基于矩分析的垄沟灌入渗湿润体特征

为指导垄沟灌溉技术参数的合理设计,利用验证的HYDRUS-2D模型模拟不同土壤物理性质、耕作技术参数和灌水技术参数组合的垄沟灌土壤水分入渗过程,采用空间矩分析方法定量分析不同因素对入渗湿润体特征量及椭圆特征值的影响。结果表明:矩分析垄沟灌溉入渗湿润体呈扁平椭圆状;初始含水量对湿润体特征量的影响较其它因素小;垄沟灌溉宜在质地重的土壤条件下应用;随沟底宽度和灌溉水深增大,椭圆面积亦增大,椭圆长短轴差异明显,显著加大水平侧渗距离,砂壤土宜窄沟种植,黏壤土宜宽沟灌溉种植,较高的灌溉水深可增加侧渗,有利于提高灌水均匀度。空间矩分析为研究土壤水空间分布特征提供了一种强有力数学方法。     

The differences of water balance components of Caragana korshinkii grown in homogeneous and layered soils in the desert–Loess Plateau transition zone

Soil texture greatly influences soil water movement, thus may affect the water balance and vegetation growth in the desert–Loess Plateau transition zone. This study is to determine if the water balance differs in homogeneous and layered soils with Caragana korshinkii stands in semiarid region. Soil water measurements up to 500-cm depth were taken in 2006 and 2007 on homogeneous sandy soil, homogeneous silt loam soil, and layered soil with sand overlying silt loam. HYDRUS-1D was used to simulate the soil water balance. The results indicated the annual water balance components were greatly affected by soil layering. The ratio of average actual evapotranspiration (ET_a) to precipitation (P) during the two years in the layered soil was slightly lower than that in homogeneous soils. The ratios of annual actual transpiration (T_r) to evapotranspiration were 50.9%, 41.2% and 30.6% in layered soil, homogeneous sandy soil, and homogeneous silt loam soil, respectively. C. korshinkii grown in layered soil had deeper soil water recharge and higher T_r/ET_a ratio, thus had more available water for transpiration than that in homogeneous soils. This study suggested the layered soil with sand overlying silt loam is more favorable to C. korshinkii growth in terms of water use than homogeneous soils in the desert–Loess Plateau transition zone.     

塔里木河下游典型绿洲滴灌防护林地土壤水盐时空动态

通过野外定位观测,对塔里木河下游典型绿洲防护林地灌溉周期内、不同滴灌年限以及不同质地类型土壤水盐动态进行监测分析。研究结果表明:①绿洲幼龄防护林地土壤水盐变化属于灌溉周期型;灌后土壤湿润体呈“半椭球型”分布,积盐区位于湿润峰附近;当前防护林（沙壤土）滴灌周期为10 d较为合适。②实施滴灌1 a、2 a和5 a林地（沙壤土）土壤水分亏缺量逐年增大;0～20 cm土层随滴灌年限的增大先脱盐后积盐,20～120 cm土层均表现为脱盐。③滴灌5 a后,粉黏土林地表层板结层的形成显著抑制40～60 cm土壤水分蒸发,盐分呈“表聚型”分布;细沙土林地土壤持水性差,各土层盐分呈“均匀型”分布;沙壤土林地持水性较细沙土林地略高,盐分呈“波动型”分布。     

Effect of grazing intensity on evapotranspiration in the semiarid grasslands of Inner Mongolia,China

The eddy covariance technique was used to measure evapotranspiration (ET) at four different grazing intensity sites to investigate the grazing effects on ET in the semiarid steppe ecosystems of Inner Mongolia. By reducing available energy, and decreasing soil water content (SWC), grazing decreased ET on a seasonal scale compared with the site ungrazed since 1979 (UG79). The most important climatic factor controlling ET on daily scale shifted from SWC to Net radiation (R_n) when grazing intensity increased. SWC, R_n and air temperature (or vapor pressure deficit) can explain 59%–71% of the variation in daily ET. On the other hand, leaf area index (LAI) affected ET slightly at UG79 under the commonly limited soil water conditions. Even no effect of LAI at the heavily grazed site was detected. This suggests that the direct effect of grazing reducing LAI on ET is not significant in this semiarid steppe ecosystem. Soil evaporation compensates for most of the loss in transpiration due to reduced LAI.     

Impact of soil conditions on the physiological characteristics of maize plants in an arid region,Northwest China

Overuse of irrigation water to ensure the crop yield of maize plants has caused serious water shortage problems in the middle reach of Heihe River, China. Thus, further research on the physiological characteristics, i.e., photosynthetic rate and leaf transpiration rate, are urgently needed to develop an efficient irrigation management system. In this paper, we selected two common soil textures (sandy loam, sand) and three one-time irrigation volumes (60 mm, 20 mm, 0 mm) in order to analyze the impact of soil conditions on the physiological characteristics of maize plants. Physiological and meteorological factors, soil water content and plant growing parameters were synchronously monitored on Jun. 30, Jul. 25 and Aug. 27 of 2012. The results indicate that sandy loam is better than sand for the growth of maize plants and single irrigation may provide limited influence on the physiological characteristics. Thus, increasing irrigation times and decreasing one-time volume is suggested for an efficient irrigation system.     

Response of the soil water content of mobile dunes to precipitation patterns in Inner Mongolia,northern China

We analyzed the relationship between soil water content (SWC) dynamics in mobile dunes to a depth of 100 cm and precipitation patterns from June to July 2010 in the Horqin Sand Land. The precipitation was dominated by small events of 0.1–3.0 mm, which accounted for 52% of the total events. Precipitation >20 mm had the highest intensity, accounting for 50% of the total precipitation. SWC differed significantly among the soil layers: mean SWC was greatest from 80 to 100 cm and lowest from 40 to 60 cm. SWC from 0 to 100 cm was significantly affected by relative humidity, water barometric pressure and minimum temperature, and the SWC of 0–40 cm was obviously influenced by precipitation amount and wind velocity. Precipitation <5 mm did not replenish SWC, precipitation between 5 and 20 mm provided some replenishment to SWC from 0 to 40 cm, and precipitation >20 mm increased significantly SWC from 0 to 100 cm. In addition, precipitation intensity significantly affected the infiltration rate, with higher intensity leading to deeper and faster infiltration. At longer intervals between precipitation events, SWC in each soil layer decreased continuously over time; however, SWC from 0 to 80 cm changed little within the first 3 days, and SWC from 0 to 100 cm started to decrease greatly after 5 days.     

地面不同垄沟形式对径流调控机制的研究

在干旱缺水、水土流失严重的黄土高原地区,地面垄沟是控制侵蚀、保持水分的有效措施。而不同垄沟形式将直接影响沟中径流量和土壤水分状况。本文设计了两种不同垄上覆盖材料和三种不同垄沟比的6组试验处理,通过2002与2003年降水季节的连续田间试验观测。结果表明:覆膜垄沟(MR)的临界产流降雨量低于不覆膜垄沟(ER),约为不覆膜垄沟(ER)的10%,两种垄沟的临界产流降雨量分别为0.4mm、4.6mm。覆膜垄沟(MR)的径流效率远高于不覆膜垄沟(ER),覆膜垄沟(MR)与土垄的平均径流效率分别在45%~70%与5%~6%之间变化。     

沙土地夏玉米灌溉方式的试验研究

在豫北耕作层保水能力较差的砂壤土地带,围绕节水和增收,开展了夏玉米沟灌、常规畦灌及减少生育期内灌水次数的试验研究,每次畦灌定额控制在630~682.5m³·hm^-2,而沟灌条件下平均灌水量仅为442.5m³·hm^-2。研究结果表明,反映夏玉米生长速率的株高、叶面积指数等性状均是以抽雄期为界,之前增长迅速;抽雄时植株高度达2.50m左右,之后增长速率明显减慢;而抽雄至灌浆初期,叶面积指数保持在5.40~5.92的最高值,往后急剧地下降。不同灌水处理下生长速率的变化则是随着供水总量的增加呈同步增长趋势。在干旱年份,畦灌夏玉米全生长期耗水4278m³·hm^-2,沟灌及减少灌水次数的处理,耗水量分别为3762m³·hm^-2和3348m³·hm^-2。按生长阶段比较,抽雄~开花期日耗水强度最大,为66.75~76.50m³·hm^-2;其次是拔节~抽雄期,平均为65.50m³·hm^-2;播种~出苗期间日耗水强度仅为13.35m³·hm^-2。不同的灌溉方式与灌水量对夏玉米的穗粒重、千粒重及粒占穗重的百分比都有影响。对于宽行稀植作物采用沟灌方式,灌溉用水量小(平均为442.5m³·hm^-2),所供的水能集中于植株的根际附近,棵间蒸发的无效损耗少,穗粒重和千粒重都较高,产量达9616.5 kg·hm^-2,比畦灌条件下节省22.8%的灌溉用水,水分生产率提高16.9%。减少夏玉米生长期内的灌水次数,在降低水量消耗的同时,易造成较大幅度的减产(13.7%),因此,在夏玉米生长过程中,遇到偏旱年份,要特别注意防止缺水而引起的水分胁迫。     

