不同耕作措施下春小麦和豌豆叶水势变化及其与环境因子的关系

以长期定位试验为基础,对不同耕作措施下春小麦和豌豆叶水势的变化特征及其与环境因子的关系进行了研究,并对叶片相对含水量和水分饱和亏的变化规律进行了探讨.结果表明：豌豆在整个生育期内的叶水势都明显高于春小麦,它们在不同生育期的日变化趋势大致相同,均为清晨最高,然后随着时间的推移而下降,在持续一段低谷后逐渐回升.春小麦各处理的叶水势在拔节和抽穗期相对较高,孕穗和开花期次之,灌浆期最低;豌豆各处理的叶水势在现蕾期达到最大值,分枝和开花期次之,结荚鼓粒期最低.春小麦各处理的叶片相对含水量在抽穗期最高,拔节和开花期次之,灌浆期最低,水分饱和亏的变化正好相反;豌豆各处理的叶片相对含水量随生育进程呈下降趋势,水分饱和亏的变化也与之相反.春小麦和豌豆各处理的叶水势与土壤含水量、气温、太阳辐射、大气相对湿度、大气水势均有显著的相关关系.通径分析表明,对春小麦和豌豆叶水势日变化影响最强的气象因子分别为大气水势和大气温度.与传统耕作相比,免耕、免耕秸秆覆盖、传统耕作秸秆还田3种保护性耕作措施可不同程度地提高作物叶水势和叶片相对含水量,其中免耕秸秆覆盖的优势最明显.     

不同耕作措施对黄土高原旱地土壤呼吸的影响

在甘肃省定西市李家堡镇设置不同耕作措施试验,对春小麦、豌豆双序列轮作下的土壤呼吸及其对应时间的冠层温度、土壤水分进行了测定.结果表明：春小麦和豌豆在整个生育期内的土壤呼吸都表现出不同的变化趋势,春小麦地土壤呼吸在拔节前期、灌浆期和收后分别达到高峰期;豌豆地土壤呼吸在五叶期、吐丝期、开花结荚期和收后分别达到高峰期.免耕秸秆覆盖处理和传统耕作处理下春小麦地土壤呼吸日变化明显,免耕秸秆覆盖处理明显低于传统耕作处理;而豌豆地土壤呼吸日变化不明显.春小麦和豌豆冠层温度均与土壤呼吸呈显著线性相关,春小麦孕穗期相关性最高,灌浆期次之;豌豆开花结荚期相关性最高,分枝期次之.土壤含水量与土壤呼吸间存在极显著的凸型抛物线型相关,保护性耕作下的相关性都高于传统耕作,其中免耕秸秆覆盖处理的春小麦地和豌豆地土壤含水量与土壤呼吸的相关性在各层次土壤中均为最高,10～30 cm土壤含水量对春小麦地土壤呼吸的影响最大,5～10 cm土壤含水量对豌豆地土壤呼吸的影响最大.与传统耕作相比,免耕秸秆覆盖、免耕、传统耕作秸秆还田、传统耕作结合地膜覆盖、免耕结合地膜覆盖5种保护性耕作措施都能不同程度地降低土壤呼吸,其中免耕秸秆覆盖优势最明显.     

保护性耕作条件下旱地农田麦-豆双序列轮作体系的水分动态及产量效应

保护性耕作(conservationtillage)能够减少水土流失、提高耕地产量,是一类具有生态保护意义的持续性农业耕作形式。2002年至2004年在定西旱地农业地区进行了保护性耕作条件下旱地农田春小麦豌豆双序列轮作土壤水分动态及产量效应的试验研究,结果表明:保护性耕作能够显著改善0～200cm土层土壤贮水量及含水量,随着降水量的增多土壤对降水的保蓄能力增强。在降水较少年份免耕秸秆覆盖的这种作用表现突出,而在降水充沛的年份免耕地膜覆盖则更具优势。耕层土壤水分因受降水等因素的影响而变化剧烈,耕层以下土壤水分变幅相对较小。播种期、五叶期及收获期土壤具有较高含水量,而开花期土壤含水量则较低。在两种轮作体系中,播种期春小麦和豌豆免耕秸秆覆盖处理0～50cm土层含水量分别较常规耕作增加28%、26%和11%、23%,降水生产效率较常规耕作提高了17.79%～26.81%。在春小麦豌豆轮作体系中免耕秸秆覆盖处理的作物产量(春小麦 豌豆)及水分利用效率分别为3420kghm2和8.11kg(hm2·mm),较常规耕作分别提高26.81%和25.39%。     

