Effect of Protective Cultivation Patterns of Rice in Cold Areas on Soil Physiological and Biochemical Status in Paddy Field

[Objective] The research aimed to explore how to use the soil reasonably,prevent the degradation of soil fertility,maintain soil fertility,improve the ecological environment of paddy field and improve the soil productivity of paddy field from the cultivation aspect.[Method] Taking kenjiandao 10 as the material,the variation laws of root weight,soil physical and chemical characteristics,soil enzyme,straw decomposition rate,soil temperature,microorganism of rice under the planting patterns of water-saving pro...

Bioturbation Effects of Benthic Fish on Soil Microorganism of Paddy Field

[Objective]The research aimed to explore the bioturbation effects of benthic fish Misgurnus anguillicaudatus on soil microorganism（microflora,biomass,and special physiological groups） of paddy field.[Method]The experiments were conducted locally and quantitatively in field,using plate count and MPN methods.[Result]In the microflora of paddy soil tested,the quantity of bacteria is the largest,followed by actinomycetes and fungus.Compared with the control paddy fields,in rice-fish paddy fields the quantities of bacteria,actinomycetes and fungus were higher,at significance level P 〈0.05,P 〈0.01,and P 〈0.01 respectively.The microbial biomass C and N in rice-fish paddy fields is remarkably higher than those in control paddy fields,both at significance level P 〈0.01;the microbial biomass P in rice-fish paddy fields is higher than that in control paddy fields,but at significance level P 〈0.05.Benthic fish promotes the growth of soil azotobacter,cellulolytic bacteria,nitrobacteria,sulfur bacteria,and ammonifying bacteria,restricts the reproduction of nitrate reducing bacteria and sulfate reducing bacteria.[Conclusion]The benthic fish had important effects on microflora,microbial biomass,and special microorganism physiological groups of paddy soil,improves the living conditions of soil microorganisms,promotes the soil fertility and bio-chemical activity,which is beneficial for improving the supply ability of soil nutrients such as N,P,S,as well as the efficiency of nutrient utilization.

Bioturbation Effects of Branchiura sowerbyi (Tubificidae) on the Vertical Transport of Sedimentary Particles in Paddy Field

[Objective] The research aimed to investigate the bioturbation effects of Branchiura sowerbyi （Tubificidae） on the vertical transport of sedimentary particles in paddy field,and explore the bioturbation effects and mechanism of benthic Annelida in coupling process of benthic-pelagic interface.[Method]Using chemically stable glass beads as tracers,the vertical transport of sedimentary particles in paddy field was analyzed comparatively with and without B.sowerbyi.[Result]After 10 days＇ bioturbation of B.sowerbyi,41.3% of the glass beads on the surface of sedimentary particles were transferred downward to the maximum depth of 9.4 cm,and the vertical transportation rate of sedimentary particles was 1.370×10-3/（g·cm2·d）. 25.8% and 17.3% of glass beads at a depth of 6 cm were transferred upwards and downwards respectively after bioturbation,to the maximum depth of 5.2 and 2.7 cm respectively,and the vertical transportation rates of sedimentary particles were 8.557×10-4 and 5.738×10-4/（g·cm2·d） respectively.[Conclusion]The sedimentary particles on the surface and deep layer of the paddy field were vertically shifted by the physical activities of B.sowerbyi,thus changed the sedimentary environment.

