Diurnal Variation of Soil CO2 Efflux and Its Optimal Measuring Time-window of Temperate Meadow Steppes in Western Songnen Plain, China

In order to study the diurnal variation of soil CO2 effiux from temperate meadow steppes in Northeast China, and determine the best time for observation, a field experiment was conducted with a LI-6400 soil CO2 flux system under five typical plant communi- ties （Suaeda glauca （Sg）, Chloris virgata （Cv）, Puecinellia distans （Pd）, Leymus chinensis （Lc） and Phragmites australis （Pa）） and an alkali-spot land （As） at the meadow steppe of western Songnen Plain. The results showed that the diurnal variation of soil CO2 effiux exhibited a single peak curve in the growing season. Diurnal maximum soil respiration （Rs） often appeared between 1 1：00 and 13：00, while the minimum occurred at 21：00-23：00 or before dawn. Air temperature near the soil surface （Ta） and soil temperature at 10 cm depth （Tlo） exerted dominant control on the diurnal variations of soil respiration. The time-windows 7：00-9：00 could be used as the optimal measuring time to represent the daily mean soil CO2 effiux at the Cv, Pd, Lc and Pa sites. The daily mean soil CO2 effiux was close to the soil COz effiux from 15：00 to 17：00 and the mean of 2 individual soil CO2 effiux from 15：00 to 19：00 at the As and Sg sites, respectively. During nocturnal hours, negative soil CO2 fluxes （CO2 downwards into the soil） were frequently observed at the As and Sg sites, the magnitude of the negative CO2 fluxes were 0.10-1.55 gmol/（m2.s） and 0.10-0.69 gmol/（m2.s）at the two sites. The results im- plied that alkaline soils could absorb CO2 under natural condition, which might have significant implications to the global carbon budget accounting.

Effect of Different Soil Regulation Measures on Yield and Soil Fertility of Eucalyptus Plantation in Southern Guangxi

In view of the problems of decreased unit yield,soil acidification,decreased soil organic matter and soil fertility caused by high generation single pure Eucalyptus plantation in southern Guangxi,a field experiment was conducted to study the yield,soil organic matter and soil fertility under six soil conditioning measures[interplanting Tephrosia candida under the forest,interplanting Sesbania cannabina under the forest,organic fertilizer application,residue to woodland,soil testing and formulated fertilization,and applying pure chemical fertilizer(CK)],and the enhancing effects of each treatment on the yield and soil improvement of Eucalyptus plantations were further comprehensively evaluated.The results showed that compared with the control,the five treatments could increase the average stock of Eucalyptus,among which the average stock under the treatment of interplanting T.candida under the forest was the highest,followed by soil testing and formulated fertilization.The soil organic matter content and soil fertility of the forest were significantly improved by interplanting green manure,organic fertilizer application and soil testing and formulated fertilization models,while the short-term(1 a)effect of the residue treatment on the improvement of soil organic matter and soil fertility was insignificant.During the actual production process,interplanting green manure and residue treatment were not effective due to the inoperability,and the applicability were not wide,which still needed further study.Therefore,organic manure application and soil testing and formulated fertilization were suitable choices to promote the improvement of productivity and soil quality of Eucalyptus plantation in Guangxi.

Requirements and Safeguard Measures for Using Soil Fertilizer in Organic Agriculture:A Case Study of Fushun City in Liaoning Province

This paper summarized the requirements of organic agriculture for soil environment,fertilizer application and irrigation water quality,put forward safeguard measures for organic agriculture in terms of soil,fertilizer and water,and finally came up with recommendations for strengthening the use of soil fertilizers in organic agriculture.

