Effect of combination of ultraviolet radiation and biocide on fungal-induced corrosion of high-strength 7075 aluminum alloy

The effect of ultraviolet(UV)radiation and biocide benzalkonium chloride(BKC)on fungal-induced corrosion of AA7075 induced by Aspergillus terreus(A.terreus)was deeply studied using analysis of biological activity,surface analysis,and electrochemical measurements.Results demonstrated that the planktonic and sessile spore concentrations decline by more than two orders of magnitude when UV radiation and BKC are combinedly used compared with the control.UV radiation can inhibit the biological activity of A.terreus and influence the stability of passive film of AA7075.Except for direct disinfection,the physical adsorption of BKC on the specimen can effectively inhibit the attachment of A.terreus.The combination of UV radiation and BKC can much more effectively inhibit the corrosion of AA,especially pitting corrosion,due to their synergistic effect.The combined application of UV radiation and BKC can be a good method to effectively inhibit fungal-induced corrosion.

Effects of Long-term Fertilization on Micro-morphological Features in Purple Soil

[Objective] The study aimed to better understand the effect of different fertilizer treatments on micro-morphological characteristics of a purple soil at the 0-20 cm topsoil in a long-term fertilizer experiment. [Method] Soil micro-morphology was observed and analyzed under a single polarizing microscope. [Result] For the CK （no fertilizer） treatment, soil structure was dense with little porosity developed. Its soil microstructure was poor, sandy fabric-granular fabric. After continuously applied chemical fertilizers only for more than two decades, the soil particles did not evolve into soil structures and formed little porosity. The microstructures of soil in N, NP and NPK treatments were porphyroskelic fabric-fine sandy granular fabric, better than that of the soil in CK treatment. Adding manure obviously improved the quantity of groundmass and endowed the soil a loose structure and plenty porosity, enriched animal and plant residues, and well-formed iron-manganese nodules and humus ma- terials, all resulting in better micro-aggregates development. The type of soil microstructures in MNPK treatment was pectized-compacted takyric fabric-intertextic fabric, the best among all the treatments. [Conclusion] Combined application of both or- ganic and inorganic fertilizers can significantly improve the structure of the purple soil, enhance soil fertility and achieve soil sustainable development.

Effects of Application of Controlled Release Nitrogen Fertilizer on N_2O Emission in Slope Cultivated Land with Purple Soil

In order to study effects of application of contmllE=d release fertilizer on ni- trous oxide （N2O） emission in slope cultivated land with purple soil, four treatments including the control group （CK）, urea （UR）, controlled release nitrogen fertilizer （CR）, and controlled release nitrogen fertilizer＋urea （25%CR, 75%UR） were set up, and their impacts on maize yield, surface runoff and nitrogen loss in the growth pe- riod of maize and N2O emission were studied. The results show that maize yield, surface runoff, nitrogen loss from subsurface flow, and N2O emission in the control group was far lower than that in the fertilization treatments, revealing that fertilization was the main reason for nitrogen loss and N2O emission. Among the four treat- ments, nitrogen loss from subsurface flow in the treatment CR was the highest, up to 31.7 kg/hm^2, but N2O emission was 0.35 kg/hm^2, which was 37% less than that in the treatment UR. Nitrogen loss from subsurface flow in the treatment 25% CR was the lowest, only 20.9 kg/hm^2, and N2O emission was 15% less than that in the treatment UR. Nitrogen was slowly released from controlled release nitrogen fertilizer in the growth period, and controlled release nitrogen fertilizer could reduce N2O emis- .sion from slope cultivated land due to low content of soil inorganic nitrogen, but it could increase the nitrogen loss from subsurface flow. Therefore, the combination of controlled release fertilizer and urea can not only reduce N2O emission but also de- crease nitrogen loss from subsurface flow.