内蒙古锡林河流域羊草草原植物生长旺季呼吸的影响因素分析和区分

Based on the static opaque chamber method,the respiration rates of soil microbial respiration,soil respiration,and ecosystem respiration were measured through continuous in-situ experiments during rapid growth season in semiarid Leymus chinensis steppe in the Xilin River Basin of Inner Mongolia,China. Soil temperature and moisture were the main factor affecting respiration rates. Soil temperature can explain most CO2 efflux variations (R2=0.376-0.655) excluding data of low soil water conditions. Soil moisture can also effectively explain most of the variations of soil and ecosystem respiration (R2=0.314-0.583),but it can not explain much of the variation of microbial respiration (R2=0.063). Low soil water content (≤5%) inhibited CO2 efflux though the soil temperature was high. Rewetting the soil after a long drought resulted in substantial increases in CO2 flux at high temperature. Bi-variable models based on soil temperature at 5 cm depth and soil moisture at 0-10 cm depth can explain about 70% of the variations of CO2 effluxes. The contribution of soil respiration to ecosystem respiration averaged 59.4%,ranging from 47.3% to 72.4%; the contribution of root respiration to soil respiration averaged 20.5%,ranging from 11.7% to 51.7%. The contribution of soil to ecosystem respiration was a little overestimated and root to soil respiration little underestimated because of the increased soil water content that occurred as a result of plant removal.     

膜下滴灌湿润体交汇区土壤水盐运移特征田间实验研究

膜下滴灌是一种既能高效节水,又能适时调控土壤水盐运移的灌水技术.滴灌湿润体交汇区土壤水盐分布特征是影响密植作物正常生长的重要因素.在田间情况下,研究滴头流量、滴头间距、灌水量对滴灌湿润体交汇区的土壤水盐运移的影响.实验结果表明:滴头流量越大,湿润体交汇区土壤含水率越高,土壤盐分淋洗效果越好,在滴头流量1.38 L/h和...     

三种土壤铅和镉的质量基准初步研究*

在制定地下水源保护区污染控制措施时,最常遇到的问题之一是缺少土壤包气带和含水层中化学物质的基准和标准。文中以铅、镉为例,结合北京、唐山地下水水源地实际情况,运用“平衡分配法”,根据土壤对铅和镉的吸附容量和分配系数研究包气带土壤中的铅和镉的质量基准。结果表明,土壤中铅和镉的质量基准与溶液pH值成对数线性关系,据此可计算不同pH条件下的土壤中重金属的质量基准。     

不同粒径沙土水分扩散率

应用水平土柱入渗法测定了科尔沁沙地典型沙质农田不同粒径沙土的水分扩散率。结果表明:不同粒径沙土湿润锋迁移速率的大小依次是0.50~0.25 mm、0.25~0.10 mm、原状土、<0.10 mm的沙土;土壤粒径与入渗性能呈正比关系,即粒径大,则入渗快,反之则小;湿润锋迁移速率与入渗距离符合幂函数关系,相关分析结果均达到了极显著水平;粒径<0.10 mm的沙土,当土壤容积含水量<0.415时,λ值随含水量的增加而缓慢降低,而当含水量>0.415时,λ值则随含水量的增加而迅速降低;随着土壤粒径的减小,土壤水分扩散率逐渐降低,其大小依次是0.50~0.25 mm、原状土、0.25~0.10 mm、<0.10 mm的沙土;土壤容积含水率与土壤水扩散率符合经验公式并呈指数曲线变化,相关分析结果具有极显著的正相关关系。     

黑河额济纳绿洲灌溉模式研究

通过对20世纪50年代以来额济纳绿洲来水条件、绿洲演变过程及绿洲灌溉方式研究后认为, 额济纳天然绿洲灌溉应结合水源条件、地形条件及绿洲分布情况, 宜以埂坝灌溉和浸润灌溉方式为主, 沟灌、畦灌等多种灌溉方式并举的绿洲灌溉模式, 并对进入额济纳绿洲的来水进行了配置。     