Application of a Soil Nutrient Measuring Instrument in Vegetable Seedling Substrate

[Objective] The aim was to find an efficient method to measure available nitrogen, phosphorus and potassium content in vegetable seedling substrate. [ Method] The suitable dosage of leaching agent, ratio of the substrate to water and leaching time for the detection of nutrient contents in the substrate by a soil nutrient measuring instrument were discussed firstly, and then the results of nutrient contents measured by the soil nutrient measuring instrument were compared with that by conventional approaches. [ Result] In compadson with the conventional methods, the av- erage content of available nitrogen measured by the soil nutrient measuring instrument was slightly higher, while the average content of available phosphorus measured by the instrument was lower; the average content of available potassium measured by the instrument was close to that by the conventional method. [ Conclusion] This study could provide us a new method to detect available nitrogen, phosphorus and potassium content in seedling substrate efficiently.

Effect of Measurement Time on Emission Flux of CO_2 and N_2O in Black Soil Region

[Objective] The aim was to investigate and reveal effect of measurement time on emission flux of CO2 and N2O to ensure the optimum time of emission flux, in order to provide scientific reference for emission reduction of greenhouse gas in black soil region. [Method] Based on experiment of long-term fertilizer location in black soil region, the paper studied on daily dynamic variation of CO2 and N2O discharge in 3 key growth periods （booting stage, grain-filling stage and mature stage） to reveal differences of CO2 and N2O emission flux in different times. [Result] Daily variations of CO2 and N2O emission flux were large, from 205 mg/（m2·h） to 552 mg/（m2·h） for CO2 and from 51 h to 295 μg/（m2·h） for N2O. Trend of CO2 discharge in different growth times showed a unimodal curve, and the peak was at noon of 12：00 and the peak valley was at 3：00 am; discharge of N2O was small in day time at booting stage and large at night. Regardless of rice growth period effect on CO2 and N2O emission flux, representative time of CO2 discharge was 6：00-8：00 or 16：00-21：00; and time of N2O was 8：00-10：00 or 16：00-21：00; if CO2 and N2O emission fluxes were measured simultaneously, the optimum time was 16：00-18：00; if the measurement was started during 9：00-12：00, correction coefficients of CO2 and N2O were 0.81 and 0.90, respectively. [Conclusion] The result provided scientific reference for reduction of greenhouse gas emission in black soil region.

A distributed measurement method for in-situ soil moisture content by using carbon-fiber heated cable

Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a distributed measurement system for in-situ soil moisture content （SM-DTS） is introduced.The system is based on carbon-fiber heated cable （CFHC） technology that has been developed to enhancethe measuring accuracy of in-situ soil moisture content. Using CFHC technique, a temperature characteristicvalue （Tt） can be defined from temperatureetime curves. A relationship among Tt, soil thermalimpedance coefficient and soil moisture content is then established in laboratory. The feasibility of theSM-DTS technology to provide distributed measurements of in-situ soil moisture content is verifiedthrough field tests. The research reported herein indicates that the proposed SM-DTS is capable ofmeasuring in-situ soil moisture content over long distances and large areas.

Performance evaluation of two types of heated cables for distributedtemperature sensing-based measurement of soil moisture content

Distributed temperature sensing(DTS)using heated cables has been recently developed for distributed monitoring of in-situ soil moisture content.In this method,the thermal and electrical properties of heated cables have a significant influence on the measurement accuracy of soil moisture content.In this paper,the performances of two heated cables,i.e.the carbon-fiber heated cable(CFHC)and the metalnet heated cable(MNHC),are studied in the laboratory.Their structures,uniformity in the axial direction,measurement accuracy and suitability are evaluated.The test results indicate that the MNHC has a better uniformity in the axial direction than CFHC.Both CFHC and MNHC have high measurement accuracy.The CFHC is more suitable for short-distance measurement(500 m),while the MNHC can be used for longdistance measurement(>500 m).

A modified soil water content measurement technique using actively heated fiber optic sensor

Soil water content measurement is critical in practical engineering.The actively heated fiber Bragg grating optic sensor(FBGS)has great potential of multi-point measurement for soil water content measurement in field.In this study,the effect of heating time on the measurement accuracy is discussed,and modifications are made for actively heated fiber optic(AHFO)sensors.The results demonstrate that if an integration data analysis method is used,the accuracy and reliability of soil water content measurement with AHFO sensors will be improved.Both a short fiber length and a short-term heating pattern are effective and can help to reduce soil disturbance.With the proposed integration method,a short heating time is guaranteed for measuring the soil water content.Such improvements will reduce the thermal disturbance to soil sample and improve the reliability of measurement.