保护性耕作对陇中旱作农田水分特征的影响

陇中旱农区生产力水平低而不稳,而保护性耕作措施是农业可持续发展的重要途径.本研究依托2001年建立在陇中旱农区的长期不同耕作措施的定位试验,研究了不同耕作措施对土壤水分入渗、蒸发、作物产量和水分利用效率的影响.该试验共设6个处理,分别为传统耕作(T)、免耕秸秆覆盖(NTS)、免耕(NT)、传统耕作+秸秆翻入(TS)、传统耕作+覆膜(TP)、免耕覆膜(NTP),春小麦和豌豆年间轮作.结果表明:与T处理相比, NTS处理的小麦地和豌豆地的土壤容重显著降低,总孔隙度显著增加.保护性耕作措施降低了豌豆地0～5 cm土壤渗吸率,NTS处理渗吸率比T处理降低56.2%.保护性耕作提高了土壤饱和导水率,无论小麦地和豌豆地,NTS均比T处理显著提高了饱和导水率,增幅为52.8%～107.1%.保护性耕作显著降低了作物生育期棵间蒸发量,NTP、TP、NTS比T处理降低了14.4%～50.8%,并减弱了雨后土壤蒸发.保护性耕作提高了作物产量和水分利用效率,NTS、TP、NTP的产量比传统耕作提高了9.5%～62.8%,水分利用效率比传统耕作提高了0.4%～50.9%.因此,在陇中旱农区,保护性耕作措施可以提高水分利用效率,增加作物产量.     

不同耕作方式对陇中旱农区春小麦和豌豆根系空间分布及产量的影响

依托陇中旱农区长期的保护性耕作定位试验,对不同耕作方式下春小麦和豌豆根系空间分布特征及作物产量进行研究,以探索耕作措施影响作物产量的机制.结果表明: 随着生育期的推进,春小麦和豌豆的总根长、根表面积呈先增后减的趋势,开花期达到最大;春小麦根系苗期以0～10 cm最多,花期、成熟期10～30 cm最多;而豌豆根系苗期和成熟期均以0～10 cm最多,花期10～30 cm最多.免耕秸秆覆盖和免耕覆膜增加了根长和根表面积,春小麦和豌豆各生育时期的根长较传统耕作增加了35.9%～92.6%,根表面积增加了43.2%～162.4%.免耕秸秆覆盖和免耕覆膜优化了春小麦和豌豆根系分布,与传统耕作相比,增加了春小麦和豌豆苗期0～10 cm土层根长和根表面积分布比例,花期和成熟期深层次根系分布也显著增加,免耕秸秆覆盖在开花期30～80 cm土层根长和根表面积的分布比例分别比传统耕作提高了3.3%和9.7%.春小麦各生育期的总根长、根表面积与产量呈显著正相关,豌豆各生育期的总根长与豌豆产量呈极显著正相关.免耕秸秆覆盖和免耕覆膜较传统耕作春小麦和豌豆产量增加23.4%～38.7%,水分利用效率提高了13.7%～28.5%.在陇中旱农区,免耕秸秆覆盖和免耕覆膜可以增加作物根长和根表面积,优化了根系在土壤中的空间分布,增强作物根层吸收能力,从而提高作物产量和水分高效利用.     

不同秸秆还田和耕作方式对夏玉米农田土壤呼吸及微生物活性的影响

采用基质诱导呼吸法和CO2释放量法,研究了冬小麦季长期不同耕作方式(常规翻耕、免耕和深松)和秸秆处理(秸秆还田和无秸秆还田)对夏玉米田土壤呼吸及微生物活性的影响.结果表明:秸秆还田和保护性耕作主要在O～ 10 cm土层起作用.秸秆还田能明显提高土壤微生物生物量碳和微生物活性,降低呼吸熵,在苗期和开花期提高土壤呼吸,而在灌浆期、腊熟期和收获期降低土壤呼吸;在相同秸秆处理条件下,深松和免耕比常规翻耕能显著降低土壤呼吸和呼吸熵,提高微生物生物量碳和微生物活性.整个生育期,秸秆还田结合保护性耕作能显著提高微生物生物量碳和微生物活性,降低呼吸熵,与常规翻耕无秸秆还田相比,深松秸秆还田和免耕秸秆还田0～10 cm土层微生物生物量碳平均提高了95.8％和74.3％,微生物活性提高了97.1％和74.2％.     

