土壤磷扩散的影响因素研究

对3种不同质地土壤磷扩散特征以及影响因素进行了试验研究。结果表明,随着土壤含水率的增加,土壤磷的扩散系数明显增加,土壤磷的扩散系数与土壤含水率的关系呈显著的幂函数相关;随土壤质地加重,土壤磷扩散系数增大;温度升高,土壤磷扩散系数增大,土壤磷扩散系数的温度效应可用磷扩散系数的温度系数定量表示;随着土壤施磷量的增大,土壤的磷扩散系数明显增加;土壤容重对磷扩散的影响与土壤的质地有关。对于质地较重的土壤,随着土壤容重的增加,磷扩散系数有降低的趋势;而对于质地轻的沙土,磷扩散系数有增加的趋势。     

施用方式和氮肥种类对砂姜黑土氮素迁移的影响

采用田间微区试验,在砂姜黑土中研究了施肥方式(上层12 cm土混施、土下12 cm点施、土下12 cm条施)和氮肥种类(尿素、磷酸氢二铵)对氮素垂直运移和水平迁移动态的影响。不同施用方式试验结果表明,在处理的90 d内,砂姜黑土中土壤NH_4~+-N和NO_3~–-N含量均呈现土下12 cm点施土下12 cm条施上层12 cm土混施的趋势。尿素在土下12 cm点施条件下,土壤NH_4~+-N主要集中在垂直方向6~18 cm土层和水平距离0~7 cm范围内;而NO_3~–-N的分布核心区土层超过21 cm,水平距离大于15 cm;NH_4~+-N和NO_3~–-N核心区浓度均随处理时间延长而明显下降。土下12 cm点施90 d后,尿素和磷酸铵的氮素养分在砂姜黑土中的横向移动距离为5~7 cm,垂直方向上养分主要集中在6~18 cm的土层范围;点施90 d时,磷酸铵处理在土下18 cm和水平距离12 cm处无机态氮(NH_4~+-N和NO_3~–-N)含量分别为148.9和77.4 mg/kg,其含量远大于尿素处理(96.3和53.2 mg/kg),而在施肥点两种氮肥处理土壤无机态氮含量差异更大,说明磷酸铵较尿素具有更高的保肥性。研究表明:点施延缓了NH_4~+-N向NO_3~–-N转化速率,提高了肥际养分供应浓度。结合作物生长和需肥特性,预示通过优化施肥位置和氮肥种类,采用一次施肥可以实现90 d持续供应高浓度养分以满足旱地作物生长发育的养分需求。     

THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS

Diffusion coefficients of soil phosphate calculated from flux to chloride form of anion-exchange resin-paper, assuming total depletion of the labile pool at the boundary, were too small and unrealistic. Thus not all the phosphate in the labile pool contributed to the diffusion process while being desorbed at constant pH in the presence of an indifferent anion—Cl—from the resin-paper. Desorption relationships under these conditions, using CaCl₂ at atmospheric CO₂ pressure, were markedly different from the relationship between the long-term ³²P-exchangeable phosphate and the corresponding pore-solution concentrations. In the same soil containing different amounts of labile phosphate, a different desorption relationship was found for each phosphate level. The constant proportionality between amount of phosphate diffusing into resin-paper and square root of time was indicative of a constant concentration at the boundary. The resin-paper: soil system was therefore considered as an infinite composite medium in which diffusion through both resin-paper and soil were rate-limiting. The constant boundary concentrations were estimated by the use of the diffusion coefficients in the resin-paper, the phosphate adsorption isotherm for the resin-paper and the desorption relationship for each phosphate level in the soil. Diffusion coefficients, calculated using the boundary concentration appropriate to each phosphate level, were related to the slopes of the corresponding desorption relationships, resulting in values of the impedance factor similar to those found for K diffusion under similar conditions. The resin-paper method, however, does not provide an accurate enough measure of the diffusion coefficient of soil phosphate to be of any practical use. Until better and simpler methods are found, the diffusion coefficient may be calculated using the slopes of the desorption relationship and the separately determined value of the impedance factor.     

THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS

The counter-diffusion of phosphate against chloride was measured in a moisture-saturated block of soil by following the efflux of phosphate into a limited volume of well-stirred CaCl₂ solution, of the same ionic composition as the soil-pore solution except for a lower initial phosphate concentration. By varying this phosphate concentration effective diffusion coefficients over a wide range of depletion were measured. The fraction of labile phosphate desorbed, and the relation between phosphate desorbed and concentration of phosphate in the equilibrium solution were measured in the same experiments. Effective diffusion coefficients varied from 0.43 to 1.50 × 10^-4cm² sec^-1, tending to decrease as depletion increased. Depletions ranged from about 0.3 to 25 per cent of the ³²P exchangeable phosphate, which corresponded to a lowering of the solution concentration by about 30 to 65 per cent of the initial concentrations. Diffusive movement of phosphate in this soil can be accounted for by diffusion through the liquid pathway only. The effective diffusion coefficient can be predicted from phosphate desorbed in response to a change in the concentration of the equilibrium solution, and an impedance factor.     

Phosphate Diffusion Coefficients in Soil as Affected by Bulk Density and Water Content

Phosphate diffusion coefficients (D_e) were determined by the quantity of P that diffused from a soil block with P addition into a soil block without P addition. To compare the results with theoretical concepts and to quantify the influencing factors, D_e was also calculated using the equation of Nye (1968). This equation takes into account the P diffusion coefficient in water, D₁, the volumetric water content, θ, the impedance factor, f, and the buffer power, b, of the soil. The results show that D_e strongly depends on volumetric water content whereas the effect of bulk density on D_e values was relatively small. If the weighted average buffer power was used, calculated D_e values were in good agreement with measured values at higher soil moisture contents. At θ < 0.22 g cm^?3 the measured values for D_e were smaller than the calculated. This effect is attributed to incomplete contact between the two soil blocks. The only small influence of bulk density on D_e is caused by the fact that bulk density affects both θ and b in a way which compensates each other.     

磷素在土壤中的扩散规律

本文应用放射性同位素示踪法,研究了黄土区几种土壤中磷素的扩散过程、影响因素以及其对作物有效性的关系。结果表明:1.磷素在土壤中一般仅能扩散3—4cm。10—15天乃基本达到平衡。各种类型土壤的磷素扩散有明显的差别,这与土壤的粘粒含量有关。磷素的扩散系数为7×10^-8-6×10^-7cm²/s;2.土壤水分和厩肥均能明显地增进磷素在土壤中的扩散作用,而无机盐的作用则相反;3.小麦和玉米幼苗从黄绵土中吸收的示踪磷比从红油土中吸     

A mechanistic model for describing the sorption and desorption of phosphate by soil

A model of phosphate reaction is constructed and its output compared with observations for the sorption and desorption of phosphate by soil. The model has three components: first, the reaction between divalent phosphate ions and a variable-charge surface; second, the assumption that there is a range of values of surface properties and that these are normally distributed; third, the assumption that the initial adsorption induces a diffusion gradient towards the interior of the particle which begins a solid-state diffusion process. The model closely describes the effects on sorption of phosphate of: concentration of phosphate, pH, temperature, and time of contact. It also reproduces the effects on desorption of phosphate of: period of prior contact, period and temperature of desorption, and soil: solution ratio. The model is general and should apply to other specifically adsorbed anions and cations. It suggests that phosphate that has reacted with soil for a long period is not ‘fixed’ but has mostly penetrated into the soil particles. The phosphorus can be recovered slowly if a low enough surface activity is induced.     

Löslichkeit des anorganischen Bodenphosphors und Phosphatdüngung

Solubility of the inorganic soil phosphorus and fertilizer phosphate The solubility of the inorganic soil phosphate of different soils was determined in up to 40 consecutive extractions with water and lactate solutions. The graphs showing the relationship between total extracted P, and P concentration in the extract ants (Fig. 1 and 3) were of an exponential type, independent of chemical bonding of the soil phosphorus, and independent of other soil properties. P contents in the first extractions were closely correlated with the sum of the P contents of all extractions with a solubility > 100 μg P/1 (fig. 2). All of the soil phosphate capable of diffusion is plant available. Therefore all phosphate in the soil which originated from fertilizer phosphate will be utilized. This follows from the data of solubility of the soil phosphorus (20–140 μg P/1) after repeated water and lactate (CAL) extractions. The slow adjustment of equilibrium, which is common with phosphate adsorption experiments is due to the influence of diffusion. The relationships between P fertilization, solubility of soil phosphate, and the recommended soil P content for economical P utilization with optimum plant growth (e.g. Tab. 2) is shown.     

Diffusion of urea, ammonium and soil alkalinity from surface applied urea

A model for predicting the concentration profiles of urea, ammonium and soil pH in a soil column following diffusion from a surface application of urea is developed, using independently derived parameters, and tested experimentally. The following processes within the model were studied separately under the same conditions as those in the diffusion run. The rate of urea hydrolysis as a function of substrate concentration and pH in the soil solution, and the sorption of urea and ammonium by the soil from solution. A theory for the propagation of changes of pH in soils was applied to describe the diffusion of soil alkalinity arising from urea hydrolysis. These processes were linked by three diffusion equations—for urea, NH₄ and soil alkalinity, which were solved numerically using finite difference methods. There was good agreement between experimental and predicted concentrations of urea and NH₄, and soil pH values at the two times tested.     

Effects of air-drying on the adsorption and desorption of phosphate and levels of extractable phosphate in a group of acid soils,New Zealand

The effects of air-drying field-moist soils on the adsorption and desorption of added phosphate and on the levels of extractable native soil phosphate were examined using the A and B horizons of a group of four acid soils.Air-drying increased the capacity of all the soil samples to adsorb phosphate. At an equilibrium solution concentration of 0.5 μg P ml^?1, the increase in the quantity of phosphate adsorbed following drying ranged from 23% to 70% of that adsorbed by the moist samples. Considerable hysteresis in phosphate adsorption—desorption isotherms was observed for both moist and dried soil samples indicating that the additional phosphate adsorbed by the dried samples was held with the same strength as that held by the moist samples.Air-drying the soil samples caused a small decrease in soil pH of approximately 0.1 pH unit and a general increase in levels of EDTA-extractable Fe, Al and organic matter. Quantities of native soil phosphate extractable with EDTA, resin and NaHCO₃ were also increased. Concentrations of oxalate- and pyrophosphate-extractable Fe and Al and exchangeable Al were, however, unaffected by drying.It was also shown that when the phosphate content of NaHCO₃ extracts is measured using the conventional molybdenum blue method, orthophosphate plus a differing amount of acid-hydrolysable organic P present in the extract is measured.     

腐殖酸对磷在石灰性土壤中迁移的影响

When humic acid (HA) and phosphorus (P) fertilizer are simultaneously applied to soil, HA may affect the movement of P. A laboratory incubation experiment was conducted to quantify the effects of a commercial HA product co-applied with monocalcium phosphate (MCP) on the distance of P movement and the concentration of P in various forms at different distances from the P fertilizer application site in a calcareous soil from northern China. Fertilizer MCP (at a rate equivalent to 26.6 kg P ha-1 ) was applied alone or in combination with HA (at 254.8 kg HA ha-1 ) to the surface of soil packed in cylinders (150 mm high and 50 mm internal diameter), and then incubated at 320 g kg-1 moisture content for 7 and 28 d periods. Extraction and analysis of each 2 mm soil layer in columns showed that the addition of HA to MCP increased the distance of P movement and the concentrations of water-extractable P, acid-extractable P and Olsen P in soil. The addition of HA to MCP could enhance P availability by increasing the distance of P movement and the concentration of extractable P in soil surrounding the P fertilizer.     

Laboratory Determination of Water Retention and Diffusion Coefficient in Unsaturated Sand

Laboratory methods were presented to measure water retention and chloride diffusion coefficient in unsaturated medium sand. A tempe-diffusion cell was designed and disturbed and undisturbed methods were used in the experiments. In the disturbed method, new sand sample was used in each diffusion test and diffusion coefficient was determined based on the observed and predicted concentrations versus soil depth, and versus time in the source reservoir. In the undisturbed method, one sand sample was used throughout a successive diffusion testing with different suctions for sand in each test. The diffusion coefficient for each test was then determined based on the concentration versus time data in the source reservoir. There was a good agreement between the observed data and theoretical predictions in all experiments. The major advantage of the apparatus over other published methods lies in the fact that both the soil–water characteristic curve and ion diffusion coefficient at any degree of saturation, can be obtained on the same soil sample in a single suite of tests. These two parameters are required for several geotechnical and geoenvironmental engineering designs involving unsaturated soils, such as the solid waste landfills overlying natural or engineered layers of unsaturated granular soils.     

腐殖酸物质对磷在褐土中迁移的影响

采用室内土柱实验研究了腐殖酸和腐殖酸钠在与磷肥共施时对磷在褐土中迁移的影响。结果表明,与单施磷酸二氢钙相比,共施腐殖酸钠缩短了磷在土壤中的迁移距离,明显降低了施肥点附近微域中的水溶性磷和酸溶性磷含量,磷向土体中的迁移量也显著下降;相比之下,共施腐殖酸则明显增加了磷的迁移距离和迁移量,对肥际微域中不同形态磷的含量均有显著提高作用。因此,腐殖酸促进了磷在褐土中的迁移,适宜与磷肥配合施用,而腐殖酸钠不适合与磷肥共施。     

花管注浆加固松散碎石土层试验与效果参数预测模型

注浆技术可用来加固松散碎石土层,以提高其防渗与承载能力。该文以渗透注浆工作原理与注浆花管技术为基础,开展了加固松散碎石土层注浆试验研究;并依据数值分析方法与Minitab 16软件,探讨了注浆加固松散碎石土层注浆量、扩散半径、扩散高度及结石体抗压强度等效果参数预测模型;同时设计试验进行了验证。研究结果表明:1)相邻注浆孔流出的浆液在松散碎石土层中相容,且侧边与底部注浆孔流出的水泥浆液在松散碎石土层渗透扩散时产生了明显的群效应,从而形成一个整体近似呈圆柱形的注浆结石体;2)由这些模型计算得到的注浆量实测值大于预测值,而扩散半径、扩散高度及结石体抗压强度的实测值都小于预测值,但均相差不大,其相对误差分别在9%、7%、6%与6%左右变动。因此,该文构建模型可作为采用注浆技术加固松散碎石土层的注浆量、扩散半径、扩散高度及结石体抗压强度等效果参数的设计基础。研究成果可为碎石土地质灾害的防灾减灾提供一定的理论参考。     

A QUANTITATIVE ANALYSIS OF THE FACTORS AFFECTING PLANT NUTRIENT UPTAKE FROM SOME SOILS

A model of solute uptake by a growing root system is discussed in relation to the ability of a soil to support the nutritional requirements of plants. It is quantitative, and should apply to the absorption of nitrate, phosphate, and potassium by grasses and arable crops. The principles, if not the detail, are relevant to all soils. The model was tested in an experiment in which the nitrogen and potassium taken up by a rape plant were measured. The results suggest that the model has identified the significant variables in the absorption process. The principal factors affecting the supply of nutrient to a given plant are the total quantity of diffusible nutrient, the rate at which the nutrient can move, and the distance it has to travel to a root surface. The exact relevance of each factor for the different nutrients is readily determined. The diffusion coefficients of potassium and phosphate are often low. Mass flow contributes little to their supply, and an adequate exploitation of the soil reserves depends on a well-developed root system. Nitrate, on the other hand, can usually move easily to roots, either by diffusion or mass flow. The whole rooting volume is depleted fairly quickly, and the amount absorbed depends solely on the quantity present in the rooting volume. These ideas have practical significance. In particular, they suggest that the soil properties which influence root growth may deserve as much attention as soil chemical composition in the drawing up of fertilizer recommendations.     

