Regime behavior for alluvial stable Egyptian canals

The design of stable alluvial canals in Egypt is based on regime formulas. These formulas are valid for conditions prevailing before the construction of the High Aswan Dam (HAD), in which the solid suspension was more than 3500 p.p.m. As the regime of Egyptian canals has changed after the construction of HAD (Suspension solid became less than 100 p.p.m.), the design adopted by old regime equations is not satisfactory and a new design concept for the new regime is necessary.In 1982, investigations were carried out in Egypt based on field study on a group of stable alluvial irrigation channels and other collected data from Irrigation Districts and others, from which a series of design formulas for stable canals has been deduced.In this paper a continuation of regime studies have been emphasized by analyzing currently the available field data measurements on thirty alluvial stable channels in Egypt. A more useful relationships have been achieved which may give an approach for a better solution in the scope of stable canal design in Egypt.An investigation of regime theory verifies that the regime formulas of Egyptian Canals are only valid for the limited range of conditions upon which they are based.     

低分子量有机酸对石灰性潮土无机磷形态转化的影响

无菌培养条件下,模拟缺磷胁迫时植物根系分泌的低分子量有机酸种类和数量,采用石灰性土壤无机磷分级方法,研究了低分子量有机酸对石灰性潮土无机磷形态转化的影响。结果表明:①在石灰性潮土中无机磷主要以有效性较低的磷酸钙盐(Ca10-P等)形式存在,而有效性较高的形式(Ca8-P等)含量较少,Ca2-P就更少。②有机酸通过结合土壤中可以使磷固定的Ca、Fe及Al,致使根际范围酸化,促进磷酸盐的形态转换,增加磷的有效性。这种促进能力因有机酸种类和性质的不同而异,其促进能力大小顺序为草酸>柠檬酸>酒石酸。     

LiDAR-derived slopes for headwater channel network analysis

Slope is one of the most important distinguishing features for channel morphology. Variations in the computation of slope from a digital elevation model can affect a wide range of hydrogeomorphically derived applications. We compare different methods for computing channel slope using LiDAR-derived digital terrain models (DTMs) with varying resolutions. We chose a headwater basin of the Eastern Italian Alps, characterized by a dense ephemeral colluvial network and a main alluvial channel as our study area. The identified alluvial morphologies are characteristic of steep mountain streams, namely, cascades and step pools. Field surveys were carried out along the main channel and in some small tributaries. Results indicate that a single method for slope calculation cannot estimate channel slope at the hydrographic network scale. The differential geometry approach for slope calculation tends to overestimate field-surveyed channel slope values for all the DTM resolutions (1, 2, 5 m). When a trigonometric approach for slope calculation is applied, 2 and 5 m DTM resolutions give more consistent results. Nevertheless, a reliable channel slope can be derived from a DTM with an appropriate resolution by choosing a suitable method only after considering the channel width.     

多年冬种紫云英对两种典型双季稻田土壤肥力及硝化特征的影响

以湖南紫潮泥和江西黄泥田两种典型稻田下的绿肥定位试验为依托,分析了晚稻收获后两种土壤的养分性状、硝化强度、硝化势及氨氧化细菌(AOB)和氨氧化古菌(AOA)的amoA基因丰度,探讨多年冬种紫云英对两类稻田土壤肥力、硝化作用及氨氧化微生物的影响。两地试验处理一致,包括:1)不施肥不种紫云英(CK);2)冬种紫云英不施化肥(GM);3)不种紫云英单施化肥(CF);4)冬种紫云英配施化肥(GM+CF)。结果表明,冬种紫云英可以改善两种典型稻田土壤pH,即提高江西酸性土壤pH、降低湖南碱性土壤pH;提高土壤全氮、有机质、无机氮和有效磷含量。两种典型水稻土的硝化能力不同,江西黄泥田的硝化强度及硝化势均明显低于湖南紫潮泥。在湖南紫潮泥中,各处理硝化强度在0.269~0.325 μg/(g·h)之间,处理间差异不显著;硝化势在培养第5周达到10.25%,紫云英配施化肥在一定程度上抑制了紫潮泥的硝化作用。江西黄泥田中,各处理硝化强度在0.010~0.021 μg/(g·h)之间,硝化势从培养第3周开始上升,在培养第5周达到5.41%;单独种植翻压紫云英相对于不施肥对照提高了土壤硝化强度及硝化势,与施用化肥处理效果相当,绿肥配施化肥对硝化作用的促进最强。AOA在紫潮泥和黄泥田中均占优势地位,紫潮泥中AOA-amoA基因丰度显著高于黄泥田,冬种紫云英对紫潮泥中AOA-amoA和AOB-amoA基因丰度均无明显影响,而显著提高了黄泥田中AOA-amoA和AOB-amoA基因丰度,与冬种紫云英对硝化强度和硝化势的影响一致。     

