ISSN:0044-3263    

DOI:10.1002/jpln.19941570302

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractIn a synoptic way the development of soil structure and its effects on processes in soils are treated, referring on more recent results of investigations in Germany. It is outlined that development of structure is an absolutely primary part of soil development which basically consists of the phenomena of loosening‐versus‐compaction and heterogenisation‐versus‐homogenisation. The process of aggregation is described together with its abiotic and biotic mechanisms and its consequences for the pore system and the processes which are influenced by it. A number of examples is given for the wide variety of mechanisms, chemisms and biologic processes which are influenced by soil structure and its

ISSN:0044-3263    

DOI:10.1002/jpln.19941570303

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractLaboratory and field measurements as well as deterministic simulation models were used to determine the water components of loess derived soils with different expositions and slopes in the hilly region South of Hannover, Germany.Studies were investigated from 1987‐1990 on three positions of a loess slope with 8 % inclination, 200 m length and northern exposition. Crop rotation was sugar beet, winter wheat, sugar beet.Results show that the soil water budget is strongly related to slope position, relief and plant available water in the rootzone. It was found that drainage at the bottom of a slope is often higher than on top of the slope. On slopes with northern exposition groundwater recharge increases with inclination whereas actual evapotranspiration decreases. For slopes with southern exposition the opposite reaction can be expected. The thickness of loess deposits and the root depth determine the plant available water; a sensitivity study demonstrates how groundwater recharge decreases with the amount of plant available water. This reaction is independent of the exposition of the slope. Field and simulation studies show that runoff occurs under sugar beet whenever soil is bare or sparsely covered, rainfall intensity is high and topsoil is sealed. Moreover, in loess derived soils interflow may occur on sites with stagnic horizons. Sensitivity analyses show that this process probably takes place whenever saturated hydraulic conductivity of this horizon is less than 10cm/

ISSN:0044-3263    

DOI:10.1002/jpln.19941570304

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractNon destructive spectroscopic methods such as13C‐ and15N‐NMR provide new insights into the structure of humic substances. Solid state NMR is capable of studying complete native soils by the CPMAS‐technique. By means of nitrogen 15‐enriched composts it is suggested that nitrogen in soil organic matter is mainly located in amide and peptide structures. Most probable assignments are given.The investigation of humification processes in forest soils is possible via an approach which uses several fractionation techniques in combination with degradative and non‐degradative analytical techniques.Besides structure analysis, the13C‐NMR‐spectroscopy provides important information about the functions of humic substances. By using13C‐enriched xenobiotics the binding mechanism to organic matter can be elucidated on a molecular basis.Molecular fluorescence spectrometry, a non‐invasive method, is a powerful tool for the quantitative characterization of metal ion complexation by dissolved organic matter in aqueous leaf litter extracts in terms of conditional stability constants and metal b

ISSN:0044-3263    

DOI:10.1002/jpln.19941570305

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractFor the development of management strategies in sustainable agriculture it is necessary to describe and predict the role of soil microbes in different management systems. The classical approach uses the microbial biomass as the key parameter for the entire system, but for ecological purposes the variability of biotic parameters in time and space has to be better described. Moreover, the biomass active in the total soil profile or its most active zones should be used as a basis for the assessment of soil activity. The sum of adenylates was found to be more closely related to the microbial biomass than was ATP, which however appeared to be a better indicator for the microbial activity. Fatty acids from phospholipids were highly correlated with the soil microbial biomass. The pattern of fatty acids from soils under different long‐term management indicated a high potential to typify the microbial community in soils and special organism populations. To overcome the problem, that only a small portion of the soil inhabiting microbes can be cultivated, first steps to use serological and genetical methods to directly identify or localize specific populations in the rhizosphere are show

ISSN:0044-3263    

DOI:10.1002/jpln.19941570306

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractAn overview of the available knowledge of long‐term impacts of different tillage systems on the soil is given. Various studies, carried out in Germany, show that with the transition from conventional (CT) to reduced (RT) and no‐tillage (NT) no reduction in yields is to be expected. Both the concentration and the amount of organic matter in the top soil is increased. However, in the transitional phase nitrogen is accumulated. The biological activity increases as well.The higher compaction has a positive effect on the water holding capacity. On the other hand, the aeration is reduced as well as the thermal conductivity. More stable pore systems cause, on the whole, a higher infiltration capacity and a reduction in erosion. The factors of influence are developed to a different extent, depending on soil texture and clim

