Antibiotic-Resistant Bacterial Group in Field Soil Evaluated by a Newly Developed Method Based on Restriction Fragment Length Polymorphism Analysis

Spreading of antibiotic resistant bacteria into environment is becoming a major public health problem, implicating affair of the indirect transmission of antibiotic resistant bacteria to human through drinking water, or vegetables, or daily products. Until now, the risk of nosocomial infection of antibiotic resistant bacteria has mainly been evaluated using clinical isolates by phenotypic method. To evaluate a risk of community-acquired infection of antibiotic resistant bacteria, a new method has been developed based on PCR-RFLP without isolation. By comparing restriction fragment lengths of the 16S rDNA gene from bacterial mixture grown under antibiotic treatment to those simulated from the DNA sequence, bacterial taxonomies were elucidated using the method of Okuda and Watanabe [1] [2]. In this study, taxonomies of polymyxin B resistant bacteria group in field soils, paddy field with organic manure and upland field without organic manure were estimated without isolation. In the both field soils, the major bacteria grown under the antibiotic were B. cereus group, which had natural resistance to this antibiotic. In field applied with organic manure, Prevotella spp., and the other Cytophagales, which were suggested to be of feces origin and to acquire resistance to the antibiotic, were detected. When numbers of each bacterial group were roughly estimated by the most probable number method, B. cereus group was enumerated to be 3.30 × 106 MPN/g dry soil in paddy field soil and 1.32 × 106 MPN/g dry soil in upland filed. Prevotella spp. and the other Cytophagales in paddy field were enumerated to be 1.31 × 106 MPN, and 1.07 × 106 MPN·g-1 dry soil.

Evaluating the Potentials of PLSR and SVR Models for Soil Properties Prediction Using Field Imaging,Laboratory VNIR Spectroscopy and Their Combination

Pedo-spectroscopy has the potential to provide valuable information about soil physical,chemical,and biological properties.Nowadays,wemay predict soil properties usingVNIRfield imaging spectra(IS)such as Prisma satellite data or laboratory spectra(LS).The primary goal of this study is to investigate machine learning models namely Partial Least Squares Regression(PLSR)and Support Vector Regression(SVR)for the prediction of several soil properties,including clay,sand,silt,organic matter,nitrate NO3-,and calcium carbonate CaCO_(3),using five VNIR spectra dataset combinations(%IS,%LS)as follows:C1(0%IS,100%LS),C2(20%IS,80%LS),C3(50%IS,50%LS),C4(80%IS,20%LS)and C5(100%IS,0%LS).Soil samples were collected at bare soils and at the upper(0–30 cm)layer.The data set has been split into a training dataset 80%of the collected data(n=248)and a validation dataset 20%of the collected data(n=61).The proposed PLSR and SVR models were trained then tested for each dataset combination.According to our results,SVR outperforms PLSR for both:C1(0%IS,100%LS)and C5(100%IS,0%LS).For Soil Organic Matter(SOM)prediction,it achieves(R^(2)=0.79%,RMSE=1.42%)and(R^(2)=0.76%,RMSE=1.3%),respectively.The data fusion has improved the soil property prediction.The highest improvement was obtained for the SOM property(R^(2)=0.80%,RMSE=1.39)when using the SVR model and applying the second Combination C2(20% of IS and 80%LS).