Geochemistry of Manganese in Neutral to Alkaline Soils of Punjab,Northwest India and Its Availability to Wheat and Rice Plants

Manganese (Mn) release in 18 soil–water suspensions after their equilibration for 24 and 240 h periods at 25°C was studied in a laboratory experiment. Total dissolved Mn released into the soil solution was observed to increase from a range of 0.03–0.41 mg L^?1 (mean = 0.13 mg L^?1) to a range of 0.45–44.44 mg L^?1 (mean = 22.40 mg L^?1) with the increase in incubation periods from 24 to 240 h, respectively. The increase in Mn released was observed to be related with the redox potential (pe) induced by incubation conditions. After 24 h of equilibration period, pe of soil–water suspension ranged from ?1.75 to 0.77 (mean = ?0.24). Increasing the incubation period to 240 h, pe of soil–water suspensions declined in the range of ?4.49 to ?2.74 (mean = ?3.29). Laboratory results of redox pe and corresponding dissolved manganese concentrations of some soil–water equilibrated systems were compared with the leaf Mn content in wheat and rice plants grown in the fields, from where soil samples were collected for laboratory experiment. These results demonstrated that decline in pe due to longer equilibration period (240 h) of soil–water systems in the laboratory experiment or keeping standing water for a couple of weeks in the fields for cultivation of rice crop results in higher release of Mn and eventually its higher uptake in rice than in wheat plants. Leaf manganese content in rice ranged from 94 to 185 mg kg^?1, which was markedly higher than its range from 25 to 62 mg kg^?1 found in the wheat grown at 10 different sites. Pourbaix diagrams were drawn for different soil–water systems containing carbonate, phosphate, or sulfate along with manganese. The presence of carbonate and phosphate anions along with manganese oxides minerals in the soil–water systems of all soils results in its precipitation as MnCO₃ and MnHPO₄, respectively, in both oxidized and reduced soil field environment. In Punjab, wheat and rice crops are generally cultivated on soils heavily fertilized with P fertilizers. The presence of phosphate anion with manganese oxides minerals in the soil–water systems of all soils results in the precipitation MnHPO₄ in both oxidized and reduced soil field environment. Thus, in P-fertilized soil, MnHPO₄ compound is even more predominant than aqueous Mn²⁺ and its solubility actually controlled the availability of Mn²⁺ to plants.     

鄂东南崩岗洪积扇土壤物理性质空间分异特征

【目的】研究崩岗洪积扇农田土壤颗粒组成、容重、土壤孔隙度、土壤持水情况、有机质并分析它们之间的相互关系,同时探索崩岗洪积扇农田土壤物理性质空间分异规律,不仅有利于农业用地规划,也为崩岗洪积扇农田土壤改良提供理论依据,对山区农林业生产具有重要的意义。【方法】运用野外调查结合室内分析的方法,以通城县杨垄小流域崩岗洪积扇农田为研究对象,选定水田和旱地两种洪积扇土地利用方式,分别采集洪积扇农田扇顶、扇中、扇缘以及对照4个区域测定其土壤物理性质,运用Pearson相关系数分析法对各指标之间的内在联系进行探究,研究崩岗对洪积扇农田的影响规律。【结果】崩岗侵蚀导致洪积扇农田土壤严重沙化,土壤结构性恶化。洪积扇农田土壤粗颗粒物质（砾石和砂粒）平均比对照区多75.89%,土壤细颗粒物质（粉粒和黏粒）平均比对照区减少39.13%。土壤有机质含量减少,洪积扇土壤有机质含量平均比对照区减少58.70%;容重增大,相对对照区平均增加0.25 g·cm^-3;土壤孔隙度均小于对照区,饱和持水性和毛管孔隙度显著低于对照区。同时,沿着洪积扇扇缘到扇顶,土壤砾石和砂粒含量呈现逐渐增加,而粉粒和黏粒含量逐渐减少,容重随之增大,土壤孔隙度减少,持水性能也逐渐减弱,有机质逐渐减少的趋势。相关性分析得出,土壤容重与有机质含量呈极显著的负相关（R=-0.907^**）,土壤容重与土壤孔隙性和土壤持水特性呈极显著的负相关,总孔隙度、毛管孔隙度与土壤持水特性均呈极显著的正相关,非毛管孔隙度与各物理性质之间没有明显的相关性。土壤各粒级大小与土壤容重、土壤持水性指标、总孔隙度和毛管孔隙度之间呈显著或极显著相关性。【结论】崩岗侵蚀发生后,洪积扇农田以土壤颗粒组成、有机质、土壤容重、孔隙度以及持水性能为代表的土壤物理性质退化严重。此外,崩岗洪积扇农田土壤物理性质存在空间分异规律,离扇顶越近,土壤物理结构性越差。洪积扇农田土壤指标间存在息息相关的联系,尤其是土壤颗粒组成和其他物理性指标之间的关系,突出了改良洪积扇土壤从土壤颗粒方面入手是可行的,如采取客土法和深耕法可有效改良被侵蚀的土壤结构。研究结果为明确洪积扇农田土壤物理性质提供了依据,为改良崩岗洪积扇土壤结构性奠定了基础,对农业生产和提高农业经济效益有重要意义。     

