高浓度臭氧对蒙古栎叶片酚类物质含量和总抗氧化能力的影响

采用开顶箱(OTC)法,研究了高浓度臭氧(80±8 nmol·mol^-1)熏蒸处理对蒙古栎叶片 中总酚、类黄酮、单宁及丙二醛(MDA)含量的影响,使用1,1-二苯基苦基苯肼(DPPH) 法测定了蒙古栎叶片的总抗氧化能力.结果表明:蒙古栎叶片中总酚、类黄酮、缩合单宁和MDA的含量都有所增加,其中总酚和缩合单宁含量分别增加了48.17%和26.77%,差异显著（P<0.05）;类黄酮和MDA含量分别增加了24.66%和5.26%,差异不显著(P＞0.05);蒙古栎叶片总抗氧化能力显著增强(P<0.05),且与叶片中总酚和缩合单宁含量呈显著的正相关关系.     

滴灌与沟灌栽培杨树人工林土壤水分动态与生产力

在北京大兴区永定河故道沙地上对9年生杨树人工林进行滴灌和沟灌栽培,于根系主要分布土层(20、40、60、80 cm)布设土壤水分传感器并利用智能采集器实时监测土壤含水率,分析不同灌溉措施下的土壤水分动态变化及杨树人工林生产力。结果表明: 单次有效的滴灌和沟灌后,沿树行形成的湿润体垂直深度分别为72和143 cm,湿润体横切面的面积分别为0.41和2.71 m²;灌溉量分别为79.20和776.47 m³·hm^-2,后者为前者的9.8倍,灌溉后杨树吸收根主要分布土层(0～40 cm)的土壤含水率下降到水分轻度亏缺临界值(土壤含水率为田间持水量的70%)的历时均为11 d左右。2019年4—10月,沟灌5、7、9月3次总灌溉量为2329.41 m³·hm^-2;滴灌18次,总灌溉量为1425.60 m³·hm^-2。沟灌下杨树人工林土壤水分中度亏缺(土壤含水率低于田间持水量的60%)累计天数达109 d,而滴灌下的杨树人工林土壤水分始终未发生中度亏缺。滴灌下杨树人工林蓄积年生长量为38.92 m³·hm^-2,是沟灌(25.43 m³·hm^-2)的1.5倍,表明不同灌溉措施下杨树人工林生产力差异显著。     

No-tillage effects on soil properties and maize (Zea mays L.) production in Western Nigeria

Summary The grain yields in the no-tillage plots were equivalent to those of conventionally plowed treatments. No-tillage treatments had higher organic matter content and, by controlling soil erosion, the silt and clay content than the plowed plots. The water holding capacity and moisture release characteristics of the surface soil horizon were significantly different for the two tillage treatments. A decrase in the maximum soil temperature and favourable moisture regime in the no-tillage plots stimulated biological activity e.g. earthworms. While the fertilizer had no response on the plowed plots, irrigation had a negative effect due probably to severe leaching losses. No-tillage techniques have a potential in achieving continuous cultivation on otherwise highly erodible and shallow tropical soils.     

温室滴灌条件下土壤水分亏缺对番茄产量及其形成过程的影响

采用小区试验,在温室滴灌条件下研究了不同生育阶段土壤水分状况对番茄果实大小、坐果数、畸形果及产量形成过程的影响,分析了温室滴灌条件下番茄总产量与灌水量的关系.结果表明：番茄苗期适度水分亏缺（田间持水量的50%～55%）可提高坐果率,畸形果形成减少,但果实总体偏小,果实成熟主要集中在采摘后期;开花坐果期过度水分亏缺（田间持水量的65%以下）虽可促进果实成熟,但降低了坐果数,易形成小果和畸形果;采摘期水分过高（田间持水量的80%以上）或过低（田间持水量的65%以下）均可降低番茄产量,水分亏缺（田间持水量的65%以下）则使坐果数降低、畸形果增加.各水分处理对果实成熟时间无明显影响;温室番茄总产量、灌溉水利用效率与全生育期灌水总量之间均呈二次抛物线关系;当番茄土壤水分（占田间持水量的百分比）下限控制在苗期60%～65%、开花坐果期70%～75%、成熟采摘期70%～75%时,番茄畸形果形成量减少,产量及坐果率较高,可作为滴灌条件下温室番茄适宜的土壤水分控制指标.     