Bioturbation Effects of Benthic Fish on the Phosphorus Dynamic in Overlying Water of Paddy Field

[Objective]The research aimed to investigate the bioturbation effects of benthic fish Misgurnus anguillicaudatus on phosphorus dynamic in overlying water of paddy field,as well as to explore the bioturbation mechanism.[Method]Based on simulation experiment,the phosphorus contents in overlying water were analyzed comparatively with and without Misgurnus anguillicaudatus by the using of ion chromatography and spectrophotometry.[Result]The concentrations of total phosphorus(TP),dissolved total phosphorus(DTP)and particular phosphorus(PP)in bioturbation group had no significant differences with those in control group in initial stage of experiment,and became significantly higher than control group in middle and late stages of experiment(P<0.05). The PP/TP ratios in bioturbation group were bigger than those in control group,the increase of TP concentration in bioturbation group was mainly due to the increase of PP. The ratios of dissolved inorganic phosphorus(DIP) to DTP (DIP/DTP) were significantly bigger than those in control group in middle and late stages of experiment(P<0.05).[Conclusion]The benthic fish had bioturbation effects on phosphorus in overlying water of paddy field,which increased the available phosphorus for rice growth.

Real-time Monitoring Scheme of Soil Moisture Content in Paddy Field

The monitoring of soil moisture content in paddy field is one of important parts and contents of regional soil moisture monitoring. But a good monitoring scheme hasn’t been established. A real-time monitoring scheme of soil moisture content in paddy field was put forward from two key links of soil moisture content monitoring and field water-layer monitoring. This scheme could meet the alternative monitoring requirements of soil moisture content in water layer and none-water layer. It had a good maneuverability and could provide references for practical work.

Changes in Soil C and N Contents and Mineralization Across a Cultivation Chronosequence of Paddy Fields in Subtropical China

Dynamics of soil organic matter in a cultivation chronosequence of paddy fields were studied in subtropical China.Mineralization of soil organic matter was determined by measuring CO2 evolution from soil during 20 days of laboratoryincubation. In the first 30 years of cultivation, soil organic C and N contents increased rapidly. After 30 years, 0-10 cmsoil contained 19.6 g kg-1 organic C and 1.62 g kg-1 total N, with the corresponding values of 18.1 g kg-1 and 1.50g kg-1 for 10-20 cm, and then remained stable even after 80 years of rice cultivation. During 20 days incubation themineralization rates of organic C and N in surface soil (0-10 cm) ranged from 2.2% to 3.3% and from 2.8% to 6.7%,respectively, of organic C and total N contents. Biologically active C size generally increased with increasing soil organicC and N contents. Soil dissolved organic C decreased after cultivation of wasteland to 10 years paddy field and thenincreased. Soil microbial biomass C increased with number of years under cultivation, while soil microbial biomass Nincreased during the first 30 years of cultivation and then stabilized. After 30 years of cultivation surface soil (0-10 cm)contained 332.8 mg kg-1 of microbial biomass C and 23.85 mg kg-1 of microbial biomass N, which were 111% and 47%higher than those in soil cultivated for 3 years. It was suggested that surface soil with 30 years of rice cultivation insubtropical China would have attained a steady state of organic C content, being about 19 g kg-1.

A GIS-Based Database Management Package for Fertilizer Recommendations in Paddy Fields

Over-use of fertilizer in paddy fields could lead to agro-environmental pollution. Therefore, the Paddy Fertilizer Recommendation System (PFRS) application package was designed to aid in the dissemination of fertilizer recommendations for paddy fields. PFRS utilized geographical information system (GIS) ActiveX Controls, enabling the user to select a location of interest linked to a spatial database of paddy field soil characteristics. The application package also incorporated different soil fertilizer recommendation methods, forming a relational database. The application's structure consisted primarily of building database queries using Standard Query Language (SQL) constructed during run-time, based on user provided spatial parameters of a selected location, the type of soil desired and paddy production criteria. PFRS, which was comprised of five modules including: File, View, Edit, Layer and Fertilizer/Model, provided the user with map-based fertilizer recommendations based on selected soil nutrient P and K map layers as well as N characteristics and land use maps.