Estimation of Some Chemical Properties of an Agricultural Soil by Spectroradiometric Measurements

The contents of nitrogen and organic carbon in an agricultural soil were analyzed using reflectance measurements （n = 52） performed with an ASD FieldSpee-Ⅱ spectroradiometer. For parameter prediction, empirical models based on partial least squares （PLS） regression were defined from the measured reflectance spectra （0.4 to 2.4 μm）. Here, reliable estimates were obtained for nitrogen content, but prediction accuracy was only moderate for organic carbon. For nitrogen, the real spatial pattern of within-field variability was reproduced with high accuracy. The results indicate the potential of this method as a quick screening tool for the spatial assessment of nitrogen and organic carbon, and therefore an appropriate alternative to time- and cost-intensive chemical analysis in the laboratory.

The Impacts of Supplemental Irrigation Based on Soil Moisture Measurement and Nitrogen Use on Winter Wheat Yield and Nitrogen Absorption and Distribution

Based on split plot design method of field test,the impacts of supplemental irrigation based on soil moisture measurement and nitrogen use on winter wheat yield and nitrogen absorption and distribution were studied.Supplemental irrigation had three levels: 60%(W_1),70%(W_2) and 80%(W3) of the targeted relative water content at 0-40 cm of soil layer during jointing period of winter wheat.Nitrogen fertilization had three levels: not using nitrogen(N_0),using pure nitrogen of 195 kg/hm^2(N_(195)) and 255 kg/hm^2(N_(255)).Results showed that:(i)different supplemental irrigation and nitrogen fertilization significantly affected plant height and leaf area of winter wheat during key growth period.Under the same supplemental irrigation treatment,both plant height and leaf area of winter wheat showed as N_(255)> N_(195)> N_0(P <0.05).Plant height in N_(195) and N_(255)treatments was significantly higher than that in N_0 treatment,but there was not significant difference between N_(195) and N_(255)(P >0.05).Under the same nitrogen fertilization,plant height in W_2(569.4 m^3/hm^2) and W3(873.45 m^3/hm^2) treatments was significant higher than that in W_1(265.2 m^3/hm^2),but there was not significant difference between W_2 and W3(P >0.05).It illustrated that excessive nitrogen fertilization and supplemental irrigation did not significantly affect plant height and leaf area of winter wheat.(ii) Under the same nitrogen fertilization level,yield increase effect of winter wheat by supplemental irrigation showed a declining trend with nitrogen application amount increased.It illustrated that nitrogen fertilization and supplemental irrigation had certain critical values on the yield of winter wheat.When surpassing the critical value,the yield declined.When nitrogen fertilization amount was 195 kg/hm^2,and supplemental irrigation amount was 70% of field moisture capacity(569.4 m^3/hm^2),the highest yield 8500 kg/hm^2 could be obtained.(iii) During mature period of winter wheat,nitrogen accumulation amount of plant treated by nitrogen was significantly higher than that not treated by nitrogen(P <0.05).But under the treatments of W_2 and W3,nitrogen accumulation amount in N_(255) significantly declined when compared with N_(195)(P <0.05).Especially under W3(873.45 m^3/hm^2) level,nitrogen accumulation amount in N_(255) was even lower than N_0.Under the treatments of N_0 and N_(195),nitrogen accumulation amount of plant significantly increased with supplemental irrigation increased(P < 0.05).But under N_(255) treatment,there was not significant difference(P > 0.05).It illustrated that moderate supplemental irrigation and nitrogen fertilization could improve nitrogen absorption ability of winter wheat,but excessive supplemental irrigation and nitrogen fertilization were not favorable for plant's nitrogen absorption.(iv) Although the increase of supplemental irrigation during jointing period improved nitrogen absorption ability of winter wheat and promoted winter wheat absorbing more nitrogen,it inhibited nitrogen transferring and distributing to seed.Comprehensively considering growth condition of winter wheat and nitrogen risk condition,it is suggested that nitrogen application amount was 195 kg/hm^2,and supplemental irrigation reached 70% of field moisture capacity(569.4 m^3/hm^2),which could be as the suitable water and fertilizer use amounts in the region.