控墒补灌对新疆春玉米产量和穗叶光合特性的影响

为探讨北疆绿洲区滴灌春玉米的高产栽培水分管理模式,以‘郑单958’(ZD958)和‘垦玉2号’(KY02)为试验材料,研究了控墒补灌对滴灌春玉米大喇叭口期(V12)至蜡熟期(R5)叶片SPAD值以及灌浆期(R3)穗叶色素、光合和荧光等参数的影响.结果表明: 土壤墒度过低或过高均会显著(P<0.05)降低V12-R3期叶片SPAD值,R5期宜保持在田间持水量的65%以上.灌浆期土壤墒度<75%时玉米叶绿素a、b及叶绿素总含量、类胡萝卜素、叶绿素a/b显著下降,但土壤墒度>85%时差异并不显著;土壤墒度<75%时玉米净光合速率(P_n)、蒸腾速率(T_r)及气孔导度(g_s)显著下降,胞间CO₂浓度(C_i)显著上升,但土壤墒度>85%时并未观察到g_s的降低.土壤墒度过高或过低均可显著降低最大光化学效率(F_v/F_m)、潜在活性(F_v/F_o)、PSⅡ实际光化学效率(Φ_PSⅡ)、光化学淬灭(q_P)和光合电子传递速率(rETR)等荧光参数,热耗散量子比率(F_o/F_m)、非光化学淬灭(NPQ)显著升高;通径分析发现,P_n降低主要由F_v/F_o和rETR的下降导致,最终表现为产量的降低.这表明各生育时期土壤墒度保持在V6>60%、V12 >70%、R1 >75%、R3 >80%、R5 >65%是本地区滴灌春玉米获得高产的最佳水分管理模式.     

Drip irrigation,soil characteristics and the root distribution and root activity of olive trees

A study was carried out on the root distribution and root activity of the olive tree (Olea Europaea, L., var. manzanillo) as influenced by drip irrigation and by several soil characteristics such as texture and depth. The experiments were conducted in two plots within a drip-irrigated grove of 20-year-old trees planted at 7×7 m spacing. One soil was a sandy loam, the other a clay-loam. Both cylinder and trench methods were used to determine root distribution. Labelling with ³²P was used to determine root activity. Under dryland conditions the adult tree adapted its rooting system, following the installation of a drip system, by concentrating the roots within the wet soil zones near the drippers. The highest root densities occur in those zones, down to a 0.6 m depth, the most abundant being the <0.5 mm diameter roots. The most intensive root activity was also found in that zone. For a given irrigation system, wet soil bulbs are more extensive and therefore root distribution expands to a larger soil volume when the soil is more clayey and with a hard calcareous pan present at about 0.8 m depth which prevents deep drainage.     

隔沟交替灌溉条件下玉米根系形态性状及结构分布

为揭示根系对土壤环境的适应机制,研究了隔沟交替灌溉条件下玉米根系形态性状及结构分布。以垄位和坡位的玉米根系为研究对象,利用Minirhizotrons法研究了根系（活/死根）的长度、直径、体积、表面积、根尖数和径级变化及其与土壤水分、土温和水分利用效率（WUE）的相关关系。结果表明,对于活根,在坡位非灌水区域复水后根系平均直径减小,而根系日均生长速率、单位面积土壤根系体积密度、根尖数和表面积均增大,并随灌水区域土壤水分的消退逐渐减小;对于死根,在坡位非灌水区域复水后根系日均死亡速率、根系体积密度、根尖数和表面积变化均减小,其中根系死亡速率和死根直径随土壤水分的消退逐渐降低,而死根体积密度、根尖数和表面积分布随土壤水分降低呈增大趋势;在垄位,根系形态分布趋势与坡位一致,除根系直径与与坡位比较接近外,其他根系形态值均小于坡位。将根系分成4个径级区间分析根系的形态特征,结果表明在根系长度和体积密度分布中以2.5－4.5 mm径级的根系所占比例最大,在根尖数和根系表面积分布中以0.0－2.5 mm径级的根系为主。通过显著性相关分析,死根直径、体积密度、活根表面积等根系形态与土壤含水率、土壤温度和WUE间均存在显著或极显著的正相关关系,部分根系形态指标（如根系的生长速率、活根体积密度）只与坡位土壤含水量、土壤温度具有明显的相关性,表明隔沟交替灌溉对坡位根系形态的调控作用比垄位显著。     

