Availability of Cadmium and Zinc as Affected by the Use of Reactive Phosphate Rock,Lime, and Chicken Manure on an Indonesian Acidic Upland Soil under Field Conditions

We assessed cadmium (Cd) and zinc (Zn) availability when applying reactive phosphate rock (RPR) in combination with lime and chicken manure on Indonesian acidic upland soils. Maize plants were grown on unamended soil and soils treated with several combinations of 2 tons dolomite ha^–1, 2 tons of chicken manure ha^–1, 1 ton ha^–1 of RPRL (reactive phosphate rock containing 4 mg Cd kg^–1 and 224 mg Zn kg^–1), and 1 ton ha^–1 of RPRH (RPR containing 69 mg Cd kg^–1 and 745 mg Zn kg^–1). In addition to its positive effect on plant yield, application of RPR in combination with chicken manure did not result in toxic Cd concentrations. Although liming is effective to reduce plant Cd concentrations, it results in more soil Cd accumulation and more plant Zn deficiency. Cadmium and Zn concentrations in shoots and grains can be predicted well from amounts extracted from the soil by 0.5 M ammonium (NH₄) acetate + 0.02 M ethylenediaminetetraacetic acid (EDTA) at pH 4.65.     

Effect of Lime and Flooding on Phosphorus Availability and Rice Growth on Two Acidic Lowland Soils

Abstract

Loss of soil‐water saturation may impair growth of rainfed lowland rice by restricting nutrient uptake, including the uptake of added phosphorus (P). For acidic soils, reappearance of soluble aluminum (Al) following loss of soil‐water saturation may also restrict P uptake. The aim of this study was to determine whether liming, flooding, and P additions could ameliorate the effects of loss of soil‐water saturation on P uptake and growth of rice. In the first pot experiment, two acid lowland soils from Cambodia [Kandic Plinthaqult (black clay soil) and Plinthustalf (sandy soil)] were treated with P (45 mg P kg^?1 soil) either before or after flooding for 4 weeks to investigate the effect of flooding on effectiveness of P fertilizer for rice growth. After 4 weeks, soils were air dried and crushed and then wet to field capacity and upland rice was grown in them for an additional 6 weeks. Addition of P fertilizer before rather than after flooding depressed the growth of the subsequently planted upland rice. During flooding, there was an increase in both acetate‐extractable Fe and the phosphate sorption capacity of soils, and a close relationship between them (r²=0.96–0.98). When P was added before flooding, Olsen and Bray 1‐extractable P, shoot dry matter, and shoot P concentrations were depressed, indicating that flooding decreased availability of fertilizer P. A second pot experiment was conducted with three levels of lime as CaCO₃ [to establish pH (CaCl₂) in the oxidized soils at 4, 5, and 6] and four levels of P (0, 13, 26, and 52 mg P kg^?1 soil) added to the same two acid lowland rice soils under flooded and nonflooded conditions. Under continuously flooded conditions, pH increased to over 5.6 regardless of lime treatment, and there was no response of rice dry matter to liming after 6 weeks' growth, but the addition of P increased rice dry matter substantially in both soils. In nonflooded soils, when P was not applied, shoot dry matter was depressed by up to one‐half of that in plants grown under continuously flooded conditions. Under the nonflooded conditions, rice dry matter and leaf P increased with the addition of P, but less so than in flooded soils. Leaf P concentrations and shoot dry matter responded strongly to the addition of lime. The increase in shoot dry matter of rice with lime and P application in nonflooded soil was associated with a significant decline in soluble Al in the soil and an increase in plant P uptake. The current experiments show that the loss of soil‐water saturation may be associated with the inhibition of P absorption by excess soluble Al. By contrast, flooding decreased exchangeable Al to levels below the threshold for toxicity in rice. In addition, the decreased P availability with loss of soil‐water saturation may have been associated with a greater phosphate sorption capacity of the soils during flooding and after reoxidation due to occlusion of P within ferric oxyhydroxides formed.     

