前氮后移对水稻产量形成和农田氮素流失的影响

基于太湖地区稻田养分流失主要集中在水稻生育前期的特点,以超级稻武运粳29号为供试材料,通过田间小区试验,基肥采用机械深施,在施氮量300 kg/hm2水平下,设计4个氮肥运筹比例,基肥：分蘖肥：穗肥的比例分别为5：2：3 (O1);4：2：4 (O2);3：2：5 (O3);2：2：6 (O4),研究氮肥后移对水稻产量构成和农田地表径流氮素流失量的影响。结果表明,从产量构成因素来看,前氮后移的O4处理较常规氮肥运筹的O2处理水稻有效穗数和每穗粒数均显著下降,但是其结实率和千粒重均明显增加;最终前氮后移的O4处理水稻产量略有下降,但处理间的差异不显著。水稻季农田共发生地表径流6次,径流水总量为3 567.0 m3/hm2。农田地表径流总氮流失量随着前氮后移比例的增加而减少,O4处理较O2处理地表径流总氮流失量下降了12.02%,处理间的差异均达到显著水平。同时,前氮后移能够降低稻田地表径流总氮流失率和水稻氮素偏流失率。     

有机肥部分代替无机肥条件下早稻稻田氮素动态变化

为了研究稻田氮素造成面源污染的成因,选出适宜当地水稻种植施肥模式,通过不同种类的农村常用有机肥部分代替无机肥的配比,分析稻田氮素动态变化。结果表明;NH₄⁺-N的损失以地表径流为主,NO₃^--N主要通过渗漏作用造成地下水污染;不合理的有机无机配方肥,也会造成严重的面源污染;不同腐熟程度的有机肥在氮素的损失方式上不同,新鲜猪粪在渗漏作用和地表径流两种氮源损失方面都比较严重,土壤中NO₃^--N平均含量达到13.59 mg/kg,居6个处理最高水平,地表水中全时期NH₄⁺-N总量达到5.65 mg/L,仅低于纯化肥处理。猪粪堆肥地表水中全时期NH₄⁺-N总量达到4.52 mg/L看出,通过地表径流的损失在3种有机肥处理中表现最好,且土壤中NO₃^--N含量平均0.56 mg/kg,因此通过渗漏造成的损失处于6个处理最低水平。沼渣沼液地表水中全时期NH₄⁺-N总量达到4.84 mg/L,土壤中NO₃^--N含量平均为2.87 mg/kg,认为沼渣沼液主要以地表径流的损失方式为主,且通过渗漏造成的氮源损失略低于纯化肥处理。通过实验研究可以发现,猪粪堆肥可作为适宜水稻种植的有机肥。     

Phosphorus Removal Mechanisms in Constructed Wetland under Stochastic Intermittent Inflow

Phosphorus removal and is mechanisms by horizontal subsurface(HSSF) constructed wetland to treat simulated runoff under stochastic inflow condition have been investigated based on an experiment study. The results indicate that under stochastic inflow condition and with constant inflow rate of nominal hydraulic retention time of 36 h, the removal rate of the experimental HSSF constructed wetland for total phosphorus(TP) and total phosphorus(DTP) are 59.3% and 29.8％ respectively, and the yearly removal load for TP and DTP are 13.826 and 3.310 g·m-2·a-1 respectively. Removal of phosphorus by macrophytes assimilation is 1.816 g·m-2·a-1, which makes up 13.2％ of the TP removal and 54.85％of the TDP removal in the constructed wetland. It is indicated that macrophytes assimilation is not the main mechanism for the removal of total phosphorus while it has significant effect on the removal of dissolved phosphorus. The main mechanism for phosphorus removal by the constructed wetland are phosphorus retention in sediments accumulated in the substrates and adsorption by the substrates. The yearly phosphorus retention in sediments accumulated in the substrates is 5.372 g·m-2·a-1, which contributes to 38.9% of the total phosphorus removal. And yearly phosphorus adsorption by the substrates is 6.640 g·m-2·a-1 , which contributes to 48.0% of the total phosphorus removal.     

Distribution Characteristics and Control Measures of Nitrogen Composition in Urban Stormwater Runoff from Different Underlying Surfaces

Nitrogen composition in urban stormwater runoff from five underlying surfaces was studied and discussed. It is shown that the highest EMCs of TN(Total Nitrogen) came from urban traffic road(i.e. 10.6 mg/L), and the lowest was from campus catchment areas(i.e. 2.4 mg/L). Meanwhile, EMCs of NH3-N from traffic road and commercial district (i.e. 3.4~4.6 mg/L) were much higher than that from concrete roofs and tile roofs(i.e. 1.2~1.6 mg/L). Although PEMC10 of TN was greater than EMCs, the proportion of nitrogen was still similar. Nitrogen in stormwater was predominantly dissolved (73%~82%), with DIN (Dissolved Inorganic Nitrogen) the abundant form (63%~82% of TN). The highest concentrations of nitrogen species form commercial district, concrete roofs, campus catchment and tile roofs were NO3-N, which made up of 39%, 39%, 44% and 52% of TN respectively. However, it was NH3-N that had greatest concentration in runoff from urban traffic road, and the ratio of NH3-N /TN was as high as 43%. The removal of TN could be enhanced through improvement of stormwater management measures. The key factor was that conditions to drive nitrification must be created, retention time of stormwater runoff in treatment systems should be increased and material with low nitrogen content should be selected as construction media.     

