3种土壤灌溉后通气小白菜的水分及养分利用特性

选取3种河南省典型土壤(郑州黏土、洛阳粉壤土和驻马店砂壤土),以小白菜为供试作物,采用地下滴灌供水,设置常规灌溉为对照组(CK)、灌溉后通气(MV)为试验组开展盆栽试验,研究灌溉后通气对小白菜水分和养分利用的影响.结果表明,与CK相比,处理MV显著地提高了3种土壤小白菜根系活力、根干质量和净光合速率.处理MV显著提高了小白菜蒸腾速率,其中,黏土、粉壤土的分别提高了20.61%和15.98%.黏土在处理MV时,小白菜产量和水分利用效率分别提高了38.08%和52.70%;小白菜氮、磷、钾吸收效率分别增大了61.65%,66.54%,104.83%.粉壤土在处理MV时,小白菜磷、钾吸收效率分别增大了50.60%,73.65%.砂壤土在处理MV时,小白菜磷、钾吸收效率分别增大了40.84%,26.19%.以上差异均具有统计学意义(P<0.05).综上,黏土灌溉后通气处理对小白菜水分、养分利用及产量的提高效果最为显著.     

紫茄生长及养分利用对增氧地下滴灌的响应研究

【目的】探究不同土壤条件下增氧灌溉方式对作物生长、产量及养分利用的影响。【方法】以郑州黄黏土、洛阳粉黏质壤土和驻马店砂壤土为供试土壤,以常规地下滴灌为对照(CK),设置曝气灌溉(AI)与化学增氧灌溉(HP)2种增氧方式,研究了温室紫茄生长及养分利用对增氧地下滴灌的响应。【结果】与CK相比,AI和HP处理提高供试土壤中紫茄净光合速率,黄黏土、粉黏质壤土和砂壤土下分别增加19.66%和8.49%、14.02%和7.51%、10.13%和5.91%。同时,AI和HP处理均显著促进根系生长、提升根系活力,进而提高紫茄的养分吸收效率、产量和水分利用效率(P<0.05)。其中,黄黏土下AI和HP处理作物氮吸收效率分别提高136.16%和65.43%,紫茄产量提高46.85%和28.49%,水分利用效率提高44.59%和27.38%;粉黏质壤土AI和HP处理作物氮素吸收效率分别提高141.23%和88.76%,产量分别提高41.52%和20.68%,水分利用效率提高41.06%和21.39%;砂壤土AI和HP处理作物氮素吸收效率分别提高112.60%和45.47%,产量提高49.86%和17.59%,水分利用效率提高48.81%和17.97%。【结论】曝气地下滴灌对紫茄生长、水分和养分利用的促进作用较为显著,而在不同土壤类型下,曝气地下滴灌对砂壤土紫茄产量增产及水分利用效率提升效果最优。     

基于水稳定同位素技术的生物炭对土壤持水性影响分析

以不同生物炭配比的土壤样品为研究对象,通过低温真空抽提和稳定同位素光谱技术,进行不同抽提时间下的土壤水稳定同位素分析,采用绘制土壤抽提曲线和计算抽提贡献率的方法,探讨生物炭对土壤持水性的影响。结果表明,低温真空抽提下,砂土的最短抽提时间(T_(min))为30 min,壤土为45 min,粘土为60 min。土壤持水性的变化会导致抽提过程中水稳定同位素值、T_(min)和抽提贡献率发生变化,通过分析不同生物炭配比下土壤的T_(min)、水稳定同位素分馏情况以及计算贡献率可得出,生物炭显著影响砂土持水性,且与生物炭添加量呈线性正相关;而对壤土和粘土的持水性有一定影响,但过量或过少则不明显,壤土对生物炭更为敏感。     

滴灌条件下山区典型土壤水分运移规律分析

在广西山区选择沙土、壤土和黏土等3种典型土壤,并开展滴灌在这3种土壤条件下的土壤水分运移规律研究。试验结果表明:1在地埋黏土、壤土和沙土以及0.10 MPa工作压力条件下,滴灌管的单米流量为4.17、5.92和6.10 L/h,为地表自由出流的67.58%、95.05%和98.87%;2滴灌在黏土的水分运移形状基本为圆形,在沙土和壤土的湿润形状为上小下大的椭圆形;3同等条件下,水分在沙土的水平和垂直向下运移速率最大,壤土次之,黏土最小;4在土箱相同位置,黏土的土壤含水率最大,壤土次之,沙土最小;5根据滴灌的土壤水分运移规律,提出滴灌管在广西山区沙土、壤土和黏土的适宜埋深分别为10、15和20 cm;6滴灌应用在山区条播作物时,在黏土、壤土、沙土的适宜滴孔间距应为35、30和25 cm。     

土壤斥水性与有机质质量分数的变化关系研究

土壤有机质质量分数是影响土壤斥水性的最主要因素之一,为研究二者之间的关系,选用以色列3类不同质地斥水性土壤为对象,分别在田间和实验室测定土壤斥水性和有机质质量分数,并绘制土壤斥水性和有机质质量分数的等值线图和关系图。结果表明,对于粘性土壤和沙质土壤,土壤斥水性随有机质质量分数成幂指数关系,但对于壤土,二者之间没有非常明显的线性关系。研究结果可为分析不同土壤的斥水性影响因素和土壤改良提供理论依据。     

Compressibility of Some Trinidadian Soils as Affected by the Incorporation of Peat

The effect on compressibility of incorporating peat into four remoulded Trinidadian agricultural soils was investigated over a range of stresses from 0 to 1000 kPa using a compression machine. Air-dry peat was applied at four levels (0, 4, 8 and 12% by mass) to the soils (two sandy loams, clay loam and clay) and tested at three moisture contents close to the Proctor optimum moisture content of the soils. Compression curves (bulk density versus log applied stress) for each soil at the moisture levels tested were almost linear and parallel over the range of stresses from about 100 to 1000 kPa.Mean values of dry bulk density declined significantly at 0.001 level with increasing peat content from 1·23 to 0·87 Mg m^-3. Mean bulk density values increased significantly at 0·001 level with increasing applied stress and moisture content and declined with increasing clay content. Significant interaction effects were observed between soil type and peat content and between peat content and moisture content. Peat incorporation resulted in greater soil compression, but the increases were less evident in clay than in sandy loam soils. Soil compression refers to the decrease in soil volume with the application of external load. The compression index, C (slope of the dry bulk density versus log applied stress relationship), increased significantly at 0·05 level from 0·21 Mg/m³ in one sandy loam soil to 0·38 Mg/m³ in the clay soil. While the C value did not differ significantly with increasing peat content in the sandy loams and the clay loam, it decreased significantly at 0·01 level in the clay soil. An equation expressing C as a function of initial soil bulk density before compression and a strain parameter was developed in order to explain the variation of C in the soils tested. A method is described that can be adopted to quantify the effect of peat on soil compressibility.     

An assessment of the energy inputs and greenhouse gas emissions in sugar beet (Beta vulgaris) production in the UK

Reducing the energy derived from fossil fuels within agricultural systems has important implications for decreasing atmospheric emissions of greenhouse gases, thus assisting the arrest of global warming. The identification of crop production methods that maximise energy efficiency and minimise greenhouse gas emissions is vital. Sugar beet is grown in a variety of locations and under a variety of agronomic conditions within the UK. This study identified thirteen production scenarios, representative of over 90% of the UK beet crop, which included five soil types, nine fertiliser regimes and nine crop protection strategies. The fossil energy input, the overall energy efficiency and the global warming potential (GWP) of each production scenario was assessed. This study did not consider the processing of the beet to extract sugar.The overall energy input of the UK beet crop ranges between 15.72 and 25.94 GJ/ha. It produces between 7.3 and 15.0 times as much energy in dry matter at the sugar factory gate as consumed in its production, with an average ratio of 9.7. It has an average GWP of 0.024 eq. t CO₂ per tonne of clean beet harvested, equivalent to 0.0062 eq. t CO₂ per GJ output. The energy input into each scenario was dictated largely by the energy associated with crop nutrition. The smallest energy inputs per hectare were to crops grown under organic conditions or conventional crops grown on fertile soils (clay loam, silt or peat) or sand soil with broiler manure applied. Those crops with the greatest energy input were grown on sand soil that was irrigated and had mineral fertiliser applied. Although the organic scenario grown on sandy loam soil had one of the smallest energy inputs per hectare, the low yield meant that the energy input was similar per tonne of beet harvested to the conventional crops grown on sandy loam soil. The extra distance travelled by organic beet from the farm to the factory increased the energy input per tonne above that of the conventional scenarios. The GWP was smallest for the conventional crops on the fertile peat and silt soils and greatest on the irrigated sand soils and the sandy loam soils. The organic scenario had a similar GWP to the conventional scenarios on sandy loam to the farm gate, although the greater diesel requirement for transport increased the GWP overall. The GWP per GJ of output for sugar beet in England is similar to published values for wheat.     

