三江源区草地退化与人工恢复对土壤理化性状的影响

以三江源区不同退化程度的天然草地及不同恢复年限的人工草地为研究对象,系统分析土壤理化性质随取样深度的动态变化。结果表明:(1)人工草地土壤含水量及全氮、全钾、全磷、速效钾、速效磷的含量随恢复年限均表现出先减小后增大的"V"形变化趋势;(2)随着退化程度增加,退化草地土壤中含水量逐渐降低,全氮、全钾、有机质、速效钾含量未表现出逐渐降低趋势,而草地的裸斑面积、土壤及养分的流失量逐渐增加;(3)人工草地及退化草地土壤中全氮、速效钾、有机质含量均随着取样深度增加而逐渐降低,草地恢复年限和退化程度基本不影响养分在土壤中的空间分布;(4)人工草地建设使退化草地有机质、全氮、全钾的含量增加,尤其有利于0-4cm的土壤养分增加。因而,人工草地建设可以作为三江源区退化草地土壤恢复的措施之一。     

再生水灌溉对土壤理化性质影响的试验研究

通过室内土柱模拟试验的方法，研究了再生水灌溉对土壤理化性质的影响。结果表明：再生水灌溉对土壤扩散率和饱和导水率的影响与连续灌溉再生水的次数有关，短时间灌溉有降低的作用，但随着灌溉次数的增加，土壤扩散率和饱和导水率有增加的趋势；同时，随着灌溉次数的增加，土壤pH值降低，土壤有机质和全盐量增加；土壤溶液中各离子浓度有显著变化。灌溉5次之后，除0～10cm土层全盐量为0．107％外，其他各层均低于0．1％的限度；0～10，10～20，30～40cm土层的ESP均在5％～10％范围之内，20～30cm土层的ESP基本保持在原始的水平。再生水灌溉对土壤次生盐渍化的影响不显著。     

Influence of Water Content and Plants on the Dissipation of Chlorinated Volatile Organic Compounds in Soil

To devise effective procedures for the remediation of soil contaminated by VOCs, an improved understanding of their fate and transport mechanisms in soil is essential. To show the effect of plants on the dissipation of 1,1,1-trichloroethane (TCA), trichloroethylene (TCE) and tetrachloroethylene (PCE), two types of experiments, vial and column, were conducted. The results suggested that keeping the soil moisture content at field capacity is desirable for VOCs dissipation. All VOCs were dissipated quickly in unplanted columns than planted conditions in early periods of the experiment because more volatilization occurred in unplanted conditions. The plants could take up and retard volatile contaminants, and prevent contamination of ambient air. Although the time for acclimation for microbial communities to contaminants for enhanced biodegradation should be considered, phytoremediation is potentially a cost-effective remediation technique for soils contaminated by volatile organic compounds (VOCs).     

沙棘林退化对土壤性质及水土流失的影响

辽宁省建平县有亚洲最大的人工沙棘(Hippophae rhamnoides Linn.)林,对防治当地水土流失具有重要的作用。然而由于多种原因,该区沙棘林呈现大面积死亡的现象。通过样地调查沙棘林的死亡程度,并进行土壤理化性质和水土流失的测定,研究了沙棘林退化对土壤性状和水土流失量的影响。结果表明,随着沙棘活立木数量的减少,土壤容重增加1.40%~7.31%,有机碳含量和全氮含量分别降低7.81%~21.89%和9.33%~27.65%,说明沙棘林退化对土壤结构和养分产生显著的破坏作用。人工模拟降雨试验表明,纯沙棘林地的水土流失较轻,侵蚀模数为539t/(a·km2)。随着沙棘死亡率的提高,水土流失逐步加剧,入侵树种榆树纯林(Vlmus pumila)地达到1 526t/(a·km2)。土壤性质的恶化和水土流失的加剧,会对土壤有机质和土壤结构进一步破坏,使沙棘死亡速度加快,从而形成恶性循环。     

