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1.
The present study deals with the effects of addition of sulfur along with other acidifying agents for their ability to lower and maintain the pH in a given range for a longer period of time. The chemicals were subjected to batch test individually and in combinations. Treatments were applied to three soils of different textures: sandy clay loam, clay loam, and silt loam. A 1:1 soil/water paste along with the added amendment was maintained at room temperature for 2 months. Most of the chemical treatments lowered the pH significantly. Combinations containing S/Al2(SO4)3/H2SO4, S/Al2(SO4)3/H2O2, and S/H2O2/H2SO4 were found to be very effective in lowering the pH. The soil pH remained acidic for 2 months, indicating the suitability of chemically amended soil for the plantations requiring acidic soil pH.  相似文献   

2.
To date our knowledge is limited with regard to the cycling of ethylene (C2H4) in temperate forest soils containing volcanic ash, and the effect of forest‐to‐orchard conversion on its cycling. We studied ethylene accumulation in such forest soils by oxic and anoxic incubations, along with the stimulatory effect of glucose addition on soil C2H4 accumulation. We also studied the effect of antibiotics and autoclaving on C2H4 production and consumption by volcanic forest soils, and the cycling of C2H4 and CH4 in surface soils after conversion of a Japanese cedar forest to an orchard. Ethylene production and consumption by forest surface soils results from a microbial process, and soil streptomycin‐sensitive bacteria make a minor contribution. Soil C2H4 accumulation was much larger during anoxic than during oxic incubation, which indicates that anoxic conditions can induce C2H4 accumulation in forest soils. Glucose addition as a carbon source can sharply increase C2H4 accumulation rates in the anoxic and oxic forest soils during the first week of incubation. However, there was no difference in total C2H4 accumulation in the amended and non‐treated soils after 35 days of anoxic incubation. Ethylene production of the 0–5 cm and 5–10 cm soils beneath forest and orchard showed the greatest rate after 2 weeks of anoxic incubation when soil CH4 production started to increase sharply, and later it was strongly suppressed. The forest‐to‐orchard conversion showed little influence on the CH4 production of surface soils during short‐term anoxic incubation, but significantly reduced soil C2H4 production. The conversion also significantly decreased the consumption of soil CH4 and C2H4, the former more than the latter. Soil properties such as total C, water‐soluble organic C and pH contribute to the consumption and production of C2H4 in the 0–5 cm and 5–10 cm soils, and there are the parallels between CH4 and C2H4 consumption in soils, which suggests the presence of similar microorganisms. Long‐term anoxic conditions of in situ surface upland soils are normally not prevalent, so it can be reasonably concluded that there is a larger C2H4 accumulation rather than CH4 accumulation in surface soils beneath forest and orchard after heavy rainfall, especially beneath forest.  相似文献   

3.
Abstract

A new soil extractant (H3A) with the ability to extract NH4, NO3, and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (H3A) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1 M KCl and water‐extractable NH4 and NO2/NO3. The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants×2 reps×32 soils=320 samples) and was shown to be highly influential on extractable P but has no effect on extractable NH4 or NO2/NO3. H3A was highly correlated with soil‐extractable inorganic N (NH4, NO2/NO3) from both water (r=0.98) and 1 M KCl (r=0.97), as well as being significantly correlated with water (r=0.71), Mehlich 3 (r=0.83), and Olsen (r=0.84) for extractable P.  相似文献   

4.
According to the German soil classification, Reductosols (German: “Reduktosole”) are soils with a redoximorphic color pattern, but without water saturation for lengthy periods. They are formed by reducing conditions due to oxygen deficiency caused by the accumulation of reduct gases such as CH4, CO2, NH3, or H2S in the soil atmosphere. Soil oxygen may have been displaced by the ascent of CO2 from post‐volcanic mofettes or by CH4 from sanitary landfills. Furthermore, a lack of oxygen causing redoximorphism can occur in unsaturated soils if they contain or receive large quantities of easily decomposable organic matter (i.e., organic urban waste or sludge). Under such circumstances, a gleyic color pattern (e.g., an oxidized Bg horizon above a Cr horizon with strongly reducing conditions) forms without the influence of an aquic moisture regime. Waste‐water and petrol infiltration in soil can form a stagnic color pattern without the stagnation of surface water. Such more or less well‐drained but strongly redoximorphic horizons should be named as Yg instead of Bg. In some cases, such soils only exist for a short time due to the loss of reduct gases or termination of infiltration of organic liquids. Reductosols are ecotops with oxygen deficiency. Natural Reductosols dominate in recent and former volcanic areas, whereas Reductic Technosols are formed in urban‐industrial agglomerations. Their morphology, chemistry, dynamics, genesis, and ecology is summarized and discussed in this paper. Natural gas and CO2 gas are deposited in deeper zones of the earth crust since some time. Leakages of these depots let form reductosols as well.  相似文献   

