Effects of Soil Water Content on Cotton Root Growth and Distribution Under Mulched Drip Irrigation

The relation between soil water content and the growth of cotton root was studied for the scheme of field water and cotton yield under mulched drip irrigation. Based on the field experiments, three treatments of soil water content were conducted with 90%, 75%θf, and 60%θf （θfis field water capacity）. Cotton roots and root-shoot ratio were studied with digging method, and the soil moisture was observed with TDR （time domain reflector）, and cotton yield was measured. The results indicated that the growth of cotton root accorded with Logistic growth curve in the three treatments, the cotton root grew quickly and its weight was very high under 75%θf because of the suitable soil water condition, while grew slowly and its weight was lower under 90%θf due to water moisture beyond the suitable condition, and the root weight was in between under 60%θf For the three water treatments, the cotton root weight decreased with soil depth, and decreased more significantly in deeper soil layer with the soil moisture increasing. And the ratio of cotton root weight in 0-30 cm soil layer to the total root weight was the highest under 75%θf. The cotton root system was distributed mainly in the soil of narrow row and wide row mulched with plastic film, and little in the soil outside plastic film. The weight of cotton root was the highest in the soil of narrow row or wide row mulched with plastic film under 75%θf. Root-shoot ratio decreased with the soil moisture increasing. The soil water content affected cotton yields, and cotton yield was the highest under 75%θf. The higher soil moisture level is unfavorable to the growth of cotton root system and yield of cotton under mulched drip irrigation.

Root length density distribution and associated soil water dynamics for tomato plants under furrow irrigation in a solar greenhouse

Furrow irrigation is a traditional widely-used irrigation method in the world. Understanding the dynamics of soil water distribution is essential to developing effective furrow irrigation strategies, especially in water-limited regions. The objectives of this study are to analyze root length density distribution and to explore soil water dynamics by simulating soil water content using a HYDRUS-2D model with consideration of root water uptake for furrow irrigated tomato plants in a solar greenhouse in Northwest China. Soil water contents were also in-situ observed by the ECH_2O sensors from 4 June to 19 June and from 21 June to 4 July, 2012. Results showed that the root length density of tomato plants was concentrated in the 0–50 cm soil layers, and radiated 0–18 cm toward the furrow and 0–30 cm along the bed axis. Soil water content values simulated by the HYDRUS-2D model agreed well with those observed by the ECH_2O sensors, with regression coefficient of 0.988, coefficient of determination of 0.89, and index of agreement of 0.97. The HYDRUS-2D model with the calibrated parameters was then applied to explore the optimal irrigation scheduling. Infrequent irrigation with a large amount of water for each irrigation event could result in 10%–18% of the irrigation water losses. Thus we recommend high irrigation frequency with a low amount of water for each irrigation event in greenhouses for arid region. The maximum high irrigation amount and the suitable irrigation interval required to avoid plant water stress and drainage water were 34 mm and 6 days, respectively, for given daily average transpiration rate of 4.0 mm/d. To sum up, the HYDRUS-2D model with consideration of root water uptake can be used to improve irrigation scheduling for furrow irrigated tomato plants in greenhouses in arid regions.

Root zone soil moisture redistribution in maize (<i>Zea mays</i>L.) under different water application regimes

Soil moisture availability to plant roots is very important for crop growth. When soil moisture is not available in the root zone, plants wilt and yield is reduced. Adequate knowledge of the distribution of soil moisture within crop’s root zone and its linkage to the amount of water applied is very important as it assists in optimising the efficient use of water and reducing yield losses. The study aimed at evaluating the spatial redistribution of soil moisture within maize roots zone under different irrigation water application regimes. The study was conducted during two irrigatation seasons of 2012 at Nkango Irrigation Scheme, Malawi. The trials consisted of factorial arrangement in a Randomised Complete Block Design (RCBD). The factors were water and nitrogen and both were at four levels. The Triscan Sensor was used to measure volumetric soil moisture contents at different vertical and lateral points. The study inferred that the degree of soil moisture loss depends on the amount of water present in the soil. The rate of soil moisture loss in 100% of full water requirement regime (100% FWRR) treatment was higher than that in 40% FWRR treatment. This was particularly noticed when maize leaves were dry. In 100% FWRR treatment, the attraction between water and the surfaces of soil particles was not tight and as such “free” water was lost through evaporation and deep percolation, while in 40% FWRR, water was strongly attracted to and held on the soil particles surfaces and as such its potential of losing water was reduced.