Estimating in situ soil–water retention and field water capacity in two contrasting soil textures

A priori knowledge of the in situ soil field water capacity (FWC) and the soil-water retention curve for soils is important for the effective irrigation management and scheduling of many crops. The primary objective of this study was to estimate the in situ FWC using the soil-water retention curve developed from volumetric water content (θ), and water potential (ψ) data collected in the field by means of soil moisture sensors in two contrasting-textured soils. The two study soils were Lihen sandy loam and Savage clay loam. Six metal frames 117 cm × 117 cm × 30 cm high were inserted into the soil to a depth of 5–10 cm at approximately 40 m intervals on a 200 m transect. Two Time Domain Reflectrometry (TDR) sensors were installed in the center of the frame and two Watermark (WM) sensors were installed in the SW corner at 15 and 30 cm depths to continuously monitor soil θ and ψ, respectively. A neutron probe (NP) access tube was installed in the NE corner of each frame to measure soil θ used for TDR calibration. The upper 50–60 cm of soil inside each frame was saturated with intermittent application of approximately 18–20 cm of water. Frames were then covered with plastic tarps. The Campbell and Gardner equations best fit the soil–water retention curves for sandy loam and clay loam soils, respectively. Based on the relationship between soil ψ and elapsed time following cessation of infiltration, we calculated that the field capacity time (t _FWC) were reached at approximately 50 and 450 h, respectively, for sandy loam and clay loam soils. Soil-water retention curves showed that θ values at FWC (θ _FWC) were approximately 0.228 and 0.344 m³ m⁻³, respectively, for sandy loam and clay loam soils. The estimated θ _FWC values were within the range of the measured θ _FWC values from the NP and gravimetric methods. The TDR and WM sensors provided accurate in situ soil–water retention data from simultaneous soil θ and ψ measurements that can be used in soil-water processes, irrigation scheduling, modeling and chemical transport.     

土培条件下重金属Cr(Ⅵ)对作物种子发芽影响的试验研究

不同土壤中Cr(Ⅵ)在质量浓度小于25 mg/kg时,对3种作物种子的发芽率均无显著性影响。在壤土和砂壤土条件下,Cr(Ⅵ)质量浓度小于2 mg/kg时,对试验种子发芽的根伸长及鲜质量均无显著性影响,粘土条件下,Cr(Ⅵ)质量浓度小于1 mg/kg时对种子的根伸长及鲜质量的影响也不显著,但随着质量浓度的增高转变为越来越强烈的抑制作用。经相关分析可知,土壤Cr(Ⅵ)质量浓度与作物种子的根伸长抑制率呈极显著正相关。由回归方程计算得到抑制率达到25%的EC25值,通过比较得出Cr(Ⅵ)在粘土中的抑制作用最强,在壤土和砂壤土中相差不大。     

Effects of snowmelt on phosphorus and sediment losses from agricultural watersheds in Eastern Canada