ISSN:0044-3263    

DOI:10.1002/jpln.19941570307

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractUrban areas are expanding rapidly. Therefore the interest in soil science activities on urban and industrial sites grows. The paper gives an overview of the research and mapping activities in Germany. A model of soils in urban ecosystems shows the relationships of development of soils and soil quality to land use. The water regime of soils is influenced by the characteristics of urban landscape and sealing. Of special interest are the typical substrates. Some properties of soils which develop on tipped substrates of natural material are discussed. Of importance are technological substrates as rubble, ash, slag, waste material and sludges in urban environments. Proposals of classification of urban and industrial soils are presented. For proper use by the municipal authorities availability and application of information on urban soils must be a part of research.

ISSN:0044-3263    

DOI:10.1002/jpln.19941570308

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractGenetic variation in nutrient efficiency may be attributed to two multifactorial components: (i) genotypes may differ in the efficiency with which the nutrients in the plant are utilized to produce yield (utilization efficiency) and/or (ii) they may differ in their effectiveness in absorbing nutrients from the soil (uptake efficiency).This contribution surveys major aspects of physiological and morphological factors affecting N‐and P‐efficiency. The potential importance of the various factors is discussed and exemplified mainly by own experimental w

ISSN:0044-3263    

DOI:10.1002/jpln.19941570309

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractPhosphorus uptake is often enhanced by ammonium compared to nitrate nitrogen nutrition of plants. A decrease of pH at the soil‐root interface is generally assumed as the cause. However, an alteration of root growth and the mobilization of P by processes other than net release of protons induced by the source of nitrogen may also be considered. To study these alternatives a pot experiment was conducted with maize using a fossil Oxisol high in Fe/Al‐P with low soil solution P concentration. Three levels of phosphate (0, 50, 200 mg P kg−1) in combination with either ammonium or nitrate nitrogen (100 mg N kg−1) were applied. Plants were harvested 7 and 21 d after sowing, P uptake measured and root and shoot growth determined. To assess the importance of factors involved in the P transfer from soil into plants, calculations were made using a model ofBarberandClaassen.In the treatments with no and low P supply NH4‐N compared to NO3‐N nutrition increased the growth of the plants by 25 % and their shoot P content by 38 % while their root growth increased by 6 % only. The rhizosphere pH decreased in the NH4‐N treatments by 0.1 to 0.6 units as compared to the bulk soil while in the NO3‐N treatments it increased by 0.1 to 0.5 units. These pH changes had a minor influence on P uptake only, as was demonstrated by artificially altering the soil pH to 4.7 and 6.3 respectively. At the same rhizosphere pH, however, P influx was doubled by the application of NH4‐compared to NO3‐N. It is concluded that in this soil the enhancement of P uptake of maize plants after ammonium application cannot be attributed to the acidification of the rhizosphere but to effects mobilizing soil phosphate or increasing P uptake efficiency of roots. Model calculation showed that these effects accounted for 53 % of the P influx per unit root length in the NO3‐N and 72 % in the NH4‐N supplied plants if no P was applied. With high P application the respective figur

ISSN:0044-3263    

DOI:10.1002/jpln.19941570310

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe cultivation of symbiotic legumes and the consequent small uptake of nitrate by the host plant depresses soil pH and impairs subsequent legume growth. The rate of soil pH decline depends on the soil H+buffer power, climatic conditions, soil permeability, and on the kind of legume cropping.It is shown for some leguminous crop species from the temperate climate that in many cases the N2fixation performance of Rhizobium/Bradyrhizobium symbiosis is more dependent on the growth conditions of the host plant than on the nitrogenase potential of the bacteroid. This is true for the supply of the host plant with phosphate, potassium and water as well as for light intensity. Nitrogen deficiency of the host plant because of insufficient nitrogenase activity was observed at low soil pH where nodulation and the development of the nitrogenase activity were delayed. Nodulation and nitrogenase activity are suppressed by high levels of available nitrogen in the soil. There are indications that the nitrogenase activity is very flexible and adjusts to the demand of the host plant. The mechanism of this regulation is not yet understood.

ISSN:0044-3263    

DOI:10.1002/jpln.19941570311

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY