黄土丘陵区深层干化土壤中节水型修剪枣树生长及耗水

黄土丘陵区人工林地深层土壤干层是否影响后续植物的生长是众多学者关心的热点。该文在砍伐23 a生旱作山地苹果园地后休闲4 a又栽植枣树,连续3 a观测干化土壤中枣树的生长及土壤水分变化,研究采用节水型修剪的再植枣林的生长及耗水情况。结果表明,前期23 a生苹果园地已使0~1 000 cm深土壤干化,休闲4 a后0~300 cm土层水分得到恢复,300~500 cm范围为中度偏重亏缺,500~700 cm为中度亏缺,700~1 000 cm为轻度亏缺;3龄枣树时开始采取节水型修剪,0~300 cm土层有效水分被消耗34.97%,至4龄时0~300 cm范围内前期恢复的土壤水分已消耗殆尽;在此情况下采取节水型修剪的枣树仍可保持良好生长,产量及其水分利用效率均高于相同水分条件下的常规修剪枣树,产量可达正常水分条件下枣树的1.39倍以上,产量水分利用效率可达1.52倍以上。研究结果证明节水型修剪是半干旱区深层干化土壤中枣树克服雨量不足和土壤水分亏缺的一条有效途径。     

Umsetzung von Cyanamid,Harnstoff und Ammonsulfat in Abhängigkeit von Temperatur und Bodenfeuchtigkeit

Transformation of cyanamide, urea and ammonium sulfate as influenced by temperature and moisture of soil The conversion of cyanamide, urea and ammonium sulfate solutions to nitrate was investigated in a sandy silt loam (pH 6.2) in relation to temperature and soil moisture conditions. 1. Cyanamide was transformed to urea within 1–5 days. Increasing temperature (2°–100°C) accelerated the breakdown, whereas high moisture conditions (120 % of total water capacity) decreased transformation. 2. The hydrolysis of urea to ammonia took place within 5–10 days even at 2°C regardless of whether cyanamide or urea was added. Low soil moisture (40 % of total water capacity) and high temperature (up to 50°) accelerated the breakdown. 3. Following urea application (20 mg N) there was a transient formation of up to five times more nitrite (0.5 mg NO₂-N) as compared with cyanamide or ammonium sulfate treatments. 4. Clear differences were observed in the rates of nitrification. The rate was greater for urea than for cyanamide and ammonium sulfate. The formation of nitrate began at 2°C, with an optimum between 20° and 30°C. Under flooded conditions (120 % of total water capacity) and low temperature the rate of nitrification was slow. At higher temperatures rapid denitrification took place.     

Seasonal growth and composition and accumulation of N‐P‐K in dryland and irrigated pumpkins

Growth and N‐P‐K uptake in pumpkin (Curcubita moschata Poir.) cv ‘Libby‐Select’ were studied in dryland and irrigated culture. In both moisture regimes, maximum rates of dry matter accumulation occurred between the early and mid‐fruiting developmental stages. Higher total dry matter production with irrigated than dryland culture was primarily associated with increased shoot growth. Concentrations of N, P, and K in foliage generally decreased as pumpkin age increased. Irrigated pumpkins in conjunction with higher total vegetative dry matter accumulated more N, P, and K than dryland pumpkins. Up through early fruit development, N, P, and K accumulation was primarily in leaves and vines and by the late growth stages was almost entirely in the fruit. Total N, P, and K uptake at late fruiting was estimated at 219, 32, and 228 kg/ha in irrigated pumpkins and 180, 21, and 177 kg/ha in dryland pumpkins. Approximately 58% of the N, 52% of the K, and 68% of the P accumulated by late‐fruiting was absorbed by the plant after the early‐fruiting stage in both moisture regimes. Potassium redistribution from vegetative tissues during late fruit development decreased foliar K contents 32% in dryland pumpkins and 21% in irrigated pumpkins.     

Einflüsse von Moorbodeneigenschaften auf die kapillare Wassernachlieferung

Influences of some peat soil features on the capillary water supply In the Weiße Moor near Gifhorn the grassland suffered in summer 1972 from extreme drought (Fig. 2), on peat soil profiles with a thin top layer of medium decomposed high bog over layers of only slightly decomposed transition forms from bog to fen (Fig. 1). This transition peat form was marked by the nature of its pores (Fig. 1). It is supposed that this led to the considerable reduction of the unsaturated water flow (Fig. 3). By this the capillary water supply of the grassland from still largly saturated deeper peat layers (>30 cm) was limited.     

