Effects of Soil Rhizosphere Aeration on the Root Growth and Water Absorption of Tomato

Soil rhizosphere aeration status is an important aspect of soil quality and soil ecology. The objective of the current study was to determine the appropriate moisture environment that facilitates rhizosphere soil aeration and ensures normal root respiration in tomato. In the potted experiment, five treatments of soil aeration were used (0.4, 0.8, 1.2, 1.6 ventilation volume of 50% porosity of soil, and no ventilation) under conditions of the different soil moisture upper limits. The effects of different rhizosphere soil aerations on the physiological indicators and water absorption of tomato were studied. Under the same soil moisture condition, plant growth and root vitality initially increased, and then decreased when the soil ventilation volume increased. The combination of soil moisture with 80% of field capacity and 0.8 ventilation volume with 50% soil porosity raised the chlorophyll content by 29.98% and the root vitality by 61.55%, as compared with the non‐ventilated treatment. Therefore, the appropriate volume of rhizosphere ventilation can effectively improve the capacity of water absorption in tomato. The result provides a new view about soil quality and soil ecology in terms of soil–root system.     

Improving Soil Enzyme Activities and Related Quality Properties of Reclaimed Soil by Applying Weathered Coal in Opencast‐Mining Areas of the Chinese Loess Plateau

There are many problems for the reclaimed soil in opencast‐mining areas of the Loess Plateau of China such as poor soil structure and extreme poverty in soil nutrients and so on. For the sake of finding a better way to improve soil quality, the current study was to apply the weathered coal for repairing soil media and investigate the physicochemical properties of the reclaimed soil and the changes in enzyme activities after planting Robinia pseucdoacacia. The results showed that the application of the weathered coal significantly improved the quality of soil aggregates, increased the content of water stable aggregates, and the organic matter, humus, and the cation exchange capacity of topsoil were significantly improved, but it did not have a significant effect on soil pH. Planting R. pseucdoacacia significantly enhanced the activities of soil catalase, urease, and invertase, but the application of the weathered coal inhibited the activity of catalase. Although the application of appropriate weathered coal was able to significantly increase urease activity, the activities of catalase, urease, or invertase had a close link with the soil profile levels and time. This study suggests that applying weathered coals could improve the physicochemical properties and soil enzyme activities of the reclaimed soil in opencast‐mining areas of the Loess Plateau of China and the optimum applied amount of the weathered coal for reclaimed soil remediation is about 27 000 kg hm^?2.     

Soil Microbial Abundances and Enzyme Activities in Different Rhizospheres in an Integrated Vertical Flow Constructed Wetland

Rhizosphere microorganism is an important bio‐component for wastewater treatment in constructed wetlands (CWs). Microbial abundance and enzyme activities in the rhizospheres of nine plant species were investigated in an integrated vertical‐flow CW. The abundance of denitrifiers, as well as urease, acid, and alkaline phosphatase activities were positively correlated to plant root biomass. The abundance of bacteria, fungi, actinomycetes, ammonifiers, denitrifiers, and phosphorus decomposers, related to nutrient removal efficiencies in CWs, greatly varied among rhizospheres of different plant species (p < 0.05). Significant differences in rhizosphere enzyme activity among plant species were also observed (p < 0.05), with the exception of catalase activity. The principal component analysis using the data of microbial abundance and enzyme activity showed that Miscanthus floridulus, Acorus calamus, and Reineckia carnea were candidates to be used in CWs to effectively remove nitrogen and phosphorus from wastewater.     