骨粉生物质炭对酸性土壤的改良作用

以猪、鸡、牛和羊骨为原材料厌氧热解制备成生物质炭（骨炭）作为改良剂,探究骨炭最佳制备条件及其对酸性土壤改良效果,并从土壤固相和液相二个角度探究骨炭对酸性土壤铝（Al）形态的影响。结果表明：高温厌氧热解制备的骨炭富含CaO、CaCO3和Ca5(PO4)3(OH),同时含有NaO、MgO等碱性物质及-OH等多种官能团。但骨炭碱含量受热解温度影响较大,鸡骨和牛骨在800℃、猪骨和羊骨在900℃时其炭碱含量接近峰值并保持稳定,约为生石灰的90%,是最佳制备温度。此温度下制备的四种骨炭均可有效地提高pH<6.0的酸性红黏土、红砂土和砖红壤pH。骨炭中的碱性物质主要以H+缓冲剂的形式存在,从而导致其提高土壤pH的幅度与初始土壤pH成反比。pH=4.40的红黏土中添加5 g?kg-1猪、鸡、羊和牛骨炭后土壤溶液Al浓度分别较对照降低33%、34%、47%和41%,固相有机结合态Al含量无显著变化（P>0.05）。骨炭增加了酸性土壤阳离子交换量,并通过促进活性Al向土壤固相吸附态羟基Al和更稳定态Al转化从而降低土壤溶液Al及交换态Al含量。骨炭富含植物生长所需营养元素,具备无机和有机改良剂的双重特性,是可替代传统石灰作为酸性农田土壤改良剂的优质材料。     

Improved Structural Stability of an Acidic Hardsetting Soil Attributable to Lime Application

Abstract

Lime [calcium carbonate (CaCO₃)] has been used for acid soil amelioration of acid soils in Australia and elsewhere, but its effects on soil physical properties are not clear. Mechanisms responsible for the beneficial changes in the soil physical and structural properties of an acidic hardsetting soil in southern NSW, Australia, as a result of lime application were investigated. Changes in water‐stable aggregation, a mechanical property, were related to changes in physicochemical properties, and soil organic carbon forms as a result of liming. The improved soil structure due to liming can be explained in terms of reduction in SAR (Sodium absorption ratio) and increase in EC (Electrical conductivity) (both lead to less dispersion) as well as increases in labile carbon (less slaking). The combined effects of reduced dispersion and slaking were responsible for the reduced bulk density and tensile strength of the hardsetting surface soil. These beneficial effects of liming on soil structural and physical properties were detectable 4 years after but not 18 years after lime application.     

Lime and Nutrients Effects on Jatropha curcas Cultivated on an Amazonian Soil

We evaluated the effects of macronutrient and micronutrient omission, and of liming, on Jatropha curcas (JC) in greenhouse study. The experimental design was a factorial combination of 2 liming treatments (nil or 4.5 t. ha^?1 of dolomitic lime) x 7 combinations of fertility status, with five replications. The concentrations and uptake of nutrients by JC plants follow the order: nitrogen > potassium > calcium ≥ Magnesium > sulfur > phosphorus > iron > boron > manganese > zinc > copper (N > K > Ca ≥ Mg > S > P > Fe > B > Mn > Zn > Cu), but the growth of JC plants was negatively affected mainly by omission of macronutrients, in the following order: P > N = K = S, on limed soil. Phosphorus is the most critical element for development. JC is responsive to micronutrients only when applied together with macronutrients. Potassium chloride is not recommended as K⁺ source for JC crop. Lime is recommended to improve growth and nutritional status of JC plants.     

Evaluation of Coconut Wastes as an Amendment to Acidic Soils in Low-Input Agricultural System

The effectiveness of plantation wastes along with locally available organic materials in ameliorating acidic soil was studied by conducting an experiment with coconut husk, poultry manure, vermicompost, and compared with limestone. Application of organic amendments significantly increased the soil pH, and it was greatest in poultry manure–amended soils followed by vermicompost and coconut husk + poultry manure treatments. The relative liming efficiency was greatest for poultry manure through out the observation period of 180 days. The coconut husk alone showed the least liming effect and its liming efficiency had increased when applied in combination with poultry manure and or vermicompost. This increase in soil pH was mirrored by significant reductions in exchange acidity, exchangeable aluminum (Al³⁺), diethylenetriaminepentaacetic acid (DTPA)–extractable iron (Fe²⁺), and manganese (Mn²⁺) and increases in cation exchange capacity, exchangeable bases, especially calcium (Ca), and Olsen-extractable phosphorus (P) by addition of organic amendments and lime. This study indicated the potential of using coconut husk along with poultry manure for managing acidic soils in low-input agricultural systems, especially in tropical islands.     