Snowmelt is the most important hydrological event in cold climates. However, snowmelt effects on suspended sediment (SS) and phosphorus (P) loss are poorly documented in Canada. Using two agricultural watersheds in Eastern Canada, this study aimed to quantify SS and P loss during the snowmelt period and to investigate how snowmelt contributes SS and P loss. Water samples were collected from the outlets of the Bras d’Henri watershed (BHW, 2007-2009) and Black Brook watershed (BBW, 2008-2009) and measured for SS and P concentrations. Hydrological parameters (precipitation, snow water equivalent, and runoff discharge), soil frozen status and soil temperature were also measured. Results revealed inter-annual variation of snowmelt conditions and SS and P losses in each watershed. The 2008 snowmelt in BHW and BBW mainly occurred on unfrozen soils, while the 2007 and 2009 snowmelts in BHW and 2009 snowmelt in BBW mainly on frozen soils. In BHW, 2008 snowmelt caused much higher median concentrations of SS, total P (TP), dissolved P (DP) and particulate P (PP) in stream water than 2007 and 2009; ratios of PP fractions in TP were variable with events but the median values were similar, suggesting both DP and PP important contrubutors to TP loss. In BBW, the median concentration of dissolved reactive phosphorus (DRP) in stream water was greater in 2008 snowmelt than in 2009 snowmelt; PP dominated TP loss. This study also suggests that soil state (i.e. frozen status) and rainfall were the most important factors influencing SS and P losses during snowmelt. Furthermore, snowmelt P export represented more than 20% of the total annual P export in BHW, and more than 12% of the annual DRP export in BBW. Thus, we strongly recommend adopting Best Management Practices (BMPs) that specifically target sediment and P loss during snowmelt.     

Effect of Peat on the Compactibility of Some Trinidadian Soils

The effect on compactibility of incorporating peat into four Trinidadian agricultural soils before compaction was investigated in a laboratory experiment. A factorial experiment was used to study the effect of peat applied at four levels (0, 4, 8 and 12% by mass) on the maximum dry bulk density (MDBD) and optimum moisture content (OMC) of the four soils (two sandy loams, clay loam and clay) compacted using 5, 15 and 25 Proctor hammer blows. The compaction tests were carried out at different moisture contents which varied according to the values of the plastic limits of the soils.Results showed that while the mean values of MDBD of the soils declined significantly (p = 0.001) from 1·51 to 0·92 Mg m^-3 with increasing peat content, the mean values of OMC increased from 24·2 to 42·6%. While MDBD increased, OMC decreased with increasing compaction levels. This applied to all the soils tested. The clay soils had significantly lower values of MDBD and greater values of OMC than the sandy loam soils. There were significant interaction effects between soil type and level of added peat and between compaction level and level of added peat. These interactions were used to describe the effect of peat on soil compactibility. Multiple linear regression equations based on compactive effort, sand content, clay content and percentage peat content, were generated for predicting values of MDBD and those of OMC of compaction of the soils used in this study. There was reasonable agreement between the equation for predicting MDBD and a similar equation derived for Nigerian soils in previous work. A good negative relationship obtained between MDBD and OMC is also similar to the one derived from previous research.     

循环曝气灌溉条件下小白菜生长及水分与养分利用

研究循环曝气灌溉对不同土壤作物水分及养分利用影响的规律可为循环曝气灌溉技术在不同土壤中的应用提供理论指导。以河南省3种典型土壤(郑州黏土、洛阳粉壤土和驻马店砂壤土)为供试对象,小白菜为供试作物,设置常规地下滴灌为对照组(CK)、循环曝气灌溉为试验组(CAI)开展盆栽试验,研究了循环曝气灌溉对作物生长生理指标及水分与养分利用的影响。结果表明,与CK相比,CAI可促进根系生长,其中郑州黏土和洛阳粉壤土CAI根系活力分别显著增大46.36%和16.79%(P0.05),根干质量分别显著增大35.33%和26.22%(P0.05)。CAI处理净光合速率较CK有显著提高(P0.05),其中郑州黏土、洛阳粉壤土、驻马店砂壤土依次增大了17.69%、12.41%和21.43%。循环曝气处理有效提高了作物氮、磷、钾的吸收效率,其中,郑州黏土和洛阳粉壤土氮素吸收量较CK分别显著提高23.68%和27.72%(P0.05);3种土壤CAI作物磷、钾吸收效率均有显著提高(P0.05),其中郑州黏土分别增加了27.54%和62.81%,洛阳粉壤土增加了25.20%和63.26%,驻马店砂壤土增加了26.86%和23.97%。循环曝气灌溉能显著提高小白菜产量和水分利用效率,其中,郑州黏土和洛阳粉壤土小白菜地上部鲜质量较CK分别提高了58.42%和62.03%,水分利用效率分别提高了27.86%和16.47%。综合比较小白菜生长指标、产量、水分利用及养分吸收效率,郑州黏土循环曝气灌溉处理具有最为显著的改善作用。     