植物根系特征与根区土壤水分高通量监测管道机器人研制

研究水分胁迫下的根系特征对于节水农业的发展具有重大意义。针对现有根系观测与土壤水分监测方法难以满足野外条件下根系和根区水分的同步、原位、高通量监测的不足,该研究研制了一种基于STM32芯片的管道机器人系统。系统由管道机器人、数据基站与PVC透明管道组成,通过在土壤中埋设管道机器人系统,控制机器人搭载的微距相机与土壤水分传感器在巡航时拍摄根系图像,并获取土壤水分数据。由根系图像识别分割与提取程序对图像进行畸变校正与根系识别,获取管道方向上植株的根系面积、长度与密度等特征参数。实验室条件下进行相机拍摄效果、图像畸变校正、识别与分割误差及里程轮测距误差测试,以及土壤水分传感器标定试验。测试结果表明:1)管道机器人能够清晰地拍摄到根系图像,图像畸变校正效果较好,单个像素点长度和面积分别为44μm和0.002 mm^(2),单张根系图像的拍摄范围为14.17 mm×10.60 mm;2)土壤水分传感器输出电压与土壤体积含水率之间呈现良好线性关系,决定系数R^(2)为0.990;3)自主巡航定位准确度较高,平均相对误差为1.47%。在田间条件下进行的根系生长动态监测、根系信息提取、土壤水分监测与电池续航试验表明:1)管道机器人系统能够在田间环境下高通量地拍摄根系图像,监测根系的生长动态,并进一步提取出根系长度、面积、根面积密度等特征参数;2)根区土壤水分监测较为准确,测量结果与烘干法结果平均相对误差为2.23%;3)在系统初始满电量状态下,管道机器人系统独立运行时长不少于7 d,最大巡航监测距离约为48 m。本文研制的管道机器人系统可在田间条件下实现根系特征以及根区土壤水分的原位、高通量测量,为节水灌溉与根系生长研究提供技术支持。

植被根系含量对膨胀土持水和渗透特性的影响

为探究植被根系含量对膨胀土持水和渗透特性的影响规律,选取南宁市膨胀土地区的膨胀土,掺入狗牙根根系制备不同含根率的试样,进行室内压力板仪试验和变水头渗透试验,采用Van Genuchten-Mualem模型预测不同含根率的膨胀土非饱和渗透系数。结果表明:掺入根系后,膨胀土持水能力减弱,根系掺入增加膨胀土内部大孔隙的比例,含根率越高,大孔隙体积占总孔隙体积比例越大,持水能力相较于纯土下降的幅度越大;饱和状态下,膨胀土渗透系数随含根率增大而增大;非饱和状态下,低吸力阶段(0~25 kPa)的膨胀土渗透性随含根率的增大而增大,随着基质吸力增加到高吸力阶段(200~1 000 kPa),根系优势流效果减弱,含根膨胀土渗透性逐渐趋近低于纯土;细观结果表明根系的掺入使膨胀土内部产生贯通裂缝,是影响膨胀土持水和渗透能力的关键因素。研究进一步揭示了植被根系对膨胀土增渗作用的机理和规律,为综合评价植被防护膨胀土边坡效果提供参考。

