995-2004 Studies

From studies undertaken during 1995-2004,annual budgets of CH_4 emissions from natural wetlands and its temporal and spatial variations were examined throughout China,and various factors influencing CH_4 emissions were also evaluated. The seasonal variation in CH_4 emissions that increased with increasing plant growth reached its peak in August;decrease in the emissions was found in freshwater marshes but not in peatlands.Emissions were mainly controlled by temperature and depth of standing water.Low CH_4 emissions at the early plant growing stages were not because of deficiency of organic C for CH_4 production but because of low temperatures.Low temperatures not only reduced CH_4 production but also stimulated CH_4 oxidation by lowering the activity of other aerobic microbes which left more O_2 in the rhizosphere for methanotrophs.Low summer temperatures (below 20℃) in the Qinghai-Tibetan Plateau lowered CH_4 production and CH_4 emission resulting in little or no seasonal variation of emissions.Diel and spatial variation in CH_4 emissions depended on plant species.For plants that transport CH4 using the pressure-driven convective through-flow mechanism, diel variation in CH_4 emissions was governed by diel variation of solar energy load (that produces temperature and vapor pressure differences within various plant tissues) and stomatal conductance.For plants that transport gases using the molecular diffusion mechanism only,the diel variation of CH4 emissions was because of differences in the magnitude of O_2 produced through photosynthesis and then delivered into the rhizomes and/or rhizosphere for CH_4 oxidation.Emergent plants could transport more CH_4 than submerged plants because the former transport CH_4 directly into the atmosphere rather than into water as do submerged plants where CH_4 can be further be oxidized during its diffusion from water to the atmosphere.Emergent plants with high gas transport capacity could not only transport more CH4 into the atmosphere but also live in deeper water,which in turn would inundate more plant litter,resulting in increased availability of C for CH4 production.Annual CH_4 emission from natural wetlands in China was estimated to be 1.76 Tg, up to 1.17 Tg of which was emitted from freshwater marshes. CH4 emission from freshwater marshes mainly occurred during the growing season and less than 8% was released during the freeze-thawing period despite the fact that thawing efficiently released CH_4 fixed in ice column into the atmosphere.
Nitrogen Runoff and Leaching Losses During Rice-Wheat Rotations in Taihu Lake Region, China

Although nitrogen (N) loss through runoff and leaching from croplands is suspected to contribute to the deterioration of surrounding water systems,there is no conclusive evidence for paddy soils to prove this hypothesis.In this study,field plot experiments were conducted to investigate N losses through runoff and leaching for two consecutive years with 3 N fertilization rates in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) rotations in the Taihu Lake region,China.A water collection system was designed to collect runoff and leachates for both the rice and wheat seasons. Results showed that dissolved N (DN),rather than particulate N (PN),was the main form of N loss by runoff. The NO_3~--N concentration in runoff was between 0.1 and 43.7 mg L~(-1),whereas the NH_4~+-N concentration ranged from below detection limit to 8.5 mg L~(-1).Total N (TN) loads by runoffwere 1.0-17.9 and 5.2-38.6 kg ha~(-1) during rice and wheat seasons,respectively,and the main loss occurred at the early growing stage of the crops.Nitrogen concentrations in leachates during the rice seasons were below 1.0 mg L~(-1) and independent of the N application rate,whereas those during the wheat season increased to 8.2 mg L~(-1) and were affected by the fertilizer rate.Annual losses of TN through runoff and leaching were 13.7-48.1 kg ha~(-1) from the rice-wheat cropping system,accounting for 5.6%-8.3% of the total applied N.It was concluded that reduction in the N fertilization rate,especially when the crop was small in biomass,could lower the N pollution potential for water systems.
Effect of Oxalic Acid on Potassium Release from Typical Chinese Soils and Minerals

Oxalic acid plays an important role in improving the bioawilability of soil nutrients.Batch experiments were employed to examine the influences of oxalic acid on extraction and release kinetics of potassium (K) from soils and minerals along with the adsorption and desorption of soil K~+.The soils and minerals used were three typical Chinese soils,black soil (Mollisol),red soil (Ultisol),and calcareous alluvial soil (Entisol),and four K-bearing minerals,biotite,phlogopite, muscovite,and microcline.The results showed that soil K extracted using 0.2 mol L~(-1) oxalic acid was similar to that using 1 tool L~(-1) boiling HNO_3.The relation between K release (y) and concentrations of oxalic acid (c) could be best described logarithmically as y=a+blogc,while the best-fit kinetic equation of K release was y=a+b t~(1/2),where a and b are the constants and t is the elapsed time.The K release for minerals was ranked as biotite>phlogopite》muscovite>microcline and for soils it was in the order:black soil>calcareous alluvial soil>red soil. An oxalic acid solution with low pH was able to release more K from weathered minerals and alkaline soils. Oxalic acid decreased the soil K~+ adsorption and increased the soil K~+ desorption, the effect of which tended to be greater at lower solution pH, especially in the red soil.
Effects of Long-Term Application of Inorganic Fertilizers on Biochemical Properties of a Rice-Planting Red Soil