Changes in Soil Properties of Paddy Fields Across a Cultivation Chronosequence in Subtropical China

Rice production plays a crucial role in the food supply of China and a better understanding of the changes in paddy soil fertility and the management effects is of practical importance for increasing rice productivity. In this study, field sampling in a typical red soil region of subtropical China, Jiangxi Province, was used to observe changes in the soil physical, chemical, and biological properties in a cultivation chronosequence of paddy fields. After cultivation, clay (< 0.002 mm) content in the soil…

Response of CH_4 emission of paddy fields to land management practices at a microcosmic cultivation scale in China

The terrestrial ecosystem may be either a source or a sink of CH_4 in rice paddies, depending, to a great extent, on the change of ecosystem types and land use patterns. CH_4 emission fluxes from paddy fields under 4 cultivation patterns (conventional plain culture of rice(T1), no-tillage and ridge culture of rice(T2), no-tillage and ridge culture of rice and wheat (T3), and rice-wheat rotation(T4)) were measured with the closed chamber technique in 1996 and 1998 in Chongqing, China. The results showed that differences existed in CH_4 emission from paddy fields under these land management practices. In 1996 and 1998, CH_4 emission was 71 48% and 78 82%(T2), 65 93% and 57 18%(T3), and 61 53% and 34 22%(T4) of that in T1 during the rice growing season. During the non-rice growing season, CH_4 emission from rice fields was 76 23% in T2 and 38 69% in T1 The accumulated annual CH_4 emission in T2, T3 and T4 in 1996 decreased by 33 53%, 63 30% and 65 73%, respectively, as compared with that in T1 In 1998, the accumulated annual CH_4 emission in T1, T2, T3 and T4 was 116 96 g/m^2, 68 44 g/m^2, 19 70 g/m^2 and 11 80 g/m^2, respectively. Changes in soil physical and chemical properties, in thermal and moisture conditions in the soil and in rice plant growth induced by different land use patterns were the dominant causes for the difference in CH_4 emission observed. The relative contribution of various influencing factors to CH_4 emission from paddy fields differed significantly under different land use patterns. However, the general trend was that chlorophyll content in rice leaves, air temperature and temperature at the 5 cm soil layer play a major role in CH_4 emission from paddy fields and the effects of illumination, relative humidity and water layer depth in the paddy field and CH_4 concentration in the crop canopy were relatively non-significant. Such conservative land use patterns as no-tillage and ridge culture of rice with or without rotation with wheat are thought to be beneficial to reducing CH_4 emission from paddy fields and are, therefore, recommended as a significant solution to the problems of global(climatic) change.

Pollen and Phytolith Analyses of Ancient Paddy Fields at Chuodun Site, the Yangtze River Delta

A number of paddy fields pertaining to the Majiabang Cultures (5500-3800 years BC) were discovered during the archaeological excavations that were carried out since 1998 at the Chuodun site in the Yangtze River Delta. The pollen and phytolith analyses of two soil profiles from the northeastern part of this site were carried out to trace the agricultural practices of the Neolithic period. The phytolith results showed that rice domestication in the Yangtze River Delta could be traced back to as early as the Majiabang Culture. The pollen assemblage also revealed low levels of aquatic species, similar to that in modern paddy fields. This finding suggested that humans might have removed weeds for rice cultivation during the Neolithic period. Thus, pollen analysis in association with phytolith analysis was a promising method for identifying ancient paddy fields.

Effects of nitrogen application rate and hill density on rice yield and nitrogen utilization in sodic saline–alkaline paddy fields