Effect of irrigation frequency and nitrogen on groundnut yield and nutrient uptake

Summary Field experiments were conducted during 1979 and 1980 summer seasons on sandy loam soils of low moisture retentive capacity to study the effect of high frequency irrigation at different levels of N on groundnut yield and nutrient uptake (NPK). Four irrigation frequencies (irrigation at 2, 4, 6 and 8 cm cumulative can evaporation, corresponding to irrigation once in 3, 5, 7 and 10 days respectively) and four levels of nitrogen (0, 20, 40 and 60 kg N/ha) were tested in a factorial randomized block design with three replications. Pod yield of groundnut was maximum (3,293 kg/ha) when irrigations were scheduled at 4 cm cumulative can evaporation (once in 5 days). Addition of N did not increase the pod yield. N and P uptake by the crop was maximum (180 kg N and 18 kg P/ha) with high frequency irrigation of scheduling irrigation at 4 cm cumulative can evaporation. Highest uptake of N (183 kg/ha) and P (19 kg/ha) was with a combination of 20 kg N/ha and high frequency irrigation (4 cm CCE). K uptake was low with low irrigation frequency, while it was highest (67 kg K/ha) at 20 kg N/ha.     

科尔沁沙地东南缘大青沟自然保护区土壤水分的时空分布特征

用TDR分层对科尔沁沙地东南缘大青沟国家级自然保护区土壤水分进行定位观测,采用多重比较等方法,对土壤水分与环境因子关系的差异进行分析,通过Kriging插值法用Surfer软件绘制土壤水分等值线图,研究结果表明:土壤含水率在不同的生长季节上变化,表现为夏季>秋季>春季,各层间没有显著差异;月均(5、7、9月)土壤含水率的变异系数坡向>植被类型>坡位;层均(0~60cm)土壤含水率变异系数坡位>植被类型>坡向>样带。月均土壤含水率从高到低依次为:阔叶林>矮林>樟子松林>疏林草原>灌丛,不同植被类型各层月均土壤含水率总体上差异极显著,阔叶林远远高于其它植被类型;层均土壤含水率,各植被类型各月份间总体差异极显著,总体趋势从高到低为:阔叶林>矮林>樟子松林>灌丛>疏林草原,阔叶林明显高于其它类型。月均土壤含水率坡向间总体上差异显著,层间无显著差异;东、西坡与北坡有显著差异,东西坡高于南北坡;层均土壤含水率,同一月份各个坡向间差异不明显,7月明显高于其它月份;各月总体表现为:东>西>南>北坡。月均土壤含水率除31~45cm外,3个坡位间各层均有极显著差异,下坡位明显高于上坡位与中坡位;中坡位各层月均土壤含水率差异极显著;层均土壤含水率各月份各坡向间差异极显著,下坡位远大于上坡位与中坡位。该区从沟底到坡顶的植被变化逐渐由湿生-中生-旱生逐渐过度,垂直分布明显,这类天然残遗植被与土壤水分及其与环境因子的关系,对于促进周边沙地植被恢复具有重要的参照意义,据此建议了大青沟周边沙地植被恢复模式相应的最低土壤水分阈值,沙地0~30cm土层土壤含水率9.1%~11.5%、8.1%~9.0%、6.0%~8.0%;沙地31~60cm土层土壤含水率11.1%~13%、8.5%~11%、6.0%~8.4%,分别适合恢复为疏林、灌丛、半灌丛。     

卫星土壤水分产品在青藏高原地区的适用性评价

为了分析土壤水分产品在青藏高原地区的可靠性和适用性,利用青藏高原地区地下5 cm深度的地面实测土壤水分数据,结合多种评价指标(相关系数R、均方根误差RMSE、偏差Bias和无偏均方根误差ubRMSE)对土壤水分主动-被动探测卫星(SMAP)、高级微波扫描辐射计2(AMSR2)、风云三号(FY-3B)土壤水分产品,从时间和空间两个方面进行了适用性研究。结果表明:(1)土壤水分产品均能反映青藏高原的土壤水分变化,在降水较多的季节,三种产品精度均有不同程度的下降。(2)土壤水分产品在夏季和秋季反演效果好于冬季和春季,并且在秋季与实测值更接近。其中,SMAP产品在各个区域都能反映土壤水分的季节变化趋势,并普遍在夏季高估、冬季低估;AMSR2产品在夏季低估,冬季明显高估;FY-3B产品在夏季普遍低估。(3)土壤水分产品在那曲和狮泉河地区反演结果较好,在那曲地区与实测值相关性最高;在玛曲地区表现出较大的不确定性,虽然相关系数较高,但RMSE和Bias同样较高,整体精度较差;SMAP产品在阿里地区满足目标精度。综合来看,SMAP产品在青藏高原地区反演结果较为稳定,受气候和环境的影响较小,具有相对较大...     

不同土层测墒补灌对冬小麦耗水特性与光合速率和产量的影响

于2012—2014年两个冬小麦生长季,在大田条件下设置：全生育期不灌水(W₀)处理,当地定量节水灌溉(拔节期和开花期均灌水60 mm,W₁)处理,依据0～20 cm (W₂)、0～40 cm (W₃)、0～60 cm (W₄)和0～140 cm (W₅)土层土壤含水量测墒补灌处理,于拔节期和开花期补灌至土壤相对含水量为田间持水量的65%和70%,研究依据不同土层土壤含水量测墒补灌对冬小麦耗水特性、光合速率和籽粒产量的影响.结果表明：各处理拔节期灌水量为W₁、W₄＞W₃＞W₂、W₅,开花期灌水量和总灌水量均为W₅＞W₁、W₄＞W₃＞W₂,W₃总耗水量显著高于W₂处理,与W₁、W₄和W₅处理无显著差异.W₃土壤贮水消耗量高于W₁、W₄和W₅处理,其中,W₃在拔节至开花阶段和开花至成熟阶段对40～140 cm和60～140 cm土层土壤贮水消耗量均显著高于其余灌水处理.灌浆中期W₃处理小麦旗叶光合速率、蒸腾速率和水分利用效率最高,W₁和W₄处理次之,W₀处理最低.W₃处理两个生长季的籽粒产量分别为9077和9260 kg·hm^-2,水分利用效率分别为20.7和20.9 kg·hm-2·mm^-1,均显著高于其余处理,灌溉水生产效率最高.综合考虑灌水量、籽粒产量和水分利用效率,小麦拔节期和开花期适宜进行测墒补灌的土层深度为0～40 cm.     

灌水定额对旱区苹果园土壤水盐再分布的影响

以甘肃省秦安县盐渍化苹果园土壤为研究对象,采用大田试验的方法在苹果花期研究了不同灌水定额(0、900、1800、2700、3600 m3.hm-2)对果园0～100 cm土层水盐再分布(10、20、30 d)的影响.结果表明:随着灌水定额的增大,Na+淋溶深度增加,且再分布的滞后效应明显;Ca2+的"零通量面"逐渐消失;Mg2+的"零通量面"面宽逐渐增加;Cl-淋溶迁移方式由波动式变为直线式,蒸发迁移方式由波动式变为阶梯式;SO42-再分布方式呈点穴式;HCO3-再分布累积层位逐渐上移.在地下水位埋藏较深的土壤剖面中部存在一个"盐分零通量面",在水分再分布过程中,"盐分零通量面"的位置逐渐向下移动,体现旱地土壤水分耗竭特征.灌水定额在2700～3600 m3.hm-2时,灌溉有利于土壤剖面0～100 cm土层盐分和水溶性Na+的淋洗;灌水定额在1800 m3.hm-2以下时,灌溉加速了土壤表层盐分的累积.从钠盐淋洗和节水两方面综合考虑,旱区盐渍化果园土壤春季适宜的灌水定额为1800～2700 m3·hm-2.     

Abscisic acid signalling when soil moisture is heterogeneous: decreased photoperiod sap flow from drying roots limits abscisic acid export to the shoots

To investigate the contribution of different parts of the root system to total sap flow and leaf xylem abscisic acid (ABA) concentration ([X-ABA]_leaf), individual sunflower ( Helianthus annuus L.) shoots were grafted onto the root systems of two plants grown in separate pots and sap flow through each hypocotyl measured below the graft union. During deficit irrigation (DI), both pots received the same irrigation volumes, while during partial root zone drying (PRD) one pot ('wet') was watered and another ('dry') was not. During PRD, once soil water content ( θ ) decreased below a threshold, the fraction of sap flow from drying roots declined. As θ declined, root xylem ABA concentration increased in both irrigation treatments, and [X-ABA]_leaf increased in DI plants, but [X-ABA]_leaf of PRD plants actually decreased within a certain θ range. A simple model that weighted ABA contributions of wet and dry root systems to [X-ABA]_leaf according to the sap flow from each, better predicted [X-ABA]_leaf of PRD plants than either [X-ABA]_dry, [X-ABA]_wet or their mean. Model simulations revealed that [X-ABA]_leaf during PRD exceeded that of DI with moderate soil drying, but continued soil drying (such that sap flow from roots in drying soil ceased) resulted in the opposite effect.     

Survival and recovery of Phytophthora capsici and oomycetes in tailwater and soil from vegetable fields in Florida

A current trend in Florida agriculture to conserve water is to irrigate with surface runoff water (tailwater) recovered in retention ponds and canals. Water filtration and lemon leaf baiting recovered Phytophthora capsici and other plant pathogenic Oomycetes in runoff water from ponds and canals. A total of 196 isolates of Phytophthora spp. and 471 isolates of Pythium spp. were recovered. Phytophthora spp. included P. capsici, P. cinnamomi, P. lateralis, P. nicotianae, P. citricola, P. cryptogea and P. erythroseptica. Species of Pythium were P. aphanidermatum, P. catenulatum, P. helicoides, P. irregulare, P. myriotylum, and Pythium‘group F’. Isolates of P. aphanidermatum, P. irregulare, P. myriotylum, and Pythium‘group F’ were pathogenic on pepper and tomato. Recovery of P. capsici propagules was related to soil moisture‐holding capacity and time interval but not temperature. Recovery of P. capsici propagules at 100% soil moisture‐holding capacity and 30° C was 57 days. In tailwater, recovery of propagules of P. capsici was 63 days at 24°C to 25°C. The potential exists to reintroduce and disseminate species of Phytophthora and Pythium when using tailwater for irrigation or other practices.     

Effect of alginite amendment on microbial activity and soil water content in forest soils

The effect of the amendment with alginite, an organic rock originating from the biomass of fossilized unicellular algae, on microbial activity of forest soils was tested using a pot experiment. Five variants of soil-alginite mixtures were tested in three replicates with two forest soils: a loose sandy soil and a sandy loam. Gravimetric moisture closely correlated with the dose of alginite in both soils. Basal respiration and catalase activity increased with the dose of alginite in the sandy soil, but not in the sandy loam, where the highest response was observed at intermediate doses of alginite. The correlations of microbial activity parameters with moisture in the sandy soil were also much closer than in the sandy loam. The amendment with alginite was thus effective in improving some of the selected microbial activity indicators, but the optimum dose of alginite strongly depends on soil texture.     