5.
Theory and experimental results have shown that neutral salts in the precipitation or supplied to the ground by other means reduce the acidification of soils by acid precipitation. This salt effect is caused by the cation exchange occurring after the entry of the rain water into the soil.The acid components of precipitation consist of H2SO4, HNO3 and HCl and of NH4+ after nitrification in the soil. The magnitude of the salt effect depends on the relative bonding energy of H3O+ and of Ca2+, Mg2+, Na+, K+, NH4+ in the soil as well as on the concentrations of H3O+ and the above cations in the precipitation. The salt effect may be considerable in very acid soils. It decreases with rising pH to become very small or negligible in neutral soils, chiefly due to the increasing bonding energy of H3O+ in this direction.The adverse effect of acid precipitation, therefore, is likely to be less in very acid soils, such as podsols, than in slightly acid and neutral soils with low buffering capacity against pH change. Soil texture and calcite content are very important factors in this respect as fine material and calcite increase the buffering.  相似文献   

6.
Some physical (density, coefficient of filtration, particle-size composition, etc.) and chemical (contents of carbonates, organic carbon, nitrogen, etc.) properties of an alluvial calcareous soil were studied in Central Anatolia (Konya province, Çumra region). These heavy-textured (medium clay) soils with a low content of organic carbon (less than 1%) have favorable agrophysical properties due to the stable structure of the pore space. The studies of the water regime of soils under drop irrigation confirm the favorable hydrological properties of these soils. The use of the known agrophysical estimates (after Medvedev, the index of the optimal water regime, etc.) has revealed the high dispersal of the data related to the low humus content in these heavy-textured soils. The favorable structure of the pore space is suggested to be stipulated by the active activity of the numerous and diverse representatives of soil biota. Four phyla predominate in the microbio-logical composition of the soils studied; among them, Actinobacteria is the dominant. The composition of this phylum is dominated by the elevated number of both higher (Streptomyces) and lower (three species of Rhodococcus) actinobacteria. The high biodiversity of bacteria against the background of their great total number and the developed trophic interactions in the microbial community promote the well-balanced production of specific metabolites, including gaseous ones (CO2, H2). This circumstance allows this clayey soil to function rather actively while protecting the pore space against compaction and maintaining the optimal density, porosity, and hydrological properties.  相似文献   

7.
The importance of soil heterogeneity for methane emission from a wetland soil is assessed by in situ point measurements of depth-specific O2 and CH4 concentrations and simultaneous soil CH4 fluxes at contrasting water levels. Profile measurements, and associated assumptions in their interpretation, were validated in a controlled mesocosm drainage and saturation experiment applying planar O2 optodes and membrane inlet mass spectrometry. Results show that peat soil is heterogeneous containing dynamic macropore systems created by both macrofauna and flora, which facilitate preferential flow of water, O2 and CH4 and vary temporally with changes in the moisture regime. The O2 content above the water table after drainage varied horizontally from 0 to 100% air saturation within few mm. Oxic zones were observed below the water level and anoxic zones were observed in layers above the water level in periods up to days after changes in the water level. This study shows that although water table position is a competent proxy of soil CH4 fluxes at larger spatio-temporal scales, it becomes inadequate at higher spatial resolution, i.e. at the scale of the soil pedon and below. High resolution O2 measurements using planar O2 optodes have great potential to enhance our understanding of the effect of the water table position on O2 dynamics on scales of several cm to mm in wetland soils.  相似文献   