基于15N示踪的东北黑土地保护性耕作农田减氮增产调控机制

保护性耕作是退化黑土地培肥地力的重要措施，但地力提升后氮肥减施条件下保护性耕作农田的稳产增产是否具有可持续性尚不明晰。本研究依托中国科学院保护性耕作研发基地的长期免耕定位试验研究平台，设置常规垄作(RT)、免耕无秸秆还田(NT0)、免耕100%秸秆还田(NTS)和连续9年免耕100%秸秆还田培肥后氮肥减施20%(RNTS)4个处理，采用¹⁵N示踪田间微区试验，探究长期保护性耕作培肥地力下氮肥减施对玉米产量和肥料氮转化的影响。结果表明：经过一个完整生育期，不同耕作方式下肥料氮在东北黑土农田中的土壤残留率、植株利用率和气态损失率平均比例分别为34%、50%和16%;与常规垄作相比，保护性耕作(NTS和RNTS)使肥料氮当季利用效率显著提高了10%～14%。通过氮素来源分析发现，不同耕作方式下植株及各部位(籽粒、秸秆、根和玉米芯)吸收的肥料氮占其总吸氮量的比例均在40%左右，土壤始终是为作物供应氮素的主体；与常规垄作相比，保护性耕作通过降低土壤扰动、增加有机质输入显著提高了0～40 cm土壤全氮储量，有效保障了退化黑土地农田土壤氮库扩容增效。2016—2018年，NTS...     

不同保护性耕作措施对旱作农田土壤水分的影响

研究了黄土高原西部旱农区传统耕作措施和五种保护性耕作措施对土壤水分垂直分布、动态变化、作物耗水量、水分利用效率及作物产量的影响。结果表明,不同保护性耕作措施对表层0~10cm土壤水分含量影响较大,免耕秸秆覆盖(NTS)在作物播种期可以显著增加播种期表层土壤含水量。0~200cm土壤剖面贮水量年变化分春夏作物旺盛生长失墒期(5月中旬~7月中旬)、夏秋雨季增墒期(7月中旬~10月下旬)和冬春稳墒期(11月~翌年5月上旬)3个阶段。尽管不同保护性耕作措施对0~200cm剖面贮水量影响不大,但作物耗水量却存在显著差异。免耕秸秆覆盖在增加作物耗水量的同时也提高了作物产量以及水分利用效率。地膜覆盖在有些年份也有利于降水的高效利用和作物产量的提高,但与秸秆覆盖相比不利于土壤肥力的持续提高。而且,如果种植小麦,出苗前若一次性降水较多时地膜覆盖将造成严重板结,影响出苗,进而降低产量和水分利用效率。因此,在黄土高原西部旱农区实施免耕 秸秆覆盖的保护性耕作措施,既有利于作物对有限降水的高效利用,提高作物产量,也可以促进农业可持续发展。     

保护性耕作对农田土壤水分和冬小麦产量的影响

保护性耕作是提高土壤蓄水保墒能力并增加作物产量的重要农艺措施之一.基于河南省长期定位试验2011-2016年数据,分析不同耕作措施(传统耕作、免耕和深松处理)对土壤水分、作物产量和水分利用效率的影响.结果表明: 2011-2016年免耕和深松耕作处理下冬小麦拔节期平均相对保墒率分别为7.3%和-0.68%,且免耕较传统耕作显著提高了冬小麦拔节期0～60 cm土壤贮水量.与传统耕作相比,免耕提高了冬小麦拔节期、扬花期、灌浆期和成熟期0～100 cm土壤平均含水量,而深松耕作并未明显提高冬小麦拔节期土壤平均含水量.此外,免耕较传统耕作能够显著提高冬小麦产量和水分利用效率,尤其在较干旱年份其增产效果更优.因此,免耕的蓄水保墒及增产效果在较干旱年份明显优于深松耕作.     