Effects of Enhanced UV-B Radiation on Soil Respiration of Barley Field

[Objective] The aim was to investigate the changing characteristics of soil respiration in clear day with enhanced UV-B radiation and in cloudy day without external UV-B radiation forcing.[Methods] Based on measuring soil respiration rate of barley field at jointing stage in typical clear day and cloudy day by means of Li-8100,the effects of enhanced UV-B radiation by 20% on soil respiration rate were studied. [Results] The results showed that enhanced UV-B radiation inhibited soil respiration of barley field obviously. In clear day,the average soil respiration rate of normal barley field(B) was 1.02 μmol/(m2·s) higher than that of barley field with the enhanced UV-B radiation by 20%(BU) . For cloudy day,the average soil respiration rate of B treatment was 0.71 μmol/(m2·s) lower than BU treatment without external UV-B radiation forcing. In clear day,UV-B radiation rise resulted into the decrease of Q10 value of soil respiration in barley field,but there was an increase in cloudy day without external UV-B radiation forcing,leading to various changes of soil respiration rate. [Conclusions] Supplemental UV-B radiation could inhibit soil respiration rate of barley filed significantly,thus affected the increase of crop yield.

Characteristics of In-Situ Soil Water Hysteresis Observed through Multiple-Years Monitoring

A soil water retention curve (SWRC) is an essential soil physical property for analyzing transport and retention of water in a soil layer. A SWRC is often described as a single-valued function that relates the soil water potential ψ to volumetric water content θ of the soil. However, an in-situ ψ − θ relation should show soil water hysteresis, though this fact is often neglected in analyses of field soil water regimes while long-term in-situ soil water hysteresis is not well characterized. This study aimed at probing and characterizing in-situ ψ − θ relations. The developments of large hysteresis in the in-situ ψ − θ relations were observed only a few times during the study period of 82 months. Any of the large hysteretic behaviors in the ψ − θ relations began with an unusually strong continual reduction in ψ. The completion of a hysteresis loop required a recorded maximum rainfall. Because the study field had very small chances to meet such strong rainfall events, it took multiple years to restore the fraction of soil water depleted by the unusually strong continual reduction in ψ. While wetting-drying cycles had occurred within a certain domain of ψ, hysteretic behaviors tended to be so small that the in-situ ψ − θ relation can be approximated as a single-valued function of θ(ψ). These observed patterns of the in-situ ψ − θ relations were characterized by kinds of difference in dθ/dψ between a drying process and a wetting process at a given ψ. Thus, more amounts of experimental facts about wetting SWRCs in parallel with drying SWRCs should be needed for correct modelling, analyzing, and predicting soil water regimes in fields. It is also necessary to increase our understandings about the long-term trends of occurrences of extreme weather conditions associated with possible change in climate.

Effects of heavy metals on soil microbial community of different land use types

To evaluate soil environmental quality of introduced new crops and other traditional crops,and to understand the importance of response of soil microbial community to heavy metal stress,rhizosphere soil samples of different land use types(Sphagnum farming,rice field,grassland and bare land) in Dading Village,Duyun City,Guizhou Province of China were selected as research objects.The differences of soil chemical properties,heavy metal concentration and microbial community among different land use types were compared.The abundance and structural diversity of microbial communities in soil samples were analyzed by 16S rDNA sequencing,the relationship between soil pollution characteristics and microbial community in farmland was studied.The results showed that the different land use types planting different agricultural products under the same growing environment were subject to different heavy metal pollution.Soil chemical properties and heavy metals had significant effects on the soil microbial community.Proteobacteria,Actinobacteriota and Acidobacteriota were the most dominant groups of bacteria.The soil microorganisms responded more actively to the variability of pH,SOM and AK contents,although the variability was not high.With the increase of pH value,the abundance of the dominant species Proteobacteria also increased.Verrucomicrobiota had a better tolerance to the heavy metal Hg.Verrucomicrobiota and Firmicutes had strong resistance to the heavy metal Cd.These results deepen our understanding of the changes and aggregation of microorganisms under different land use patterns in heavy-metal contaminated farmland soils.