含水率对根-土石复合体抗剪强度影响的试验研究——以垂丝海棠为例

【目的】探究含水率对根-土石复合体抗剪强度的影响规律。【方法】以四川农业大学雅安校区老板山典型固坡植物垂丝海棠为研究对象,固定剪切面含根量为0.2%、含石量为30%,设置5种含水率梯度(10%、15%、20%、25%、30%),分别在50、100、150和200 kPa的四级正应力下进行室内直接剪切试验,分析含水率对抗剪强度及其指标(黏聚力和内摩擦角)的影响规律。【结果】根-土石复合体的抗剪强度随正应力的增大而增高,符合莫尔-库伦强度准则,其抗剪强度随含水率的升高呈先下降后上升随之再下降的趋势,呈多峰曲线变化,在含水率为20%时取得最小值;含水率对根-土石复合体的黏聚力影响较大,在含水率为25%时取得临界峰值,但含水率对根-土石复合体的内摩擦角影响较小。【结论】含水率的变化主要影响根-土石复合体的黏聚力,从而影响根-土石复合体的峰值抗剪强度,而对内摩擦角的影响较小。研究结果可为植被加固土石混合体边坡提供一定的理论支撑。

Root distribution of three co-occurring desert shrubs and their physiological response to precipitation

Root distribution of three desert shrubs,Tamarix ramosissima Ledeb.,Haloxylon ammodendron(C.A.Mey.) Bunge and Reaumuria soongorica(Pall.) Maxim.was investigated under co-occurring conditions using a method for excavating the whole root system.Assimilation shoot water potential and transpiration rates were monitored during the wet-dry cycle.Leaf-specific apparent hydraulic conductance and the index of water stress impact for the three species were calculated from shoot water potential and transpiration rate.The results showed that,along the soil profile,the root system of T.ramosissima mainly distributed at 50 to 310 cm interval,with an average total absorbing root-surface area of 30,249.2 cm2 per plant;the root system of H.ammodendraom distributed at 0 to 250 cm interval with an average total absorbing root-surface area of 12,847.3 cm2 per plant;the root system of R.soongorica distributed at 0-80 cm interval,with an average total absorbing root-surface area of 361.8 cm2.The root distribution shows the following:T.ramosissima uses groundwater as its main water source;H.ammodendraom uses both groundwater and rainwater;and R.soongorica uses rainwater only.During the wet-dry cycle,the hydraulic parameters of T.ramosissima showed no responses to precipitation.R.soongorica responded most significantly,and the responses of H.ammodendraom were intermediate.In conclusion,the plant response to rain events is closely related to their root distribution and plant water-use strategy.

Effects of Two-Year Variation in Soil Moisture Condition on the Development of Larch Root System in Eastern Siberia

Recent climate changes, including an increase in precipitation, have affected tree physiology in eastern Siberia. We investigated the response of larch to wet and dry soil water conditions in pot experiments using larch seedlings grown under near-natural conditions in eastern Siberia over two growing seasons. Three patterns of wet- and dry-treatment combinations were applied over 2 years: wet treatments in 2006 and 2007 (WW treatment), dry in 2006 and wet in 2007 (DW treatment), and dry in 2006 and 2007 (DD treatment). After 1 year of treatment, no significant difference between the dry and wet treatment was found in root distribution and needle water content, except for the content of abscisic acid in roots. After 2 years of treatment, the DW treatment induced different tendencies in the gas exchange activity and in the needle biomass and root distribution of seedlings in comparison with WW treatments, despite the same water condition in 2007. We suggest a possibility that seedlings that experience drought stress might store some memory of drought that influences their physiology in the next growing season.