Plant Species Mediate Rhizosphere Microbial Activity and Biodegradation Dynamics in a Riparian Soil Treated with Bensulfuron‐methyl

A pot experiment was conducted to investigate microbial characteristics and the biodegradation process of bensulfuron‐methyl (BSM) in a rhizosphere soils planted with different riparian plants. The results showed that microbial population decreased with BSM addition in the rhizosphere, especially for bacteria and fungi. The activities of the dehydrogenase (DHase) were stimulated firstly, due to BSM addition, but then were inhibited, and recovered to the initial level, while the activities of the phosphatase and urease showed obviously decreasing trend throughout the whole experiment. Rhizosphere soil substrate‐induced respiration (SIR) was depressed by BSM, especially at the initial 14 days of incubation. Compared to Zizania aquatica and Phragmites australis, Acorus calamus showed a significantly (p < 0.05) higher DHase activity and larger SIR in the rhizosphere soils treated with BSM, which means that A. calamus can effectively alleviate inhibitory effect of the sulfonylurea herbicide addition on microbial activity. There were significant (p < 0.05) differences in microbial degradation dynamics of BSM in the rhizosphere soils among three kinds of riparian plants. A. calamus displayed a significantly (p < 0.05) higher degradation efficiency of BSM in the rhizosphere soils, followed by Z. aquatica and P. australis. The residual BSM concentration in A. calamus rhizosphere soil was 23.1 and 32.2% lower than that in Z. aquatica and P. australis rhizosphere soils, respectively, indicating a greater improvement effect on biodegradation of BSM in A. calamus rhizosphere soils.     

土地利用与覆被变化对巢湖湖滨带土壤有机碳组分及酶活性的影响

为了揭示湖滨带土地利用与覆被改变对土壤有机碳库及生态功能的影响,本文选取了巢湖湖滨带（北岸）9个典型样方,分析和比较了表层（0~30 cm）土壤有机碳组分特征以及相关酶的活性.结果表明,巢湖湖滨带不同采样点土壤总有机碳（TOC）含量变化范围为2.88~11.2 g/kg,平均含量为9.12 g/kg,其中原生芦苇（Phragmites australis）湿地土壤TOC含量最高（11.2 g/kg）,而芦苇群落消失后形成的荒滩土壤TOC含量最低,仅为2.88 g/kg.表征湖滨带湿地缓冲性能的土壤阳离子交换量（CEC）也以原生芦苇湿地土壤为最高,并与TOC含量呈现明显正相关.湖滨带表层土壤溶解性有机碳（DOC）和易氧化有机碳（EOC）含量变化范围分别为150~370 mg/kg和1.7~5.2 g/kg,其变化幅度明显高于TOC,其中DOC含量各采样点差异最为显著.除多酚氧化酶外,次生水柳林（Homonoia riparia Lour.）表层土壤几种酶的活性较原生芦苇湿地土壤皆有所上升,特别是蔗糖酶活性增加幅度最为明显.受人类活动干扰较大的湖滨绿地公园和人工草滩土壤过氧化氢酶、脲酶和蔗糖酶酶活性普遍显著低于原生芦苇湿地.除多酚氧化酶外,土壤中几种酶活性与土壤有机碳组分EOC和DOC含量均呈现显著的正相关,其中蔗糖酶活性与DOC含量之间相关系数最高（r=0.907）,其相关性均达到极显著水平.土壤溶解性有机碳和蔗糖酶可以作为表征因土地利用与覆被变化导致湖滨带湿地退化以及生态恢复效果的敏感性指标.     

Soil Microbial and Enzyme Activities Response to Pollution Near an Aluminium Smelter