Influence of Artificial Zeolite and Hydrated Lime Amendments on the Erodibility of an Acidic Soil

In this study, the effectiveness of artificial zeolite and hydrated lime, as amendments, to reduce surface runoff and soil loss from acidic soil taken from Yamaguchi prefecture in Japan was assessed. Air‐dried soil aggregates (?2 mm) were amended with zeolite at 10% and with lime at 0.5%. The amended aggregates were packed to an average dry‐bulk density of 1.30 Mg m^?3 in small soil trays and subjected to simulated rain intensities of 30 and 60 mm h^?1. Two pretreatments were used before subjecting them to simulated rainfall: (a) soil incubated for 2 weeks and (b) soil kept for 5 months, irrigated every two days. The data indicated that surface runoff was characterized by three phases. The amendments' impact was most significant during the first two phases as the amendments induced the formation of particles sized ? 106 µm, which are mostly responsible for the crusting. Amendments decreased soil losses, and the magnitude of reduction became higher when the irrigation pretreatment was applied before simulated rainfall. The amendment led to increase in soil organic carbon, wet aggregate stability, saturated hydraulic conductivity, and the large particle size in the sediment. The results suggest that surface runoff and soil loss in acidic soils can be substantially reduced by application of zeolite or lime, and this is attributed to the increase in wet aggregate stability and the large particle size in the sediment because of the amendments, and in this regard zeolite is more effective than lime.     

Impact of Boron on Biomass Production and Nutrition of Aluminum‐Stressed Apple Rootstocks

Abstract

The aim of the experiment was to examine the effect of boron (B) on biomass production and nutrition of aluminum (Al)‐stressed apple (Malus sp.) rootstocks. The study was carried out under greenhouse conditions on Polish rootstock (P22) and Malling 26 (M.26) planted singly into 1‐L plastic pots filled with perlite and supplied with Hoagland's medium at pH 4.5 without or with Al (100 µM as AlCl₃). Boron was added into the Al‐containing medium at 20, 40, or 60 µM whereas into the medium without Al only at 20 µM as boric acid. The results showed that the presence of Al in the medium reduced biomass production of P22 and M.26 rootstocks by 22% and 41%, respectively. Rates of uptake and translocation of phosphorus (P), magnesium (Mg), and calcium (Ca) to aerial plant parts were decreased for Al‐treated rootstocks. Aluminum‐stressed P22 rootstocks grown in nutrient solution at 40 and 60 µM B had higher dry weight of leaves and roots, and also higher ability to take up P, Mg, and Ca and lower Al than those grown in the presence of Al at 20 µM B in the medium. Rates of absorption and transport of B to aerial plant parts corresponded with B level in the medium. These results suggest that on acid soils with high Al availability, supra‐optimal B concentrations in soil solution (40–60 µM) can prevent/alleviate Al toxicity in apple trees grafted on P22 rootstocks.     

苜蓿培肥对灰漠土养分及胡敏酸特性的影响

通过荒地和苜蓿地土壤养分、土壤胡敏酸热解特性和红外光谱特征的比较，研究了灰漠土上种植苜蓿培肥对土壤养分和土壤有机质特性的影响。结果表明，种植苜蓿可以增加土壤有机质、全N和碱解N的含量，但速效磷和速效钾含量则下降，土壤pH不变。苜蓿地胡敏酸的脂肪族侧链较多，胡敏酸较年轻，而荒地胡敏酸侧链较少，胡敏酸相对较老。苜蓿地胡敏酸的脂族性强于荒地。种植苜蓿培肥后土壤胡敏酸变得简单化和年轻化。     