Long-term submergence of non-methanogenic oxic upland field soils helps to develop the methanogenic archaeal community as revealed by pot and field experiments

The community structure of methanogenic archaea is relatively stable,i.e.,it is sustained at a high abundance with minimal changes in composition,in paddy field soils irrespective of submergence and drainage.In contrast,the abundance in non-methanogenic oxic soils is much lower than that in paddy field soils.This study aimed to describe methanogenic archaeal community development following the long-term submergence of non-methanogenic oxic upland field soils in pot and field experiments.In the pot experiment,a soil sample obtained from an upland field was incubated under submerged conditions for 275 d.Soil samples periodically collected were subjected to culture-dependent most probable number(MPN)enumeration,polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE)analysis of archaeal 16 S r RNA gene,and quantitative PCR analysis of the methyl-coenzyme M reductase alpha subunit gene(mcr A)of methanogenic archaea.The abundance of methanogenic archaea increased from 102 to 103 cells g-1 dry soil and 104 to 107 copies of mcr A gene g-1 dry soil after submergence.Although no methanogenic archaeon was detected prior to incubation by the DGGE analysis,members from Methanocellales,Methanosarcinaceae,and Methanosaetaceae proliferated in the soils,and the community structure was relatively stable once established.In the field experiment,the number of viable methanogenic archaea in a rice paddy field converted from meadow(reclaimed paddy field)was monitored by MPN enumeration over five annual cycles of field operations.Viability was also determined simultaneously in a paddy field where the plow layer soil from a farmer’s paddy field was dressed onto the meadow(dressed paddy field)and an upland crop field converted from the meadow(reclaimed upland field).The number of viable methanogenic archaea in the reclaimed paddy field was below the detection limit before the first cultivation of rice and in the reclaimed upland field.Then,the number gradually increased over five years and finally reached 103–104 cells g-1 dry soil,which was comparable to that in the dressed paddy field.These findings showed that the low abundance of autochthonous methanogenic archaea in the non-methanogenic oxic upland field soils steadily proliferated,and the community structure was developed following repeated and long-term submergence.These results suggest that habitats suitable for methanogenic archaea were established in soil following repeated and long-term submergence.

Effect of Sweet Corn Straw Returning to the Field on Soil Fertility, Yield and Benefit

It is an important way for realizing sustainable development of sweet corn production to stabilize and improve soil fertility of cultivated land in sweet corn production region.Through the test of sweet corn straw directly returning to the field after 6seasons for 3years,the results showed that continuous single application of chemical fertilizer is not conducive to the stability of soil fertility and yield improvement,and implementation of straw returning could receive fertility,improve soil acidic conditions,and enhance the yield of sweet corn.Compared with before the test,the single application of chemical fertilizer increased soil available phosphorus,while the contents of soil organic matter,available nitrogen and available potassium decreased by 1.08,1.18 and 2.47mg/kg respectively,and the soil pH decreased by 0.15.Under the same fertilizer conditions,organic matter contents of single and double-season straw returning increased by 0.71 and 1.29g/kg,available nitrogen increased by 17.15 and 28.27mg/kg,available phosphorus increased by 0.96 and 1.73mg/kg,available potassium increased by 2.41 and 5.92mg/kg,the soil pH increased by 0.16 and 0.2.Compared with the single application of chemical fertilizer,the average yields of single and double-season straw returning increased by 7.5%and 11.8%,and their average income increased by 87.3and 117.1yuan of per mu(667m^2)respectively.

Evaluation of Heavy Metal Pollution in Dazhai Mellow-soil Field

In order to determine the pollution condition of heavy metal in Dazhai mellow-soil field,the content of Zn,Cr,Cu,Ni,Pb,As,Cd and Hg in this area were analyzed,the content of heavy metals in soils in Shanxi Soil Environment Quality Standard and the secondary standard of National Soil Environment Quality Standard were used as evaluation standard. Based on the single factor index method,the result showed that the content of 8 heavy metals in soil didn't exceed the secondary standard of National Soil Environment Quality Standard,while the content of As,Hg,Ni,Pb exceeded Shanxi Soil Environment Quality Standard. The soil in the study areas reached high pollution of As,Hg,Pb,and the pollution index of Cu,Ni,Zn,Cd reached a high level. The potential ecological risk index order was Hg ﹥ Cd ﹥ As ﹥ Pb ﹥ Ni﹥ Cu ﹥ Zn ﹥ Cr. The pollution level risk intensity was mild. The correlation analysis indicated that Cr,Ni,Zn,Cu,Cd and As were probably from the same source,while Hg and other heavy metals were not correlated. Heavy metals with high levels of pollution were closely related to agricultural fertilization,tourism,transportation,construction,daily life and production activities.