稻虾轮作模式下江汉平原土壤理化性状特征研究

稻虾轮作模式在湖北江汉平原已发展近30年,对农民增产增收具有重要作用。开展不同年限稻虾轮作对土壤理化性质影响的研究,有助于科学指导该模式下的农田管理。在同一农渠范围内选择相似的稻田,分别采集水稻单作(CK)和稻虾轮作(1、3、7、13、18和23a)的3个土层深度(0～20、20～40和40～60 cm)原状土样,分析其相应的理化指标。结果显示,与中稻单作相比,长期稻虾轮作会显著降低0～20和20～40 cm土层土壤容重并提高非毛管孔隙度、毛管孔隙度和总孔隙度,而40～60 cm土层变化较小;稻虾轮作1 a后土壤pH、全氮和易氧化有机碳含量显著增加,但速效养分和阳离子交换量增幅不明显。与稻虾轮作1 a相比,轮作7～13 a稻田的土壤pH和其他各项指标均显著增加;轮作13 a以上,0～20 cm土层的pH、全氮和速效养分增幅最为明显,但20～60 cm土层的理化性质无明显变化。随着轮作年限的延长,0～20 cm土层的pH和其他各项指标均表现为:23 a18 a13a7a1a0(CK),20～40cm和40～60cm土层的pH、全氮、碱解氮、有效磷和速效钾含量也有相似规律,但增幅并不明显。因此,长期稻虾轮作有助于改善耕层土壤结构、增强土壤缓冲能力和提高pH及氮、磷、钾等速效养分含量。     

南水北调中线水源区退耕地土壤理化特性研究

以南水北调水源区陕西省宁陕县寨沟小流域为例,选择退耕还林区退耕2,5,9,12和16 a的5块样地以及作为对照的坡耕地,对其土壤含水量、容重、孔隙度和有机质进行了采样测定.结果表明,退耕5,9,12,16 a的土壤物理性状较坡耕地有明显改善.其中土壤含水量、孔隙度和有机质均表现为逐渐增加的趋势,土壤容重则随着退耕年限的增加不断减小.而退耕2 a的土壤水分、物理状况与坡耕地相比没有明显改善.随土层深度的增加,土壤含水量、孔隙度和有机质呈逐渐减少、土壤容重呈逐渐增加的趋势.说明通过退耕还林,能够使坡地土壤肥力和保水、蓄水能力得到改良,抗侵蚀能力得以增强,但必须有较长的退耕恢复时间,才可能有明显变化.     

橡胶凋落叶覆盖对胶园土壤部分理化性质的影响

通过田间原位试验,研究橡胶凋落叶覆盖对平地和坡地胶园表层土壤理化性质的影响。试验设置平地凋落叶覆盖、平地凋落叶去除、坡地凋落叶覆盖和坡地凋落叶去除4个处理。结果表明:(1)平地胶园表层土壤含水率大于坡地,凋落叶覆盖较凋落叶去除的坡地土壤含水率显著增加;(2)表层土壤含水率与降雨量呈线性正相关关系,方程斜率表现为坡地大于平地;(3)平地和坡地凋落叶覆盖较其凋落叶去除的土壤pH分别提高了0.09~0.74和-0.09~0.47个单位;(4)与凋落叶去除相比,凋落叶覆盖的有机碳、全氮和碳氮比均有所增加,平地增幅分别为6.9%~68.5%,3.0%~44.8%,3.9%~16.2%,坡地增幅分别为23.3%~95.0%,3.5%~52.5%,7.6%~27.9%,坡地增幅大于平地;(5)与凋落叶去除相比,凋落叶覆盖显著提高平地土壤有效磷含量,增幅为6.2%~48.1%,显著提高平地和坡地速效钾含量,增幅分别为16.4%~83.3%和12.8%~94.8%。综上所述,橡胶凋落叶覆盖可以缓解胶园pH酸化,增加土壤保水能力,改善土壤养分状况。     

Effects of Nighttime Temperature During Kernel Development on Rice Physicochemical Properties

Rice quality can vary inexplicably from one lot to another and from year to year. One cause could be the variable temperatures experienced during the nighttime hours of rice kernel development. During the fall of 2004, a controlled temperature study was conducted using large growth chambers, testing nighttime temperatures of 18, 22, 26, and 30°C from 12 a.m. until 5 a.m. throughout kernel development, using rice cultivars Cypress, LaGrue, XP710, XL8, M204, and Bengal. As nighttime temperature increased, head rice yields (HRY) significantly decreased for all cultivars except Cypress and Bengal, for which HRY did not vary among nighttime temperature treatments. Kernel mass did not vary among temperature treatments for any cultivar. Grain dimensions generally decreased as nighttime temperature increased. The number of chalky kernels increased with an increase in nighttime temperature for all cultivars but Cypress. The amylose content of Cypress and LaGrue was significantly lower at the nighttime temperature of 30°C, while total brown rice lipid and protein contents did not vary among temperature treatments for all cultivars.     