Determination of drought tolerance using root activities in Robinia pseudoacada 'Idaho' transformed with mtl-D gene

Idaho locust （Robinia pseudoacacia ‘Idaho＇） is an exotic multi-purpose tree used in landscaping, soil and water conserva- tion, fodder sources and others. To improve its drought tolerance for reclaiming arid land, five lines of transformed mtl-D gene, as osmotic regulator in plant cells, have been selected and managed to determine their drought tolerance under experimental conditions. Qualitative and quantitative variables of transformed plants were studied. The critical value of drought tolerance was determined by detecting the 2,3,5-triphenyl tetrazolium chloride （TTC） reductants in roots and soil water content （SWC）. The critical value for drought tolerance was SWC 6% while for the control plants the critical SWC was 8%; a moderate level of SWC is 13% and the highest SWC for plant endurance was 18%. The method proved to be reliable and sensitive in the evaluation of drought tolerance for forest trees.

刺槐根土复合体抗剪强度试验

植被边坡的稳定性与其根土复合体的抗剪强度密切相关,其主要受根系作用与水分作用的影响。通过直剪试验和SWCC试验获取了含根量和含水率与抗剪强度及其指标的关系,推导出根土复合体的强度计算模型。结果表明:刺槐根系能显著增强土体抗剪强度,黏聚力随含根量的增加先增大后趋于平缓,内摩擦角随含根量的增加有所增大,但增长幅度较小;抗剪强度随含水率的增大迅速降低,黏聚力与内摩擦角变化趋势与抗剪强度一致,内摩擦角变化幅度较小;含根量与含水率对土体抗剪强度的影响均体现在黏聚力的变化上;将根土复合体视为含根非饱和土,推导出根土复合体强度计算模型,强度模型的计算值与试验实测值较为接近,对于根土复合体的强度计算有一定的参考价值。

残膜污染对滴灌玉米土壤水分和根冠生长的影响

为充分分析残膜量对河套灌区农业生产的影响,进一步认识和评价残膜污染的负面效应,制定合理的田间残膜防治措施.2019~2020年在河套灌区九庄农业综合节水试验站开展了2年田间试验,设置0(CK)、150(T1)、300(T2)、450(T3)和600kg/hm^(2)(T4)5个残膜量处理,研究不同残膜量对土壤水分、玉米叶片光合特性、根冠生长及产量的影响.结果表明,当残膜量在0~300kg/hm^(2)范围内,残膜以阻滞水分入渗为主,增加了0~30cm土壤含水率;当残膜量≥450kg/hm^(2)时,水分阻隔效益减弱,同时产生优先流,导致0~30cm土壤含水率减少.残膜量增加还会降低玉米的光合性能,减少玉米根干重和冠层干物质量,破坏根冠生长平衡,特别是在生育前期,与0kg/hm^(2)处理相比,600kg/hm^(2)处理苗期的根干重、干物质量和根冠比分别平均减小48.66%、34.63%和18.17%.另外,残膜污染的加剧严重影响了玉米产量形成和水分有效利用,600kg/hm^(2)处理的产量和水分利用效率较0kg/hm^(2)处理分别平均下降34.05%和28.85%.研究表明,残膜污染持续加剧的情况下,会影响土壤水分入渗,降低玉米光合能力,抑制玉米生长,最终导致玉米减产.因此,采取适当的农田残膜污染治理措施,有利于平衡根冠生长,改善光合性能,推进河套灌区膜下滴灌玉米农田绿色可持续发展.

基质及含水量不同对猕猴桃扦插生根的影响

以‘徐香’猕猴桃为试材,采用嫩枝扦插法进行繁殖,研究基质及含水量不同对猕猴桃扦插生根的影响。结果表明:不同配比基质含水量不同对猕猴桃扦插生根有影响。基质相对含水量为70%时,蛭石和珍珠岩按1∶1的扦插生根效果最好,生根率为66.50%,平均生根数量为4.50条,平均根长为5.83 cm。以期对‘徐香’猕猴桃扦插技术应用推广具有重要意义。