A long-term experiment was set up in Yingtan of Jiangxi Province to investigate the effects of long-term application of inorganic fertilizers on the biochemical properties of a rice-planting soil derived from Quaternary red earth.Noncultivated soils are extremely eroded and characterized by a low pH and deficiencies in available nutrients, in particular P and N.After 13 years of inorganic fertilization in cultivation for double-cropped rice,the biochemical properties of the soil were changed. The nitrification potential and urease activity were higher in the treatments with N application than those without N application. Acid phosphatase activity and dehydrogenase activity were also higher in the treatments with P application than in those without P application. The dehydrogenase activity correlated well with the concentrations of both total P and hydrolysable N and with rice crop yield, suggesting that dehydrogenase activity might be a suitable indicator for improvement in soil fertility.
Dynamics of Microbial Activity Related to N Cycling in Cd-Contaminated Soil During Growth of Soybean

The potential influences of cadmium (Cd) on the biochemical processes of the soil nitrogen (N) cycle, along with the dynamics of ammonification, nitrification, and denitrification processes in the rhizosphere and non-rhizosphere (bulk soil), respectively, were investigated in a Cd-stressed system during an entire soybean growing season. In terms of Cd pollution at the seedling stage, the ammonifying bacteria proved to be the most sensitive microorganisms, whereas the effects of Cd on denitrification were not obvious. Following the growth of soybeans, the influences of Cd on ammonification in the bulk soil were: toxic impacts at the seedling stage, stimulatory effects during the early flowering stage, and adaptation to the pollutant during the podding and ripening stages. Although nitrification and denitrification in the bulk soil decreased throughout the entire growth cycle, positive adaptation to Cd stress was observed during the ripening stage. Moreover, during the ripening stage, denitrification in the bulk soil under high Cd treatment (20 mg kg~(-1)) was even higher than that in the control, indicating a probable change in the ecology of the denitrifying microbes in the Cd-stressed system. Changes in the activity of microbes in the rhizosphere following plant growth were similar to those in the non-rhizosphere in Cd treatments; however, the tendency of change in the rhizosphere seemed to be more moderate. This suggested that there was some mitigation of Cd stress in the rhizosphere.
Contribution of Atmospheric Nitrogen Compounds to N Deposition in a Broadleaf Forest of Southern China

A one-year study in a typical red soil region of southern China was conducted to determine atmospheric nitrogen (N) fluxes of typical N compounds (NH_3, NH_4-N, NO_3-N, and NO_2) and contribution of three sources (gas, rainwater, and particles) to N deposition. From July 2003 to June 2004, the total atmospheric N deposition was 70.7 kg N ha~(-1), with dry deposition accounting for 75% of the total deposition. Dry NH_3 deposition accounted for 73% of the dry deposition and 55% of the total deposition. Moreover, NO_2 contributed 11% of the dry deposition and 8% of the total deposition. Reduced N compounds (NH_4~+ and NH_3) were the predominate contributors, accounting for 66% of the total deposition. Therefore, atmospheric N deposition should be considered when soil acidification and critical loads of atmospheric deposition on soils are estimated.
Saline Water Irrigation Scheduling Through a Crop-Water-Salinity Production Function and a Soil-Water-Salinity Dynamic Model

Using a crop-water-salinity production function and a soil-water-salinity dynamic model, optimal irrigation scheduling was developed to maximize net return per irrigated area. Plot and field experiments were used to obtain the crop water sensitivity index, the salinity sensitivity index, and other parameters. Using data collected during 35 years to calculate the 10-day mean precipitation and evaporation, the variation in soil salinity concentrations and in the yields of winter wheat and cotton were simulated for 49 irrigation scheduling that were combined from 7 irrigation schemes over 3 irrigation dates and 7 salinity concentrations of saline irrigation water (fresh water and 6 levels of saline water). Comparison of predicted results with irrigation data obtained from a large area of the field showed that the model was valid and reliable. Based on the analysis of the investment cost of the irrigation that employed deep tube wells or shallow tube wells, a saline water irrigation schedule and a corresponding strategy for groundwater development and utilization were proposed. For wheat or cotton, if the salinity concentration was higher than 7.0 g L~(-1) in groundwater, irrigation was needed with only fresh water; if about 5.0 g L~(-1), irrigation was required twice with fresh water and once with saline water; and if not higher than 3.0 g L~(-1), irrigation could be solely with saline water.
Rangeland Grasshoppers in Relation to Soils in the Qinghai Lake Region, China