Tillage Effects on Crop Yield and Physicochemical Properties of Sodic Soils

Tillage modifies soil structure and has been suggested as a practice to improve physical, hydrological and chemical properties of compacted soils. But little is known about effect of long‐term tillage on physicochemical soil properties and crop yield on sodic soils in India. Our objective was to investigate the effect of different tillage regimes on crop yield (wheat and paddy rice) and physicochemical properties of sodic soils. Two sodic sites under conventional tillage for 5 (5‐YT; 5‐year tillage) and 9 (9‐YT; 9‐year tillage) years were selected for this study. Changes in crop yield and physicochemical soil properties were compared with a control, sodic land without any till history, that is, 0‐year tillage/untilled (0‐YT). Five replicated samples at 0‐ to 10‐cm and 10‐ to 20‐cm soils depths were analysed from each site. In the top, 0‐ to 10‐cm soil depth 5‐YT and 9‐YT sites had higher particle density (Pd), porosity, water holding capacity, hydraulic conductivity, organic carbon, total nitrogen (N_t), available nitrogen (N_avail), phosphorus (P_avail) and exchangeable calcium (Exch. Ca⁺⁺) than 0‐YT, whereas bulk density (Bd), C : N ratio and CaCO₃ were significantly lower. Bd, pH, EC and CaCO₃ increased significantly with depth in all the lands, whereas Pd, porosity, water holding capacity, hydraulic conductivity, organic carbon, N_t, N_avail, P_avail and Exch. Ca⁺⁺ decreased. We conclude that continuous tillage and cropping can be useful for physical and chemical restoration of sodic soils. Copyright © 2014 John Wiley & Sons, Ltd.     

生物质炭对旱地红壤理化性状和水力学特性的影响

[目的]研究生物质炭对旱地红壤基本理化性质及水分特征曲线的影响,为红壤地区土壤改良提供依据。[方法]分层测定不同生物质炭施用量水平下的土样容重、孔隙度和有机碳含量,采用原状土压力膜法分层测定土壤的水分特征曲线。[结果]施用生物质炭能显著降低土壤的容重,提高土壤的孔隙度及有机碳含量,且随着施用量的增加,土壤容重逐渐降低,孔隙度及有机碳含量逐渐提高;随着生物质炭施用量的增加,土壤饱和含水量、田间持水量和有效水含量逐渐增加,凋萎系数逐渐减小,施用生物质炭30t/hm2的土壤处理饱和含水量、田间持水量和有效水含量最高;生物质炭施用量与土壤饱和含水量、田间持水量和有效水含量呈极显著正相关关系,与凋萎系数呈极显著负相关关系。[结论]施用生物质炭能显著提高红壤田间持水量和有效水含量。     

西双版纳橡胶种植对土壤团聚体及理化性质的影响

热带地区土地利用变化对土壤质量和环境变化具有重要影响。本研究以西双版纳种植约26年的单层橡胶林为研究对象,以热带雨林为对照,分析热带雨林垦殖为橡胶林对土壤团聚体稳定性特征及土壤理化性质的影响,旨在为热带土地管理和生态环境保护提供科学参考。结果表明:与热带雨林相比,单层橡胶林表土(0～5 cm)土壤容重、水稳性微团聚体(<0.25 mm)含量显著升高(P <0.05),EC、p H、土壤孔隙度、土壤含水量、水稳性大团聚体(> 0.25 mm)含量、团聚体平均值重量直径(MWD)和平均几何直径(GMD)显著降低(P <0.05);土壤碳、氮积累量减少,其中表土(0～5 cm)碳、氮积累量显著降低(P <0.05)。这表明热带雨林开垦为橡胶林后,土壤理化性质变差,团聚体稳定性降低,土壤碳、氮积累量减少,从而导致土壤质量退化。此外,相关分析表明:土壤团聚体稳定性指标(水稳定性大团聚体含量、MWD和GMD)均与土壤容重呈负相关,而与土壤孔隙度、含水量、p H、EC、TC、TN呈正相关,说明团聚体稳定性的降低将影响土壤的碳、氮固定能力及部分理化性质,加速土地退化进程。     

