灌溉前后沙质裸地表层土壤蒸发量的时空变异性

利用野外实测数据建立的表层土壤日蒸发量和含水率间的函数关系,估算了灌溉前后3个时段的土壤日蒸发量,并以多种数学方法对其空间特征进行了探讨。结果表明:(1)灌溉后前期(1周)与后期(3周)的土壤蒸发量呈显著的负相关关系,其余各时段蒸发量的相关性不显著;(2)灌溉前土壤蒸发量的总体差异较大,空间关联性很弱,呈随机的斑块状分布,灌溉后总体差异明显减小,空间关联性增强,分布类型转为区域化分布;(3)由随机因素引起的空间异质性在灌溉后则更多地受空间自相关控制;(4)由于林带、芦苇丛和微地形的影响,灌后1周时采样区西边的土壤蒸发量大于东面,其余两个时段东西向无明显差异;灌溉前南部区域土壤蒸发量较北部区域大,灌后1周时该种情形被逆转,灌后3周时又转为向灌溉前回归。     

塔里木沙漠公路防护林土壤盐结皮化学特征及其对土壤蒸发的影响

盐结皮是广泛分布于塔里木沙漠公路防护林土壤表层的一个特殊层次,目前对其化学特征及其对土壤蒸发的影响尚无系统研究。文中对塔克拉玛干沙漠腹地不同定植年限防护林土壤盐结皮有机质含量、全盐量、八大离子含量和pH值进行了分析,并进行了盐结皮抑制土壤蒸发试验,结果表明:土壤盐结皮有机质含量随着防护林定植年限的增加而增加;全盐量、各离子含量、pH值均随着防护林定植年限的增加而逐渐降低。其中,全盐量均远高于流沙地;各离子含量与流沙地相比有不同程度的增加,Cl-、Na+和SO24-增加量最为明显,Mg2+、K+、Ca2+和HCO-3次之,CO23-含量极微且基本没有变化,pH值均呈碱性,定植11年防护林盐结皮pH值甚至低于流沙地;盐结皮可以有效的抑制土壤水分的蒸发。     

不同耕作措施下旱地春小麦田和豌豆田的蒸发蒸腾特性及产量效应

为探明土壤水对旱地作物产量形成的有效性,通过田间定位试验研究了不同耕作措施下旱地农田蒸发蒸腾特性及产量效应。结果表明:免耕秸秆覆盖(NTS)能够增加作物生长期间总蒸散量(ET),麦-豆和豆-麦两种轮作序列下春小麦田和豌豆田的总蒸散量均表现为免耕秸秆覆盖(NTS)>传统耕作(T)>免耕(NT)>传统耕作加秸秆覆盖(TS)。传统耕作土壤棵间蒸发量(E)均高于保护性耕作,春小麦田的土壤棵间蒸发量表现为TS>T>NT>NTS,棵间蒸发量占总蒸散量的比率(E/ET)依次为53.8%,48.8%,37.2%,34.9%;豌豆田棵间蒸发量表现为T>TS>NTS>NT,棵间蒸发量占总蒸散量的比率依次为44.1%,40.9%,35.1%,33.3%。蒸散量及腾发比与产量和WUE在其主要受影响的月份呈正相关关系,且产量与WUE随蒸散量与腾发比的增加而增加。     

Modelling the nitrogen-driven trade-off between nitrogen utilisation efficiency and water use efficiency of wheat in eastern Australia

The nitrogen-driven trade-off between nitrogen utilisation efficiency (yield per unit nitrogen uptake) and water use efficiency (yield per unit evapotranspiration) is widespread and results from well established, multiple effects of nitrogen availability on the water, carbon and nitrogen economy of crops. Here we used a crop model (APSIM) to simulate the yield, evapotranspiration, soil evaporation and nitrogen uptake of wheat, and analysed yield responses to water, nitrogen and climate using a framework analogous to the rate-duration model of determinate growth. The relationship between modelled grain yield (Y) and evapotranspiration (ET) was fitted to a linear-plateau function to derive three parameters: maximum yield (Y_max), the ET break-point when yield reaches its maximum (ET^#), and the rate of yield response in the linear phase (ΔY/ΔET). Against this framework, we tested the hypothesis that nitrogen deficit reduces maximum yield by reducing both the rate (ΔY/ΔET) and the range of yield response to evapotranspiration, i.e. ET^# − E_s, where E_s is modelled median soil evaporation.     

淮北平原1966～2007年蒸发量变化趋势及其影响因素分析

选择安徽淮北平原五道沟实验站1966～2007年的逐年器皿蒸发、不同深度的潜水蒸发资料以及对应的气温、相对湿度、水汽饱和差、风速、日照时数等气象数据计算淮北平原40年来蒸发过程的变化趋势及其与气象因子的关系,分析其相互作用关系。结果表明,近40年来淮北平原温度呈上升趋势,年均温度的增幅逐渐减小有利于蒸发能力增加,而太阳辐射、风速等减少和相对湿度增加蒸发阻力,且后者作用大于前者。在此基础上建立以气象变化因子的蒸发能力预测模型,能很好地反映气候变化过程对水面蒸发、潜水蒸发的影响,有利于评估未来水量平衡关系分析和预测。     