8.
Ethylene production was monitored in 12 desert soils. In all but two soils with high organic matter content, C2H4 production was low. Statistical analysis showed a good correlation between organic matter content and C2H4, production. Minimum levels of C2H4 were observed in saline and sodic soils.Addition of l-methionine to soil significantly increased C2H4 formation, indicating its possible role as a precursor for C2H4.Addition of salt to the high C2H4-producing soils suppressed C2H4 production most probably because of a direct effect on C2H4-producing microorganisms through toxic salt levels, high osmotic pressure, increased pH or a combination of these factors. Leaching of four saline soils and subsequent incubation resulted in significant increases in C2H4 in two soils. Ethylene producers, previously inhibited by salinity, were probably reactivated when the salts were removed.A Fusarium isolated from the high C2H4-producing soil, produced the most C2H4 in pure culture followed by isolates belonging to the genera Aspergillus, Penicillium, Curvularia and Rhizopus.A sterilized saline soil produced significant C2H4 when inoculated with spores of Mucor hiemalis or the Fusarium isolate, indicating an originally low population of C2H4-producing organisms in the saline soil. The two high organic matter soils when sterilized and similarly inoculated produced only a fraction of the C2H4 produced in non-sterilized samples, indicating the involvement of a number of species in the production of C2H4 in these soils.  相似文献   

9.
利用15N同位素标记方法,研究在两种水分条件即60％和90％ WHC下,添加硝酸盐(NH4NO3,N 300 mg kg-1)和亚硝酸盐(NaNO2,N 1 mg kg-1)对中亚热带天然森林土壤N2O和NO产生过程及途径的影响.结果表明,在含水量为60％ WHC的情况下,高氮输入显著抑制了N2O和NO的产生(p＜0.01);但当含水量增为90％ WHC后,实验9h内抑制N2O产生,之后转为促进.所有未灭菌处理在添加NO2-后高氮抑制均立即解除并大量产生N2O和NO,与对照成显著差异(p＜0.01),在60％ WHC条件下,这种情况维持时间较短(21 h),但如果含水量高(90％ WHC)这种情况会持续很长时间(2周以上),说明水分有效性的提高和外源NO2-在高氮抑制解除中起到重要作用.本实验中N2O主要来源于土壤反硝化过程,而且加入未标记NO2-后导致杂合的N2O(14N15NO)分子在实验21 h内迅速增加,表明这种森林土壤的反硝化过程可能主要是通过真菌的“共脱氮”来实现,其贡献率可多达80％以上.Spearman秩相关分析表明未灭菌土壤NO的产生速率与N2O产生速率成显著正相关性(p＜0.05),土壤含水量越低二者相关性越高.灭菌土壤添加NO2-能较未灭菌土壤产生更多的NO,但却几乎不产生N2O,表明酸性土壤的化学反硝化对NO的贡献要大于N2O.  相似文献   

10.
《Applied soil ecology》2011,48(3):184-194
Concerns about groundwater contamination as well as pesticide residues in food and soil have fuelled vigorous debates about the sustainability of chemical-intensive agriculture. Search has been prompted for agronomic strategies with lower environmental hazards. In this multidisciplinary study we compared the characteristics of soils from 20 agricultural farms selected in five geographical areas of Southern Italy with different soil types. In each farm, fields with management regime classified as high-input (HIMR, intensive cultivation under plastic tunnels) or low-input (LIMR, tree orchards) were selected. Soil samples were analyzed for 31 parameters including physical and chemical properties (bulk density, water holding capacity, texture, pH, limestone, electrical conductivity, organic C to a depth of 0–20 and 20–40 cm, total N, P2O5, Ca2+, Mg2+, K+, Na+, cation exchange capacity), enzymatic activities (dehydrogenase, arylsulphatase, β-glucosidase, phosphatase and urease) and microbiological features (potential respiration, functional diversity of microbial populations by BIOLOG EcoPlates™, microbial biomass, fungal mycelium, culturable actinomycetes, bacteria and fungi, pseudomonads and bacterial species richness by 16S rDNA-DGGE). Finally, a soil bioassay was performed in order to evaluate the plant growth of a biotest plant (Lactuca sativa) and soil suppressiveness of the Rhizoctonia solani–L. sativa pathosystem.Results showed that many soil properties were influenced by management regime more than by the sampling area. Compared to LIMR, HIMR soils consistently had reduced soil organic C (−24%), enzymatic activities, microbial biomass and fungal mycelium (−40% and −18%, respectively), functional diversity (−18%) and bacterial species richness (−14%). On the contrary, the same soils showed a remarkable increase in the values of the parameters related to the mineral soil fraction (electrical conductivity +370%; P2O5 +72%; Na+ +86%). Management regime did not affect cation exchange capacity, pH, limestone and soil texture. The lettuce bioassay showed a higher plant growth (+17%) in the LIMR compared to HIMR soils, despite the lower content of mineral nutrients. Suppression of R. solani was not influenced by management regime, but significant differences were recorded among farms. Differences among the assessed soil parameters indicate a trend of soil quality deterioration under the high-input management regime.  相似文献   