Zum Einsatz von TRIME-TDR zur Messung der Bodenfeuchte auf leichten Sandböden

Using TRIME-TDR for the determination of soil water dynamics on sandy soils In this study the suitability of the TRIME-TDR system for the determination of soil water content was analysed. For this purpose a period of three years with continuous data of soil water contents, measured by TRIME-TDR, and soil water suction measured by tensiometer were available. Additionally soil samples at different times were taken for gravimetric moisture analysis. The determinations of soil moisture with the TRIME-TDR is based on a new measuring technique. The soil water contents measured by TRIME-TDR were analysed by comparison with corresponding soil moisture values from gravimetric measurements of soil samples. The soil water contents determined by TRIME-TDR in comparison with gravimetric soil moisture values show an absolute mean error of 7.9 Vol%. In most cases the soil water contents measured by TRIME-TDR were distinctly higher than the corresponding soil moisture values from gravimetric measurements. After correcting the TRIME-TDR the absolute mean error was reduced to 2.5 Vol%. Due to the results of this study soil water contents measured by TRIME-TDR-technique cannot be used in hydrological or ecological studies without a check based on the comparison with gravimetric soil moisture values.     

Phosphorus fractions in an acid soil continuously fertilized with mineral and organic fertilizers

The effect of different treatments on the fate of applied P was investigated in a long-term field experiment started in 1972–1973 following a maize–wheat sequence. The soil samples were collected after 29 years of continuous addition of mineral fertilizers and amendments such as farmyard manure (FYM) and lime. The total P content of all the treatments increased compared to the original soil; NaOH-inorganic P (P_i) (NaOH-P_i) representing Fe and Al-bound P was the dominant P_i fraction. At the beginning of the experiment (1972–1973), the various P pools could be quantitatively ranked in the following order: residual P>NaOH-organic P (P_o)>NaOH-P_i>NaHCO₃-P_o>NaHCO₃-P_i>HCl-P>H₂O-P. As a result of continued P fertilization and cropping, the order changed as follows: residual P>NaOH-P_i>NaOH-P_o>NaHCO₃-P_i>NaHCO₃-P_o>HCl-P>H₂O-P. Compared to the imbalanced mineral fertilizer application, the balanced as well as integrated application of nutrients resulted in significantly lower P adsorption capacity of soils. The Olsen extractable-P fraction (plant-available P) increased from about 12 mg kg^–1 soil in 1972 to about 81 mg kg^–1 soil in the treatments receiving P for the last 29 years.     

WELL–POINT TECHNIQUES AND THE SHALLOW WATER TABLE IN BOULDER CLAY

The reliability of water-table measurements in clay soil is currently under review (Twocock, 1971; Bonell, 1971; Visvalingam, 1972). This paper summarizes some of the experimental results from a boulder clay catchment in East Yorkshire. The experiments investigated the functioning characteristics of cased auger holes and piezometers in clay soil and compared the results with observations made with a neutron moisture probe. It appears that well-point technique, especially piezometers, are extremely unreliable in clay soil. The measured water level is demonstrated to be influenced by not only the position of the ‘water table’ but also the permeability of the soil; in which context the type, diameter, and length of tubing, as well as the time of installation, become important considerations.     

水分调控对日光温室油桃生理生化及果实品质的影响

为探索水分调控下设施油桃生长发育机制,完善日光温室条件下水分调亏灌溉理论,给油桃生产实践提供理论支持,以陇油桃1号为试材,采用膜下滴灌控制水分供应,以土壤相对含水量 80%～90%为对照,研究不同水分调控(30%～40%、40%～50%、50%～60%)处理对油桃“营养生长-生殖生长”的调控效应及生理生化和果实品质的影响。结果表明,缩冠修剪后,油桃树体营养生长态势呈“双峰”曲线。各处理枝条生长长度、果实横径与土壤水分含量呈正相关关系。土壤相对含水量为40%～50%时,叶片膜透性增幅最小,但水分利用效率最高,较土壤相对含水量为80%～90%时增加19%。4个处理的叶片OJIP曲线中,J-I相呈降低趋势,土壤相对含水量为30%～40%时I点和P点的最低,其余处理间无显著差异。土壤相对含水量与果实有机酸、Vc、还原糖含量均呈负相关,而与糖酸比呈正相关,除土壤相对含水量为30%～40%的处理外,其余处理间差异不显著。综上所述,日光温室油桃栽培中,适当修剪结合控水有利于枝条生长发育,同时可提高果实品质。土壤相对含水量40%～50%为温室较适宜的控水范围。     