The aim of this research was to assess the impact caused by a long‐term pollution by fluoride and heavy metals in two soils (PS1 and PS2) near an aluminium smelter in Slovakia, on soil microbial biomass C (MBC), basal respiration, metabolic quotient (qCO₂) water‐soluble organic C (WSOC) and enzymes activities involved in the C, N and P biogeochemical cycles. An unpolluted soil was used as control (C0). Results obtained for soil fluoride content reflected a gradient of fluoride exposure in topsoils of contaminated sites. Decreases in microbial and enzymatic activities and in MBC to organic C ratio were found in PS2 site, which is closer to the smelter and exhibited the highest fluoride content. PS1‐soil showed an extreme alkaline pH caused by leaching of waste effluents from the smelter dumping site, higher contents of Zn, Cu, Pb and Cd, significantly larger MBC, qCO₂ and catalase and urease activities, and much larger basal respiration and dehydrogenase activity than PS2 and C0‐soil. Phosphatase, β‐glucosidase and BAA‐protease were negatively correlated with WSOC, basal respiration and dehydrogenase activity, and showed some degree of inhibition in polluted sites. These results may indicate different responses of microbial communities to ecosystem disturbances, caused by the drastic changes in soil's physicochemical properties as result of the long‐term emissions of fly ash with high levels of contaminants that are still affecting soil microbial and enzymatic activities.     

A comparison of groundwater recharge estimation methods in a semi‐arid,coastal avocado and citrus orchard (Ventura County,California)

We assess the relative merits of application of the most commonly used field methods (soil‐water balance (SWB), chloride mass balance (CMB) and soil moisture monitoring (NP)) to determine recharge rates in micro‐irrigated and non‐irrigated areas of a semi‐arid coastal orchard located in a relatively complex geological environment. Application of the CMB method to estimate recharge rates was difficult owing to the unusually high, variable soil‐water chloride concentrations. In addition, contrary to that expected, the chloride concentration distribution at depths below the root zone in the non‐irrigated soil profiles was greater than that in the irrigated profiles. The CMB method severely underestimated recharge rates in the non‐irrigated areas when compared with the other methods, although the CMB method estimated recharge rates for the irrigated areas, that were similar to those from the other methods, ranging from 42 to 141 mm/year. The SWB method, constructed for a 15‐year period, provided insight into the recharge process being driven by winter rains rather than summer irrigation and indicated an average rate of 75 mm/year and 164 mm/year for the 1984 – 98 and 1996 – 98 periods, respectively. Assuming similar soil‐water holding capacity, these recharge rates applied to both irrigated and non‐irrigated areas. Use of the long period of record was important because it encompassed both drought and heavy rainfall years. Successful application of the SWB method, however, required considerable additional field measurements of orchard ET_c, soil‐water holding capacity and estimation of rainfall interception – runoff losses. Continuous soil moisture monitoring (NP) was necessary to identify both daily and seasonal seepage processes to corroborate the other recharge estimates. Measured recharge rates during the 1996 – 1998 period in both the orchards and non‐irrigated site averaged 180 mm/year. The pattern of soil profile drying during the summer irrigation season, followed by progressive wetting during the winter rainy season was observed in both irrigated and non‐irrigated soil profiles, confirming that groundwater recharge was rainfall driven and that micro‐irrigation did not ‘predispose’ the soil profile to excess rainfall recharge. The ability to make this recharge assessment, however, depended on making multiple field measurements associated with all three methods, suggesting that any one should not be used alone. Copyright © 2000 John Wiley & Sons, Ltd.     

Responses of canopy transpiration and canopy conductance of peach (Prunus persica) trees to alternate partial root zone drip irrigation

We investigated canopy transpiration and canopy conductance of peach trees under three irrigation patterns: fixed 1/2 partial root zone drip irrigation (FPRDI), alternate 1/2 partial root zone drip irrigation (APRDI) and full root zone drip irrigation (FDI). Canopy transpiration was measured using heat pulse sensors, and canopy conductance was calculated using the Jarvis model and the inversion of the Penman–Monteith equation. Results showed that the transpiration rate and canopy conductance in FPRDI and APRDI were smaller than those in FDI. More significantly, the total irrigation amount was greatly reduced, by 34·7% and 39·6%, respectively for APRDI and FPRDI in the PRDI (partial root zone drip irrigation) treatment period. The daily transpiration was linearly related to the reference evapotranspiration in the three treatments, but daily transpiration of FDI is more than that of APRDI and FPRDI under the same evaporation demand, suggesting a restriction of transpiration water loss in the APRDI and FPRDI trees. FDI needed a higher soil water content to carry the same amount of transpiration as the APRDI and FPRDI trees, suggesting the hydraulic conductance of roots of APRDI and FPRDI trees was enhanced, and the roots had a greater water uptake than in FDI when the average soil water content in the root zone was the same. By a comparison between the transpiration rates predicted by the Penman–Monteith equation and the measured canopy transpiration rates for 60 days during the experimental period, an excellent correlation along the 1:1 line was found for all the treatments (R² > 0·80), proving the reliability of the methodology. Copyright © 2005 John Wiley & Sons, Ltd.     