The relationship between rangeland grasshopper density and soil type as well as topsoil moisture content was analyzed with in situ soil data collected in the Qinghai Lake region of China. Grasshoppers were confined mainly to the areas with light chestnut soil or chestnut soil, and very few were found in areas with subalpine meadow soil. Grasshoppers were almost absent from other types of soil, such as aeolian soil. In addition, analysis of 14 soil samples collected in the study area revealed that a soil moisture content between 18 and 32 g kg~(-1)coincided spatially with a higher density of grasshoppers, with the grasshopper density averaging 15 head m~(-2). In areas with a soil moisture content above 42 g kg~(-1) or below 10g kg~(-1), grasshopper density dropped to less than 5 head m~(-2). These indicated that for the study area, soils with very high or very low moisture contents were not conducive to the survival of grasshoppers.
Adsorption of Metsulfuron and Bensulfuron on a Cationic Surfactant-Modified Paddy Soil

Adsorption isotherms of metsulfuron and bensulfuron on a hexadecyltrimethylammonium (HDTMA) bromide-modified paddy soil under different ionic strengths, with divalent cation Cu~(2+), or having different pH were studied to describe their adsorptive behavior, and to try to explain the adsorption process of a sulfonylurea compound with a carbamoylsulfamoyl group in the modified soil environment. All the adsorption isotherms fitted the Freundlich equation well, and the HDTMA treatment of paddy soil dramatically enhanced adsorption capacity of metsulfuron or bensulfuron. Also, an increase of ionic strength and the addition of divalent heavy metal cation Cu~(2+) on the HDTMA-modified paddy soil increased the adsorption of metsulfuron or bensulfuron. Additionally, for metsulfuron and bensulfuron in the aqueous phase, adsorption capacity of the HDTMA-modified paddy soil gradually increased with decreasing pH.
Catalysis of Manganese(Ⅱ) on Chromium(Ⅵ) Reduction by Citrate

The catalysis of manganese(Ⅱ) (Mn~(2+)) on chromium(Ⅵ) (Cr~(6+)) reduction by citrate was studied through batch experiments with the concentration of citrate greatly in excess of Cr~(6+) at 25℃ and in pH ranges of 4.0 to 5.0. Results showed that at pH 4.5 within 22 h direct reduction of Cr~(6+) by citrate was not observed, but for the same time when Mn~(2+) (50 to 200 μmol L~(-1) was added,nearly all Cr~(6+) was rdeuced ,with the higher initial Mn~(2+) concentration having faster Cr~(6+) reduction. In the initial stage of the reaction, the Cr~(6+) reduction could be described with a pseudo-first-order kinetics equation. In the later stage of the reaction, plots of lnc(Cr~(6+)) versus t, where c(Cr~(6+)) is the Cr~(6+) concentration in the reaction and t is the reaction time, deviated from the initial linear trend. The deviations suggested that the pseudo-first-order kinetics did not apply to the whole experimental period and that some reaction intermediates could have greatly accelerated Cr~(6+) reduction by citrate. The catalysis of the intermediates increased with the reaction time and gradually reached stability. Then, the plot of lnc(Cr~(6+)) versus t in the presence of Mn~(2+) was linear again, with the rate constant increasing by 102 times compared with the absence of Mn~(2+). Complexation between Mn~(2+) and citrate was likely a prerequisite for the catalysis of Mn~(2+) on the reaction. Additional experiments showed that introducing ethylenediaminetetraacetic acid (EDTA) into the reaction system strongly suppressed the catalysis of Mn~(2+).
National Scale Analysis of Soil Organic Carbon Storage in China Based on Chinese Soil Taxonomy

Patterns of soil organic carbon (SOC) storage and density in various soil types or locations are the foundation for examining the role of soil in the global carbon cycle. An assessment of SOC storage and density patterns in China based on soil types as defined by Chinese Soil Taxonomy (CST) and the recently compiled digital 1:1000 000 Soil Database of China was conducted to generate a rigorous database for the future study of SOC storage. First, SOC densities of 7292soil profiles were calculated and linked by soil type to polygons of a digital soil map using geographic information system resulting in a 1:1000 000 SOC density distribution map of China. Further results showed that soils in China covered 9 281 ×10~3 km~2 with a total SOC storage of 89.14 Gt and a mean SOC density 96.0 t ha~(-1). Among the 14 CST orders, Cambosols and Argosols constituted high percentage of China's total SOC storage, while Andosols, Vertosols, and Spodsols had a low percentage. As for SOC density, Histosols were the highest, while Primosols were the lowest. Specific patterns of SOC storage of various soil types at the CST suborder, group, and subgroup levels were also described. Results obtained from the study of SOC storage and density of all CST soil types would be not only useful for international comparative research, but also for more accurately estimating and monitoring of changes of SOC storage in China.
Nitrogen Cycling and Losses Under Rice-Wheat Rotations with Coated Urea and Urea in the Taihu Lake Region