Vorläufige Ergebnisse der messung gravitativer bodenbewegungen auf bewaldeten Hängen im Taunus

Within the last decades only little attention has been paid to the problem of contemporary soil movements on wooded slopes in Central Europe. In order to get further information about the existence and intensity of these movements instruments for measuring soil creep have been installed at 11 sites in the Taunus Mountains (NW Frankfurt a.M.). The investigations are primarily carried out to test three different methods (holes filled with sand, plastic tubes, pegs) under field conditions and to gather information about the installation, the operation and the evaluation of measuring sites For that reason (and because the measurements shall be continued for at least two more years) the results which have been obtained so far over a 5 year-period are only of preliminary character. Regarding the results, there can, however, be no doubt, that there are considerable soil movements even on slopes of small to moderate inclination. Soil creep movements occur only in the upper soil horizons, approximately down to a depth of 10 – 15 cm. The amount of material transported by these processes is supposed to be of the order of 1.5 – 2.5 cm³/cm/year.

Zusammenfassung

Es wird die Frage untersucht, ob und in welchem Ausmaß es gegenwärtig in Mitteleuropa auf bewaldeten Hängen geringer bis mäßiger Neigung verbreitet zu einer hangabwärts gerichteten Verlagerung des Bodens kommt. Dazu wurden im Taunus an Standorten unterschiedlicher naturräumlicher Ausstattung 11 Bodenbewegungsmeßfelder mit insgesamt ca. 300 Meßpunkten eingerichtet. In diesen Meßfeldern werden drei Verfahren im Vergleich zur Messung der Bodenbewegungen eingesetzt. Das wichtigste Ziel der Untersuchungen besteht vorerst darin, Erfahrungen bei der Einrichtung, dem Betrieb und der Auswertung von Bodenbewegungsmeßfeldern zu sammeln. Die Ergebnisse, die während der ca. 5-jährigen Meßzeit, zuletzt im Juni 1976, gewonnen werden konnten, haben daher nur vorläufig Gültigkeit. Nach den bisher vorliegenden Resultaten kann jedoch m.E. kein Zweifel daran bestehen, daß es gegenwärtig auch unter Wald zu einer eindeutig meßbaren Verlagerung der obersten Bodenhorizonte kommt. Die Bewegungen reichen allerdings nur bis in ca. 10 cm Tiefe. Bezogen auf den obersten Dezimeter des Bodenprofils liegen die jährlichen Bewegungsraten zwischen 2 und 3 mm.     

Bestimmung von hydraulischen Parametern für die Wasserhaushaltsuntersuchungen im natürlich gelagerten Boden. Ein Vergleich von Feld- und Laboratoriumsmethoden

Determination of hydraulic parameters to estimate water movement and water storage in undisturbed soil. A comparison of field and laboratory methods. The soil moisture characteristics and the unsaturated conductivity were measured under field and laboratory conditions. In an undisturbed soil monolith in continous connection with the underlying loess-soil-layer 60 tensiometer and a neutronprobe-accestube were used respectively to determine the matric potential and water content changes during a transient drainage experiment. Within the matric potential range of 0 to approximately ?50 to ?100 mbar the soil moisture characteristics determined in the laboratory and in the field are substantially different. When the matric potential is more negative than ?100 mbar the slope of these curves and hence the specific moisture capacities are relatively well comparable. The field-measured conductivity functions differ considerably from those values which were either measured under lab-conditions or computed from the soil moisture characteristics data. The conductivities are expressed as a function of the matric potential which is possibly the major reason for these remarkable differences. However, the changes in water content in this dense silty clay loam are too small to express the unsaturated conductivity as a function of the absolute water content. The most serious problems in extrapolating the results of the less time consuming laborcalculation methods to field conditions arise in that range of matric potentials where water movement is significant.     