有机无机肥配施锌肥和石灰对双季稻产量及土壤养分特性的影响

在南方典型双季稻种植区,通过2年试验综合评价在有机无机肥配施基础上施用锌肥和石灰对双季稻产量与土壤养分特性的影响,以期提出培肥土壤和提高水稻产量的理想施肥模式。设置有机肥+无机肥(T1)、锌+有机肥+无机肥(T2)、石灰+有机肥+无机肥(T3)、锌+石灰+有机肥+无机肥(T4)4个处理,测定了土壤有效锌、碱解氮、有效锌含量和pH,分析了水稻产量和土壤综合肥力。结果表明:(1)相比T1处理,T2处理显著提高了早晚稻千粒重和结实率,显著增产8.7%,而T3处理不利于水稻稳产,显著降低了千粒重,并在第2年减产(5.6%)显著;T4处理表现出来的产量规律与T3处理类似,均于第2年表现减产。(2)施用锌肥、石灰均有利于提高土壤有效磷和碱解氮含量,石灰显著提高土壤pH,但T3、T4处理土壤有效锌含量显著下降,较T1处理分别下降39.0%和31.9%,而连年施用锌肥有利于有效锌的提高,T2较T1处理土壤有效锌含量提高22.2%。(3)土壤综合肥力表现为T2T4T1T3,施用锌肥相比石灰更有利于提高土壤肥力。综上所述,施用锌肥能显著提高土壤速效养分含量,增产显著,而连年施用石灰显著降低了土壤中有效锌含量。因此,在缺锌土壤中需慎施石灰,而长期施用石灰的土壤,应追施锌肥。综合土壤养分含量和水稻产量评价,有机+无机+锌肥的施肥模式为理想施肥模式。     

Effects of Boron and Lime on Productivity of Garden Pea under Acidic Soils in Northwestern Himalayas

An experiment comprising seven treatments was conducted to study the effect of boron and lime integrated with organic manures and nitrogen, phosphorus, and potassium (NPK) fertilizers on garden pea productivity. Seed yield along with growth parameters were significantly influenced by combined use of farmyard manure and NPK fertilizers either alone or in combination with boron and lime. Treatment combination of 20 t farmyard manure / ha + 100% NPK + borax (T₄) resulted in 37% increase in seed yield over recommended practice of 20 t farmyard manure / ha + 100% NPK (T₃). In addition, recommended practice supplemented with granubor (T₅) and lime (T₆) also significantly surpassed T₃ with respective increase of 14 and 10% in seed yield. Similarly, maximum nutrient was observed in T₄. Hence, application of boron along with farmyard manure and NPK fertilizers could be the best option to maximize pea productivity in acidic soils under humid subtemperate climate.     

施用石灰与钙蒙脱石对酸性土壤硝化动力学过程的影响

土壤酸化是粘土矿物缓慢风化的自然过程,但近年来随着人类高强度的农业利用,土壤酸化现象逐渐加剧,而铵态氮肥的硝化作用是土壤酸化的主要贡献者之一。传统的施用石灰改良酸性土壤,常常会有反酸现象,并可能导致土壤板结。蒙脱石是碱性或中性土壤的主要粘土矿物组分,而在土壤酸化的过程中,蒙脱石被进一步风化掉。本文通过室内模拟实验,采用硝化动力学拟合及对净硝化速率的计算,分别研究了蒙脱石(Ca-M)和石灰(Ca-OH)对酸性黄壤硝化作用的影响。结果表明:酸性黄壤添加石灰或蒙脱石后,土壤均发生了显著的硝化作用,且硝化过程符合一级动力学模型N_(NO3)=N_0+N_p(1-exp(-k_1t))(P0.001)。Ca-OH处理土壤样品的净硝化速率(3.429 mg·kg~(-1)·d~(-1))显著大于Ca-M处理(2.381 mg·kg~(-1)·d~(-1));Ca-OH处理土壤样品的潜在硝化速率(V_p)和平均硝化速率(V_a)在pH值5.7和6.2时分别为6.42、8.58 mg N·kg~(-1)·d~(-1)和2.71、3.87 mg N·kg~(-1)·d~(-1),均显著大于钙基蒙脱石处理(pH值5.7和6.2时分别为3.40、4.56 mg N·kg~(-1)·d~(-1)和2.36、3.04 mg N·kg~(-1)·day~(-1))。结果表明采用石灰改良酸性土壤发生复酸化现象的可能性及程度大于钙基蒙脱石,本研究为酸性土壤改良提供了新的参考。     

Effect of Ralstonia solanacearum on Mineral Nutrients and Infrared Temperatures in Two Tomato Cultivars