A lysimeter experiment with undisturbed soil profiles was carried out to study nitrogen cycling and losses in a paddy soil with applications of coated urea and urea under a rice-wheat rotation system in the Taihu Lake region from 2001 to 2003. Treatments for rice and wheat included urea at conventional, 300 (rice) and 250 (wheat) kg N ha~(-1), and reduced levels, 150 (rice) and 125 (wheat) kg N ha~(-1), coated urea at two levels, 100 (rice) and 75 (wheat) kg N ha~(-1), and 150(rice) and 125 (wheat) kg N ha~(-1), and a control with no nitrogen arranged in a completely randomized design. The results under two rice-wheat rotations showed that N losses through both NH_3 volatilization and runoff in the coated urea treatments were much lower than those in the urea treatments. In the urea treatments N runoff losses were significantly (P ＜ 0.001) positively correlated (r = 0.851) with applied N. N concentration in surface water increased rapidly to maximum two days after urea application and then decreased quickly. However, if there was no heavy rain within five days of fertilizer application, the likelihood of N loss by runoff was not high. As the treatments showed little difference in N loss via percolation, nitrate N in the groundwater of the paddy fields was not directly related to N leaching. The total yield of the two rice-wheat rotations in the treatment of coated urea at 50% conventional level was higher than that in the treatment of urea at the conventional level. Thus, coated urea was more favorable to rice production and environmental protection than urea.
Effect of Long-Term Rice Straw Return on Soil Glomalin, Carbon and Nitrogen

A long-term experiment was conducted to investigate how long-term fertilization and rice straw incorporation into soil affect soil glomalin, C and N. The combined application of chemical fertilizer and straw resulted in a significant increase in both soil easily extractable glomalin (EEG) and total glomalin (TG) concentrations, as compared with application of only chemical fertilizer or no fertilizer application. The EEG and TG concentrations of the NPKS (nitrogen, phosphorus, and potassium fertilizer application + rice straw return) plot were 4.68% and 5.67% higher than those of the CK (unfertilized control) plot, and 9.87% and 6.23% higher than those of the NPK (nitrogen, phosphorus, and potassium fertilizer applied annually) plot, respectively. Application of only chemical fertilizer did not cause a statistically significant change of soil glomalin compared with no fertilizer application. The changes of soil organic C (SOC) and total N (TN) contents demonstrated a similar trend to soil glomalin in these plots. The SOC and TN contents of NPKS plot were 15.01% and 9.18% higher than those of the CK plot, and 8.85% and 14.76% higher than those of the NPK plot, respectively. Rice straw return also enhanced the contents of microbial biomass C (MBC) and microbial biomass N (MBN) in the NPKS plot by 7.76% for MBC and 31.42% for MBN compared with the CK plot, and 12.66% for MBC and 15.07% for MBN compared with the NPK plots, respectively. Application of only chemical fertilizer, however, increased MBN concentration, but decreased MBC concentration in soil.
Fate of ~(15)N-Labeled Urea Under a Winter Wheat-Summer Maize Rotation on the North China Plain

A field experiment was conducted to investigate the fate of ~(15)N-labeled urea and its residual effect under the winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation system on the North China Plain. Compared to a conventional application rate of 360 kg N ha~(-1) (N360), a reduced rate of 120 kg N ha~(-1) (N120) led to a significant increase (P ＜ 0.05) in wheat yield and no significant differences were found for maize. However, in the 0-100 cm soil profile at harvest, compared with N360, N120 led to significant decreases (P ＜ 0.05) of percent residual N and percent unaccounted-for N, which possibly reflected losses from the managed system. Of the residual fertilizer N in the soil profile, 25.6%-44.7% and 20.7%-38.2% for N120 and N360, respectively, were in the organic N pool, whereas 0.3%-3.0% and 11.2%-24.4%, correspondingly, were in the nitrate pool, indicating a higher potential for leaching loss associated with application at the conventional rate. Recovery of residual N in the soil profile by succeeding crops was less than 7.5%of the applied N. For N120, total soil N balance was negative; however, there was still considerable mineral N (NH_4~+-N and NO_3~--N) in the soil profile after harvest. Therefore, N120 could be considered agronomically acceptable in the short run, but for long-term sustainability, the N rate should be recommended based on a soil mineral N test and a plant tissue nitrate test to maintain the soil fertility.