甘南高寒草甸退化过程中土壤理化性质和微生物数量动态变化

研究甘南高寒草甸退化草地土壤理化性质和微生物数量动态变化特征,为退化草地改良修复提供理论依据。于2017年5,7,10月分别采集极度(ED)、中度(MD)和轻度(LD)退化草地,以及未退化的对照草地(CK)土壤,测定其理化特性及微生物数量特征。结果表明:CK的土壤含水量在5,7月均显著小于LD、MD和ED的土壤含水量,而在10月显著大于LD、MD和ED的土壤含水量;随着退化程度的加剧,土壤pH逐渐增大,有机碳、全氮和全磷含量逐渐减小;土壤细菌数量对草地的退化反映更敏感,放线菌次之,真菌最小;CK和LD的土壤微生物数量随土层深度下降更为明显;冗余分析结合蒙特卡罗置换检验结果发现,各月份影响微生物数量的环境因子不同,显著影响5月微生物数量的是土壤全磷和土壤含水量,而7月除土壤pH外,其余指标均有显著影响,10月除土壤pH和土壤碳氮比外,植被盖度和生物量等均有显著影响。可见,甘南高寒草甸土壤理化特征和三大微生物数量对退化程度的响应具有季节差异,不同时期影响因素和权重需在草地管理中予以重视。     

生物质炭施用量对旱地酸性红壤理化性质的影响

我国南方旱地酸性红壤区,土壤酸化与干旱等问题突出。近几年生物质炭在土壤改良方面的研究应用已有较多的文献报道,但针对南方旱地酸性红壤区土壤改良方面的研究与应用相对较少。对此,本研究设置了生物质炭施加量分别为1%、2%、3%、4%及对照CK共5个处理,每个处理5次重复的室内盆栽试验;每盆一次性均匀浇洒1 L蒸馏水后在温室内自然放置,模拟干旱30 d,随后测定土壤含水量、p H、电导率与氮、磷含量。结果表明:土壤pH、电导率、有效磷含量随生物质炭施加量的增加而显著提高,NH₄⁺-N含量降低,而NO₃^–-N含量无显著影响;模拟干旱后的土壤含水量与生物质炭施加量呈二次函数曲线关系,施加低量生物质炭(1%)显著降低了土壤含水量,而高量生物质炭(4%)的施加则使土壤含水量显著提高。本研究为生物质炭在我国南方旱地酸性红壤区土壤改良方面的应用提供了试验依据。     

播期对夏播糯玉米淀粉理化特性的影响

为明确夏播糯玉米的适宜播期,以苏玉糯5号和渝糯7号为材料,分析了播期对夏播糯玉米籽粒淀粉理化特性的影响。结果表明,2014年度2个糯玉米品种的淀粉平均粒径在早播和迟播处理下均显著降低,2013年度苏玉糯5号在早播处理下较高,渝糯7号受播期影响较小。播期对糯玉米淀粉的晶体衍射类型无影响,但使尖峰强度发生了变化。淀粉碘结合力随播期推迟逐渐降低,糊化范围在早播和迟播处理下均显著降低。淀粉最大吸收波长、糊化温度、胶凝温度(起始温度、峰值温度和终值温度)受播期影响较小。淀粉膨胀势、黏度特征值、热焓值和回生值在不同播期处理下均发生了变化。相关分析结果表明,生育期较高的积温增加了支链淀粉中长链比例,使谷值黏度升高;降雨量过多易导致淀粉膨胀势下降,热焓值降低;较长的日照时数增加了支链淀粉中长链比例,使淀粉膨胀势、谷值黏度和热焓值升高。因此,在夏播糯玉米生产中,应根据气候条件和生产目标确定适宜播期,提高黏度应提早播种,降低回生应推迟播种。本研究结果为夏播糯玉米淀粉品质调优提供了理论依据。     