耕作方式对冬小麦灌浆期光合性能日变化和籽粒产量的影响

研究耕作方式对冬小麦灌浆期光合性能日变化的影响,对灌浆期干物质积累、转运以及产量形成具有重要的理论意义.本研究以中国农业大学吴桥实验站2008年设置的长期耕作定位试验为基础,分析了免耕秸秆不还田(NT)、免耕秸秆还田(NTS)、旋耕秸秆不还田(RT)、旋耕秸秆还田(RTS)、深松秸秆不还田(DT)、深松秸秆还田(DTS)、翻耕秸秆不还田(CT)和翻耕秸秆还田(CTS)耕作处理对冬小麦灌浆期旗叶光合特性日变化、光响应曲线和产量的影响.结果表明: 不同耕作方式对冬小麦灌浆期旗叶净光合速率日变化和气孔导度日变化的影响均呈双峰曲线变化趋势,秸秆还田下不同耕作方式的冬小麦旗叶净光合速率高于相应的秸秆不还田处理;各耕作方式对冬小麦旗叶胞间CO₂浓度日变化的影响均呈“广口V型”双峰曲线变化趋势;除DTS、RTS和RT处理冬小麦旗叶的蒸腾速率日变化规律呈单峰曲线变化外,其他各处理冬小麦旗叶的蒸腾速率日变化均呈“双峰曲线”变化趋势.模拟的最大净光合速率以DTS处理最大,分别比NT、DT、RT、CT、NTS、RTS和CTS处理增加了20.0%、21.7%、19.7%、21.5%、0.8%、12.1%和4.2%;秸秆还田条件下各处理的光响应曲线拟合程度均优于秸秆不还田处理.DTS籽粒产量最高,RTS次之,CTS再次,CT处理最小,DTS处理的籽粒产量分别比NTS、RTS、CTS、NT、DT、RT和CT处理高10.8%、1.3%、2.1%、5.4%、11.9%、12.4%和12.6%.通过光合速率和气孔导度日变化趋势可得,不同耕作方式下秸秆还田技术,特别是DTS和NTS处理可减缓光合午休现象,使冬小麦维持较高的光合速率,有利于干物质积累和产量的提高.     

Role of water transport in origin of water stress

Intensity of transpiration, intensity of water absorption, water saturation deficit (w.s.d.) in different parts of samples and rate of water transport was investigated in samples from leaf tissue of fodder cabbage and banana-tree. In all experiments (at initial w.s.d. 0% and 20%, in samples from upper, middle and lower leaves of fodder cabbage and from leaves of banana-tree) a distinct gradient of w.s.d. in the direction of transport of water was determined, therefore the limiting factor in the water balance was rate of water transport and not rate of water absorption. The lowest amount of water was always transported within transpiring part of sample. When the initial w.s.d. was 0% not only the water transported by tissue from the environment, but also the water of the leaf tissue itself took part in water lost by transpiration and therefore water stress originated in the whole sample. At an initial w.s.d. of 20%, the rate of water absorption was higher than the rate of water transport and therefore the increase of w.s.d. in the transpiring part of the sample was accompanied by a simultaneous decrease of w.s.d. in the transporting part. An increase in the value of w.s.d. in leaf tissue proportionally increased the resistance of water transport in the liquid phase (on the average from 1·7 . 10³ to 6·7 . 10³ atm min cm² g^?1) and also in the gaseous phase (on the average from 2·7 . 10^?2 to 14·0 . 10^?2 min cm^?1). It was proved that insufficient rate of water transport can be responsible for the origin of water stress. At the same time the rate of water transport was influenced by the value of the w.s.d. since every change of w.s.d. in leaf tissue not only the gradient of water potential changed but also the resistance to water transport.     

Decomposition of young water hyacinth leaves in lake water

Rates of weight loss and release of nutrients during different phases of decomposition in young water hyacinth leaves were determined under laboratory conditions. The leaves decomposed solely by physical leaching during the initial 4-day phase and later by microbial processes. The largest part of weight loss and nutrient release by physical leaching took place within the first 4 h of incubation and thereafter the decomposition rate declined. Microbial processes decayed leaves at a significantly higher rate than that by physical leaching. The overall decay rate constants were related inversely and the release of nutrients directly to the levels of leaf additions in the lake water. The dissolved inorganic and organic nutrients were released chiefly by abiotic processes during the initial as well as later phases of decay. The release was significantly higher during the initial phase in comparison with that during the later phase. Microbes utilized only a small amount of nutrients that were released during decomposition of water hyacinth leaves. The % release of various elements from the decaying leaves was in the order of K > P > C > Na > N.     