Zonal Distribution of the Erosion-Landslide and Soil Micromorphological Features in Purple Hilly Region

In the purple hilly region, erosions and landslides are all serious, and it is of great scientific value and practical significance to study their formation mechanism and distribution features there. In this paper, soil micromorphological methods and techniques were used to study the erosion zonal distribution in the region. The results indicated: (1) According to erosion process, the spacial distribution zones of the erosions and landslides in the purple hilly region with different solums were divided into scouring erosion zone, transport-diffusion zone, rocks and soil turbulence zone and sediment-bury zone; (2) The soil micromorphologic taxonomic feature identifying different erosion-landslide zone were found by studying the soil micromorphology of erosive zone in purple hilly region; (3) As for the erosion–landslide formation in the region, besides the external factors, the internal factors were found more important and favorable for landslide formation through the studies on the micormorphological features of slide soil.

Distribution and Transformation of Native and Added Ni Fractions in Purple Soils from Sichuan Province

The distribution and transformation of added and native Ni in purple soils were investigated with both sequential extraction procedure and isotopic tracer technique.The distribution of added and native Ni was greatly dependent on soil properties.Low soil PH was favorable for soluble plus exchangeable (EX) Fraction,while Fe/Mn oxides and clay for Fe/Mn oxide bound (OX) and residual (RES) fractions. The added Ni,however,has not yet reached the distribution equilibrium up to the 150th day after incubation.This was reflected in the fact that the proportion of EX fraction from added Ni was 150%-600% as much as that of native Ni, while that of RES fraction was only about 80%.Once entering soil, the applied soluble Ni was rapidly transformed into Other fractions, but the organic complexed (OM) fraction of added Ni was relatively stable during incubation.The carbonate bound(CAB) fraction showed a progressive increase and attained a peak value after 0-14 d of incubation and thereafter decreased gradually. The occurrence time of this peak advanced as initial soil PH increased, but the peak would disappear when initial soil pH was higher than 7.5(or containing free CaCO3). The transformation processes of the EX,OX and RES fractions could be described by Elovich and two-constant rate equstions,and the rates were positively correlated with soil pH,CEC and clay.These findings could explain why there are differences in ecological and environmental effects of Ni in different soils and at various intervals.

Effects of Ploughing Astragalus sinicus at Maturity Stage on Rice Yield and Soil Properties of Paddy Field

[Objective] The effects of ploughing Astragalus sinicus at maturity stage as green manure on paddy soil properties were studied to provide references for ad- vancing the green manure production and field sustainable development. [Methods] A three-year field positioning experiment was carried out. In the first year, five differ- ent levels （0, 2.81, 5.61, 8.42, 11.23 t/hm~） of Astragalus sinicus ploughed at matu- rity stage were designed. And in the next two years, the amounts of ploughed As- tragalus sinicus at maturity stage were based on the natural growth amounts of As- tragalus sinicus at maturity stage of the former year in each plot field. The yields of Astragalus sinicus at maturity stage were estimated and ploughed directly before rice transplanting. Rice yield, soil nutrients, biological properties and water-stable aggre- gates of paddy fields were measured as well. [Results] The effective panicles and rice yields increased significantly after ploughing Astragalus sinicus at maturity stage. Meanwhile, the organic acid content in paddy field increased and the activities of soil phosphatases, invertase and catalase were higher. The soil dissolved organic carbon also increased with the increasing application of green manure. However, excess amount of green manure inhibited the soil microbial biomass carbon content. The macro aggregates and micro aggregates gathered to middle aggregates. [Conclusion] As green manure, the use of Astragalus sinicus at maturity stage could improve soil physiochemical and biological properties, improve soil fertility and increase rice yield significantly. But the ploughing amount of Astragalus sinicus at maturity stage before rice transplanting should be less than 8.42 t/hm2 （dry weight.

Kinetics of Nitrogen and Potassium Uptake by Various Rice Cultivars at Different Nitrogen Levels from Purple Soil