Study on Soil Improvement Measure of Plant Landscape Construction in Saline and Alkaline Area in Tianjin

A detailed research in soil improving measure was conducted during the process of plants that were cultivated in Tianjin saline and alkaline area. The results showed that the commonly used measures could improve the soil, and also we got some useful advices and suggestions for plants cultivating in Tianiin saline and alkaline areas.

Soil and water loss in the Lancang River-Mekong River watershed (in Yunnan section, China) and its control measures

According to a lot of hydrological and environmental monitoring data, the condition of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is described. The occurrence and development of soil and water loss is analyzed. The conclusion is that: (1) generally, the situation of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is light, however, soil and water loss in some regions is serious, especially in the middle reach area of the river; (2) soil and water loss in the Lancang River Mekong River (in Yunnan section, China) watershed presents developing tendency and it is mainly caused by human beings. In accordance with these results, the control measures for soil and water loss are discussed.

Research Progress in the Effect and Mechanism of Fertilization Measures on Soil Fertility

This paper firstly summarized the domestic and foreign research progress in the relationship between fertilization measures and soil fertility. It elaborated the relationship between fertilization measures and basic physical and chemical properties,soil enzyme activity,soil microorganism fertility index,and soil animal fertility index. It pointed out future researches about the relationship between fertilization measures and soil fertility include:( i) the relationship between fine and high efficient input of organic fertilizer and soil fertility,( ii) in-depth research of soil zoology fertility index,( iii) soil biology about long-term fertilization,and( iv) soil fertilization and agricultural diffused pollution. It is intended to provide scientific reference for improving farmland soil fertility and maintaining excellent ecological environment of farmland through proper fertilization measures.

Integrating water use systems and soil and water conservation measures into a hydrological model of an Iranian Wadi system

Water resources are precious in arid and semi-arid areas such as the Wadis of Iran. To sustainably manage these limited water resources, the residents of the Iranian Wadis have been traditionally using several water use systems(WUSs) which affect natural hydrological processes. In this study, WUSs and soil and water conservation measures(SWCMs) were integrated in a hydrological model of the Halilrood Basin in Iran. The Soil and Water Assessment Tool(SWAT) model was used to simulate the hydrological processes between 1993 and 2009 at daily time scale. To assess the importance of WUSs and SWCMs, we compared a model setup without WUSs and SWCMs(Default model) with a model setup with WUSs and SWCMs(WUS-SWCM model). When compared to the observed daily stream flow, the number of acceptable calibration runs as defined by the performance thresholds(Nash-Sutcliffe efficiency(NSE)≥0.68, –25%≤percent bias(PBIAS)≤25% and ratio of standard deviation(RSR)≤0.56) is 177 for the Default model and 1945 for the WUS-SWCM model. Also, the average Kling–Gupta efficiency(KGE) of acceptable calibration runs for the WUS-SWCM model is higher in both calibration and validation periods. When WUSs and SWCMs are implemented, surface runoff(between 30% and 99%) and water yield(between 0 and 18%) decreased in all sub-basins. Moreover, SWCMs lead to a higher contribution of groundwater flow to the channel and compensate for the extracted water by WUSs from the shallow aquifer. In summary, implementing WUSs and SWCMs in the SWAT model enhances model plausibility significantly.