Amending Soils with Hydrogels Increases the Biomass of Nine Tree Species under Non‐water Stress Conditions

The classical aim of the application of super absorbent polyacrylate (SAPs) hydrogels is the prolonging of plant survival under water stress. Their effect on plant growth during non‐water stress conditions is not known. This study examined the root and shoot biomass of seedlings of nine tree species; Eucalyptus grandis, Eucalyptus citriodora, Pinus caribaea, Araucaria cunninghamii, Melia volkensii, Grevillea robusta, Azadirachta indica, Maesopsis eminii and Terminalia superba. The seedlings were potted in five soil types; sand, sandy loam, loam, silt loam and clay. These were amended at two hydrogel levels: 0.2 and 0.4% w/w and grown under controlled conditions in a green house. Root and shoot growth responses of the seedlings were determined by measuring the dry weight of the roots, stems, leaves and twigs. The addition of either 0.2 or 0.4% hydrogel to the five soil types resulted in a significant increase of the root dry weight (p < 0.001) in eight tree species compared to the controls after 8 wk of routine watering. Also, the dry weight of stems and leaves and twigs were significantly (p < 0.001) higher in the nine tree species potted in hydrogel amended soil types than in the hydrogel free controls. These results suggested that hydrogel amendment enhances the efficiency of water uptake and utilization of photosynthates of plants grown in soils which have water contents close to field capacity.     

Sedimentary Enzyme Kinetics of Land/Water Ecotones with Reed Domination

Land/water ecotones, the transitional boundary zone between terrestrial and aquatic ecosystems, can effectively trap and assimilate nutrients from external sources. The changes of nutrient cycling will cause a response in enzyme activity. In this paper, the enzyme kinetics of land/water ecotones in a shallow eutrophic wetland in China, dominated by a reed (Phragmites australis) community, are studied. The results indicate that land/water ecotones exhibit a strong filtration function and nutrient factor is an important feature affecting the distribution of enzymes in the transect of the littoral zone. The obvious spatial differences of enzyme activities and nutrients are present in the transect of the reed beds. The land area is the hot zone, where significant changes in enzyme activity occur. T‐test results show that the landward spot, 1 m away from the water‐land interface, is quite different from other spots, and the 1 m spot is the hot spot where great biochemical change happens. The principal component analysis of the environmental variables shows that nutrient factors have an important affect on enzyme distribution in the transect of the littoral zone. The nutrient factor explains about 54% of the observed variance. In particular, TOC (total organic carbon) correlates with the other five factors (TN; total nitrogen, TP; total phosphorus, phosphatase, β‐glucosidase, and urease) with correlative coefficients of 0.932, 0.595, 0.488, 0.433, and –0.468, respectively. The results indicate that TOC is a very important factor in Baiyangdian wetlands.     