毛乌素沙地典型沙生灌木对土壤蒸发的影响

为了探求半干旱沙区植被恢复后沙生灌木对土壤蒸发的影响,本文利用微型蒸渗仪对盐池沙区的流动沙地、油蒿群落和沙柳群落的土壤蒸发进行了测定,并分析了2014年盐池降雨、风速、太阳辐射、相对湿度、空气温度、土壤机械组成分别与土壤蒸发的关系。结果表明:1) 植被恢复区油蒿群落和沙柳群落土壤蒸发总量比流动沙地分别高出27.91%和40.23%;2) 油蒿和沙柳样地黏粒含量比流动沙地分别高出220.59%和173.53%,油蒿样地和沙柳样地黏粒和粉粒的总含量比流动沙地分别高出63%和98%;3) 油蒿和沙柳样地土壤蒸发与风速、太阳辐射、温度等气象因子相关性不显著,流动沙地土壤蒸发与太阳辐射相关性显著。因此,在半干旱沙区植被恢复后,土壤蒸发有增大的趋势,这很可能与植被恢复后土壤中黏粒和粉粒含量的增加有关。      

The Ant Mosaic - Tropical Tree Crops and the Limiting of Pests and Diseases

Abstract

Field experiments were conducted to determine the effectiveness of herbicides in controlling Rottboellia cochinchinensis (Lour.) W. D. Clayton and Cyperus rotundus L. in upland rice (Oryza sativa L.) at different moisture regimes as imposed by a line source sprinkler system. Preemergence application of pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine] was highly effective in controlling R. cochinchinensis irrespective of soil moisture after herbicide application. Bentazon [3‐(1‐methylethyl)‐(1H)‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide] and 2,4‐D [(2,4‐dichlorophenoxy)acetic acid] applied at postemergence effectively controlled C. rotundus when moisture supply was well above pan evaporation. These herbicides also had no adverse effect on rice stand and resulted in higher yield over the control. Water application rates above upland pan evaporation for a season‐long period was essential to obtain a high response to weed control either by herbicides or hand weeding. The data suggest that proper weed control by herbicides or hand weeding will not result in high upland rice grain yields if moisture level from rains fall below the critical level.     

覆膜开孔条件下新疆地区潜水蒸发及水热关系研究

【目的】分析不同覆膜开孔率对潜水蒸发和地温的影响,并揭示水热之间的关系。【方法】2012-07-29-09-13,在新疆库尔勒巴州灌溉试验站,采用潜水蒸发试验,研究覆膜开孔率分别为0.78%,2.40%,4.80%和100%时,潜水蒸发和0~20cm土层地温的变化,并分析了潜水蒸发与地温的关系。【结果】单位面积累积潜水蒸发量、潜水蒸发系数均随着覆膜开孔率的增加而增大,覆膜开孔率为0.78%,2.40%,4.80%时对应的蒸发抑制率分别为71.27%,70.44%和65.51%。单位面积累积潜水蒸发量与覆膜开孔率和时间之间呈复杂的幂函数关系;一天当中的潜水蒸发主要集中在20:00-0:00和04:00-10:00,而12:00-18:00的潜水蒸发速率接近于0;相同土层深度下地温变幅随覆膜开孔率的增加而增大。覆膜开孔率相同时,地温变幅随着土层深度的增加而逐渐减小,覆膜开孔率越小,土壤表层的温度变幅越小;同时,土壤剖面温度上高下低时,潜水蒸发受到抑制,反之则有利于潜水蒸发。【结论】覆膜能够有效抑制蒸发并减小土壤温度变幅,晚上潜水蒸发大于白天,这与新疆地区土壤剖面温度的变化密切相关。     

Soil Evaporation and its Affecting Factors under Crop Canopy

Abstract

Based on field experiments, changing patterns and affecting factors of soil evaporation and energy balance under crop canopy were studied. Soil evaporation under crop canopy was measured directly using the microlysimetry technique. The main factors affecting soil evaporation under crop canopy including surface net radiation, leaf area index, soil water content, and crop growth period were analyzed to give scientific proof for the soil evaporation control. The results showed that no soil evaporation occurred under the crop canopy when net radiation was reduced to a threshold of 230.57 w/m². Under crop cover conditions, evaporation/evapotranspiration (E/ET) reduced with increases of crop leaf area index, followed by an exponential function to a leaf area index (LAI) threshold of 4. The cumulative evapotranspiration, transpiration, and evaporation under crop canopy conditions during the winter wheat growing season were 443.9 mm, 272.2 mm, and 171.7 mm, respectively, with E/ET having a relatively high value of 38.7%.     

不同秸秆覆盖量对盐渍土蒸发、水盐变化的影响

为探究不同秸秆覆盖量对盐渍化土壤蒸发量、含水率及含盐量的动态变化规律,于2009年在陕西省蒲城县卤泊滩试验基地进行了4个水平的秸秆覆盖量(1.05,0.75,0.45,0.15kg/m2)试验,以不覆盖为对照(C0)。试验结果表明:4个处理盐渍化土壤的日平均蒸发量较C0均显著减少,分别减少1.335 8,1.310 3,1.035 7,0.629 0mm/d;随着时间的延长,各土层土壤含水率逐渐增加,10cm土层平均土壤含水率变化幅度最大,较C0分别增加9.280%,9.000%,6.920%,2.450%;随着时间的延长,10,30cm土层土壤含盐量逐渐减少,盐分逐渐压制在50cm土层,10cm土层平均土壤含盐量变化幅度最大,较C0分别减少0.811%,0.802%,0.723%,0.381%;当秸秆覆盖量为0.75kg/m2时,再增加秸秆用量,保水和抑制盐分表聚的作用并无明显增强。研究表明,采用秸秆覆盖地表改良盐渍化土壤,减少了土壤水分蒸发损失,提高了水分利用效率,抑制了盐渍化土壤可溶性盐分的表聚作用,有效地提高了耕地面积的利用,且秸秆覆盖量以0.75kg/m2为宜。