分形在土壤空间变异性评价中的应用研究

针对土壤空间变异性问题,研究了分维数和土壤空间变异性的关系。应用Green-Ampt入渗模型模拟出十种土壤的下渗湿峰深度值,它们的大小依次是:壤质砂土、沙壤土、沙质黏壤土、壤土、粉砂壤土、砂质壤土、黏质壤土、粉砂黏壤土、黏土、粉砂黏土,然后计算出十种土壤随机组合构成的100种土壤剖面的湿峰形状分维数,用这些分维数来描述土壤空间变异性。同时用反距离加权法和相邻两参数平方均值法算出土壤区域属性值,并与分维数进行比较,再通过对土壤空间变异性(用土壤饱和水力传导度来表示)的统计分析和分维数关系的分析,得出湿峰的分形维数与KS具有较明显的分带关系,而且这种关系在实际流域中会更明显。总的来说,土壤空间变异性越大,分形维数df越大。因此可以看出,用分形来评价土壤空间变异性是可行的,并取得了不错的效果。     

土壤质地对坡地土壤水分运动与转化特征的影响研究

通过室内模拟降雨试验,研究了杨凌塿土、安塞黄绵土和神木绵砂土的水分迁移特征。结果表明,随着土壤粘粒含量的增加,坡面产流开始时间提前,坡地平均径流系数、径流量和泥沙量呈增加趋势,入渗率和累计入渗水量呈减少趋势。3种土壤降雨入渗率均可用Kostiakov公式拟合,塿土、黄绵土和绵砂土坡地的平均入渗率分别为0.32、0.83和0.88 mm/min。湿润锋运移速度应该与土壤砂粒百分含量和土层含水量的增量呈正相关关系。为了提高雨水利用率,减少水土流失量,建议加强塿土坡地的保护性耕作措施。     

Transpirational response to water availability for winter wheat as affected by soil textures

Soil texture and evaporative demand have been reported to be the main factors which influence the transpirational response to soil water deficits. However, experimental evidences are not enough. The objective of this study was to investigate the transpirational response to soil water availability in soils of different textures under different evaporative demand levels. The three main soils of the Loess Plateau of China (loamy clay, clay loam and sandy loam) were selected and six constant soil water treatments were applied for winter wheat (Triticum aestivum L.) grown in pots. In order to reduce the influence of environmental conditions and plant factors, a normalized daily transpiration rate was used to develop the relationships with volumetric soil water content and soil water suction. Results showed that, under various levels of evaporative demand, a linear-plateau function with a critical value could be used to describe the dynamic change of the normalized transpiration rate with soil drying. Soil texture significantly influenced both the critical and the slope values of the linear-plateau equations, however, evaporative demand significantly affected the critical values of volumetric soil water content and soil suction for the loamy clay and clay loam only. Therefore, for saving water, different strategies are needed for these three soils.     

Hydraulic conductivity and clay dispersion as affected by application sequence of saline and simulated rain water

Summary Saturated hydraulic conductivity HC, and degree of clay dispersion DD, were determined for a sandy loam and a clay loam soil with waters of different combinations of sodium adsorption ratios SAR (5, 15, 30 and 45 mmol^1/2l^–1/2) and total electrolyte concentration TEC (15, 30, 60 and 90 me l^–1) followed by distilled water to simulate rainwater. Increase in SAR and decrease in TEC of leaching water increased DD and decreased HC of soils. The HC values were more highly correlated with SAR than TEC. The critical ratio of TEC/SAR of water below which the relative HC is less than the hreshold value (i.e. 0.75) was 3.82 and 2.01 for clay loam and sandy loam, respectively taking the HC of initial soil with good quality water (SAR = 0.5, EC = 0.3dS m^–1) as the reference. Drastic reductions in conductivity were observed even at SAR = 5 (60–83%) when saline water was displaced by rainwater, sensitivity being greater for the sandy loam than for the clay loam; recovery was negligible when the saline water was again applied. Data of EC and clay content of the effluent on application of distilled water suggested that clay dispersion, its movement and lodgement into conducting pores, may be the major cause of HC reduction in sandy loam, whereas in clay loam, surface sealing is the major cause. With distilled water application HC values were governed by SAR rather than TEC of initial water used. The study thus suggests that existing water quality criterion may underestimate the real soil permeability hazards from saline-sodic waters during rainfall infiltration in monsoon season.     