Soil moisture variability of root zone profiles within SMEX02 remote sensing footprints

Remote sensing of soil moisture effectively provides soil moisture at a large scale, but does not explain highly heterogeneous soil moisture characteristics within remote sensing footprints. In this study, field scale spatio-temporal variability of root zone soil moisture was analyzed. During the Soil Moisture Experiment 2002 (SMEX02), daily soil moisture profiles (i.e., 0–6, 5–11, 15–21, and 25–31 cm) were measured in two fields in Walnut Creek watershed, Ames, Iowa, USA. Theta probe measurements of the volumetric soil moisture profile data were used to analyze statistical moments and time stability and to validate soil moisture predicted by a simple physical model simulation. For all depths, the coefficient of variation of soil moisture is well explained by the mean soil moisture using an exponential relationship. The simple model simulated very similar variability patterns as those observed.As soil depth increases, soil moisture distributions shift from skewed to normal patterns. At the surface depth, the soil moisture during dry down is log-normally distributed, while the soil moisture is normally distributed after rainfall. At all depths below the surface, the normal distribution captures the soil moisture variability for all conditions. Time stability analyses show that spatial patterns of sampling points are preserved for all depths and that time stability of surface measurements is a good indicator of subsurface time stability. The most time stable sampling sites estimate the field average root zone soil moisture value within ±2.1% volumetric soil moisture.     

洞庭湖湿地3种典型植物群落土壤酶活性特征

调查了洞庭湖湿地典型植物群落(短尖苔草(Carex brevicuspis)、南荻(Triarrhena sacchariflora)、辣蓼(Polygonumhy dropiper))洪水期前后(5、10月)两次表层土壤酶活性及土壤养分性状.结果表明:3种典型群落之间具有明显的土壤养分性状及土壤酶活差异.辣蓼群落具有相对较高的土壤有机质、全氮、全磷、速效磷含量,短尖苔草群落次之,而南荻群落的土壤养分含量最低.3种典型植物群落的土壤有机质、全氮、全磷含量均表现为5月高于10月,土壤速效磷、速效钾洪水期前后无显著差异.辣蓼群落的蔗糖酶活性明显高于其他2个群落;3个群落脲酶活性均表现为10月高于5月,南荻、辣蓼群落有显著差异.磷酸酶以南荻群落最高,短尖苔草群落5月显著高于10月,南荻群落则10月显著高于5月;短尖苔草、南荻群落过氧化氢酶活性显著高于辣蓼群落,短尖苔草群落5月与10月间有显著差异,其余2个群落无显著差异.相关分析表明:脲酶活性与土壤养分含量关系不密切;蔗糖酶活性与土壤有机质、全磷、全氮及速效磷素含量均呈显著正相关.总体上,洞庭湖典型湿地植物群落显示了较为明显的土壤理化状况以及土壤酶活差异;同时也显示了季节性差异.相对而言,辣蓼群落土壤具有较快的物质循环与转化代谢速率,对于氮、磷等污染物具有较高的转化作用,而短尖苔草、南荻群落低于辣蓼群落,这可能与二者较低的土壤有机质以及氮磷养分积累有关.     

Optimal intraseasonal irrigation water distribution

A dynamic programming model is presented to optimise the intraseasonal distribution of irrigation water to a single crop under the constraints of limited water available and predetermined irrigation timing. The system underlying the model is characterised by two discrete state variables: the available soil-water in the root zone and the net quantity of water to be transferred to the root zone of the crop. Transition equations from one state to another are used in response to irrigation decisions. A multiplicative yield function is employed for estimating the crop yield as it is influenced by soil moisture. A numerical example is presented to illustrate the proposed procedure.     

Uptake and Accumulation of Arsenic in Different Organs of Carrot Irrigated with As‐Rich Water