Analysis of temperature field characteristics based on subgrade site measurements of Harbin-Qiqihar High-speed Railway in a deep seasonal frozen soil region

Recent years have seen a large number of high-speed railways built and will be built in seasonal frozen soil regions ot China. Although high-speed railways are characterized by being fast, comfortable and safe, higher standards for defor- mation of the railways＇ frozen subgrade are required. Meanwhile, changes in subgrade soil temperatures are the main factors affecting the deformation of frozen subgrade. Therefore, this paper selected typical test subgrade sections of the Harbin-Qiqihar Line, a special line for passenger transport built in the deep seasonal frozen soil regions of China, to monitor field temperatures. Also, the temperature changing laws of railways＇ subgrade in this region was analyzed by using testing data, the aim of which is to provide a technical support for future design and construction of buildings and structures in a deep seasonal frozen soil region.

Effects of cotton field management practices on soil CO2 emission and C balance in an arid region of Northwest China

Changes in both soil organic C storage and soil respiration in farmland ecosystems may affect atmospheric CO2 concentration and global C cycle. The objective of this field experiment was to study the effects of three crop field management practices on soil CO2 emission and C balance in a cotton field in an arid region of Northwest China. The three management practices were irrigation methods（drip and flood）, stubble managements（stubble-incorporated and stubble-removed） and fertilizer amendments（no fertilizer（CK）, chicken manure（OM）, inorganic N, P and K fertilizer（NPK）, and inorganic fertilizer plus chicken manure（NPK＋OM））. The results showed that within the C pool range, soil CO2 emission during the whole growing season was higher in the drip irrigation treatment than in the corresponding flood irrigation treatment, while soil organic C concentration was larger in the flood irrigation treatment than in the corresponding drip irrigation treatment. Furthermore, soil CO2 emission and organic C concentration were all higher in the stubble-incorporated treatment than in the corresponding stubble-removed treatment, and larger in the NPK＋OM treatment than in the other three fertilizer amendments within the C pool range. The combination of flood irrigation, stubble incorporation and application of either NPK＋OM or OM increased soil organic C concentration in the 0-60 cm soil depth. Calculation of net ecosystem productivity（NEP） under different management practices indicated that the combination of drip irrigation, stubble incorporation and NPK＋OM increased the size of the C pool most, followed by the combination of drip irrigation, stubble incorporation and NPK. In conclusion, management practices have significant impacts on soil CO2 emission, organic C concentration and C balance in cotton fields. Consequently, appropriate management practices, such as the combination of drip irrigation, stubble incorporation, and either NPK＋OM or NPK could increase soil C storage in cotton fields of Northwest China.

MECHANISM OF ELECTRIC FIELD ON PHYSICAL AND CHEMICAL PROPERTIES OF SOIL

Using The Electric Fertilization Apparatus which was made by the Forestry Instiute of Jilin City, the mechanism of the electric field on the physical-chemical characteristics of soil, in this paper were studied. The preliminary conclusion is that the amount of chemical fertilizer may be saved under the effect of electricity.