11.
Abstract

A laboratory study was conducted with large (20‐cm i.d., 110‐cm long PVC pipe) intact soil columns to determine the movement of fertilizer NO3 ‐ in poorly drained, conventionally tilled soil under simulated low (7.6 cm) and heavy (15.2 cm) rainfall. Soil in the columns was brought to near‐maximum water‐holding capacity (9 kPa) to simulate the typical field soil moisture regime during the spring. A constant‐level water table was imposed at the base of the column to further simulate field conditions of the Drummer silty clay loam (mixed, mesic, Typic Haplaquoll) soil used. Fertilizer was applied in solution at a rate equivalent to 168 kg N ha‐1 as 15N‐labeled KNO3. Water was then applied in three applications, spaced one wk apart. To minimize the movement of water along the soil‐pipe interface, a 3 mm‐wide band of air‐dried disturbed soil was packed around the core to ensure a seal along the interface. Recovery of fertilizer NO3 ‐‐N below the water table at the end of the 28‐d study was < 0.06% (0.1 kg N ha‐1) and 0.5% (0.9 kg N ha‐1) of that applied for the low and high treatments, respectively. Denitrification losses were negligible for both water treatments (≤ 1 kg N ha‐1). Fertilizer N distribution in the columns indicated significant movement of N beyond estimated water‐displacement depths, apparently caused by preferential flow. However, the majority of the N was restricted to the upper portions of the columns. The results indicate that preferential flow of water in poorly drained, conventionally tilled soils during high rainfall periods can lead to the movement of fertilizer N to shallow ground water, but that the amounts are apparently very small.  相似文献   

12.
 Soils are the dominant sink in the global budget of atmospheric H2, and can be an important local source of atmospheric CO. In order to understand which soil characteristics affect the rates of H2 consumption and CO production, we measured these activities in 16 different soils at 30% and 60% of their maximum water holding capacity (whc). The soils were obtained from forests, meadows and agricultural fields in Germany and exhibited different characteristics with respect to texture, pH, total C, substrate-induced respiration (SIR), respiration, total and inorganic N, N mineralization, nitrification, N2O production and NO turnover. The H2 consumption rate constants were generally lower at 60% than at 30% whc, whereas the CO production rates were not influenced by the whc. Spearman correlation analysis showed that H2 consumption correlated significantly (r>0.5, P<0.05) at both water contents only with SIR and potential nitrification. The correlation with these variables that are largely dominated by soil microorganisms is consistent with our understanding that atmospheric H2 is oxidized by soil hydrogenases. Multiple regression analysis and factor analysis gave similar results. Production of CO, on the other hand, was significantly correlated to soil total C, respiration, total N and NH4 +. The correlation with these variables that are largely dominated by a soil's chemical composition is consistent with our understanding that CO is produced by chemical oxidation of soil organic C. CO production was also influenced by soil usage, with rates increasing in the order: arable<meadow<forest. H2 consumption was not influenced by soil usage. Received: 28 October 1999  相似文献   

13.
Soil samples were collected from the upper soil horizon within 4 m of black locust ( Robinia pseudo-acacia) and tulip poplar trees ( Liriodendron tulipifera) from the same mixed forest in south-central Pennsylvania. The soil samples were analyzed for organic C levels, pH, NO3 -, NH4 +, catabolic diversity (Shannon diversity index; catabolic H), catabolic evenness (Simpson-Yule index; catabolic E), genetic H, and genetic E. The catabolic H and genetic H of microbes in these soils were found to correlate well with the levels of mineralized N, organic C, and pH. Significant variations in these parameters were found between the soils from near black locust and tulip poplar trees. Conditions in the soil near the black locust trees were more favorable to nitrification as indicated by the elevated pH, organic C, NO3 -, and total mineral N levels, along with lower NH4 + levels. The microbial genetic H and E were greater and the catabolic H and E were lower in the black locust soils than in the tulip poplar soils. This suggests that a more specialized environment exists in the soil near the black locust trees which selects for enhanced nitrification and the use of fewer, but preferred catabolic pathways by a more genetically diverse group of microbes that grow to a greater biomass. Conversely, the soils from near the tulip poplar trees are such that they do not select for some dominant catabolic pathways, rather they allow for the use of a greater variety of catabolic pathways by a less diverse microbial population, which appear to grow to a lower biomass. We believe that the combined application of the microbial genetic and catabolic diversity analyses, microbial biomass estimates, and traditional physico-chemical characteristics in soil studies provides information not easily available that can be useful during assessment of soil processes in different terrestrial habitats.  相似文献   