Soil salinity and alkalinity can inhibit crop growth and reduce yield,and this has become a global environmental concern.Combined changes in nitrogen (N) application and hill density can improve rice yields in sodic saline–alkaline paddy fields and protect the environment.We investigated the interactive effects of N application rate and hill density on rice yield and N accumulation,translocation and utilization in two field experiments during 2018 and 2019 in sodic saline–alkaline paddy fields.Five N application rates (0 (control),90,120,150,and 180 kg N ha^(-1) (N0–N4),respectively) and three hill densities(achieved by altering the distance between hills,in rows spaced 30 cm apart:16.5 cm (D1),13.3 cm (D2) and 10 cm (D3))were utilized in a split-plot design with three replicates.Nitrogen application rate and hill density significantly affected grain yield.The mathematical model of quadratic saturated D-optimal design showed that with an N application rate in the range of 0–180 kg N ha^(-1),the highest yield was obtained at 142.61 kg N ha^(-1) which matched with a planting density of 33.3×10^(4) ha^(-1).Higher grain yield was mainly attributed to the increase in panicles m^(–2).Nitrogen application rate and hill density significantly affected N accumulation in the aboveground parts of rice plants and showed a highly significant positive correlation with grain yield at maturity.From full heading to maturity,the average N loss rate of the aboveground parts of rice plants in N4 was 70.21% higher than that of N3.This is one of the reasons why the yield of N4 treatment is lower than that of the N3 treatment.Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha^(-1)) were 81.68 and 106.07% higher in 2018 and 2019,respectively,than those in the control.The N translocation and N translocation contribution rates increased with the increase in the N application rate and hill density,whereas N productivity of dry matter and grain first increased and then decreased with the increase in N application rate and hill density.Agronomic N-use efficiency decreased with an increase in N application rate,whereas hill density did not significantly affect it.Nitrogen productivity of dry matter and grain,and agronomic N-use efficiency,were negatively correlated with grain yield.Thus,rice yield in sodic saline–alkaline paddy fields can be improved by combined changes in the N application rate and hill density to promote aboveground N accumulation.Our study provides novel evidence regarding optimal N application rates and hill densities for sodic saline–alkaline rice paddies.

Effects of cracks and some key factors on emissions of nitrous oxide in paddy fields

Paddy field is a primary agricultural landscape in the south of China and is often regarded as one of main sources emitting nitrous oxide to atmosphere. The nitrous oxide emissions under a variety of paddy field practices, such as fertilization, flooding/draining management were investigated to study on agricultural activities on paddy field affect the dynamic process of the emission. Under no addition of fertilizers the average emission flux of nitrous oxide was 8 55 μg/(m 2·h) during the rice( Oryza Sativa L.) growth season. The results indicated that most of nitrous oxide emissions occurred during the crack forming and expansion period when paddy field was being drained. The diurnal emissions peak of nitrous oxide appeared at 20∶30 at night in cracked rice fields. The statistical analysis suggested that the correlation of nitrous oxide emissions flux( Y ) with soil water content( X 1), soil temperature( X 2), and E h( X 3), could be described in a regression equation: Y =-1498 95+2895 48 X 1+50 63 X 2-96 99 X 1· X 2+0 006 X 2· X 3 There were the different power equations to simulate the correlations between the everyday dynamic N 2O emissions and the mean surface area of cracks, mean volume and depth of cracks respectively during paddy soil drying by soil columns incubation experiments. Taken all together, the current study presented a dynamic analysis of nitrous oxide emission of paddy field under various conditions, therefore provided a basis for the management to balance between environmental effect and paddy field activities.

Nitrogen and phosphorus changes and optimal drainage time of flooded paddy field based on environmental factors

While many controlled irrigation and drainage techniques have been adopted in China, the environmental effects of these techniques require further investigation. This study was conducted to examine the changes of nitrogen and phosphorus of a flooded paddy water system after fertilizer application and at each growth stage so as to obtain the optimal drainage time at each growth stage. Four treatments with different water level management methods at each growth stage were conducted under the condition of ten-day continuous flooding. Results show that the ammonia nitrogen （ NH4-N ） concentration reached the peak value once the fertilizer was applied, and then decreased to a relatively low level seven to ten days later, and that the nitrate nitrogen （NO^-N） concentration gradually rose to its peak value, which appeared later in subsurface water than in surface water. Continuous flooding could effectively reduce the concentrations of NH^-N , NO3-N, and total phosphorus （TP） in surface water. However, the paddy water disturbance, in the process of soil surface adsorption and nitrification, caused NH]-N to be released and increased the concentrations of NH4-N and NO^-N in surface water. A multi-objective controlled drainage model based on environmental factors was established in order to obtain the optimal drainage time at each growth stage and better guide the drainage practices of farmers. The optimal times for surface drainage are the fourth, sixth, fifth, and sixth days after flooding at the tillering, jointing-booting, heading-flowering, and milking stages, respectively.

