影响磷矿粉在淹水水稻土中溶解和有效性因素的研究

通过对在采自浙江省金华市的12种不同性质的水稻土添加江西省吴村磷矿粉（WPR）进行淹水培养试验,研究淹水条件下影响磷矿粉溶解和有效性的土壤因素。结果表明,磷矿粉在土壤中的溶解量与土壤pH（KCl）、交换性钙离子含量以及土壤粉粒含量呈极显著或显著的负相关,而与土壤粘粒含量呈显著的正相关。经逐步回归发现,土壤pH（KCl）是影响磷矿粉溶解的第一因素,土壤pH（KCl）和土壤磷吸附常数K共同解释了78%的磷矿粉溶解。加入磷矿粉后土壤有效磷的增加量（Resin-P）与土壤的Olsen-P含量呈极显著的正相关。施用磷矿粉后土壤有效磷增加量占溶解量的百分比与土壤Olsen-P含量呈极显著性正相关,而与土壤粘粒含量、最大吸磷量呈显著负相关。     

兽用抗生素在土壤中的衰减特征及其与土壤性状的关系研究

为了解土壤性状对兽用抗生素在土壤中的衰减及其生物有效性的影响,选择10 种理化性状相差较大的典型蔬菜地土壤,通过添加不同浓度（1、5、20 mg/kg）的4 种抗生素（土霉素、恩诺沙星、磺胺二甲嘧啶和泰乐菌素）,在保持65%的土壤田间持水量和恒温(25℃)条件下培养,观察分析各类抗生素的残留量和生物有效性的动态变化。结果表明,试验初期（20 天内）土壤中抗生素的降解速率明显高于后期（50~100 天）,进入土壤中的抗生素降解量随抗生素浓度的增加而增加,但降解比例却随抗生素添加量的增加而减小。4 种抗生素在土壤中的降解速率：磺胺二甲嘧啶＞恩诺沙星＞土霉素＞泰乐菌素。培养前期土壤中有效态抗生素含量随培养时间的下降比抗生素的残留量下降更明显。各类抗生素的降解率主要与土壤粘粒含量和氧化铁含量呈负相关,与土壤有机质含量存在轻微正相关,但与土壤pH 和CEC无明显相关。培养初期（5 天）,土壤中有效态抗生素含量与粘粒含量、氧化铁含量呈负相关,与有机质含量呈现正相关;但随培养时间的增加,其与土壤粘粒含量、氧化铁含量的相关性有所降低。     

黄河滩区（河南段）土壤营养状况分析

探明黄河滩区土壤营养状况,以期为黄河滩区经济林的适种性及合理的施肥措施提供参考依据。以河南原阳县滩区土壤为研究对象,测定土壤中大量速效养分氮磷钾,中微量元素交换性钙、交换性镁、有效硫、有效锌、有效铜、有效铁、有效锰、有效硼,及pH、有机质和土壤阳离子交换量含量,分析其土壤质地类型及土壤养分间的相关性。结果表明,黄河滩区土壤质地类型可以分为砂土、壤砂土、砂壤土、壤土、粉壤土和粉土6种;土壤平均pH 8.43,属碱性土壤;土壤有机质、土壤阳离子交换量和大量速效养分氮磷钾含量整体上较缺乏;除有效硼外,其他中微量营养元素含量均较为丰富;相关性分析表明,大多数营养元素间存在显著的相关性,且有机质、全氮、有效磷、速效钾、交换性镁、有效铜、有效铁、有效锰、有效硼、CEC与pH均呈负相关关系,交换性钙、有效硫、有效锌与其他营养成分间相关性较低。黄河滩区（河南段）非常适宜种植经济林,在栽培管理中,应注重增施有机肥,合理搭配有机肥和无机肥的比例;同时通过叶面喷施方式适量补充硼肥,从而达到提质增效的目的。     

Comparison of soil and sediment properties of a loamy sand soil

Ten 25 m² runoff plots at the Hilton experimental site, east Shropshire, UK, have been used to compare the physicochemical properties of loamy sand plot soils and sediment eroded from the plots over one year. Sediment contained more sand (2 mm–60 μm) and less clay (< 2 μm), silt (2–60 μm) and coarse fraction (> 2 mm) than soil. Erosion rates increased with slope and proportionally more silt and particularly clay were eroded on steeper slopes. Selective clay depletion has serious implications for soil structure and fertility. Correlations existed between the organic matter contents and particle size distributions of soil and sediment, but the sediment had less organic matter and lower pH values than soil. Sediment also contained lower concentrations of calcium, iron, potassium, magnesium, manganese and phosphorus than soil. Relationships between erosion and soil textural change appear to be partly technique-dependent, which suggests more uniformity in approach would be beneficial in studies on the effects of erosion on soil fertility.     