不同改良措施对滨海盐土理化性状的影响

为解决滨海盐土原土绿化的难题,合理利用滨海盐土地区丰富的咸水资源和自然降雨,通过田间试验,研究了不同改良措施对滨海盐土物理化学特性的影响。结果表明,"咸水淋盐+翻耕+改良剂Ⅱ+雨季淋盐"的改良措施效果最好,改良后0-20,20-40,40-60cm 3层土壤脱盐率分别为66.4%,69.9%和53.4%,但土壤pH变化不大,并未发生脱盐碱化现象。土壤盐分离子组成由原来的Cl--Na+为主变成了以SO42--Ca2+为主,土壤容重下降最多为27.3%,土壤总孔隙度增加了16.6%,土壤稳渗速率提高最多,土壤有机质和速效磷都有所上升。采用农艺改良措施同时利用咸水和降雨淋洗滨海盐土效果明显,秸秆深翻和施加改良剂都能够加大土壤的淋盐速度和淋盐效果,加入改良剂能够明显抑制土壤脱盐碱化现象。     

退化沙质草地开垦和封育对土壤理化性状的影响

分析了退化沙质草地开垦耕种2年和围封恢复5年后土壤理化性状的特征和变化。结果表明：（1）开垦后2年的耕作,使0－15cm耕作层＜0.1mm细颗粒组分下降了23.8%,其中0－2.5cm表层和2.5-7.5cm亚表层0.1-0.05mm的细沙损失了38.1%和27.0%,土壤的粗粒化程度已接近于流沙;土壤有机碳、全氮、全磷分别下降了38.4%,28.0%和18.4%,下降幅度随土层深度而减小,（2）围封恢复5年后,粒级分布的变化仅发生在0－2.5cm的表层土壤,极细沙（0.1-0.05mm)、粉粒（0.05-0.002mm)和粘粒（＜0.002mm)含量分别提高了43.1%,11.1%和32.5%;土壤有机碳和氮磷养分的显著提高发生在0－2.5cm表层和2.5-7.5cm亚表层,7.5cm土层以下没有变化。（3）草地开垦引发了强烈的风蚀作用,使富含营养的细微颗粒吹蚀,导致有机碳和氮磷养分的损失;采取围封措施后,植被的恢复对土壤养分产生明显的截存和保护效应。     

Effects of Drain and Harvest Dates on Rice Sensory and Physicochemical Properties

Timing of field draining and harvesting of rice with meteorological conditions can allow growers to foster conditions for high head rice yield (HRY). The effects of timing of draining and harvesting on rice sensory and physicochemical properties are not well understood. The objective of this study was to determine the effects of varying drain and harvest dates on the sensory and physicochemical properties of M‐202 grown in California under controlled field conditions. Drain date had a significant (P < 0.05), but very small, effect on amylose and protein contents, with amylose being highest at the late drain date and protein being the lowest at the early drain date. Breakdown and setback were lowest for early and normal drain dates, respectively; however, no significant (P > 0.05) differences in texture were measured as a result of these parameters being low. Drain date did not affect the volatile composition or flavor of the rice. Harvest date had no effect (P > 0.05) on amylose content and a significant (P < 0.05), but very small, effect on protein content. Harvesting at the earliest date (9/30) resulted in rice with higher setback and lower breakdown than at the last date (10/16) and, subsequently, the early harvested rice, when cooked, was harder, more cohesive, and absorbed less saliva in the mouth. However, the differences in texture measured by the panelists were very small and would possibly not be noticed by untrained palates. The lowest levels of the lipid oxidation products 1‐pentanol, hexanal, and nonanal occurred in rice with the lowest harvest moisture content (HMC): rice harvested on 10/13 and 10/16. Differences in levels of lipid oxidation products and branched chain hydrocarbons did not lead to significant (P > 0.05) differences in flavor. In summary, M‐202 demonstrated stable composition, physicochemical properties, flavor, and texture across drain and harvest dates.     