Mapping the fallowed area of paddy fields on Sanjiang Plain of Northeast China to assist water security assessments

Rice growth requires a large amount of water,and planting rice will increase the contradiction between supply and demand of water resources.Paddy field fllowing is important for the sustainable development of an agricultural region,but it remains a great challenge to accurately and quickly monitor the extent and area of fallowed paddy fields.Paddy fields have unique physical features associated with paddy rice during the flooding and transplanting phases.By comparing the differences in phenology before and after paddy field fllowing,we proposed a phenology-based fallowed paddy field mapping algorithm.We used the Google Earth Engine(GEE)cloud computing platform and Landsat 8 images to extract the fllowed paddy field area on Sanjiang Plain of China in 2018.The results indicated that the Landsat8,GEE,and phenology-based fllowed paddy field mapping algorithm can effectively support the mapping of fallowed paddy fields on Sanjiang Plain of China.Based on remote sensing monitoring,the total fallowed paddy field area of Sanjiang Plain is 91543 ha.The resultant fallowed paddy field map is of high accuracy,with a producer(user)accuracy of 83%(81%),based on validation using ground-truth samples.The Landsat-based map also exhibits high consistency with the agricultural statistical data.We estimated that paddy field fallowing reduced irigation water by 384-521 million cubic meters on Sanjiang Plain in 2018.The research results can support subsidization grants for fallowed paddy fields,the evaluation of fallowed paddy field effects and improvement in subsequent fallowed paddy field policy in the future.

Dry deposition of ammonia around paddy fields in the subtropical hilly area in southern China

This study measured the ammonia(NH3)concentration and dry deposition within 100 m around paddy fields(0.6 ha)with double rice cropping in the subtropical hilly area in southern China,with the aims to quantify the dry deposition of NH3 around the emission source and to clarify its temporal and spatial variability.The results showed that high NH3 concentrations were found during the 15 d after nitrogen(N)fertilizer application at downwind sites within 100maround the paddy fields,and the NH3 concentrations were 12–62,2.8–7.3,13–38,and 4.9–36μg N m−3 during the 15 d after basal fertilizer application and topdressing in the early rice season and after basal fertilizer application and topdressing in the late rice season,respectively.The NH3 concentrations were relatively low(1.5–-3.8μg N m−3)during other periods of the rice season at the downwind sites,which indicated that N fertilizer application in paddy fields highly affected the NH3 concentration at downwind sites.The NH3 concentrations at the downwind sites decreased significantly with the increase in distance from the paddy fields.The total NH3 dry deposition around 100 m of the paddy fields accounted for approximately 79%and 81%of the emitted NH3 from the paddy fields in the early and late rice seasons,respectively.The results indicate that dry deposition of NH3 around emission sources may be an important way to remove the NH3 volatilized from croplands in this subtropical hilly area.

Effects of Organic Manure Applications on Methane and Nitrous Oxide Emissions in Paddy Fields