不同类型土壤团聚体稳定机制的研究

土壤团聚体是土壤生态系统中重要的组成部分,影响着土壤的物理、化学和生物学性质,它的稳定性是受粘结剂和分散剂共同作用的结果。本研究目的在于探讨粘结剂和分散剂对土壤团聚体稳定机制的影响。选取全国10种主要地带性土壤类型（黑土、红壤、黄棕壤、暗棕壤、紫色土、栗钙土、黄绵土、潮土、砖红壤、风沙土）为研究对象,采用湿筛法筛分土壤团聚体并测定分析。结果表明：在10种类型土壤团聚体分布中发现砖红壤>0.25 mm大团聚体含量最高,为86.77%;黑土次之,为76.13%;潮土大团聚体含量最少,仅为42.85%。>2 mm和0.5~1 mm含量对团聚体分布影响最大。各个土壤有机质中黑土有机质含量为46.06 g/kg,显著高于其他土壤,砖红壤次之;粒径<0.053 mm时各土壤有机质差异最显著,粒径>2 mm时与全土有机质趋势一致。栗钙土在10种土壤中交换性钠含量最高,为234.48 mg/kg,其次是潮土177.08 mg/kg。从整体看,有机质含量与土壤团聚体稳定性呈正相关(r=0.615),交换性钠与土壤团聚体呈负相关(r=-0.391),有机质与团聚体稳定性的显著相关性在粒径0.053~0.25 mm最明显。土壤团聚体的稳定由有机质与交换性钠共同作用,增加相同单位的有机质与交换性钠,有机质对团聚体的稳定效果是交换性钠分散效果的10倍。为更好的保护土壤,在农业生产中应施用含钠较低的有机肥,减少人类对土壤结构的破坏。     

NaCl胁迫对土壤成分含量的影响

用不同浓度盐(NaCl)胁迫(CK、0.1%、0.3%、0.5%、0.7%、1.0%)处理盆土,以探究NaCl胁迫对土壤成分含量的影响。结果表明：随着盐胁迫处理浓度的升高,土壤氮(N)、有机质含量总体变化不明显;土壤磷(P)、有机磷、交换性钙含量总体呈下降趋势;土壤钾(K)、电导率呈上升趋势;土壤pH值、水解氮等则呈先降后升再降的趋势。     

古田县园地土壤养分状况探析

为了调查古田县园地作物土壤养分状况,探讨土壤养分供应与土壤主要性质之间的关系。在古田县5种园地作物土壤上,采集耕层土壤样品7023个,调查园地作物状况,探讨土壤养分供应与土壤主要性质之间的关系。结果表明,供试园地土壤均值有机质含量为25.38 g/kg、pH 5.07、全氮含量1.2 2 g/kg、碱解氮、有效磷、速效钾含量分别为143.5、29.95、59.3 mg/kg,交换性钙、镁含量分别是226.1、422.1 mg/kg,有效硼、锌含量分别为0.15、1.22 mg/kg,各养分含量均与土壤有机质含量和pH之间呈极显著正相关。供试园地土壤全氮含量中等,碱解氮、有效磷含量较高,土壤速效钾78.51%处缺乏水平、交换性钙含量缺乏比例占89.21%,交换性镁过量、有效硼缺乏样品达96.21%,有效锌处于中等水平。提高有机质含量和改良土壤酸度应该成为供试园地土壤改善养分供应状况的根本措施。     