Effects of Long-Term Organic Amendments on Soil Organic Carbon in a Paddy Field: A Case Study on Red Soil

Soil organic carbon （SOC） is one of the main carbon reservoirs in the terrestrial ecosystem. It is important to study SOC dynamics and effects of organic carbon amendments in paddy fields because of their vest expansion in south China. A study was carried out to evaluate the relationship between the SOC content and organic carbon input under various organic amendments at a long-term fertilization experiment that was established on a red soil under a double rice cropping system in 1981. The treatments included non-fertilization （CK）, nitrogen-phosphorus-potassium fertilization in early rice only （NPK）, green manure （Astragalus sinicus L.） in early rice only （OM1）, high rate of green manure in early rice only （OM2）, combined green manure in early rice and farmyard manure in late rice （OM3）, combined green manure in early rice, farmyard manure in late rice and rice straw mulching in winter （OM4）, combined green manure in early rice and rice straw mulching in winter （OMS）. Our data showed that the SOC content was the highest under OM3 and OM4, followed by OM1, OM2 and OM5, then NPK fertilization, and the lowest under non-fertilization. However, our analyses in SOC stock indicated a significant difference between OM3 （33.9 t ha^-1） and OM4 （31.8 t ha^-1）, but no difference between NPK fertilization （27 t ha^-1） and nonfertilization （28.1 t ha^-1）. There was a significant linear increase in SOC over time for all treatments, and the slop of linear equation was greater in organic manure treatments （0.276-0.344 g kg-1 yr^-1） than in chemical fertilizer （0.216 g kg^-1 yr^-1） and no fertilizer （0.127 g kg^-1 yr^-1）.

Soil Phosphorus Release to the Water Bodies in the Upland Fields of Yellow Soil Areas and Impacting Factor

Soil phosphorus release to the water bodies in the upland fields of yellow soil areas and impacting factor was studied in Guizhou province. The results showed that the content of dissolved active P of surface runoff from various upland fields of yellow-soil were significantly different, which the concentrations of dissolved active P of runoff correlated with the contents of available-P, amorphous oxides of A1, and organic matter in the soils. The amount of soil phosphorus release to the water bodies affected by the level of applying P fertilizer and the process of corn growth, which with fertilizing from 150 to 900 kg P205 ha^-1 in the soil with high P level, the average contents of dissolved active P in the permeability-water of the soil increased from 0.020 mg L^-1 to 0.137 mg L^-1. The amount of soil phosphorus release to the water bodies also affected by environmental factor, which the amount of soil phosphorus release significantly increased under the conditions that temperature is 30℃-35℃, water/soil ratios is 15：1-25：1, submergence-time by water is 12-18 h and pH value of acid rains is 3.82-3.73.

Radioactivity levels in soil of salt field area,Kelambakkam,Tamilnadu,India

Soil samples in and around salt field area have been analyzed for natural radioactivity concentration using gamma ray spectrometer.The activity concentration for ^(232)Th,^(238)U and ^(40)K are ranged from 27.88 to 45.27 Bq/kg, from BDL to 13.30 Bq/kg,and from 135.54 to 381.28 Bq/kg,respectively.The measured activity concentrations for these radionuclides were compared with world average activity of soil.The average activity concentration of ^(232)Th in the present study is 1.19 times higher than world median value while the activity of ^(238)U and ^(40)K is found to be lower. The absorbed dose rates due to these radionuclides were calculated.The average absorbed gamma dose rate due to the presence of ^(232)Th,^(238)U and ^(40)K in soil samples is 36.99 nGy·h^(-1).These results indicate no radiological anomaly. The data presented in this study will serve as a base line survey for primordial radionuclides concentration in the study area.