Zinc nutrition affects alfalfa responses to water stress and excessive moisture

The interactive effect of applied zinc (Zn) and soil moisture on early vegetative growth of three alfalfa (lucerne) (Medicago sativa L.) varieties was investigated in a sand‐culture pot experiment to test whether there is link between Zn nutrition and soil moisture stress or excessive moisture tolerance in alfalfa plants. Three varieties (Sceptre, Pioneer L 69, and Hunterfield) with differential Zn efficiency (ability of a variety to grow and yield well in a Zn deficient soil is called a Zn‐efficient variety) were grown at two Zn levels (low Zn supply: 0.05 mg Zn kg^‐1 of soil, adequate Zn supply: 2.0 mg Zn kg^‐1 of soil) and three levels of soil moisture (soil moisture stress: 3% soil moisture on soil dry weight basis; adequate soil moisture: 12% soil moisture on soil dry weight basis; excessive soil moisture: 18% soil moisture on soil dry weight basis) in a Zn deficient (DTPA Zn: 0.06 mg kg^‐1 soil) siliceous sand. Zinc treatments were applied at planting, while soil moisture treatments were applied three weeks after planting and continued for two weeks. Plants were grown in pots under controlled temperature conditions (20°C, 12 h day length; 15°C, 12 h night cycle) in a glasshouse. Plants grown at low Zn supply developed Zn deficiency symptoms, and there was a severe solute leakage from the leaves of Zn‐deficient plants. Adequate Zn supply significantly enhanced the leaf area, leaf to stem ratio, biomass production of shoots, and roots, succulence of plants and Zn concentration in leaves. At low Zn supply, soil moisture stress and excessive moisture treatments significantly depressed the shoot dry matter, leaf area and leaf to stem ratio of alfalfa plants, while there was little impact of soil moisture treatments when supplied Zn concentration was high. The detrimental effects of soil moisture stress and excessive soil moisture under low Zn supply were less pronounced in Sceptre, a Zn‐efficient alfalfa variety compared with Hunterfield, a Zn‐inefficient variety. Results suggest that the ability of alfalfa plants to cope with water stress and excessive soil moisture during early vegetative stage was enhanced with adequate Zn nutrition.     

Effect of Glycine,Glutamate, and Glucose on Proliferation of PCP (Pentachlorophenol)-Degrading Microorganisms in Soil

Pentachlorophenol (PCP) had been used as both herbicide and fungicide. Although its application to paddy fields as herbicide is prohibited because of its toxicity to organisms living in water-streams, it is still used as fungicide for upland crops or timber. Its microbial degradation has been reported by many authors (Cserjesi and Johnson 1972; Watanabe and Hayashi 1972; Watanabe 1973, 1975, 1977; Kuwatsuka and Igarashi 1975; Suzuki 1983a, b; Engerhardt et al. 1986), including the degradation in soil (Watanabe and Hayashi 1972; Kuwatsuka and Igarashi 1975; Watanabe 1977). Since almost all of the PCP-degrading microorganisms isolated from soil are common species which are not nutritionally fastidious (Watanabe 1973; Suzuki 1983a, b), the microorganisms can grow in utilizing some common nutrients present in soil. Therefore, it is interesting to determine how they degrade the pesticide in the presence of common nutrients in the case of mixed populations in soil because biological relations between the degrading microorganisms and the non-degrading ones for the degradation of the pesticide and utilization of the common nutrients may occur. This is an important subject from the view-point of ecology of microorganisms degrading xenobiotic compounds in soil.     