差巴嘎蒿灌丛土壤和根系含水量对降雨的响应

以科尔沁沙地半固定沙丘灌木差巴嘎蒿(Artemisia halodendron)为对象,用土钻取样法和壕沟法研究了2006年生长季降雨后差巴嘎蒿周围土壤和根系含水量的时空分布特征及其相互关系,并计算了该灌丛的水量平衡。结果表明:该灌丛在降雨后对水分有暂时存储作用;降雨结束后,灌丛主干的茎流作用使得灌丛中心位置的土壤含水量高于灌丛丛幅垂直投影1/4和3/4处的土壤含水量;雨后6h灌丛根系含水量与灌丛中心位置的土壤含水量呈极显著的负相关(r=-0.89,P<0.01);灌丛根系含水量在雨后126h内出现胁迫脉冲间歇反应。水量平衡计算表明,灌丛边缘外1m处土壤蒸散量高于灌丛覆盖区的蒸散量,灌丛覆盖可降低土壤水分蒸散速率。

干旱胁迫对春大豆叶绿素含量和根系活力的影响

以抗旱性不同的3个春大豆品种为材料,对各生育时期不同干旱胁迫条件下叶片叶绿素含量、根系活力和根系相对含水率的变化进行了研究。结果表明:随干旱胁迫程度的增加,叶绿素含量、根系相对含水率显著降低;根系活力苗期>开花期>结荚期>鼓粒期,根系相对含水率鼓粒期>结荚期>开花期>苗期。在干旱胁迫条件下,叶绿素含量在苗期、根系活力在苗期、开花期和结荚期,均表现为黑农57>改良168>绥农26;根系相对含水率在中度干旱胁迫下黑农57>改良168>绥农26。当田间持水量为30%～75%时,根系相对含水率与叶绿素含量呈极显著正相关,与根系活力呈极显著负相关。

抗旱、敏旱棉花材料苗期根系特性研究

【目的】研究棉花耐旱品种KK1543和敏旱品种新陆早26号的苗期根系特性,为棉花育种工作提供基础理论数据。【方法】以棉花耐旱品种KK1543和敏旱品种新陆早26号为材料,用1/2 Hoagland营养液培养并观察记录和测量棉花的根长密度、一级侧根数量,两叶一心时期用15%PEG6000模拟干旱胁迫0、24、48和72 h后测根的含水量、根冠比。【结果】KK1543和新陆早26号在苗期根生长速度基本相同,一级侧根生长呈S型曲线。胁迫前KK1543根含水量和新陆早26号处于相同水平。胁迫后新陆早26号根含水量下降幅度显著高于KK1543,KK1543的根冠比增加显著高于新陆早26号。【结论】KK1543和新陆早26号在1/2 Hoagland营养液中能较好的生长,15%PEG6000的处理后两个品种的根系特性变化具有一定可比性。

不同土壤水分处理对冬小麦根冠生长的影响

通过温室冬小麦不同水分处理(土壤含水量分别为田间持水量的75%～100%,65%～55%,35%～45%)盆栽试验,研究了冬小麦根冠对水分的响应。试验结果表明:不同供水量并不影响冬小麦根系、冠层干物质累积过程的总趋势,但随胁迫的增强,根、冠干物质累积速率、干物质累积总量降低,且二者并不呈线性相关关系;根冠比(R/S)随胁迫的增强而增大;水分供应量的减少缩短了冬小麦的生育周期,随胁迫的增强,根冠生物量最大值出现的时间提前;充分供水的处理则有最大的根冠比(R/S)。这可能是由于水分胁迫发生,大量的同化产物运往根系,分配于根系的同化干物质增加,调整了根系的结构,改善其功能以增大水分的吸收量,缓减植株由于缺水造成的损失,导致根系干重增加,根冠比增加。对于供水超过75%的植株,根冠比达到所有处理的最大,可能原因为过量水分促使庞大根系的建成,从而消耗较多的同化产物,使根重增加,冠重减少。