Farmland Soil Heavy Metal Pollution and Control Measures

Soil pollution has been considered as one of the main environmental problems in the world nowadays. The source of soil heavy metal pollution in farmland, the effect of heavy metal pollution on soil quality in farmland, growth of crops, quality of agricultural products and the effects of heavy metal pollution on human health were discussed in this paper. The heavy metal pollution control measures were introduced, including physical and chemical regulations, phytoremediation and agroecological restoration measures. The future research perspective was also discussed in this paper.

Current Situations,Evolution Trend,and Improvement Measures of Soil Organic Matter in Cultivated Land of Northeast China

The data of cultivated land quality monitoring sites,and the current situations and evolution trend of soil organic matter in cultivated land in Northeast China were analyzed.Then,the causes for low organic matter content were discussed.Finally,it came up with pertinent soil improvement recommendations,including actively promoting the quality protection technology model of cultivated land such as straw returning in accordance with local conditions,expanding organic fertilizer sources and increasing application of organic fertilizers,implementing reasonable crop rotation,planting green manure crops such as legumes,and realizing the combination of land use and land cultivation,establishing a reasonable fertilization system,combining organic and inorganic fertilizers with scientific fertilization,increasing fertilizer efficiency and reducing the application of chemical fertilizers,increasing financial investment and promoting the integration of funds related to cultivated land protection.

A policy and technical measures for controlling soil and water loss in the Loess Plateau of China

Loess Plateau is the most serious region of soil and water loss in China and the world. The sediment carried into the Yellow River amounts to 1.6 billion tons every year. This paper reviews the factors and reasons for erosion in this area, and puts forward a comprehensive controlling policy on the basis of the principles of ecology and practise of Chinese scientists for 40 years. In conformity with the policy, a number of technical measures for controlling soil and water loss are suggested.

Study on Humic Acids of the Soil Applied with Corn Stalk by Spectroscopy Measurements

Spectroscopy measurements （Fourier transform infrared differential spectroscopy, Carbon-13 nuclear magnetic resonance spectrometry, Matrix-assisted laser resorption/ionization-time of flight mass spectrometry） were performed to study the humic acids of the soil applied with corn stalk. The results showed that after incorporation of corn stalks into the soil, the soil humic acid （HA） changed significantly in different stages. During first 60 days, new HAs were formed by polymerization and seems to be similar to that of initial HAs from composting corn stalk, some little molecular organic matters also reacted with soil HAs and turned into parts of soil HAs. After 60 days of the corn stalk residue incorporation, new HAs were formed by polymerization of decomposed lignin molecules, some methylenes transformed into methyls and methoxyls since the 90th day. Application of corn stalk led to the increase of aliphatic components in soil HAs, the decrease in aromatic components of soil HAs and the suppression in oxidation degree of soil HAs. The average molecular weight of soil HAs also declined because of application of corn stalk.

Benefit measurement of the soil and water conservation for ecological forestry engineering

Data were collected from Three-north Region, Middle and upper reaches region of Yangtze River and Coastal region. By analysis of factors influencing soil erosion, the longitude, latitude, annual precipitation, and the slope degree were selected as regional independent variables and canopy density and stock litter were selected as independent variables, and integral diffusing models were established for evaluation of the benefit of soil and water conservation of forest. By solving the parameters of models using the package of STATISTICA, the Power function between independent variables and dependent variables was set up. The soil conservation amount of forest and economic values were estimated using the contrast method for the ecological forestry engineering of the above three areas.

Control Measures of Soil Erosion in a Typical Construction Project Area ( Dina 2 Gas Field)

To treat the relationship between project construction and ecological environment and effectively prevent new soil erosion during the construction, according to the project layout, soil erosion distribution as well as natural and socio-economic conditions, the control measures of newly increased soil erosion along the project were carried out based on site survey and analysis of relevant information. In addition, adhering to the prin- ciple of partition prevention and treatment, some guiding prevention and control measures of the natural zone passed by the project and soil erosion control district were determined, which provided scientific references and technical support for the rational layout of water and soil conservation and ecological restoration measures in Dina 2 gas field.