ABSTRACT

The objective of this study was to determine how the responses of two tomato cultivars to Ralstonia solanacearum relate to their leaf infrared temperature and acquiring of nutrients from soil. Tomato (Solanum lycopersicum L.) cultivars of disease susceptible-‘FL 47’ and resistant-‘H 7998’ were grown in soil inoculated with R. solanacearum. Bacterial wilt incidence, leaf infrared temperatures, and uptake of nutrients were measured for 28 d. In bacterial wilt-resistant cultivar ‘H 7998’, concentration of sulfur (S; +77%), calcium (Ca; +66%), boron (B; +60%) were found higher and nitrogen (N; ?26%) were found lower, compared with susceptible ‘FL 47’. Infrared temperatures were correlated with wilt percentage at 14 d, but not at 7 d. These results provide evidence that there is a correlation between bacterial wilt resistance and translocation of some nutrients in the shoots. Additionally, data indicates that the infrared thermometer could only detect wilting after obvious symptoms were visibly incited by R. solanacearum in tomato.     

Organic Amendment Effects on the Transformation and Fractionation of Aluminum in Acidic Sandy Soil

Addition of organic amendments can alleviate the level of aluminum (Al) phytotoxicity in acid soils by affecting the nature and quantity of Al species. This study evaluated the transformation of Al in an acidic sandy Alaquod soil amended with composts (10 and 50 g kg^?1 soil of yard waste, yard + municipal waste, GreenEdge^®, and synthetic humic acid) based on soil Al fractionation by single and sequential extractions. Though the organic compost amendments increased total Al in soil, they alleviated Al potential toxicity in acidic soil by increasing soil pH and converting exchangeable Al to organically bound and other noncrystalline fractions, stressing the benefits of amending composts to improve acid soil fertility. The single‐extraction method appears to be more reliable for exchangeable Al than sequential extraction because of the use of nonbuffered pH extract solution.     

灌溉和施磷对紫花苜蓿土壤水分动态及根重的影响

采用完全随机裂区设计,常规灌溉量(330mm),节水20%灌溉量(264mm)和节水40%灌溉量(198mm)作为主处理,施磷量(0,60,120和180kg/hm²)作为副处理,研究了不同灌溉量和施磷量对紫花苜蓿土壤贮水量、耗水强度、水分利用效率和根重的影响。结果表明,土壤贮水量、紫花苜蓿耗水强度和根重随灌溉量增加而增加,水分利用效率随灌溉量增加而降低。施磷对紫花苜蓿土壤贮水量和耗水强度影响不明显。紫花苜蓿水分利用效率和深度0-40cm根重随施磷量的增加表现为先增加后降低,当施磷量达到120kg/hm²时,紫花苜蓿水分利用效率﹝26.50kg/(mm·hm²)﹞和全生育期平均根重(1 320.78g/m²)达到最大值。     

磷锌配施对花生不同生育期磷锌吸收与分配的影响

对植物体内磷–锌复杂的交互关系,采用田间试验,研究了磷锌配施对花生不同生育期磷锌吸收、积累、分配及花生产量的影响。结果表明:施磷和施锌均显著提高了花生地上部干重和产量。相同锌用量下,施磷提高了花生地上部、花生壳和花生仁的磷含量和积累量,但降低了其锌含量、磷锌收获指数和荚果磷利用率。其中,施磷对地上部锌含量的降低程度取决于生育期和锌施用水平。随施磷量的增加,在花生苗期、花针前期及不施锌肥时,花生地上部锌含量显著降低;而在花针后期、结荚期和成熟期及施锌肥时,花生地上部锌含量的降低程度逐渐减弱,表明磷-锌拮抗作用在花生生育前期强于生育后期,不施锌肥强于施锌肥。施磷对花生锌积累量的影响取决于锌供应水平和花生生长部位。不施锌肥时,仅适量供磷促进了地上部锌积累,而施锌肥时,适量供磷和高量供磷均促进了地上部锌积累;不同于地上部,高量供磷显著降低了花生壳和花生仁锌积累量。相同磷用量下,增施锌肥对整个生育期花生各部位磷含量和花生生育后期磷积累量无显著影响,显著增加了花生苗期和花针前期地上部及成熟期花生壳和花生仁的磷积累量、磷收获指数和荚果磷利用率。总之,花生体内磷–锌相互作用大小受其生育期、生长部位和锌...     