Reduction of Urban Green Space on Stormwater Runoff Pollutant

In order to explore the effectiveness and feasibility of urban green space on regulating urban rainfall-runoff pollution, the simulated test of soil column was adopted to study the effects of vegetation cover, runoff pollution concentration, soil depth and groundwater, and hydraulic loading rate and residence time on reducing the pollutants by green space. The results indicate that green space has a good and stable ability to reduce three stormwater runoff pollution concentrations, which COD are 68, 137 and 550 mg/L, TN are 3.01, 7.51 and 30.06 mg/L, TP are 0.29, 0.69 and 2.73 mg/L, and NH+4 are 0.44, 1.61 and 2.19 mg/L respectively, with 3.5, 3.0 and 2.5 cm/h hydraulic loading rate respectively and continuous inflow 1h. The pollution reduction rates of COD, TN, TP and NH+4 by green space reach to 41.52%, 78.96% and 84.68%, 50.21%, 70.23% and 60.91%, 73.18%, 95.88% and 94.99%, and 62.72%, 55.16% and 69.98% respectively. Restricted by the soil reaeration capacity and hydraulic retention time, the effect of vegetation cover on pollution reduction rates of COD and TN is not significant. With the rainfall-runoff pollution concentration increased, the pollutant reduction rate of green space shows a gradually increasing trend. The reduction of green space on the stormwater runoff pollution mainly occurs in the soil depth of 35~65 cm. The reduction rate of each pollutant for the low, medium and high pollution concentration level decrease with the hydraulic loading rate increased.     

幼穗形成期水分胁迫后复水对水稻叶片光合特性及物质生产的影响

以杂交籼稻品种冈优527为试材,于幼穗形成期设置短期轻度水分胁迫（ Short and light water stress ,SLS）、长期轻度水分胁迫（ Long and light water stress ,LLS）、短期重度水分胁迫（ Short and heavy water stress ,SHS）以及长期重度水分胁迫（Long and heavy water stress,LHS）4个水分处理,并以习惯水层灌溉（Traditional flooding,TF）为对照。研究复水后水稻叶片光合特性、干物质积累与运转。试验结果显示：在幼穗形成期水分胁迫后,水稻叶面积、叶绿素a/b、SPAD值、净光合速率均降低;短期轻度水分胁迫（ SLS）处理复水后叶面积、叶绿素a/b、SPAD值、净光合速率均远远高于对照,同时茎鞘物质转化率和输出率也都高于其他水分处理。结果说明：在幼穗形成期,经过短期轻度干旱复水后,叶绿素、光合速率、叶面积等能迅速恢复甚至激发更高的光合水平,表现为后期干物质积累多、转运高,能达到节水的效果。     

村落的社会分化——基于M村的案例分析

为了深入解读村落的社会分化,通过访谈调查和案例分析。从村落的经济结构、职业结构以及收入来源等方面对发生在M村的社会分化过程展开调查研究。研究结果表明:村落的社会分化是在多种因素的共同作用下得以实现的,并且这些影响因素主要包括国家的土地政策、土地的"倒逼"机制、农民自身自主性的发挥以及外部市场的引力这4种因素。村落不仅是一种静态的社会形态,也是一种动态的社会过程;并且村落的社会分化过程,也是其社会分工程度不断加深、有机性不断增强的过程。农民的理想图景应该是成为理性小农以及农民市民化,同时设想了3种村落的未来走向。     

2,4-D浓度对玉米花粉诱导小麦产生单倍体幼胚得胚率的影响

在玉米花粉诱导普通小麦产生单倍体技术中,2,4-D浓度是影响幼胚得胚率的重要因素之一.为了确定2,4-D的适宜浓度,利用9个玉米材料和16个小麦材料进行了研究.在小麦散粉前和散粉后,授玉米花粉后12h和36 h分别用150、200、250、300、350 mg/L的2,4-D蘸穗2次,调查数据显示,散粉前处理得胚率平均值分别为6.74%、7.19%、8.44%、7.53%和6.61%;散粉后分别为2.53%、3.11%、4.70%、2.81%和2.67%.结果表明,小麦散粉前授玉米花粉后用250 mg/L的2,4-D处理得胚率最高.     

高温肉制品风味物质的形成机理及其影响因素

肉制品作为蛋白质的重要来源,在人们生活中具有很重要的地位。高温肉制品因其能在常温下储藏且货架期长的特点而备受消费者欢迎,其风味在一定程度上影响着消费者的接受度。本文基于国内外对肉制品的相关研究现状,对高温肉制品风味物质形成机理进行了总结,并对影响其形成的因素进行了分析,为促进高温肉制品产业发展提供理论参考。     

乙烯抑制剂对钾缺乏棉花根系生长和侧根形成的影响

The relationships between increased ethylene levels induced by potassium deficiency and the inhibition of root elongating and branching of cotton, were investigated by treating roots and leaves of cotton seedlings in hydroponic cultures containing ethylene precursor ACC(1-aminocyclopropane-1-carboxylic acid) and ethylene inhibitors AOA(aminooxyacetic acid), Co²⁺ and Ag⁺, respectively. The addition of ACC to K⁺-rich culture medium simulated the effects of K deficiency on root growth and branching, and aggravated the effects of K deficiency in K⁺-poor culture medium. In contrast, treatment with high concentrations of the ethylene synthesis inhibitor AOA decreased primary root length (PRL), lateral root length (LRL), and lateral root number(LRN) under low K conditions, and this was similar for the ethylene action inhibitor Ag⁺. Treatment with Co²⁺ under low K conditions significantly increased LRL and, at high concentrations, PRL, but caused reduced LRN at high concentrations. Our results indicated increased ethylene levels induced by K deficiency might account for inhibition of root elongation, but not for the suppression of root branching. Leaf application of Co²⁺ enhanced leaf area, root growth (PRL and LRL), and branching(LRN) of cotton seedlings grown under low K condition, though the effects of different Co²⁺ concentrations were not significant. These findings suggest that improving leaf growth might positively regulate root morphology.