14.
Xu  R. K.  Ji  G. L. 《Water, air, and soil pollution》2001,129(1-4):33-43
The difference in effect on acidification and species of aluminum speciation between HNO3 and H2SO4for two contrasting types of soils in surface charge was investigated. The results show that the effect of H2SO4 on acidification of variable charge soils (Ferric Acrisol and Haplic Acrisol) of subtropical regions wasweaker than that of HNO3, due to the specific adsorption of SO4 2- and the accompanied release of OH-. For two constant charge soils, Haplic Luvisol andEutric Cambisol, the difference in effect between the two acids is small. The concentrations of total inorganic monomeric aluminum, Al3+, Al-F complexes and Al-SO4complexes in the extract from variable charge soils are alsolower in H2SO4 systems than those in HNO3 systems, whereas the reverse is true for constant charge soils, except the concentration of Al3+. For variable charge soils, Al-F complexes are the major species of inorganic monomeric aluminum at high pH butAl3+ might contribute to a largepart at low pH, while for constant charge soils Al-F complexes contribute almost exclusively to the inorganic monomeric aluminum. The presence of a large amount of SO4 2- in the extract from the constant charge soilsleads to a higher proportion of Al-SO4 complexes in totalinorganic monomeric aluminum than that from variable charge soil, although the numerical value of proportion is small.  相似文献   

15.
Soil amended with 1% glucose was treated with H2SO4, fuming H2SO4, HCl, H3PO4, HNO3, fuming HNO3 or with combinations of fuming and non-fuming H2SO4 and HNO3 to lower the bulk soil pH to values ranging from 5.0 to 2.0. There was a difference in the amount of toxicity caused by the different acids at the same bulk pH of soils. Acidification to pH 2.8 or 2.9 prolonged the lag phase of glucose degradation; fuming HNO3 had the greatest effect, and fuming H2SO4 was only slightly more toxic than non-fuming H2SO4. At pH 2.3–2.4, fuming HNO3, alone or in combination with H2SO4, inhibited CO2 evolution. Both fuming and non-fuming HNO3 also reduced the amount of C mineralized to a greater extent than did fuming and non-fuming H2SO4. The amounts of C mineralized from soils treated with combinations of H2SO4 and HNO3 were intermediate between those from soils treated with each of these acids alone. HCl and H3PO4 had a similar effect on prolonging the lag as did non-fuming H2SO4. H3PO4 was less toxic than the other acids and sometimes increased the total amount of C mineralized. The “anionic effect” of acid rain must, therefore, be considered in addition to the effect of the proton. When the soil was inoculated with a suspension of microbiologically-active soil, more C was mineralized, in general, and the inhibitory effects of acidification on C mineralization were less pronounced than in soil that had not been inoculated. The addition of montmorillonite, but not of kaolinite, enhanced the growth of Aspergillus niger in soils amended with 2:1 combinations of H2SO4 and fuming HNO3 however, growth was inhibited completely at pH 3.4.  相似文献   

16.
Formation and classification of humus-rich marshland soils of the Weser marshland, Germany The formation and classification of marshland soils are still controversial. To improve the knowledge on the formation of humus-rich marshland soils 11 soil profiles have been investigated. The soils mostly showed Phragmitis in the subsoil. The Gr-horizons began at low depths (40–60 cm). The clay content was often about 60% and the Corg content up to 480 g kg?1. The amount of total sulfur was up to 29.6 g kg?1, that of exchangeable sulfate up to 4608 mg kg?1 and that of sulfate in the saturation extract 51.2 mg l?1. With pH (H2O) values between 2.0 and 7.4, Carbonate/S ratios < 3 and total sulfur contents > 7.5 g kg?1 some soils showed “Actual Acid Sulfate Soil” (AASS) properties. The pH(per) values varied between 2.4 and 7.1, thus some profiles showed “Potential Acid Sulfate Soils” (PASS) properties. Brakish as well as marine environments with an intensive sulfur dynamics and carbonate leaching are likely within the geogenetic phase of soil development. Via the control of the water regime the pedogenetic phase is mainly of anthropogenic influence. We propose to classify humus-rich marshland soils into “Organomarsch” and “Thiomarsch” on the soil type level of the German systematics.  相似文献   