A pot experiment was conducted to study the effect of nitrogen fertilizer on nitrogen and potassium uptake by four rice cultivars. Results showed that the quadatic parabola relationship between biomass of rice and nitrogen levels was observed, with the maximum biomass at the nitrogen level of 150 mg kg-1.The rates of nitrogen and potassium uptake by the four rice cultivars depended on growth stage and rice cultivar with the maximum rate of N in Shanyou-63 and maximum rate of K in Kaiyou-5 (hybrid rice),respedively. The kinetics of nitrogen and potasssium uptake by rice plant could be quantitstively described by the following equations: y = a + blogt, y = ab + t1/2 and y = ae-bt. The b value in the equations was correlated significantly to the rates of nitrogen and potassium uptake (NR and KR, r=0.901**～0.990**),suggesting that the b value could be used to distinguish the index of nitrogen and potassium uptake capacity of rice. The maximum values of nitrogen uptake by plant (b value) and apparent recovery of fertilizer nitrogen were observed in Shanyou-63, and the minimum value in Eryou-6078. However, the capacity of potassium uptake (b value) by Kaiyou-5 ranked first and that by Shanyou-63 second. There was a significant linear relationship between nitrogen level and nitrogen uptake by rice, but a quadratic parabola relationship was found between nitrogen level and patassium uptake by rice. The application of nitrogen fertilizer decreased the ratios of potassium to nitrogen uptake by rice plant. The greatest reduction in the ratio was observed at high nitrogen level, and the least reduction was found in Kaiyou-5 and Shanyou-63 due to their greater ability to absorb potassium.

Effects of slope gradient on runoff from bare-fallow purple soil in China under natural rainfall conditions

Purple soil is highly susceptible for overland flow and surface erosion, therefore understanding surface runoff and soil erosion processes in the purple soil region are important to mitigate flooding and erosion hazards. Slope angle is an important parameter that affects the magnitude of runoff and thus surface erosion in hilly landscapes or bare land area. However, the effect of slope on runoff generation remains unclear in many different soils including Chinese purple soil. The aim of this study was to investigate the relationship between different slope gradients and surface runoff for bare-fallow purple soil, using 5 m × 1.5 m experimental plots under natural rainfall conditions. Four experimental plots(10°, 16°, 20° and 26°) were established in theYanting Agro-ecological Experimental Station of Chinese Academy of Science in central Sichuan Basin. The plot was equipped with water storage tank to monitor water level change. Field monitoring from July 1 to October 31, 2012 observed 42 rainfall events which produced surface runoff from the experimental plots. These water level changes were converted to runoff. The representative eight rainfall events were selected for further analysis, the relationship between slope and runoff coefficient were determined using ANOVA, F-test, and z-score analysis. The results indicated a strong correlation between rainfall and runoff in cumulative amount basis. The mean value of the measured runoff coefficient for four experimental plots was around 0.1. However, no statistically significant relationship was found between slope and runoff coefficient. We reviewed the relationship between slope and runoff in many previous studiesand calculated z-score to compare with our experimental results. The results of z-score analysis indicated that both positive and negative effects of slope on runoff coefficient were obtained, however a moderate gradient(16°-20° in this study) could be a threshold of runoff generation for many different soils including the Chinese purple soil.

Spatial and Temporal Patterns of Soil Nitrogen Distribution under Different Land Uses in a Watershed in the Hilly Area of Purple Soil,China

Quantification of soil spatial and temporal variability at watershed scale is important in ecological modeling, precision agriculture, and natural resources management. The spatio-temporal variations of soil nitrogen under different land uses in a small watershed （12.10 km^2） in the hilly area of purple soil at the upper reaches of the Yangtze River in southwestern China were investigated by using conventional statistics, geostatistics, and a geographical information system in order to provide information for land management and control of environmental issues. A total of 552 soil samples （o to 15 cm） from 276 sites within the watershed were collected in April and August of 2o11, and analyzed for soil total nitrogen （STN） and nitrate nitrogen （NO3-N）. We compared spatial variations of STN and NO3-N under different land uses as well as the temporal variations in April （dry season） and August （rainy season）. Results showed that STN contents were deeply affected by land-use types; median STN values ranged from 0.94to 1.27g.kg-I, and STN contents decreased in the following order： paddy field 〉 foresfland 〉 sloping cropland. No significant difference was found for STN contents between April and August under the same land use. However, NO3- N contents were 23.26, 10.58, and 26.19 mg·kg^-1 in April, and 1.34, 8.51, and 3.00 mg·kg^-1 in August for the paddy field, sloping cropland and forestland, respectively. Nugget ratios for STN indicatedmoderate spatial dependence in the paddy field and sloping cropland, and a strong spatial dependence in forestland. The processes of nitrogen movement, transformation, absorption of plant were deeply influenced by land use types; as a result, great changes of soil nitrogen levels at spatial and temporal scales were demonstrated in the studied watershed.