五华县崩岗洪积扇土壤分形特征及空间变异性研究

以广东省五华县典型崩岗洪积扇为研究对象,通过GPS RTK获取从扇顶到扇缘64个采样点的坐标、高程信息,并采集土壤样品进行理化性质的测定及分析,通过分形理论、回归分析和地统计学相结合的方法研究洪积扇土壤分形特征和空间变异规律,以及分形维数与土壤颗粒组成和养分含量的相关关系。结果表明:土壤颗粒组成和养分含量具有明显的空间分异特征,且与分形维数的空间分布呈现出一定的规律性。从扇顶到扇缘,土壤粉粒、粘粒质量分数和养分含量逐渐增加,与分形维数呈显著正相关线性关系,砂粒质量分数则逐渐减少,与分形维数呈显著负相关线性关系,其中洪积扇土壤粘粒含量对土壤颗粒分形特征影响最大,相关系数达到0.969。研究结果表明,土壤分形维数是能反映土壤质地差异以及土壤肥力状况的一项综合性定量指标。     

基于主成分-聚类分析评价崩岗洪积扇土壤施肥效应

崩岗产生的大量沙石使洪积扇位置土壤受到不良影响,土壤肥力下降。为了比较不同施肥方式对土壤肥力的改良效果,采用室外采样结合室内分析的方法,选择安溪县龙门镇崩岗洪积扇5种施肥方式下的土样进行研究,通过分析土壤的基本理化性质(颗粒组成、p H、CEC、有机质以及氮磷钾含量),利用这些指标进行主成分分析,同时结合系统聚类方法对不同施肥方式进行肥力评价。结果表明,主成分分析中不同施肥方式下的土壤肥力综合得分由高到低依次为:施厩肥、施沼液肥+绿肥、施沼液肥、施化肥、对照。崩岗洪积扇通过长期的施肥,土壤肥力水平均得到了提高,其中以施厩肥和施沼液肥+绿肥的改良效果最好。同时,采用系统聚类分析对主成分分析的结果进行验证,土壤肥力最高的施肥方式是施厩肥和施沼液肥+绿肥;其次是施化肥和施沼液肥;最差的是对照区土壤,2种方法所得结果一致。     

冲积河流河型影响因素及判别式研究

通过对河型的影响因素分析,确定出河槽边界条件、来沙条件、来水条件为河型的形成和转化的主要条件.将河型按从稳定-不稳定的原则分为6级,并对河型进行量化编码.以黄河、长江等河流12个河段的实测资料为依据,采用Cp统计量作为变量选择准则及多元线性回归分析法建立了新的河型判别式.得出对河型影响最大的因素为河槽边界条件,其次为来水条件,来沙条件对河型影响较小.     

不同土壤类型下杂交籼稻地上部器官对重金属镉和铅的富集特征

于2008年选用江苏省两种典型土壤(潮土和水稻土),采用盆栽试验研究杂交籼稻K优818地上部不同器官对土壤重金属镉(Cd)和铅(Pb)的富集特征。结果显示,水稻地上部不同器官对土壤Cd和Pb的富集特征差异显著,总体上呈现茎鞘叶片大米的趋势。水稻土栽培下重金属对水稻株高、单穗重等的抑制效应显著强于潮土,且抑制效应随土壤重金属浓度的升高而增强。与对照相比,当外源Cd和Pb的浓度为7mg/kg和900mg/kg时,单穗重降幅最大,分别下降了28.4%和36.6%。不同土壤类型下,重金属的生物有效性差异明显,水稻土栽培下水稻各器官的Cd与Pb含量显著高于潮土。