Irrigation with arsenic (As)‐rich water in agricultural soil may increase high levels of As in crops and cause food chain contamination. In this study, a greenhouse experiment was established using Spanish agricultural soil (Valladolid and Segovia provinces), that are extensively cultivated for carrot plant, to investigate the process of As uptake, bioaccumulation, and translocation of As from root to shoot and leaves in carrot plant. Arsenic concentrations in different organs of carrot plant, rhizosphere soil, and soil solutions were determined by hydride generation atomic absorption spectrometry (AAS). High concentrations of As in irrigation water, and the alkaline and sandy character of this soil enhanced As uptake in carrot plants indicating the potential health risk from consumption of carrots cultivated in these areas. Bioaccumulation of As into the leaves and roots increased with increase of As concentration in irrigation water. Both roots and leaves demonstrated a higher accumulation rate of As at an As concentration of 41 than 131 µg L^?1 in the soil solution. The ratios of As_root/As_leaves showed no statistically significant differences for the different irrigation treatments, and had an average value of 0.36 indicating the high magnitude of As translocation from roots to leaves in carrot plants. The leaves of carrots had a higher affinity for As than roots did. The correlation between As uptake by leaves or roots of carrots and the soluble As in rhizosphere soil did not demonstrate a linear or a plateau curve, indicating a slow but continuous constant As absorption which could be prolonged over time with high potential environmental risks.     

Analysis on the Seismic Response of Soil Slopes Based on the Multi-point Input Method

In general, the seismic response analysis in earthquake engineering assumes that the vibration parameters of the target and the contact surface of the external media are identical, i. e., single point input. However, earthquake energy has an attenuation phenomenon in wave propagation, so a wide range of soil slopes and the external medium contact surface of different input points on motion are not identical. If we consider single point input only, it may not correspond with reality, so it is necessary to carry out research on multi-point input methods. Based on the 2-D slope model, single-point input and multi-point input are performed respectively to analyze and compare their similarities and differences in the perspectives of the characteristics of seismic response of soil layer and plastic zone distribution to provide a reference for the seismic design of slopes. The results show that in the perspective of soil seismic response analysis, the peak acceleration output and peak velocity output under multi-point input are greater than the peak values under single point input at the same monitoring point, the peak appearing time is also earlier than that of the single point input; in terms of the plastic zone distribution, the multi-point effect is manifested as the presence of more obvious tensile shear failures; in the perspective of safety coefficient, the safety coefficient under each multi-point input is smaller than that of single point input, a difference of about 7% or so. In summary, multi-point input is more reasonable and practical than single point input, so multi-point input should be considered in seismic design.     

Soil saturation index of salt marshes subjected to spring‐neap tides: a new variable for describing marsh soil aeration condition

Organized spatial distribution of plants (plant zonation) in salt marshes has been linked to the soil aeration condition in the rhizosphere through simplistic tidal inundation parameters. Here, a soil saturation index (ratio of saturation period to tidal period at a soil depth) is introduced to describe the soil aeration condition. This new index captures the effects of not only the tidal inundation period and frequency but also the flow dynamics of groundwater in the marsh soil. One‐dimensional numerical models based on saturated flow with the Boussinesq approximations and a two‐dimensional variably saturated flow model were developed to explore the behaviour of this new soil aeration variable under the influence of spring‐neap tides. Simulations revealed two characteristic zones of soil aeration across the salt marsh: a relatively well aerated near‐creek zone and a poorly aerated interior zone. In the near‐creek zone, soils undergo periodic wetting and drying as the groundwater table fluctuates throughout the spring‐neap cycle. In the interior, the soil remains largely water saturated except for neap tide periods when limited drainage occurs. Although such a change of soil aeration condition has been observed in previous numerical simulations, the soil saturation index provides a clear delineation of the zones that are separated by an ‘inflexion point’ on the averaged index curve. The results show how the saturation index represents the effects of soil properties, tidal parameters and marsh platform elevation on marsh soil aeration. Simulations of these combined effects have not been possible with traditional tidal inundation parameters. The saturation index can be easily derived using relatively simple models based on five non‐dimensional variables. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of Visitor Activities on Surface Soil Environmental Conditions and Aboveground Herbaceous Biomass in Ayder Natural Park

The effects of visitor activities on surface soil environmental conditions and aboveground herbaceous biomass in Ayder Natural Park, Turkey, were investigated. Soil properties and aboveground herbaceous biomass were identified and characterized as heavily trafficked site (HTS), moderately trafficked sites (MTS) and control (non‐trafficked site) in grassland in a forest gap. Some soil properties were measured on 60 pits at 0–5 and 5–10 cm soil depths. The intensity of visitor activities had a negative impact on both surface soil properties and the aboveground herbaceous plant biomass and root mass in the study area in Ayder. The soil bulk density and soil penetration resistance increased from 0.94 to 1.47 g cm^–3 and 0.55 to 1.65 MPa, respectively, saturated hydraulic conductivity decreased from 77.98 to 8.85 mm h^–1, and soil organic matter decreased from 6.71 to 1.77% in moderately and heavily trafficked sites, respectively, at 0–5 cm soil depth. The soil properties were degraded at both the surface layer and the subsurface layer and the greatest degradation was measured in the heavily trafficked site followed by the moderately trafficked site. There was a strong negative linear relationship between soil degradation and aboveground herbaceous plant biomass, which decreased by 50.05 and 78.19% in moderately and heavily trafficked sites, respectively.     

A Screening Procedure for Heavy Metals in Soil Extracts by Alcohol Dehydrogenase and Urease Inhibition Eine Screening-Methode für Schwermetalle in Extrakten aus Bodenproben,basierend auf der Inhibierung der Enzyme Alkoholdehydrogenase und Urease

A screening method for heavy metals in aqueous extracts of soil is presented which is based on inhibition of the enzymes urease and alcohol dehydrogenase. The method is suitable to detect cupric and mercury ions in concentrations below 0.01 mg/L and several other heavy metal ions in 1000 fold higher concentration. It is shown that the test may be used for screening of mercury ion concentrations exceeding 0.03 mg/L in aqueous solution when copper chelators are added to the test system. The usefulness of the presented tests to detect heavy metals eluted from soil was verified with samples from ore mining waste. The concentration of copper, lead, and zinc eluted from these samples to different amount was determined by atomic absorption spectrometry and was in good agreement with the enzyme inhibition data obtained with these samples.     

Effective Photoinactivation of Alpha‐Amylase,Catalase and Urease at 222 nm Emitted by an KrCl‐Excimer Lamp

The inactivation of enzymes is of great interest for many industrial applications. The effectiveness of photoinactivation of alpha‐amylase, catalase, and urease with 222 nm radiation was investigated in comparison to that at 254 nm. The enzymes were irradiated with different fluence rates of 222 nm radiation emitted by a KrCl‐excimer lamp and with 254 nm radiation produced by a low‐pressure mercury lamp. The relative activities were calculated before and after irradiation. Degradation caused by UV‐radiation was assessed by SDS‐PAGE analysis. The results clearly demonstrated that inactivation of the proteins is much more effective with the 222 nm excimer lamp compared to the 254 nm mercury lamp. Irradiation with the excimer lamp and a UV‐fluence rate of 1000 J/m² was sufficient to reduce the relative activities of amylase and urease to 15% and that of catalase to 60%. After irradiation with 4000 J/m², the enzyme activity was almost completely inhibited. In contrast, after irradiation with the mercury lamp with an UV‐fluence rate of 4000 J/m², the relative activity was still above 85%. The gel patterns showed no visible degradation after irradiation at 254 nm, but a strong and unspecific degradation was obvious after treatment at 222 nm, presumably caused by cleavage of the peptide bonds.     

A Modified Soil Moisture Model for Two‐Layer Soil

There can be marked variations in soil hydraulic properties in a soil vertical profile from the soil surface to the base of the root zone. Many existing two‐layer soil moisture (TLSM) models cannot well describe typical stratified soil profiles. A modified TLSM model is presented in this study. The modified model results and those from two existing models are compared with field observations. The modified TLSM model had the best agreement with the field observations. In both the surface layer and the root zone layer, the root mean square errors of soil moisture estimated by the modified model were smaller than those for the other models. The parameters in the modified TLSM model are relatively easy to determine. The modified TLSM model offers clear advantages over current TLSM models.