Nutrient Balance in Relation to High Yield and Good Quality of Potato on an Acid Purple Soil in Chongqing,China

A field experiment was carried out to study nutrient balance among N, P, K and Mg in potato cultivation on an acid purple soil in Chongqing, China. The experiment included 8 treatments with equal P rate of 120 kg P2O5 hm-2: N0K2, N1K2, N2K2, N3K2, N2K0, N2K1, N2K1Mg and N2K3, where N0, N1, N2 and N3 stand for the N rates of 0, 75, 150 and 225 kg N hm-2, and K0, K1, K2 and K3 for the K rates of 0, 165, 330 and 495 kg K2O hm-2, respectively. Among the treatments designed, Thatment N2K2 with a nutrient supply ratio of N:P2O5:K2O:MgO = 1.25:1:2.75:0.28 gave the highest tuber yield and dry matter, highest starch and Zn and lowest NO3- contents in tuber, and high N, P and K use efficiency with an uptake ratio of N:P:K:Mg = 11.38:1:13.32:0.33 by tuber. Yield and starch and protein contents of tuber were the lowest in Treatment N0K2. Dry matter was the lowest but protein and NO3- contents were the highest in Treatment N2K0. Treatment N2K1Mg had the highest N, P and K utilization rates. Statistical analysis showed that yields of tuber and starch were in a positive linear correlation with the uptake amount of various nutrients and protein of the potato tuber was in a significantly positive linear correlation with tuber N cotent and in a significantly negative linear correlation with tuber K and Mg contents. Balanced application of N, P, K and Mg fertilizers (Treatmeat N2K2) was recommended for realization of high yield and good quality in potato cultivation.

The Effects of Land Uses on Purplish Soil Erosion in Hilly Area of Sichuan Province,China

In order to evaluate the soil erosion rate for different land uses and make recommendations on land-use alternatives for erosion control in hilly and mountain areas on a Purplish soil (Regosols in FAO taxonomy), experimental data were obtained from three continuously monitored sites located at Yanting, Nanbu and Pengxi of Sichuan province. The data showed that the rank of erosion rate is farmland > unfenced grassland > fenced grassland > forestland. The erosion rate of farmland was more than 3 times higher than that of forestland and fenced grassland, indicating that restricting human activity is crucial for over-erosion. The erodibility was higher at the initial period of rainy season for all the three types of land use. The erosion rates of fenced grassland and mature afforestation land were not proportional to rainfall intensity because these land uses changed impact energy of the rainfall. This research showed that restricting human activity, intensifying the management of initial period of rainy season, and increasing the cover rate of land surface are the three major measures for soil erosion prevention. It is recommended that farmers should cease cultivation on farmland at the top of hills and steep slope land return those lands back to grassland or forestland.

Alleviation of Copper Toxicity to Maize by Phosphorus Fertilizer in Purple Soil

A pot experiment was conducted to evaluate the effects of phosphorus fertilizer in inhibiting the copper toxicity to maize(Zea mays L.) in neutral purple soil. Results indicated that the growth of the shoot and roots of maize plant was obviously reduced by copper and the height and biomass were significantly negatively correlated to the application levels of copper (r=-0.899**^-0.994**) at no P and low P (100 mg kg-1).However, the maize biomass was relatively increased and the high Cu (100 and 200 mg kg-1) induced toxicity of maize was greatly alleviated in all treatments with medium P (300 mg kg-1) and high P (500 mg kg-1).To maintain the normal growth of maize plant (≥3.68 g pot-1), the critical application rates of phosphorus fertilizer should be 160, 210, 300 and 500 mg P kg-1 at 10, 50, 100 and 200 mg Cu kg-1 levels of the soil,respectively. The increases in polyphenol oxidase and catalase activities in maize leaf and dehydrogenase activity in roots by phosphorus fertilizer were in the order of medium p>high p>low p>no P. Activities of polyphenol oxidase and catalase were significantly positively correlated to the application levels of copper (r=0.892**~0.924**), whereas that of dehydrogenase was just reverse (r=-0.966**) at no P. Medium and high P repressed the influence of copper on activities of three enzymes. Phosphorus fertilizer reduced the copper concentrations of maize roots and leaf and the change ranges of the P/Cu ratio of maize roots and the P/Cu, N/Cu and K/Cu ratios of maize leaf. The three ratios of maize leaf were 256±71.5, 2643±839 and 1133±440 at normal growth of maize plant, respectively. Soil available Cu could be markedly cut down by application of phosphorus fertilizer, especiallly at high phosphorus level.