This study was carried out in paddy fields to explore how organic manure applications would affect greenhouse emissions in South China. The results showed that the seasonal emission of CH4 under the chemical fertilizer （CF） treatment was 271.47 kg/hm^2. In comparison, the seasonal emissions of CH4 under the treatment of pig manure （PM）, chicken manure （CM） and rice straw （RS） increased by 50.61,260.22 and 602.82 kg/hm^2, respectively. N2O emission under the CF treatment was 1.22 kg/hm^2, while the N20 seasonal emissions under tile PM, CM and RS treatment decreased by 23.6% （P〈0.05）, 31.7% （P〈0.05） and 30.9% （P〈0.05）, respectively. Meanwhile, the readily oxidized organic carbon （which was oxidized by 167 mmol/L potassium permanganate, ROC167） of manure, paddy soil Eh value and temperature could also affect the CH4 emissions. The average yield of the organic fertilizer treatments increased by 6.8% compared with that of the CF treatment. Among all the organic fertilizer treatments, the PM treatment offered the lowest global warming potential and greenhouse gas intensity, in which the PM was of no significant difference from NF （no fertilizing） and CF. Therefore, the pig manure is capable of coordinating the relationship between environment and yield, and it also has a low ROC167 content, so the PM is considered worthy of recommendation.

Nitrogen and Phosphorus Loss Law and Emission Reduction Effects Under Water and Fertilizer Management Integrated Mode in Dike Paddy Field

To achieve the purpose of reducing farm non-point source pollution, we integrated site specific nitrogen management precise irrigation, controlled drainage, and wetland eco-repair system in dike area of Taihu basin. During investigation, it had given prominence for the water and fertilizer coupling effects of precise irrigation and site specific nutrient management, the characteristics of integration on controlled irrigation, controlled drainage and wetland ecosystem non-point source pollution control. Then the water and fertilizer integrated management mode of paddy field was put forward in Taihu basin where the water production efficiency increased to 1.64 kg. m-3, water saved 37.8%, fertilizer use efficiency raised 15,4%, yield raised 10%, and N, P load decreased 26%-72%. The modern agricultural and farmland ecosystems that control and cut down the farm non-point source pollution came into being, which can be a reference by Taihu basin to control its agricultural non-point source pollution and eutrophicated water body.

Effects of Paddy Field Rotation on Diseases,Pests and Weeds of Rice

[ Objective] The paper was to explore ecological effect of paddy field rotation on reducing disease, pests and weeds of rice. [ Method] With long-term continuous cropping rice as control, according to field location experiments for consecutive 14 years, the effects of paddy field rotation on diseases, pests and weeds of rice were studied in details. [ Result] Paddy field rotation in some extent could reduce diseases, pests and weeds of rice. The diseased plant rate and disease in- dex of rice sheath blight in early rice under paddy field rotation treatment were averagely 10% and 0.4% lower than those in continuous cropping treatment, respec- tively. The diseased plant rate and disease index of rice sheath blight in late rice were 17.7% and 13.3% lower than those in treatments with continuous cropping mode, respectively. The diseased plant rate and disease index of rice false smut in both early rice and late rice under rotation treatments were lower than those in treatments with continuous cropping mode. White leaf rate caused by rice leaf roller and dry heart rate caused by striped rice borer under rotation treatments were significantly lower than those under continuous cropping treatment. The growth status of weeds under rotation treatments was weaker than that under continuous cropping treatment. [ Conclusion] The paper has important significance on alleviating diseases, pests and weeds of rice and improvement of ecological environment of farmland, and provides theoretical basis for sustainable development of agriculture.

Modeling the fate of paddy field pesticide in surface water and environmental risk assessment

The risk of drinking water is greatly concerned because of the large amount of pesticide applied to paddy field and the contamination of drinking water sources due to the runoff. A mathematical model is developed, based on the mass balance, to predict the fate of paddy field pesticides from application, runoff and mixing in a river, taking account of the physical chemical properties and processes of volatilization, degradation, adsorption and desorption. The model is applied to a river basin in Japan to estimate the contaminant level of several popularly used pesticides at the water intakes. The health risk in drinking water induced by each pesticide concerned is estimated and evaluated by comparing with the acceptable daily intake values(ADI) and with that induced by trihalomethanes. An index to evaluate the total risk of all pesticides appearing in water is proposed. The methods for risk management are also discussed.

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.