Changing soil and surface conditions during rainfall: Single rainstorm/subsequent rainstorms

During rainstorms, physical properties of the soil surface change significantly. As a result of surface sealing, variations in infiltration rate, water content, water suction, bulk density and surface roughness can be observed and quantified. Dynamic processes taking place on the soil surface were investigated in laboratory and field experiments on a typical loess-derived soil in Germany. This study focused on the effects of continuous and subsequent rainfall treatments. Furthermore, all laboratory experiments were carried out in two different initial moisture regimes. In the laboratory experiments, a capillary rainfall simulator was used. Water suction was measured with microtensiometers 2 cm below the sealed surface in a 30 s time interval. The water content was determined with TDR probes in a variable time step, depending on the movement of the infiltration front. Compared to the continuous rainfall treatment, the decline of infiltration rate was much steeper in the subsequent rainfall events. After 2 h of continuous rainfall, a ‘drying effect' could be observed underneath the surface sealing at a depth of 2 cm. This was not the case in the intermittent treatment. Saturated conditions 10 cm below the surface sealing were reached in none of the treatments. The variation of bulk density within the first centimeter of the soil was determined via computed tomography and also with two simple methods using micro soil cores [Fohrer, N., 1995. Auswirkungen von Bodenfeuchte, Bodenart und Oberflächenbeschaffenheit auf Prozesse der Flächenerosion durch Wasser. PhD Thesis, Technical University Berlin, Bodenökologie und Bodengenese, No. 19, 183 pp.] and immersion as described by Roth [Roth, C.H., 1997. Bulk density of surface crusts: depth functions and relationships to texture. Catena 29 (3–4) 223–237.]. Under continuous rainfall conditions, the initially dry plots showed a higher compaction than the initially moist treatments. In the case of subsequent rainstorms, it was shown that the bulk density–depth function is not constant with time. The alteration of surface roughness was measured using a laser relief meter. The levelling effect of the intermittent rainfall regime proved to be much stronger in comparison to the continuous event.     

Behaviour of leaf water potentials of wheat and mungbean under field conditions as a function of available soil moisture and relative humidity

Field experiments were conducted with wheat and summer mungbean on an alluvial sandy loam soil (Typic Ustochrept). Data were obtained concurrently on soil moisture, leaf water potentials and relative humidity above crop canopy, in order to establish correlations between plant water status and soil moisture and aerial environment. In case of wheat, leaf water potentials correlated well with available soil moisture percentage remaining in the root zone as well as relative humidity above the crop canopy, only for the reproductive phase of crop growth. For the vegetative phase of crop growth, no relationships could be established, possibly because of high and non-limiting soil moisture. For mungbean, which is capable of avoiding drought, only 0900 hours leaf water potential correlated with available moisture remaining the root zone. For adapting the regressions for scheduling irrigation, important growth phases have to be considered separately.     

切沟对沟岸地土壤水分的影响

In order to preliminarily look at rules for soil moisture changes in the bank of the gully and to provide some recommendations for vegetative restoration in gully bank regions in the Loess Plateau, changes of soil moisture with depth and distance to the gully edge and their dynamic changes with time were observed to study the soil water characteristics in the bank of the gully. The results showed that soil water content increased with increasing distance from the gully edge, whereas for the same time period, the closer the distance to the gully wall, the greater the water loss; and that the influential distance of side evaporation decreased as depth increased.     

Umsatz von 15N markiertem Nitratstickstoff im Boden in Abhängigkeit von Strohdüngung und Bodenfeuchte

Turnover of ¹⁵N labelled nitrate nitrogen in soil as related to straw application and soil moisture In incubation experiments the effect of straw application on the turnover of ¹⁵N labelled nitrate has been studied at two soil moisture levels (brown podzolic soil). High ¹⁵N losses were found at the high soil moisture level. These losses are supposed to originate from denitrification. At both soil moisture levels straw application reduced significantly the ¹⁵N losses. Straw application resulted in a remarkable decrease of the ¹⁵NO₃ content in the soil and promoted the incorporation of ¹⁵N into the organic soil fraction. The incorporation of ¹⁵N into α-amino N and particularly into the rest hydrolyzable-N fraction was favoured by straw, while the incorporation into the amide-N fraction was hampered. Exhaustive cropping (Lolium multiflorum and Sinapis alba) on the soil incubated before with ¹⁵N, showed that the ¹⁵N incorporated into the organic fraction was poorly available. Thus straw application resulted in significant yield depression. It is assumed that the fraction of the rest hydrolyzable N is hardly available to plants.     