Tillage Pedogenesis of Purple Soils in Southwestern China

Land cultivation and tillage process, and their consequent impacts on soil erosion, have been criticized as the main cause of degradation of land or soil quality. However, purple soils, classified as Regosols in FAO Taxonomy or Entisols in USDA Taxonomy, are formed from purple rocks of the Trias- Cretaceous system, have been developed or at least accelerated the development due to continual tillage operation, especially digging and ridging. The present study took micromorphological investigation on the sedimentary rocks and the soils under different operations of tillage. Results show that the purple rock of Feixiangguan Formation of the Trias system （Tlf） is the easiest to physical weathering and the most fertile soil material enriched in nutrients, and it has been, therefore, mostly cultivated and intensively tilled around the year. It has the fastest soil formation rate. Soil formation rate in the cropland with conventional tillage is higher than that in the forestiand and the grassland. It implies that the artificial brokenness and tillage disturbance play a great role in physical weathering and initiating soil formation processes.

Rainfall and Tillage Impacts on Soil Erosion of Sloping Cropland with Subtropical Monsoon Climate- A Case Study in Hilly Purple Soil area, China

Under global warming, storm events tend to intensify, particularly in monsoon-affected regions. As an important agricultural area in China, the purple soil region in the Sichuan Basin, where it has a prevailing monsoon climate, is threatened by serious soil erosion. Tillage operations alter runoff and soil erosion processes on croplands by changing the physical properties of the soil surface. To clarify the relationship between tillage and soil erosion in the purple soil region, three different tillage practices in this region were investigated at the plot scale over 4 years： bare land with minimum tillage （BL）, conventional tillage （CT） and seasonal no-tillage ridges （SNTR） which was initially designed to prevent soil erosion by contoured ridges and no-tillage techniques. The results showed that although there were no significant differences in the surface runoff and soil erosion among the three oractices, BL caused relatively high surface runoff and soil erosion, followed by CT and SNTR. Classification and comparison of the rainfall events based on cluster analysis （CA） verified that the surface runoff was not significantly different between most intensive event and long intensive events but was significantly different between most intensive and short and medium-duration events. Only the rainfall events with the highest rainfall intensity could trigger serious soil erosion, up to 1000 kg ha^-1 in the region. Further detailed investigations on the effects of tillage operations on the soil erosion in a subtropical region with a monsoon climate are needed to provide a basis for modeling catchments and designing better management practices.

Assessment of the Performance of WEPP in Purple Soil Area with Simulated Rainfall Experiments

The water erosion prediction project （WEPP） model is a popular water erosion prediction tool developed on the basis of the physical processes of water erosion. Although WEPP has been widely used around the world, its application in China is still insufficient. In this study, the performance of WEPP used to estimate the runoff and soil loss on purple soil （Calcaric Regosols in FAO taxonomy） sloping cropland was assessed with the data from runoff plots under simulated rainfall conditions. Based on measured soil properties, runoff and erosion parameters, namely effective hydraulic conductivity, inter-rill erodibility, rill erodibility, and critical shear stress were determined to be 2.68 mm h-1, 5.54 x l0^6 kg s-1 m-4, 0.027 s m-1 and 3-5 Pa, respectively, by using the recommended equations in the WEPP user manual. The simulated results were not good due to the low Nash efficiency of 0.41 for runoff and negative Nash efficiency for soil loss. After the four parameters were calibrated, WEPP performed better for soil loss prediction with a Nash efficiency of 0.76. The different results indicated that the equations recommended by WEPP to calculate parameters such as erodiblity and critical shear stress are not suitable for the purple soil areas, Sichuan Province, China. Although the predicted results can be accepted by optimizing the runoff and erosion parameters, more research related to the determination of erodibility and critical sheer stress must be conducted to improve the application of WEPP in the purple soil areas.

Assessment of Soil Erosion by Compensatory Hoeing Tillage in a Purple Soil

This study explores the role of a traditional tillage method,i.e.,compensatory hoeing,for sustainable agro-ecosystem management in the hilly areas of the Chongqing municipality,south-western China.To validate the effects of compensatory tillage on the terraced slopes,the tillage method of noncompensatory hoeing was conducted on a linear slope.To acquire information about 137 Cs inventories and soil texture,soil samples were collected by a core sampler with a 6.8-cm diameter at 5.0-m intervals along the toposequence and the linear slope in the dry season(March) of 2007.Meanwhile,a tillage erosion model was used for evaluating the spatial pattern of tillage erosion.The 137 Cs data showed that on the terraced slope,soil was lost from the upper slope,and soil deposition occurred at the toe slope positions on each terrace.As a result,abrupt changes in the 137 Cs inventories of soil were found over short distances between two sides of terrace boundaries.Results obtained from the tillage erosion model and the 137 Cs data indicate that soil redistribution mainly results from tillage erosion in the terraced landscape.Consecutive non-compensatory tillage caused soil redistribution on the linear slope,resulting in thin soil profile disappearing at the top and soil accumulating at the bottom positions of the linear slope.This result further validates that compensatory tillage could avoid the complete erosion of the thin soil layer at the summit position.Therefore,this traditional tillage.method,i.e.,compensatory tillage,has maintained the soil quality at the summit of the slope in the past decades.

Characteristics of Organo－Mineral Complexing of Microaggregates in Paddy Soils Developed from Purple Soils

This paper deals with characteristics of organo-mineral complexing of microaggregates in the paddy soils developed from purple soils in Sichuan, China. Results show that the contents of organic matter in microaggregates are in the order of 1--0.25 mm > smaller than 0.05 mm > 0.05-0.25 mm. But the organic matter in 1-0.01 mm microaggregates accounts for 68.1%-78.7% of that in soil. The organic matter in<0.05 mm microaggregates is complexed humus on the whole, of which the degree of organo-mineral complexing varies between 96.1% and 99.5%, which is higher than that of the soil or>0.05 mm microaggregates. The contents of loosely combined humus and the ratios of loosely and tightly combined humus markedly decline with the size of microaggregates. Fresh soil humus formed from semi-decomposed organic material or organic manure added is combined first with<0.001 mm clay, and then aggregated with other organic and mineral particles to form larger microaggregates, in which the aging of humus happens at the same time; whereas organic matter of the light fraction is mainly involved in the formation of>0.05 mm microaggregates.

Observation and modeling on irregular purple soil water infiltration process

The infiltration process is a critical link between surface water and groundwater. In this research, a specific device to observe infiltration processes in homogeneous and heterogeneous soils with triangular and inverted triangular profiles was designed, and the Green-Ampt model was employed for the process simulation. The results indicate that(1) the wetting front in coarse texture soils transports faster than in fine texture soils;(2) for the homogeneous case, the wetting front in triangularshaped soils transports faster than the inverted triangular type, but the triangular-shaped soils show a lower infiltration rate;(3) in the initial step, the wetting front in triangular-shaped soils shows higher transport speed, but depicts lower speed with increase in the time;(4) both the wetting front and infiltration rate show a significant exponential relation with the time. From these findings, an empirical model was developed which agrees well with the observed data and provides a useful method for this field of soil research.

A Quantification of the Effects of Erosion on the Productivity of Purple Soils

Research on the effects of soil erosion on soil productivity has attracted increasing attention.Purple soil is one of the main soil types in China and plays an important role in the national economy.However,the relationship between erosion and the productivity of purple soils has not been well studied.The purpose of this research was to determine if soil depth,which is dependent on the rate of erosion,has an influence on crop yield and growth.Plot and pot experiments at different soil depths were performed.Results indicate that soils from different parental materials had different growth features and crop yields due to the differential fertility of the derived soils.The yield reduction rate increases exponentially with the depth of eroded soil(level of erosion).The yield reduction rate per unit eroded soil horizon(10 cm) is approximately 10.5% for maize and wheat.