Decomposition of water hyacinth detritus in eutrophic lake water

A study was conducted to determine the seasonal production of detritus by water hyacinths [Eichhornia crassipes (Mart.) Sohns] cultured in eutrophic Lake Apopka water, and the decomposition of detritus in situ and under laboratory conditions. Annual averages for C, N and P deposited through detritus production at the sediment-water interface were 2870, 176 and 19 kg ha^-1 yr^-1, respectively.Decomposition rates were faster in the root zone of hyacinth mats than at the sediment-water interface. Approximately 92% of the detritus C deposited at the sediment-water interface was decomposed in one year, while only 11% of the detrital organic N was mineralized. Detrital tissue gained P during decomposition, suggesting P limitation for the system. Dry-weight loss of detrital tissue was significantly correlated with the mass of C lost (r ² = 0.947^**), C/N ratio (r ² = 0.644^**) and C/P ratio (r ² = 0.428^**).Florida Agricultural Experiment Stations Journal Series No. R-00348.     

水的饱和辛醇溶液水分标准物质的研制

生物燃料的国家标准规定了产品的技术指标和相应的检测方法。水的饱和辛醇溶液的水分标准物质,用于生物燃料水分测量时仪器的校准和方法的验证,能够保障测量结果的准确可靠和等效一致。该标准物质采用卡尔·费休库仑法、卡尔·费休容量法和定量核磁共振等三种不同原理的方法定值。通过方法研究和改进,实现了库仑法和容量法的一致;通过引入新的核磁共振方法,提高了结果的准确性。最终标准物质的水分量值为4.76％,扩展不确定度为0.09％。     

Relative water content and water potential of tissue 1

Relative water content (RWC) and water potential as measuredwith the pressure chamber were evaluated as indicators of waterstatus of tissue-cultured apple shoots and plantlets (shootswith roots). During the hydration required for RWC measurement,both water content and water potential exhibited the same hydrationkinetics, indicating that 10 h were required for full hydration.Once full hydration was reached, shoot mass remained relativelyconstant. Moisture release characteristics were also constructedand the associated shoot and plantlet water relations parameterswere estimated. Underin vitroconditions, both shoot and plantletwater potential were similar to the water potential of the culturemedium in which they were grown. The moisture release characteristicof shoots and plantlets was consistent with that expected fortypical plant tissues, and gave estimates of maximum modulusof elasticity (6.201.14 MPa), osmotic potential at saturation(–0.85 0.10 MPa), osmotic potential at zero turgor (–1.16 0.14 MPa) and RWC at zero turgor (78 2%) which were similarto values in the literature. Higher values of leaf conductanceand RWC were found in shoots and plantlets placed at 95% RH(21 C) compared to those at 90% RH. Plantlets had higher valuesof both conductance and RWC compared to shoots, suggesting thatinvitroroots are functional in water uptake. Relative water contentwas related to measures of physiological activity such as leafconductance, and it was also easier to measure than water potential.Relative water content is suggested as a sound index of waterstatus in tissue culture plants. Key words: Conductance, microculture, water status, water stress.     

Inferring foliar water uptake using stable isotopes of water

A growing number of studies have described the direct absorption of water into leaves, a phenomenon known as foliar water uptake. The resultant increase in the amount of water in the leaf can be important for plant function. Exposing leaves to isotopically enriched or depleted water sources has become a common method for establishing whether or not a plant is capable of carrying out foliar water uptake. However, a careful inspection of our understanding of the fluxes of water isotopes between leaves and the atmosphere under high humidity conditions shows that there can clearly be isotopic exchange between the two pools even in the absence of a change in the mass of water in the leaf. We provide experimental evidence that while leaf water isotope ratios may change following exposure to a fog event using water with a depleted oxygen isotope ratio, leaf mass only changes when leaves are experiencing a water deficit that creates a driving gradient for the uptake of water by the leaf. Studies that rely on stable isotopes of water as a means of studying plant water use, particularly with respect to foliar water uptake, must consider the effects of these isotopic exchange processes.     

Global monthly water scarcity: blue water footprints versus blue water availability

Freshwater scarcity is a growing concern, placing considerable importance on the accuracy of indicators used to characterize and map water scarcity worldwide. We improve upon past efforts by using estimates of blue water footprints (consumptive use of ground- and surface water flows) rather than water withdrawals, accounting for the flows needed to sustain critical ecological functions and by considering monthly rather than annual values. We analyzed 405 river basins for the period 1996-2005. In 201 basins with 2.67 billion inhabitants there was severe water scarcity during at least one month of the year. The ecological and economic consequences of increasing degrees of water scarcity--as evidenced by the Rio Grande (Rio Bravo), Indus, and Murray-Darling River Basins--can include complete desiccation during dry seasons, decimation of aquatic biodiversity, and substantial economic disruption.