Performance of Slag-Based Gypsum on Maize Yield and Available Soil Nutrients over Commercial Gypsum under Acidic and Neutral Soil

ABSTRACT

Effect of slag-based gypsum (SBG) and commercial gypsum (CG) on maize was investigated in acidic and neutral soils. A randomized complete block design (RCBD) with seven treatments consisting of three levels (150, 450, and 750 kg ha^?1) of SBG and CG with recommended dose of fertilizer (RDF) and one control was maintained. Application of SBG @750 kg ha^?1 recorded significantly higher (8.61 and 8.69 t ha^?1, respectively) cob yield of maize compared to CG and control treatments in both soil condition. Increased levels of SBG application increased soil pH and EC in both the soils, but decreased with the application of CG. Application of 750 kg SBG ha^?1 recorded significantly higher soil available nutrients like phosphorus in acidic soil and potassium in neutral soil. Higher exchangeable calcium and magnesium in acidic soil and exchangeable calcium in neutral soil were recorded with the application of CG @750 kg ha^?1. Available sulfur was significantly higher with CG @750 kg ha^?1 applied treatment in both soils. CaCl₂Si content in acidic soil varied significantly and recorded higher with application of SBG, while CaCl₂Si content in neutral soil and AASi in both soils had no significant effect by application of SBG. Significantly higher DTPA extractable micronutrients in acidic and neutral soil were noticed in SBG @750 kg ha^?1 applied treatment. However, application of SBG had no significant effect on iron and copper content in neutral soil. Higher uptake of nutrients was recorded with 750 kg SBG ha^?1 compared CG applied and other treatments.     

Vegetative and Reproductive Responses of Apple Trees to Zinc Fertilization under Conditions of Acid Coarse-Textured Soil

ABSTRACT

The aim of this study was to examine response of apple (Malus domestica Borkh.) trees to zinc (Zn) fertilization under conditions of acid coarse-textured soil with low 1M hydrochloric acid (HCl)-soluble Zn level. The experiment was carried out during 2004-2005 at a commercial orchard in Central Poland on mature ‘Jonagold’ apple trees/M.26 EMLA, planted at a spacing of 4 × 2.5 m. The trees were sprayed with Zn: (i) prebloom, at the stage of silver tip, and tight cluster at a rate of 140 and 100 g ha^{? 1}, respectively, (ii) postbloom, at the stage of petal fall, and 2 weeks later at a rate of 80 g ha^{? 1} in each spray treatment, and (iii) postharvest, 4–5 weeks before the natural leaf fall at a rate of 500 g ha^{? 1}. Other trees were supplied with Zn to soil at a rate of 3 kg ha^{? 1}. In all the studied treatments, Zn was used as ethylenediaminetetraacetic acid (EDTA). Trees unsupplied with Zn served as the control. Tree vigor, fruit set, yield and fruit quality at harvest (mean fruit weight, firmness, color, russeting, soluble solids concentration, and acidity) were not influenced by Zn fertilization. Postharvest Zn sprays slightly damaged leaf tissues but did not cause defoliation. Soil Zn application raised Zn concentrations in flowers, and leaves 28, 56, and 84 days after petal fall. Pre- and postbloom Zn sprays increased Zn status in flowers and leaves 28 days after flowering, respectively. The obtained results indicate that Zn fertilization of ‘Jonagold’ apple trees with Zn status in mid-summer leaves and flowers of 17 mg kg^{? 1} and 27 mg kg^{? 1}, respectively, is not successful in improving vigor and tree yield.     

黄土旱塬施肥对土壤颗粒组成及其有效磷富集的影响研究

通过田间试验与室内分析相结合的方法研究长期不同施肥处理下土壤颗粒组成及其有效磷富集。结果表明,各施肥处理土壤颗粒组成都呈现颗粒愈小比例愈高的规律,而不同施肥处理对同一粒径颗粒含量又有一定的影响。在单施磷肥(P)的基础上,配施氮肥、有机肥(NP、PM、NPM)有利于增加<0.25mm颗粒的比例,以NPM处理最为明显。长期施用有机肥改善了土壤颗粒中有效磷水平,但也提高了土壤颗粒有效磷中水溶性磷的比例。土壤中的有效磷(包括速效磷、水溶性磷)主要富集在<2mm粒径的土壤颗粒中,<0.25mm的土壤颗粒中有效磷富集率最高。氮磷配施(NP)、氮磷有机肥配施(NPM)有利于增加<0.25mm颗粒中土壤有效磷的富集,PM处理更促进土壤有效磷在0.25～2mm粒径中富集。