干旱荒漠区沙蒿种群根系生态特征研究

用全挖取样法研究了干旱荒漠区不同类型沙地上沙蒿种群的根系生态特征。结果表明,沙蒿根系总生物量在不同类型沙地上有所变化,其排序为流动沙地（122.43 g）〉封育沙地（106.35g）〉半固定沙地（90.15 g）;从根系分布深度看,在不同类型沙地上,沙蒿根系生物量集中分布在0-40cm土层中,占75%以上;沙蒿的主根生物量在0-20cm土层中最多,其根系生物量占全部根系生物量的比例在封育沙地为67.11%,流动沙地为53.52%,半固定沙地为62.48%;侧根生物量在封育沙地和半固定沙地中在0-20cm土层中最多,而流动沙地集中于20-40cm土层;在不同类型沙地上,沙蒿根系生物量与土壤含水量之间均相关紧密。

毛乌素沙地不同水分梯度根系垂直分布与土壤水分关系的研究

通过对毛乌素沙地不同水分梯度根系垂直分布的研究表明:不同水分梯度根系分布随土壤深度的增加呈指数形式下降,不同梯度由于土壤水分、植被根系类型的差异,不同水分梯度植被根系的空间分布也有差异,不同梯度根量随土壤垂直深度的模拟方程分别为:y=9.5736e-0.1341x,R2=0.8859(I);y=16.246e-0.2037x,R2=0.9301(II);y=32.001e-0.1904x,R2=0.9544(III);y=28.336e-0.1993x,R2=0.9484(IV)。不同水分梯度土壤含水率变化程度不同,同一水分梯度各层土壤含水率变化幅度亦有差异,0.1m土壤含水率变异系数最大,随着土壤深度增加变异系数减小,根据土壤含水率变异系数分析我们将各层土壤水分垂直变化划分为活跃层(0-0.1m)、次活跃层(0.2-0.6m)、相对稳定层(1m)(I、II、III);而对IV梯度划为活跃层(0-0.1m、1m)、相对稳定层(0.3m)。根系生物量垂直分布与其对应土壤含水率有明显相反的关系,土壤含水率的变化与根系生物量的变化趋于相反,当土壤含水率增大时相应区域根系生物量减小;反之则增加。随水分梯度的增加各梯度最高水分利用层逐渐向表层发展,从第I梯度0.4m的6.84到第IV梯度0.1m的14.33。

土壤水分与温度共同作用对植物根系水分传导的效应

本文根据不同大气环境温度和土壤温度及不同土壤含水率处理条件下的玉米、向日葵、台湾相思（Ａｃａｃｉａｃｏｎｆｕｓａ）、银合欢（Ｌｅｕｃａｅｎａｇｌａｕｃａ）的试验资料，分析了土壤水分和温度以及土壤水分与温度共同作用对植物根系水分传导的效应。台湾相思和银合欢的试验结果表明，在一定的土壤水分范围内，高温（白天／夜晚的温度为４０／３０℃）环境中的根系水分传导大于低温（３０／２５℃）环境中的，但当根系水分胁迫十分严重（台湾相思根系水势小于－１．５ＭＰａ，银合欢根系水势小于－２．０ＭＰａ）时，３０／２５℃环境的根系水分传导反而大于４０／３０℃环境的；玉米、向日葵的试验结果表明，在一定土壤温度范围内，根系水分传导随土壤温度增加而增加，其增加的幅度与生育阶段有关；在向日葵生育期土壤温度高于３５℃、玉米生育期高于３０℃时，其根系水分传导随温度增加而降低。通过植物根区土壤逐渐干旱和干旱复水后的试验，其结果表明复水后根系水分传导上升较快，银合欢复水１．５ｄ、向日葵复水３ｄ后测得的根系水分传导即可达到受旱前的水平，其后的水分传导还略高于一直充分供水处理的，表明根系经受一定程度的干旱锻炼后，对其水分传导具有明显的补偿效应。在干旱和复?