膜下滴灌条件下滴水量和滴水频率对棉田土壤水分分布及水分利用效率的影响

通过两年的田间试验,研究了滴水量和滴水频率对膜下滴灌棉田土壤水分分布及棉花水分利用效率的影响.结果表明:从整个生育期来看,当滴水量(375 mm)相同时,高频滴灌(每3天1次)处理0～20 cm土层含水率较高而深层土壤湿润不够;低频滴灌(每10天1次)处理有利于水分的下渗和侧渗,深层土壤含水率较高,但水分补给不及时,表层土壤偏低;总体上中频滴灌(每7天1次)处理有利于水分在土壤剖面中的均匀分配.当滴水频率相同时,滴水量越大,土壤含水率越高,40 cm以下土层含水率也越高.不同处理的棉田耗水规律基本一致,苗期较低,平均不高于1.7 mm·d-1,蕾期开始上升至花铃期达到最高,日均耗水量可达8.7 mm·d-1,吐絮期回落到1.0 mm·d-1左右.总耗水量与降水和滴水量密切相关,而与滴水频率无关;滴水频率对棉花水分利用效率无显著影响,但水分利用效率随滴水量的增大而显著降低.少量滴灌(300 mm)虽然可以获得较高的水分利用效率,但减产严重,过量滴灌(450mm)无显著增产效应,水分浪费严重.在当地棉田自然条件下,采用中量(375 mm)+中低频(每7天或10天1次)的滴灌模式为宜.     

膜下滴灌条件下滴水量和滴水频率对棉田土壤水分分布及水分利用效率的影响

通过两年的田间试验,研究了滴水量和滴水频率对膜下滴灌棉田土壤水分分布及棉花水分利用效率的影响.结果表明： 从整个生育期来看,当滴水量(375 mm)相同时,高频滴灌(每3天1次)处理0～20 cm土层含水率较高而深层土壤湿润不够;低频滴灌(每10天1次)处理有利于水分的下渗和侧渗,深层土壤含水率较高,但水分补给不及时,表层土壤偏低;总体上中频滴灌(每7天1次)处理有利于水分在土壤剖面中的均匀分配.当滴水频率相同时,滴水量越大,土壤含水率越高,40 cm以下土层含水率也越高.不同处理的棉田耗水规律基本一致,苗期较低,平均不高于1.7 mm·d^-1,蕾期开始上升至花铃期达到最高,日均耗水量可达8.7 mm·d^-1,吐絮期回落到1.0 mm·d^-1左右.总耗水量与降水和滴水量密切相关,而与滴水频率无关;滴水频率对棉花水分利用效率无显著影响,但水分利用效率随滴水量的增大而显著降低.少量滴灌(300 mm)虽然可以获得较高的水分利用效率,但减产严重,过量滴灌(450 mm)无显著增产效应,水分浪费严重.在当地棉田自然条件下,采用中量(375 mm)+中低频(每7天或10天1次)的滴灌模式为宜.     

耕作和覆盖对黄土高原果园土壤水分和温度的影响

研究了几种不同耕作方式（免耕、旋耕和翻耕）和覆盖措施（覆草、生草和覆膜）对黄土高原果园土壤水分和温度的影响.结果表明：5月不同耕作方式下0～1 m土层土壤水分差异极显著,表现为免耕（14.28%）>旋耕（14.13%）>翻耕（13.57%）,9月差异不明显;不同覆盖措施中,覆草处理的土壤水分最高,且与生草、覆膜、裸地处理间差异极显著;不同耕作方式和覆盖组合处理中以免耕覆草保水效果最好.不同覆盖处理白天土壤平均温度表现为覆膜>裸地>生草>覆草,土壤温度变幅表现为裸地>覆膜>生草>覆草.各覆盖处理的蓄水量与其土壤温度并不都呈负相关,而是由不同覆盖物的保水效果和保温性质共同决定.综上所述,黄土高原果园的保护性耕作体系应以免耕覆草为主.     

低压喷灌对土壤-小麦系统氮素时空分布及产量的影响

为建立冬小麦节水省肥的高效灌溉模式,以传统地面灌溉方式(漫灌)为对照,研究不同水量的低压喷灌对冬小麦土壤-作物系统氮素时空分布及产量的影响。结果表明:低压喷灌显著降低了土壤紧实度,增大了开花期后土壤脲酶活性,使土壤硝、铵态氮集中分布在0～60cm的根系密集土层范围内,防止了水分和氮肥的深层渗漏;低压喷灌显著降低了氨挥发速率峰值和氨挥发总量,同时,植株冠层叶片、叶鞘和茎秆垂直分布的全氮含量及氮素转运率均大于传统漫灌,产量及水氮利用效率均有不同程度增加。在本试验条件下,低压喷灌减量15%的处理小麦产量及水氮利用效率最高,水氮损失最少。