河流底泥粒径分形维数与重金属含量相关性——以海南岛南渡江塘柳塘为例

为了揭示河流底泥重金属含量与粒径分形维数、有机质之间的数量关系,借助统计分析和土壤分形维数分析法,分析了南渡江塘柳塘52个底泥样品的粒径分形维数特征;开展了底泥重金属含量与有机质、粒径分形维数的相关性分析、主成分分析及模型回归等。研究结果表明：所调查河流底泥粒径分形维数在2.453~2.971之间,不同粒径分级的分形维数平均值不同;重金属含量与有机质含量、极细砂分形维数、细砂分形维数呈显著的正相关,与粘粒、粉粒分形维数呈负相关,底泥中Zn、Hg受粒径的影响较小。底泥中有机质与粘粒分形维数可作为表征底泥基本理化形状的关键指标。底泥重金属含量（Zn、Hg除外）与有机质存在一元线性数量化关系;底泥重金属（Zn、Hg除外）含量与有机质、粘粒分形维数之间存在二元回归模型的数量化关系,上述模型间的数量化关系对于研究底泥的理化性状有着重要的意义。     

丹参有效成分含量与土壤因子的关系研究

摘 要：为研究丹参有效成分含量与土壤因子的关系,进行多点田间试验结合室内成分含量分析,所得数据用SPSS 11.0软件进行分析。试验结果得到：同一产地不同丹参品种及同一品种在不同产地种植其有效成分的含量有明显的差异。（系）99-2中丹参酮Ⅰ的含量与土壤细粉粒的比例呈极显著性正相关,与土壤中全氮的含量呈显著正相关;隐丹参酮的含量与土壤细粉粒的比例及全氮的含量呈极显著性正相关,丹参酮ⅡA的含量与土壤细粉粒的比例呈显著性正相关;丹酚酸B与土壤黏粒呈显著负相关。品种（系）99-5中丹参酮Ⅰ的含量与土壤细粉粒的比例呈显著性正相关,与全氮的含量呈极显著正相关;隐丹参酮的含量与土壤细粉粒比例呈显著性正相关,与土壤全氮含量呈极显著性正相关;丹参酮ⅡA的含量与土壤中细粉粒比例呈极显著性正相关;迷迭香酸的含量与土壤中细沙粒比例呈显著负相关。土壤中细粉粒比例及全氮含量的提高有利于丹参脂溶性成分的积累,而黏粒比例的增加不利于水溶性成分的积累,因而,在丹参种植过程中,针对不同类型有效成分,需要选择不同的土壤类型来生产。     

污灌区盐渍化土壤重金属Cd的形态分析及其影响因素

以受盐渍化及重金属Cd污染的天津污灌区土壤作为研究对象,探讨盐渍化土壤重金属的形态分布及其影响因素。研究的盐分种类主要为NaCl和Na_2SO_4,盐度7个[添加质量分数依次为0%(CK)、0.2%、0.4%、0.6%、1%、2%和5%],采用Tessier连续提取法测定土壤前3种重金属的形态(可交换态、碳酸盐结合态、铁锰氧化态),得出重金属的形态分布规律。结果表明:在添加NaCl盐度条件下,土壤中Cd碳酸盐结合态可交换态铁锰氧化态,可交换态含量与盐度、重金属总量、pH值和有机质均呈显著相关。在添加Na_2SO_4盐度条件下,土壤中Cd铁锰氧化态可交换态碳酸盐结合态,可交换态、碳酸盐结合态与pH值和有机质均呈极显著相关,铁锰氧化态与pH值呈显著负相关。盐度与Cd各形态也有不同程度的相关性。在添加NaCl盐度条件下,pH值对可交换态含量有重要影响;有机质对碳酸盐结合态含量有重要影响;Cd含量对铁锰氧化态含量有重要影响。在添加Na_2SO_4盐度条件下,有机质对可交换态含量有重要影响;pH值、有机质对碳酸盐结合态含量有重要影响;CEC对铁锰氧化态含量有重要影响。得出的Cd形态分布规律以及土壤各理化性质对Cd形态含量的影响分析对土壤重金属的污染防治和生态风险评价提供了基本的理论依据。     

Management of soil organic matter in the farming systems of the low land humid tropics of West Africa: a review

Soil organic matter is the key to successful and sustained productivity of soils of the tropics. This is because soil organic matter positively affects structure, aggregation, porosity, microbial activity, pore size distribution and water retention capacity of the soil.Furthermore, soil organic matter is the major nutrient storage site for the low-activity-clay soils of the tropics and so affect nutrient retention capacity, availability and mobility of macro- and micro-nutrients. It increases the water use efficiency, and therefore attenuate runoff and erosion and consequently the productivity of the soil.The low land humid tropics is characterised by high temperature, high relative humidity, high rainfall intensity and high microbial activity which all encourage rapid mineralisation, depletion and erosion of organic matter leading to soil deterioration.Many cultural practices and operations encourage rapid depletion of soil organic matter while others are associated with soil organic matter build up. Practices like crop rotation, multiple cropping, mulching, alley cropping, following and farm yard manuring, encourage soil organic matter accretion. However, the effectiveness of these practices in increasing soil organic matter depends on:

• 1.(a) amount and frequency of residue application;
• 2.(b) the nature and C:N ratio of the mulching material, or manure;
• 3.(c) rainfall amounts, intensity and distribution, soil moisture and clay contents.

Land clearing with heavy machinery is associated with removal of biomass from the field, while conventional ploughing and harrowing lead to soil organic matter depletion. These practices should be discouraged or modified to reduce their negative effects on soil organic matter.Effects of green manuring and burning, on soil organic matter are questionable.Research is needed on processes and pathways of crop residue decomposition to provide clues to possible interventions aimed at management of soil organic matter. Work is also needed to improve the efficiency of agro forestry systems in accreting soil organic matter in soils of the low land humid tropics.     

四川冕宁县新植烟区土壤养分特征及施肥对策

为明确四川冕宁县新植烟区土壤养分状况并合理指导施肥,2013 年和2014 年采集冕宁县后山乡、回龙镇、哈哈乡和回坪乡4 个新植烟区耕层(0~20 cm)土壤样品186 个,对植烟土壤养分状况进行了评价。结果表明：冕宁县新植烟区土壤平均pH 6.26,总体处于适宜范围;土壤有机质、有效磷、交换性钙和交换性镁总体处于适宜或丰富水平,但变异系数较大,仍有15.15%的土壤有机质缺乏,24.74%的土壤有效磷不足,约有15.00%的土壤交换性钙和镁偏低;土壤碱解氮和速效钾属于缺乏或极缺乏水平,有68.50%的土壤碱解氮缺乏,土壤速效钾属于缺乏和极缺乏分别占36.01%和54.28%。烟叶生产过程中,应根据各乡镇土壤养分含量的具体情况,进行科学施肥。     

Effect of Pulp and Paper Mill Effluent Irrigation on Carbon-di-oxide Evolution in Soils

Pulp and paper mill waste water irrigation increased pH, EC, organic carbon and exchangeable sodium content of soils. The increase in organic matter content of soils accelerated microbial activity and hence accelerated substrate decomposition with the release of CO₂. There exhibited a peak followed by a steady-decline in the rate of CO₂ evolution in effluent irrigated soils. The irrigation of pulp and paper mill combined effluent to soils did not affect microbial activity.     

Stärke- und Amylosesynthese in Samen von Mark- und Futtererbsen

Changes of clay soils under organic and conventional farming
Chemical, mineralogical and soil-physical measurements were performed on clay soils, which were cultivated under conventional and organical production system for the last 14 years. Soils in the organic system [TNL soils] were loosened from 10–35 cm and organic residues and manure were incorporated into the 0–10 cm layer by a rotowator. Soils in the conventional system [TKL soils] were plowed to a depth of 22 cm. Humus and nitrogen reserve and the amount of mobile phosphate in the top soils of the TNL soils were higher than in those of the TKL soils. The exchangeable potassium in the top soil was higher in TKL soils than in TNL soils, whereas the organic system (TNL) showed a more equal distribution within top and subsoil. This observation was confirmed by measurements of the mobile potassium (ARo-values).
The contents of 2:1 layer silicates with expanded layers was lower in the top soil of TKL soils than in TNL soils. This can be explained by the reduced application of liquid manure (Gülle) and the missing application of potassium fertilizer on TNL soils. The layer charge of the expanded minerals ranged from -0.80 to -0.68 for the vermiculites, and from -0.45 to -0.35 for the smectites, per formula unit respectively.
No influence on the percentage of the fine and mid pores was found. The amount of slow draining large pores (Ø 50-10 μm) was higher in TNL soils than in TKL soils, only in a neighbouring pasture soil the proportion of these pore exceeded those of TNL soils. Measurements of pore continuity did not show such a clear difference between TKL and TNL soils, but was higher for TNL soils.     