生物质炭长期施用对旱地红壤微生物特性及理化性质的影响

为了解生物质炭施于旱地红壤较长时间后对土壤物理、化学及微生物特性的影响,以江西典型旱地红壤为对象,采用田间长期定位试验的方法观察了不同用量生物质炭(0、2.5、5、10、20、30 t hm~(-2)和40 t hm~(-2))在施用4年后旱地红壤基础理化性质、土壤微生物生物量碳、氮、土壤基础呼吸强度及微生物商、微生物代谢熵等的变化。结果表明,施用生物质炭4年后,旱地红壤pH、有机碳、全氮、微生物生物量碳和生物量氮均随生物质炭施用量的增加呈上升趋势,土壤容重、微生物碳氮比呈下降趋势。以生物质炭用量40 t hm~(-2)时的改良效果最好,与对照相比,土壤容重显著(P0.05)降低了0.17 g cm-3,微生物碳氮比显著降低了7.97,土壤pH、有机碳、全氮、微生物生物量碳和生物量氮分别显著提高了6.1%、47%、21.5%、43.3%和162.6%。试验证明施用生物质炭较长时间后对旱地红壤的改良效果依旧良好,并且生物质炭施用量越高,对土壤理化性质和微生物特性的影响越显著。     

REVIEW: Rye Arabinoxylans: Molecular Structure,Physicochemical Properties and Physiological Effects in the Gastrointestinal Tract

Arabinoxylans (AX) are the main dietary fiber (DF) polysaccharides in rye where they represent ≈55% of the total polysaccharides. Rye AX consist of a backbone of (1→4)‐β‐d ‐xylopyranosyl residues (X) mainly substituted with α‐l ‐arabinofuranosyl residues (A) to varying degrees at the O‐2 position, the O‐3 position, or both. The A/X ratio of total AX is 0.49–0.82 and extractable AX ratio is 0.34–0.85 in different studies. AX also contain small amounts of ferulate residues bound to arabinose as esters at its O‐5 position. The weight average molecular weight varies from 40,000 to 900,000 with an average of ≈200,000. AX influence physiology in different segments of the gastrointestinal tract. The complex molecular structure of rye AX makes them resistant against microbial modification in the small intestine; consequently, rye AX have a much higher influence on the viscosity in the small intestinal digesta than does β‐glucan from oats and barley. In spite of that, it has not been possible in studies with AX‐rich foods such as bread to demonstrate a significant effect on the postprandial glucose response, however, a significantly reduced insulin response has been seen. Nevertheless, addition of 6 g and 12 g of AX‐rich wheat fiber to a breakfast meal has significantly lowered postprandial glucose and insulin response. Studies with hypercholesterolemic pigs fed rye buns rich in AX have resulted in dramatic reductions in plasma total and LDL cholesterol, whereas a gender difference was seen in studies on the effect of AX on plasma lipids in humans. Only certain species of bacteria from the human gut produce the enzymes needed for the degradation of AX. Nevertheless, wheat AX stimulate prebiotic bacteria presumably brought about by cross feeding of lactobacilli and bifidobacteria with degradation products from versatile carbohydrate‐degrading bacteria. Soluble AX are readily fermented in the large intestine, the majority is broken down between the ileum and the cecum. AX, characterized by a low degree of substitution and virtually no doubly substituted xylose, are slowly degraded at more distal locations. The remaining AX, characterized by a high degree of substitution, are not degraded at all. Although the fermentation pattern of AX may vary in different experimental models, in vitro fermentation studies and in vivo intervention studies with animals and humans point to AX as substrates that enhance the formation of butyrate in the large intestine.     

Effects of Roasting and Malting on Physicochemical Properties of Select Cereals and Legumes

Pearl millet, teff, cowpea, and peanut used in the formulation of experimental weaning foods were evaluated for changes in physicochemical properties resulting from roasting and malting. The particle size index (PSI) value for cowpea was significantly higher, indicating a finer flour than that obtained from pearl millet. Pearl millet and teff flours did not have significantly different PSI values, water absorption index values, or gruel viscosities. Viscosities for control and roasted cowpea gruels (15%, w/v) were significantly higher than those obtained from peanut gruels. Malting had the greatest impact on physicochemical properties for all grains, whereas roasting produced no significant differences from control flours. Malting yielded apparent increases in grain protein content, and malted seeds yielded finer flours with reduced water absorption and pasting qualities.