Effects of Long-term Fertilization on Soil M icrobial Com m unity Structure,Labile Organic Carbon and Nitrogen and Enzym e Activity in Paddy Field and Upland

To investigate the effects of long-term fertilization systems on soil microbial community structure,labile organic carbon and nitrogen and enzyme activity in yellow sand paddy field and upland,a field experiment was conducted at the experimental station of Dongyang Institute of Maize Research in Zhejiang Province,China in 2009.The experiment consisted of six treatments with three replicates,and they were arranged in a completely randomized design,including no fertilization in paddy field (PCK),conventional fertilization in paddy field (PCF),formulated fertilization by soil testing in paddy field (PSTF),formulated fertilization by soil testing with organic manure in paddy field (PSTF+OF),conventional fertilization on upland (DCF),and formulated fertilization by soil testing with organic manure on upland (DSTF+OF).Soil nutrients,enzyme activity,microbial biomass and community structure were determined in 2015.The results showed that compared with no fertilization in paddy field (PCK),fertilization increased soil phosphorus and potassium content,and decreased pH value.No fertilization in paddy field (PCK) had no significant effect on soil culturable microorganisms in paddy field and upland,but formulated fertilization by soil testing with organic manure on upland (DSTF+OF) significantly increased the number of fungi.Formula fertilization by soil testing with organic manure (PSTF+OF) also significantly increased soil microbial biomass carbon and nitrogen in paddy field and upland.Moreover,fertilization had no significant effect on soil cellulase activity,but formula fertilization by soil testing with organic manure (PSTF+OF) significantly increased soil dehydrogenase and catalase activity.Therefore,long-term application of chemical fertilizer with organic fertilizer can effectively improve soil fertility.

A Study of Soil Nutrients in the Terrace Field Changed from Mountain Slope in Three Gorges Reservoir Region

In order to accurately grasp the soil fertility in Three Gorges Reservoir Region after changing mountain slope into terrace field,we take Wushan County for example,and use the spatio-temporal substitution method to analyze the soil nutrient status and trend about the terrace field changed from mountain slope under different length of implementation.The results show that the soil fertility is generally low in the study area,and according to the soil nutrient grading standards in the second national land survey,the average content of total nitrogen,available potassium,organic matter and available phosphorus reaches Standard III,Standard III,Standard IV and Standard V,respectively,and the spatial heterogeneity of soil nutrients is small.Compared to the sloping land,the terrace field changed from mountain slope has increasing soil nutrients on the whole with the length of farming.The mean of various indicators about soil nutrients in the terrace field changed from mountain slope for 2 years is lower than in the sloping land,and there is the biggest difference in soil fertility,while the mean of various indicators about soil nutrients in the terrace field changed from mountain slope for 14 years shows a linear upward trend,and the difference in soil fertility decreases.

Characterization of Orchard Fields Based on Soil Fertility Index (SOFIX)

Soil samples from 139 agricultural orchard fields (apple, grape, tea, and others) were analyzed using the soil fertility index. From these samples, an orchard field database was constructed and the soil properties between orchard, upland, and paddy fields were compared. The average value of bacterial biomass in the orchard fields was 7.4 × 108 cells/g-soil, ranging from not detected (lower than 6.6 × 106 cells/g-soil) to 7.7 × 109 cells/g-soil. The average values of total carbon (TC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK), were 24,000 mg/kg (2670 to 128,100 mg/kg), 1460 mg/kg (133 to 6400 mg/kg), 1030 mg/kg (142 to 5362 mg/kg), and 5370 mg/kg (1214 to 18,155 mg/kg), respectively. The C/N and C/P ratios were 19 (3 to 85) and 27 (2 to 101), respectively. Soil properties of the orchard fields were compared with those of the upland and the paddy fields. The average value of bacterial biomass in the orchard fields was almost the same as that in the upland fields (8.0 × 108 cells/g-soil), but the number was lower than that in the paddy fields (12.9 × 108 cells/g-soil). The average values of TC and TN in the orchard fields fell between those in the upland fields (TC: 33,120 mg/kg, TN: 2010 mg/kg) and the paddy fields (TC: 15,420 mg/kg, TN: 1080 mg/kg). The relationship between the bacterial biomass and TC in the orchard fields resembled that in the upland fields. A suitable soil condition for the orchard fields was determined as TC: ≥25,000 mg/kg, TN: ≥1500 mg/kg, TP: ≥900 mg/kg and TK: 2500 - 10,000 mg/kg. These recommended values will be effective for the improvement of the soil quality in the orchard fields by enhancing the number and activities of microorganisms.