乌兰布和沙漠灌溉农田深层渗漏特征与水量平衡

中国干旱区分布着大面积的灌溉农田，改造沙漠（包括戈壁）为灌溉农田仍为治沙的重要途径，深层渗漏是地表水温过程及优化灌溉制度的重要参数。针对乌兰布和沙漠熟化的灌溉农田，保留50 cm的耕作层熟化土壤，分别客换50~150 cm砂土、壤土和黏土，配置成为3种土壤类型样地，实时监测了当地农民对农田的实际灌溉量与灌水量、土壤含水率及深层渗漏量。结果表明：（1）2017年4月17日的单次灌水量118.64 mm后，砂土、壤土、黏土样地150 cm深层出现渗漏的时间分别为灌溉后的13、72、257 h。（2）单次灌水量118.64 mm的15 d后，砂土、壤土、黏土样地150 cm深层渗漏量分别为110.87、12.2、0.8 mm。（3）2017年生长季内（4月1日至10月30日）5次灌溉水总量为641.53 mm时，渗漏水总量为砂土449.60 mm、壤土270.60 mm；土壤的蓄水量变化为砂土-48.79 mm、壤土-35.32 mm。（4）砂土、壤土和黏土的渗漏水量差异是影响灌溉水量和频率的重要因素。     

Wind tunnel test of the influence of moisture on the erodibility of loessial sandy loam soils by wind

Loessial sandy loam soils are the major soil categories in the northern Loess Plateau, China. Owing to a dry, windy climate and sparse surface cover, wind erosion is a serious problem and dust (sand) storms occur frequently. Soil moisture is one of the most important factors influencing resistance to wind erosion. The influence of moisture content on the erodibility of sandy loam soils was investigated through wind tunnel simulations. Results showed that the threshold velocity for soil particle movement by wind increases with increasing soil moisture by a power function. The intrinsic factor in the increase in soil resistance due to moisture content is the cohesive force of soil water. Cohesive forces of the film and capillary water are different; the influence of soil moisture on threshold velocity was shown to follow a step-like pattern. The wind erosion modulus of sandy loam was directly proportional to the cube of the wind velocity or the square of the effective wind velocity (V−V_t). There existed a negative exponential relationship between the wind erosion rate and soil moisture content. Initially, as soil moisture increased the decrease in the wind erosion rate was rather rapid. When the moisture content reached more than 4%, the rate of decrease in erosion slowed and became almost constant with successive increments of moisture. This suggests that different soil moisture contents can prevent wind erosion at different levels. Four percent soil moisture could only reduce the erodibility of the sandy loam soil by a small degree.     

The response of drainage basins to the late Quaternary tectonics in the Sicilian side of the Messina Strait (NE Sicily)

Despite more than 40 yr of research attributing temporal changes in streambank erosion rates to subaerial processes, little quantitative information is available on the relationships between streambank erodibility (k_d) and critical shear stress (τ_c) and the environmental conditions and processes that enhance streambank erosion potential. The study goal was to evaluate temporal changes in k_d and τ_c from soil desiccation and freeze–thaw cycling. Soil erodibility and τ_c were measured monthly in situ using a multiangle, submerged jet test device. Soil moisture, temperature, and bulk density as well as precipitation, air temperature, and stream stage were measured continuously to determine changes in soil moisture content and state. Pairwise Mann–Whitney tests indicted k_d was 2.9 and 2.1 times higher (p < 0.0065) during the winter (December–March) than in the spring/fall (April–May, October–November) and the summer (June–September), respectively. Regression analysis showed 80% of the variability in k_d was explained by freeze–thaw cycling alone. Study results also indicated soil bulk density was highly influenced by winter weather conditions (r² = 0.86): bulk density was inversely related to both soil water content and freeze–thaw cycling. Results showed that significant changes in the resistance of streambank soils to fluvial erosion can be attributed to subaerial processes. Water resource professionals should consider the implications of increased soil erodibility during the winter in the development of channel erosion models and stream restoration designs.     