涌泉根灌湿润体特征值变化规律研究

在米脂山地微灌枣树示范基地进行原状土涌泉根灌人渗试验,研究了不同流量、不同灌水历时条件下涌泉根灌湿润体特征值的变化规律.结果表明:湿润体的水平扩散半径、向上人渗距离、向下人渗深度随流量的增大而增大,且均与入渗时间有显著的幂函数关系;在相同流量情况下,向上人渗最快.水平扩散次之,向下人渗最慢;湿润体体积受灌水量和流量的影响;在不同流量条件下,湿润体体积与灌水量间,湿润体水平扩散半径、垂直扩散距离与灌水量间均存在极显著的幂函数关系;针对五年生枣树根系分布特征,确定了枣树适宜灌水时间和灌水量.     

The self-diffusion of strongly adsorbed anions in soil: a two-path model to simulate restricted access to exchange sites

The consequences of slow diffusion of strongly adsorbed solutes into soil aggregates are not fully understood. The distribution of ³²P after diffusing down a soil column cannot be explained from a consideration of liquid-phase impedance factor and isotopic exchange alone, as can that of ³⁶CI. A model was developed that considers the soil to provide linked parallel intra-aggregate and inter-aggregate pathways. With this geometry, simulations agreed fairly well with experimental data when the intra-aggregate impedance factor was 0.001, using other model parameters that had been determined in independent equilibration studies. With this intra-aggregate impedance factor, the model yielded straight-line plots for chloride and the overall impedance factor derived agreed closely with the experimental one. The intra-aggregate impedance factor for ³²P also agreed with the rate of reaction of the rapidly-exchanging P fraction previously determined. The slowly-exchanging P fraction has little influence on the P concentration profiles up to 10 d, but the small exchanged amount does have an effect at run times of 57 d. The slow intra-aggregate diffusion of strongly adsorbed solutes decreases the amount adsorbed from a surface source of supply, and it also decreases the amount that is taken up by a surface sink. However, the interaggregate solution concentration remote from a source of supply is considerably increased, which may be important if the solute is a pollutant or a nutrient.     

不同形态磷酸盐及施用方式对石灰性土壤磷移动性和有效性的影响

  【目的】  磷的固定是石灰性土壤中磷肥效益低的重要原因,研究两种施肥方式下不同形态磷源在石灰性土壤中的迁移以及有效性,为实现磷肥减施增效提供理论基础。  【方法】  采用土柱模拟试验方法进行研究,供试土壤为粘质和壤质石灰性土壤。供试磷酸盐为磷酸脲、焦磷酸和聚磷酸,壤土施磷量为0.0581 g/柱,粘土为0.0594 g/柱。施用方式包括一次施用和分4次滴施,同时以不施用磷酸盐土柱为对照。于地下室内 (27 ± 1.0)℃培养28天后将土柱在?80℃条件下快速冷冻固形,从土表向下0—100 mm内每隔5 mm作为一个切割单元,100—300 mm间每隔20 mm作为一个切割单元,测定每层土壤的水溶性磷和Olsen-P含量。  【结果】  培养28天后,一次施用条件下,磷在壤土中的移动距离表现为聚磷酸 (90 mm) > 焦磷酸 (60 mm) > 磷酸脲 (50 mm),粘土中表现为聚磷酸 (80 mm) > 焦磷酸 (70 mm) > 磷酸脲 (60 mm)。分次滴施条件下,聚磷酸 (95 mm) 在壤土中的移动距离比磷酸脲 (65 mm) 和焦磷酸 (70 mm) 分别增加46.2%和35.7%,在粘土中聚磷酸 (90 mm) 的移动距离较磷酸脲 (70 mm) 和焦磷酸 (75 mm) 分别增加28.6%和20.0%。磷浓度下降到一半时所达到土柱深度 (半运移深度) 的结果表明,在壤土一次施用条件下,半运移深度表现为聚磷酸 (15.1 mm) > 焦磷酸 (11.4 mm) > 磷酸脲 (10.5 mm),分次滴施条件下半运移深度为聚磷酸 (20.0 mm) > 焦磷酸 (14.4 mm) > 磷酸脲 (14.3 mm)。在粘土一次施用条件下,半运移深度为聚磷酸 (17.7 mm) > 焦磷酸 (15.8 mm) > 磷酸脲 (14.8 mm),分次滴施条件下,聚磷酸、焦磷酸和磷酸脲的半运移深度依次为51.3、27.1和41.4 mm。相关性分析结果表明,不论一次施用还是分次滴施,聚磷酸和焦磷酸处理均随着水溶性磷含量的增加,有效磷含量在粘土上的增加量大于在壤土上的,分次滴施聚磷酸较一次施用在同样水溶性磷含量下,有效磷的含量在粘土和壤土中的差距减小,焦磷酸处理中水溶性磷与有效磷在两种土壤上较为接近。磷酸脲一次施用后,有效磷在粘土中随水溶性磷的变化量大于在壤土中,分次滴施结果则相反。  【结论】  在质地为壤土和粘土的石灰性土壤中,不论是一次性施用还是分次滴施,磷的移动性均表现为聚磷酸 > 焦磷酸 > 磷酸脲,且分次滴施3种磷源时磷的移动性和有效性均显著高于一次施用。同样水溶性磷含量条件下,粘土中磷的有效性高于壤土,分次滴施提高土壤磷素有效性的效果表现为粘土优于壤土。     