黄土区五种土壤抗冲性试验分析

通过室内放水冲刷实验,分析了黄土高坡5种土壤在不同坡度下的下切冲刷过程及影响冲刷的坡度、水流特征以及水流含沙量等影响因素。结果表明,在流量为120 L/h条件下,5种土壤的抗冲系数均随着坡度的增大而降低,且呈现指数回归关系,决定系数R~2较高,土壤抗冲性大小依次为杨凌黏壤土延安砂质黏壤土周至黏壤土志丹砂质壤土靖边砂质壤土;5种土壤的抗冲系数和水流流速均呈现出负相关的线性变化规律;5种土壤的冲刷强度基本都随着坡度的增加而增加,随着冲刷时间的推移,冲刷强度逐渐减小,且坡度越大,前期的冲刷强度越大;5种土壤的抗冲系数与水流含沙量呈现出负相关的线性变化规律,决定系数R~2在0.857 7~0.957 5之间,随水流含沙量的变化,抗冲性越好的土壤其本身的抗冲系数变化越显著。     

基于黏粒量的土壤水分特征曲线预测模型

[目的]建立基于黏粒量的土壤水分特征曲线预测模型.[方法]设计12种不同黏粒量的质量混合比处理,获得一系列合成土样,通过测定合成土样的土壤水分特征曲线,研究了在体积质量一致的条件下,黏粒量对土壤水分特征曲线参数和孔隙分布的影响.[结果]在体积质量为1.55 g/cm3条件下,黏粒量增加1.9倍,土壤中传导孔隙(0.03...     

Modeling the impact of alternative drainage practices in the northern Corn-belt with DRAINMOD-NII

The hydrologic and water quality impacts of subsurface drainage design and management practices are being investigated through field and simulation studies throughout the northern Corn-belt. Six years of data from an ongoing field study in south central Minnesota (Sands et al., 2008) were used to support a modeling effort with DRAINMOD-NII to investigate: (1) the performance of the model in a region where soils are subject to seasonal freeze-thaw and (2) the long-term hydrologic and water quality characteristics of conventional and alternative subsurface drainage practices. Post-calibration model prediction and efficiency were deemed satisfactory using standard model performance criteria. Prediction errors were primarily associated with early spring snowmelt hydrology and were attributed to the methods used for simulating snow accumulation and melting processes, in addition to potential sublimation effects on ET estimates. Long-term simulations with DRAINMOD-NII indicated that drainage design and/or management practices proposed as alternatives to conventional design may offer opportunities to reduce nitrate (NO₃)-nitrogen losses without significantly decreasing (and in some cases, increasing) crop yields for a Webster silty clay loam soil at Waseca, Minnesota. The simulation study indicated that both shallow drainage and controlled drainage may reduce annual drainage discharge and NO₃-nitrogen losses by 20-30%, while impacting crop yields from −3% (yield decrease) to 2%, depending on lateral drain spacing. The practice of increasing drainage intensity (decreasing drain spacing) beyond recommended values appears to not significantly affect crop yield but may substantially increase drainage discharge and nitrate-nitrogen losses to surface waters.     

毛细节水灌溉条件下蔗区土壤水分运移规律研究

毛细节水灌溉作为一种类似滴灌的新型灌溉技术逐渐得到关注。在室内模拟了毛细管水分在蔗区沙土、壤土和黏土中的运移情况。通过室内试验和HYDRUS-3D建模分析表明:土壤类型对土壤各方向入渗有明显的影响,水分运移速度和土壤各方向湿润范围顺序为:沙土壤土黏土;3种土壤含水率等值线变化规律基本一致,同样湿润位置土壤含水率顺序为:黏土壤土沙土。根据毛细管的水分在沙土、壤土和黏土运移规律,提出毛细管在蔗区沙土、壤土和黏土的合理埋深应为40、30和20cm。