沙地渗灌系统的自动监测与控制

通过沙地渗灌系统的应用实践以及与沟灌、漫灌进行的比较研究,着重介绍了其对水分实行自动监测与控制的功能;分析了其可向植物根群区直接供给水分和养分,减少水分蒸发,保持沙地良好水分状态的优越性。     

Physical and chemical properties of soils under some piñon-juniper-oak canopies in a semi-arid ecosystem in New Mexico

Piñon (Pinus edulis)-juniper (Juniperus monosperma)-ecosystems increased substantially in the western USA during the 20th century. Sustainability of these ecosystems primarily depends on soil quality and water availability. This study was undertaken with the objective of assessing the effect of tree species on soil physical quality in a semi-arid region in the western part of Sugarite Canyon, northeast of Raton, Colfax County, NM (37°56′32″N and 104°23′00″W) USA. Three cores and three bulk soil samples were obtained from the site under the canopy of three juniper, Gambel oak (Quercus gambelii) and piñon trees for 0–10 and 10–20 cm depths. These samples were analyzed for particle size distribution, soil bulk density (ρ_b), water stable aggregation (WSA), mean weight diameter (MWD) of aggregates, pH, electrical conductivity (EC) and soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks. Sand content was greater under juniper (48%) than oak (32%), whereas clay content followed the opposite trend. The ρ_b, WSA, MWD, pH and EC were similar under juniper, piñon, oak canopies for both depths. Estimated (from Philip and Green and Ampt infiltration models) and measured water infiltration parameters did not vary among these sites and were in accord with the values for ρ_b, WSA and MWD. The SOC concentrations and stocks were greater under oak (43.1 Mg ha⁻¹ for 0–10 and 37.5 Mg ha⁻¹ for 10–20 cm depths) than piñon (23.3 Mg ha⁻¹ for 0–10 and 18.5 Mg ha⁻¹ for 10–20 cm depths). The TN concentrations were greater under oak (3.4 g kg⁻¹) than piñon (1.7 g kg⁻¹) for the 0–10 cm depth only. Accumulation of detritus material under tree canopies reduced soil compaction and crusting caused by raindrop impact and increased SOC, and TN concentrations, and water infiltration. Coefficients of variation ranged from low to moderate for most soil properties except infiltration rate at 2.5 h, which was highly variable. Overall, soil quality for each site was good and soil aggregation, water infiltration and SOC concentrations were high, and soil ρ_b was low.     

Water-saving potential in aeolian sand soil under straight tube and surface drip irrigation in Taklimakan Desert in Northwest China

Evaporation loss from the saturated soil beneath drip irrigation emitters highly influences the irrigation efficiency of drip irrigation (DI). Subsurface drip irrigation (SDI) is one good approach to curb this inefficiency, but in a new irrigation method, straight tube irrigation (STI), the irrigation tubes do not need to be buried and thus STI is recommended to increase the irrigation efficiency under normal surface-applied DI. STI consists of only connectors and water-transference tubes that can directly transfer irrigation water from the lateral emitters in the drip line to the root zone of plants. Five-month field experiments were carried out in Aeolian sand soil in the forest-belts of the Taklimakan Desert, which have poor water storage capacity, to compare the potential water saving between STI and DI. The preliminary results showed that, compared with DI, STI (1) improved the soil water content in soil depths from 40 to 100 cm under the soil surface; (2) achieved the same irrigation effects in relatively shorter irrigation durations; (3) had very little water loss due to deep seepage; and (4) formed a layer of dry sand about 10 to 30 cm thick immediately below the soil surface, which lessened evaporation loss of soil water beneath the emitters on the soil surface. This demonstrates that STI can maximize the water-saving potential of DI through the reduction of wetted soil perimeters on the soil surface. This is valuable information for water-saving engineering applications and projects with STI in arid and semiarid regions.     

In-situ rainwater harvesting and gravel mulch combination for corn production in the dry semi-arid region of China

A field study was conducted to determine the effect of a combination of ridge and furrow method of in-situ rainwater harvesting with gravel mulch on corn production, soil moisture storage, and water-use efficiency in the dry semi-arid region of China. Results showed that plastic-covered ridges had an average runoff efficiency (runoff/rainfall) of 87% as compared to 7% for bare ridges, and could generate runoff at a threshold value of 0·8±0·2 mm rainfall. Bare ridges produced runoff only under high intensity rainfall events, and was ineffective for harvesting rainfall in the study area. The plastic-covered ridge and gravel-mulched furrow method of rainwater harvesting was effective in conserving moisture and increasing yield and water-use efficiency. The grain yield in this treatment was 1·9 times that of the conventional flat soil cultivation (control), and the water-use efficiency was 1·8 times that of the control. The good performance of the film-covered surface ridges and gravel-mulched furrows is attributed to the better utilization of light rains, improvement of infiltration in the root zone, and suppression of evaporation losses.