Elevation and Land Use Types Have Significant Impacts on Spatial Variability of Soil Organic Matter Content in Hani Terraced Field of Yuanyang County,China

Soil organic matter （SOM） content is one of the most important indicators of the sustainability of soil. To maintain sustainable soil utilization and management in fragile Hani terraced field, it is meaningful to investigate the effects of topography and land use type on SOM content. Descriptive statistics and geostatistics were used to analyze the data and the kriging method was applied to map the spatial patterns of SOM content. The results showed that the mean SOM content was 32.76 g/kg, with a variation coefficient of 40%. The SOM content was affected by elevation and land use type. As the increase of elevation, the SOM content in Hani terraced field also increased obviously. The SOM content in tea garden, which is almost at high elevation, was the highest in all six land use types, and the SOM content decreased in a following sequence： tea garden 〉 paddy field 〉 corn field 〉 banana garden 〉 cassava field 〉 sugarcane field. In addition, at the same elevation, the paddy field had the highest SOM content compared with other land use types. All these results demonstrate that paddy field is the most efficient and suitable land use type for SOM conservation at high, middle or low elevations in the fragile Hani terraced field. In order to protect soil quality and maintain the sustainable agricultural development, it is necessary to maintain or even to enlarge the area of paddy field in Yuanyang county, Yunnan Province, China.

Effects of Nitrogen Dosage on the Yield and Nitrogen Use Efficiency of Machine Transplanted Rice Using Dry Soil Preparation in Rice Paddy Field

[Objective] The aim was to analyze the effects of nitrogen dosage on the yield and nitrogen use efficiency of machine transplanted rice using the technology of dry soil preparation in rice paddy field. [Method] With conventional Japonica rice cultivar Shengdao 18 as the study material, the effect of nitrogen dosage on stem and tillers dynamics, yield components and nitrogen use efficiency were investigated using the technology of dry soil preparation in rice paddy field. [Result] The highest yield was 10 957.20 kg/hm^2 as the nitrogen application was 315.00 kg/hm^2. Meanwhile, the roughness ratio, grain-straw ratio and nitrogen use efficiency remained at a higher level. Low nitrogen application could not obtain high yield. In contrast, high nitrogen application quantity led to a significant decline in nitrogen use efficiency. [Conclusion] The study could provide a scientific basis for the further promotion of the technology of dry soil preparation in rice paddy field.

Status and circulation characteristics of soil water in dryland field of southeast Shanxi Province

Based on the observed soil water data from experimental site located in southeast of Shanxi Province, the physical characteristics of soil water, crop effect on soil moisture, and the field water circulation pattern were studied by using the water balance method. The results suggested that soil water deficit often exists in fields of these areas. From May to June, the amount of water deficit in bare land rises to the maximum (232 8 mm) and falls to the minimum (66 6 mm) from August to September. By comparison, because of crop transpiration, both soil water deficit and dry soil layer in cultivated land are 15 1—40 4 mm more and 20—70 mm deeper respectively than those of bare land. Crops mainly planted in these areas have a relatively weak utilization ability to soil water. Winter wheat has the highest utilization ability to soil water among the crops planted in these areas. The soil water utilization ability of winter wheat is 26 2%—30 6% and winter wheat can use soil water that lies in soil layer below a depth of over 200 cm. Spring corn and millet can only consume soil water with the maximum ability of 13 4% and the deepest layer of 0—50 cm or 0—100cm, which shows that the soil water utilization ability of winter wheat is higher than that of spring crops. After crop is ripe, more than 41% of available soil water remains unused in field. So, increasing soil water storage and improving crop utilization ability to soil water by adopting efficient agrotechnique measures are the main ways for improving agricultural productivity in dry farming areas of Northern China.