N-Umsatz von verschiedenem Pflanzenmaterial im Boden in Gefäß- und Feldversuchen

Turnover of nitrogen of different plant material in the soil in pot and field trials In pot and field trials, effects of various plant materials like green rape, sugar beet leaves, potato foliage, straw of wheat, maize, or field beans, on the turnover of N in the soil (mineralization, N_min-concentrations, NO₃-leaching) and on yield and N uptake by some crops was tested in relation to mineral N fertilizer application. In both experiments, widely corresponding results were obtained: Irrespective of the N contents of the plant material, biological immobilization of N always was combined with beginning mineralization (pot trial: decrease of NO₃ leaching in late fall). Green rape (C/N = 12/1) showed already after 4 weeks in the field trial a marked net mineralization (N_min) of 20–30% of the added nitrogen which was quantitatively reflected in higher removals of N. Beet leaves (C/N = 20/1) were decomposed at a much slower rate in combination with an increase in N removals of subsequent crops by 6-20 % depending on the rate of mineral fertilizer application. All types of straw (CM = 57-8611) and potato foliage (CM = 73/1) caused a marked biological immobilization of N which resulted in reduced N removals depending on turnover rate (potato foliage: fast, wheat straw: slow) and N contents of the organic material. Different plant residues (straw, leaves) were applicated on a harvested field with cereal to test comparatively one part of the total value of different preceding crops; at onset of vegetation the N_min-contents in soil, depending on the climatic conditions during the non-growing season for mineralization, were analyzed.     

Impact of Lower Boundary Condition of Richards'' Equation on Water, Energy, and Soil Carbon Based on Coupling Land Surface and Biogeochemical Models

Soil moisture has a significant influence on water, energy, and carbon biogeochemical cycles. A numerical method for solving Richards' equation is usually used for simulating soil moisture. Selection of a lower boundary condition for Richards' equation will further affect the simulation results for soil moisture, water cycle, energy balance, and carbon biogeochemical processes. In this study, the soil water movement dynamic sub-model of a hydrologically based land surface model, the variable infiltration capacity (VIC) model, was modified using the finite difference method (FDM) to solve a mixed form of Richards' equation. In addition, the VIC model was coupled with a terrestrial biogeochemical model, the Carnegie Ames Stanford Approach model of carbon, nitrogen, and phosphorus (CASACNP model). The no-flux boundary (NB) and free-drainage boundary (FB) were selected to investigate their impacts on simulations of the water, energy, and soil carbon cycles based on the coupling model. The NB and FB had different influences on the water, energy, and soil carbon simulations. The water and energy simulations were more sensitive, while the soil carbon simulation was less sensitive to FB than to NB. Free-drainage boundary could result in lower soil moisture, evaporation, runoff, and heterotrophic respiration and higher surface soil temperature, sensible heat flux, and soil carbon content. The impact of the lower boundary condition on simulation would be greater with an increase in soil permeability. In the silt loam soil case, evaporation, runoff, and soil respiration of FB were nearly 16%, 13%, and 1% smaller, respectively, compared to those of NB.     

Patterns of harvesting foliage and bark from the multipurpose tree Khaya senegalensis in Benin: Variation across ecological regions and its impacts on population structure

Non-timber forest products (NTFPs) represent important resources for millions of communities worldwide. Concerns over NTFP overexploitation has led to a growing number of studies on the ecological impacts of harvest. Few studies however, have addressed species harvested for multiple parts or investigated how spatial variation affects harvest patterns and their impacts. We documented rates and patterns of pruning and debarking and their impacts on density and population structure, for 12 populations of the multiuse tree, Khaya senegalensis (Meliaceae) in two ecological regions (Sudano-Guinean versus Sudanian) of Benin, West Africa. Half of the populations had low or no harvest and half were highly harvested. Patterns of pruning and debarking were size-specific, with harvesters tending to prefer larger trees. Foliage harvest pressures were very high across both regions, with >70% of trees harvested for 100% of their crowns. A significantly greater proportion of trees were harvested for foliage in the wetter Sudano-Guinean region than in Sudanian region. The reverse was true for the proportion of foliage and bark-harvested per tree. In the Sudano-Guinean region, high harvest populations had significantly lower densities of seedlings and saplings than low harvest populations. The size-class distribution coefficient of skewness was significantly correlated with rainfall, habitat, and soil type. Variation in harvesting patterns and their ecological impacts can be explained in large part by differences in water availability between the two regions. Effective conservation plans for K. senegalensis require close consideration of the environmental and land-use context in which populations occur.