17.
Denitrification represents one of the main microbial processes producing the primary and secondary greenhouse gases nitrous oxide (N2O) and nitric oxide (NO) in soils. It is well established that abiotic factors like the soil water content and the availability of nitrogen (N) are key parameters determining the activity of denitrifiers in soils. However, soils differing regarding their characteristics such as the content of Corg, the soil texture or the pH value may respond in specific manners to equivalent changes in soil moisture and N input. Thus, short-term incubation experiments were performed to test and compare the capacity of two contrasting Austrian forest soils to respond to mineral N application at increased soil water contents. Soils from the pristine Rothwald forest (rich in Corg) and the more acidic Schottenwald forest (poor in Corg) were amended with either NH 4 + -N or NO 3 ? -N and were incubated at 40% and 70% water-filled pore space for 4 days. Changes in mineral N pools, nitrite reductase activity and NO and N2O emission rates were measured, and the abundance and structural community composition of the functional group involved in nitrite reduction were analysed via quantitative real-time polymerase chain reaction and terminal restriction fragment length polymorphism analysis of the nirK gene. Rapid and distinct activity responses to increased soil moisture and altered mineral nitrogen availability were observed in two contrasting forest soils. In both soils, nitrogen oxide emission rates were stimulated by N inputs and, depending on the soil moisture status, either NO or N2O emission was prevailing. However, different N cycling processes appeared to predominate in either soil under equivalent treatment. Nitrogen oxide emissions peaked following NO 3 ? application in Schottenwald soils but were the highest after NH 4 + application in Rothwald soils. Denitrifying (nirK) communities differed significantly in Rothwald and Schottenwald soils; however, changes in the community structure were marginal during the short-term incubation. Abundances of nirK genes remained unaffected by N application in either soil. The soil water content affected nirK gene abundances only in Rothwald soil, indicating a distinct reaction of nitrite reducing communities in the two soils.  相似文献   

18.
On the Determination of Capillary Conductivity at Unsteady-State Conditions . Therefore it is stated that for obtaining the effective ku-values. Considering the importance of capillary conductivity for the soil water regime the large differences up to 2 orders of magnitude between determinations on core samples from the same soil using the double-membrane-method (Henseler and Renger 1969) and the evaporation-method (Becher 1971a) initiated a study concerning the error caused by a possible nonlinearity of suction changes between two measuring levels using the latter method. The study was carried out on disturbed and undisturbed core samples from the three textural classes sand, silt and clay and with modified evaporation method. Comparing the geometric means of the obtained ku-values calculated at unsteady-state and quasisteady-state conditions for different suctions resulted in that with usual application of the method the measured ku-values must be diminished for obtaining the effective ku-values. This correction factor increased with suction and is considered to be more important in laboratory than in field use.
  • 1 For sandy soils a correction factor of 2 at 150 cmH2O increasing to 6 at 1000 cm H2O must be applied. The coarser the sand would be, at the lower suction nonlinearity will start and the more rapidly the correction factor will increase;.
  • 2 For silty soils a correction factor of 2–4 must be applied for suctions > 300 cm H2O;.
  • 3 For clayey soils a correction factor of 2 rapidly increasing to 10 must be applied for suctions > 150 cm H2O, but depending on soil cracks.
. The overestimation of water through-put resulting from the uncorrected ku-values amounts to 1.5–4.0 [l/m2 · d] at 100 cm H2O, but these values are within the variation of the effective ku-values. For 800cm H2O the overestimation amounts to 0.002–0.065 [l/m2 · d], but this makes up 300–1000 % of the effective water through-put.  相似文献   

19.
土壤氧化还原状况的空间分异和特征   总被引：3，自引：1，他引：3       下载免费PDF全文
  相似文献   

20.
Abstract

A measure of biologically available B (BAB) was obtained by assaying the amount of B removed from a small volume of soil by sunflowers grown until they displayed B deficiency symptoms. Four different mineral soils and one organic soil which had been treated in the field with variable lime and B applications 2 years prior to sampling were compared. The amount of B extracted with hot water from soils before cropping was well correlated with BAB. The B extracted by the more intensive hot water extraction methods was closely related to the absolute level of BAB. Digestion of soils with concentrated H3PO4 resulted in the dissolution of larger amounts of B than that extracted with hot water. The proportion of H3PO4 soluble B that was measured as BAB was quite variable. Thus H3PO4 was a less suitable extractant than hot water for assaying the amount of soil B available to plants during a short growing period. In no case was the difference between the B extracted from soils before and after cropping as large as the BAB values.  相似文献   

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