氮肥对磷在红壤肥域微域中迁移和转化的影响

The effects of two different nitrogen fertilizers （urea and NH4C1） with monocalcium phosphate （MCP） on the movement and transformation of fertilizer P in soil microsites along with soil pH changes at different distances from the fertilizer application site were studied in an incubation experiment. A highly acidic red soil （Ultisol, pH 4.57） from south China with MCP fertilizer alone or in combination with NH4C1 or urea was added to the surface of soil cylinders and packed in wax blocks. After 7 and 28 days, the extraction and analysis of each 2 mm layer from the interface of the soil and fertilizer showed that added NH4C1 or urea did not change the movement distance of fertilizer P. However, P transformation was significantly affected （P 〈 0.05）. After 7 days, at 0-8 mm distance from the fertilizer site the addition of urea significantly decreased the water-extractable P concentration; however, after 28 days the effect of N addition had disappeared. Also,at limited distances close to the fertilizer site NH4Cl application with MCP significantly increased acid-extractable P and available P, while with the addition of urea they significantly decreased. Compared with application of MCP alone,addition of urea significantly increased soil pH in fertilizer microsites, whereas the addition of NH4Cl significantly decreased soil pH.     

Wirkungen organischer Substanzen auf Boden- und Düngerphosphat. Teil 2: Einfluß verschiedener organischer Stoffe auf die Mobilität von Dünger-P

Effekt of various organic substances on the mobility of fertilizer P Using model trials, studies were carried out on the influence of long-term organic manuring as well as incubation with rotted straw, maize roots, and slurry, on both the diffusion of ³²P from added (NH₄)₂H³²PO₄ in a ‘soil block’and the fixation rate of fertilizer phosphate in the soil. 1. In the “soil block experiment”, preincubation for 7 days with slurry (added to a low-P brown earth soil at a rate of 5% D. M.) increased diffusion of P as compared to an equivalent amount of added inorganic P. Preincubation with rotted straw resp. maize roots had only insignificant effects. 2. Long-term organic manuring with farmyard manure (P-long-term field trials Weihenstephan) had a significant positive effect on the diffusion of P in the soil block in contrast to annual application of mineral P. Effects of straw manuring were markedly less. 3. Addition of maize roots (5% D. M. to a non P-treated or P-enriched brown earth soil) resulted in a reduced fixation of labelled fertilizer phosphate (by 2–8%), longer preincubation periods, however, increased fixation. Preincubation with rotted straw increased P fixation by 2 to 4% as compared to an equivalent addition of inorganic P (diammonium phosphate).