Effect of water quality and amendments on the hydraulic properties and erosion from several mediterranean soils

The response of six sandy-loam soils from Portugal and Israel to leaching with sodic and saline water and to simulated rain was studied. The dominant clay mineral in the soils from Portugal was kaolinite, whereas smectite predominates in the soils from Israel. The permeability of the soils depended on the soil texture: it decreased with an increase in the silt and clay content. The response of the soils to sodicity depended on the electrolyte concentration; salt concentrations exceeding 10 mmol_c·L⁻¹ was enough to prevent the deleterious effect of exchangeable sodium (≤20%). When leaching with distilled water (stimulating rain water), the presence of primary minerals and lime determine the susceptibility of the soils to sodicity. The calcareous loess from Israel was the least susceptibility to sodicity.The six soils were susceptible to sealing, high runoff and erosion when exposed to rain. The soil surface was particularly vulnerable to sealing due to both the mechanical impact of raindrops and the low concentration of electrolytes in the rainwater. Seal formation was due to two mechanisms:

• 1.(i) physical disruption of aggregates at the soil surface which depended on the impact energy of raindrops and the inherent aggregate stability; and
• 2.(ii) chemical dispersion which depended on the mineralogy of the clay, the ESP, and the electrolyte concentration.

When the impact of the drops was prevented, or when the anionic polymer was sprayed at the soil surface, physical breakdown of the aggregates was reduced and runoff and erosion were slight. When the electrolyte concentration was high, the chemical dispersion was small and runoff and erosion decreased, compard with the control. The smectite soils from Israel were more susceptible to sealing than the kaolinitic soils from Portugal.     

Susceptibility of soils to physical degradation in Hungary

A simple category system was elaborated by the authors expressing the susceptibility of Hungarian soils to physical degradation, as structure destruction and compaction. The main soil characteristics which were taken into consideration in the category system were as follows: type, subtype and local variant of the soil, parent material, texture, hydro-physical properties, carbonate-, salinity/alkalinity- and organic matter status, and depth of the soil. Based on detailed territorial information on the above mentioned soil characteristics Hungarian soils were classified into 8 physical degradation sensitivity (susceptibility) categories:

• 1.1. Non-susceptible soils;
• 2.2. Slightly susceptible soils;
• 3.3. Moderately susceptible soils;
• 4.4. Soils susceptible to compaction and surface crusting, but not to structure destruction;
• 5.5. Soils susceptible to both structure destruction and compaction;
• 6.6. Soils susceptible to both structure destruction and compaction due to salinity and/or alkalinity;
• 7.7. Organic soils;
• 8.8. Shallow soils (solid rock or cemented layer near to the surface).

The map of these categories was prepared in the scale of 1:500 000.For medium (1:100 000) and large-scale (1:25 000 - 1:10 000) mapping a more detailed category-system (including more categories and subcategories with precise numerical limit values) will be elaborated.     

Drainage — tillage effects on a Crosby-Kokomo Soil Association in Ohio III. Organic matter content and chemical properties

Soil organic matter content and soil chemical properties were examined for the Crosby-Kokomo Association near Columbus, Ohio. The soils are classified as fine, mixed, mesic, Aeric Ochraqualf and fine, mixed, mesic, Typic Argiaquoll, respectively. Effects of four tillage methods were studied, with and without subsurface drainage. Tillage methods were: ridge till, beds, no-till and conventional till. The tillage treatments were laid out according to the Randomized Block Design with three replicates on each drainage site.Soil samples, obtained in August, 1987 to 50 cm depth in 10 cm increments, were analyzed for soil chemical properties. Tillage methods has significant effects on soil organic matter, Bray-1 P, CEC and exchangeable Ca and K. In general, no-till and beds had significantly higher concentrations of organic matter in the surface layer than the other tillage treatments. Soil pH was lowest in the 10–20 cm depth soil layer and increased with increasing depth. Organic matter and Bray-1 P decreased significantly with depth. Improved soil drainage significantly decreased soil pH by 0.5 units, and soil organic matter content by 33% in the top layers. Subsurface drainage also decreased the concentration of Bray-1 P.     

芦笋种植对冷凉沙化区土壤改良的效果研究

为探索芦笋种植对冷凉沙化区土壤的改良效果,在山西省朔州市右玉县,以未种植芦笋裸沙地为对照（CK）,设置种植芦笋1、2、3和4年共4个处理,通过田间试验测定不同种植年限芦笋田土壤理化特性和芦笋生长发育情况。结果表明,与CK相比,随种植年限增加,土壤黏粒和粉砂粒含量递增,砂粒含量递减,土壤容重递减,土壤田间持水量递增;土壤pH和可溶性盐浓度（EC）递减;土壤有机质、全氮、有效磷和速效钾含量逐年递增。种植芦笋3年的土壤粒级、土壤容重、田间持水量、pH、EC值、土壤肥力发生显著变化;连续种植芦笋4年的土壤黏粒含量较CK增加到29.8%,粉砂粒含量增加到12.6%,砂粒含量降低到57.6%,田间土壤持水量显著提高,土壤容重显著降低,土壤由砂质壤土向砂质黏土转变;土壤pH降低0.75,EC值降低0.08mS/cm;土壤有机质含量增加28.89%,全氮、有效磷和速效钾含量分别增加95.12%、94.92%和45.40%;芦笋产量达6 037.5kg/hm ²。综合分析,连续种植芦笋4年可改善沙化土壤的物理结构,提高土壤养分,降低盐碱程度。芦笋是冷凉沙化区土壤改良的先锋作物之一,可实现生态效益与经济效益并举。     

长期施肥对不同有机质含量农田黑土胡敏酸、富里酸含量的影响

腐殖质是土壤有机质的主体部分,并且在碳截获、土壤结构、养分保持、生物地球化学循环等方面都占有重要的作用。本文以5种不同有机质含量农田黑土为主要研究对象,对比分析了长期施肥对不同有机质含量农田黑土富里酸(FA)、胡敏酸(HA)、胡敏素(HM)的含量的影响。结果表明:5种农田黑土FA、HA、HM的含量随土壤有机质含量的增加而增加,长期施肥可以增加农田黑土FA、HA、HM的含量,5种农田黑土FA含量差异达到了显著水平(P0.05)。相关分析表明:FA、HA含量与土壤有机碳、全氮、全磷呈显著正相关,与土壤pH值呈显著负相关(P0.05),HM含量与土壤有机碳、全氮、全磷含量、土壤p H值之间差异没有达到显著水平(P0.05)。     

Changes in microrelief and their effects on infiltration and erosion during simulated rainfall

The erosivity of soils under a given rainfall energy appears to vary greatly among soil orders, probably reflecting differences in clay composition and organic matter content. This study was conducted to quantify microrelief, infiltration, and sediment yield changes during three consecutive simulated rain events on a Udic Haploboroll and a Typic Hapludalf from Minnesota, and a Mollic Kandiudalf, and Typic Palehumult from Uganda. Air dry aggregates (< 5 mm) were packed in 19 1 containers tilted to a 5% slope and were subjected to three consecutive high energy rain storms (63 mm h⁻¹) for a duration of 1 h. Runoff and sediment were continuously monitored during a storm. Infiltration was measured by continued weighing of the soil and containers. An automated non-contact laser relief meter was used to measure changes in soil roughness initially and after each storm. Soil surface roughness decreased during the rain events indicating that aggregate breakdown was the dominant process in seal formation. For example, random roughness decreased form 5.9 to 4.0 mm on Barnes loam and from 9.7 to 6.9 mm on Renova silt loam with cumulative rainfall of 0 and 126 mm. These infiltration rates indicated that the Barnes Loam (Haploboroll) and Kabanyolo clay (Kandiudalf) were unstable soils while Kachwekano clay (Palehumult) and Renova silt loam (Hapludalf) were quite stable. Final infiltration rates after 3 consecutive rainfalls on Kachwekano clay (15 mm h⁻¹) and Renova silt loam (13 mm h⁻¹) [the stable aggregate soils] were significantly higher than those of Barnes loam (4 mm h⁻¹) and Kabanyolo clay (3 mm h⁻¹). For the two stable soils a high infiltration rate on a rough surface was maintained until aggregate breakdown occurred and runoff began. Sediment yield from Barnes loam (29 kg m⁻²) and Kabanyolo clay (28 kg m⁻²) was significantly greater than soil loss from Kachwekano clay (0 kg m⁻²) and Renova silt loam (6 kg m⁻²). The microrelief method to quantify aggregate stability is an improvement over wet sieving and other related measurements because of its rapidity and because the statistical quantification can be linked to physical processes.