Grain yield and water use efficiency of super rice under soil water deficit and alternate wetting and drying irrigation

This study investigated if super rice could better cope with soil water deficit and if it could have better yield performance and water use efficiency （WUE） under alternate wetting and drying （AWD） irrigation than check rice. Two super rice cultivars and two elite check rice cultivars were grown in pots with three soil moisture levels, well watered （WW）, moderate water deficit （MWD） and severe water deficit （SWD）. Two cultivars, each for super rice and check rice, were grown in field with three irrigation regimes, alternate wetting and moderate drying （AWMD）, alternate wetting and severe drying （AWSD） and conventional irrigation （CI）. Compared with that under WW, grain yield was significantly decreased under MWD and SWD treatments, with less reduction for super rice than for check rice. Super rice had higher percentage of productive tillers, deeper root distribution, higher root oxidation activity, and greater aboveground biomass production at mid and late growth stages than check rice, especially under WMD and WSD. Compared with CI,AWMD increased, whereasAWSD decreased grain yield, with more increase or less decrease for super rice than for check rice. Both MWD and SWD treatments and eitherAWMD orAWSD regime significantly increased WUE compared with WW treatment or CI regime, with more increase for super rice than for check rice. The results suggest that super rice has a stronger ability to cope with soil water deficit and holds greater promising to increase both grain yield and WUE by adoption of moderate AWD irrigation.

Influence of Soil Water Deficit and Phosphorus Application on Phosphorus Uptake and Yield of Soybean (<i>Glycine max</i>L.) at Dejen, North-West Ethiopia

A green house experiment was conducted at Dejen, Northwest Ethiopia, with the objective of quantifying the critical soil water deficit and P levels that affect yield and yield components of soybean, and determine the critical soil water deficit levels influencing P uptake in soybean. The treatment consisted of factorial combination of four available soil water (ASW) deficit levels (0%, 25%, 50% and 75%) and four levels of phosphorus (0, 10, 20, and 30 kg·ha-1) laid out in RCBD with four replications using soy bean variety Jalale as a planting material. The experiment was conducted under green house condition at Dejen, South Ethiopia during the 2011 academic year. Air dried soil was filled in the pots and seeds were sown on May 13, 2011. Four plants were maintained on each pot after thinning till flowering but after flowering, the total number of plants per pot was reduced to three as one plant which was used for measurement of root biomass. The water deficit treatments were imposed after the plants have been fully established 2 weeks after emergence just before branching stage. The water deficiency was imposed through maintaining the soil moisture content below field capacity at the deficit levels of 25%, 50% and 75%. The 75% of ASW deficit resulted in the longest days (45) to flowering and maturity (99) compared to the 0%, 25% and 50% deficit levels. Also, the 75% of ASW deficit level resulted in shorter plants (55 cm), the lowest leaf area (82.6 cm2), the highest root to shoot ratio (0.0168) and the lowest DM accumulation (161.3 gm-2) compared to the other ASW deficit levels. Likewise, the 75% of ASW deficit level gave the lowest number of pods per plant (4.13), seeds per pod (1.69), 100 seed weight (2.54 g), seed yield (13.4 g·m-1), above ground biomass (174.6 g·plant-1) and harvest index (0.08) compared to the other ASW deficit treatments. The degree of sensitivity to drought increased dramatically (from 0.0423 at 25% to 0.9604 at 75%) with increase in water deficit level. Tissue analysis results indicated that the highest seed P concentration (1.285%) and uptake (432.5 g·plant-1) were obtained at the 0 ASW deficit and 30 kg·P·ha-1 and the lowest were obtained at 75% ASW deficit and all rate of applied P. On the contrary, the highest straw P concentration (1.88%) and uptake (552.7 g·plant-1) were recorded at 75% and 25% of ASW deficit levels and 30 kg·P·ha-1, respectively. However, the total P uptake was influenced only by ASW deficit levels in that the relatively minimum and maximum values were observed at 75% and 0% of ASW deficit levels, respectively. It can be concluded that the critical ASW deficit levels that affect yield and yield components of soybean and uptake of total P lie between 25% and 50% of available water deficit levels. The parameters started to decline significantly from the 50% of ASW deficit onwards. As it is a green house experiment, further study on more number of ASW deficit levels and soil types under different field conditions needs to be done to reach at a conclusive recommendation.

Soil water deficit and vegetation restoration in the refuse dumps of the Heidaigou open-pit coal mine,Inner Mongolia,China

The sustainability of ecosystem restoration of refuse dumps in open-pit coal mines depends on plant species selection, their configuration, and the optimal usage of water resources. This study is based on field experiments in the northern refuse dump of the Heidaigou open-pit coal mine in Inner Mongolia of China established in 1995. Eight plant configurations, including trees, shrubs, grasses, and their combinations, as well as the adjacent community of natural vegetation, were selected. The succession of the revegetated plants, soil water storage, the spatiotemporal distribution of plant water deficits degree and its compensation degree were also studied. Results indicated that the vegetation cover （shrubs and herbaceous cover）, richness, abundance, soil nutrients （soil organic matter, N and P）, and biological soil crust coverage on the soil surface are significantly influenced by the vegetation configurations. The average soil water storage values in the shrub ＋ grass and grass communities throughout the growing season are 208.69 mm and 206.55 mm, which are the closest to that of in the natural vegetation community （215.87 mm）. Plant water deficits degree in the grass and shrub ＋ grass communities were the lowest, but the degrees of water deficit compensation in these configuration were larger than those of the other vegetation configurations. Differences in plant water deficit degree and water compensation among the different config- urations were significant （P 〈0.05）. Plant water deficit degrees were predominantly minimal on the surface, increased with increasing soil depth, and remained stable at 80 cm soil depth. The soil moisture compensation in the natural vegetation, shrub ＋ grass, and grass communities changed at 10%, while that in other vegetation communities changed between 20% and 40%. Overall, we conclude that the shrub ＋ grass and grass configuration modes are the optimal vegetation restoration models in terms of ecohydrology for future ecological engineering projects.

Improvement in estimation of soil water deficit by integrating airborne imagery data into a soil water balance model

In this study,an approach that integrates airborne imagery data as inputs was used to improve the estimation of soil water deficit(SWD)for maize and sunflower grown under full and deficit irrigation treatments.The proposed model was applied to optimize the maximum total available soil water(TAWr)by minimizing the difference between a water stress coefficient ks and crop water stress index(1-CWSI).The optimal value of maximum TAWr was then used to calibrate a soil water balance model which in turn updated the estimation of soil water deficit.The estimates of SWD in the soil profile of both irrigated maize and sunflower fields were evaluated with the crop root zone SWD derived from neutron probe measurements and the FAO-56 SWD procedure.The results indicated a good agreement between the estimated SWD from the proposed approach and measured SWD for both maize and sunflower.The statistical analyses indicated that the maximum TAWr estimated from CWSI significantly improved the estimates of SWD,which reduced the mean absolute error(MAE)and root mean square error(RMSE)by 40%and 44%for maize and 22%for sunflower,compared with the FAO-56 model.The proposed procedure works better for crops under deficit irrigation condition.With the availability of higher spatial and temporal resolution airborne imagery during the growing season,the optimization procedure can be further improved.

Response of plant physiological parameters to soil water availability during prolonged drought is affected by soil texture

Soil water deficit is increasingly threatening the sustainable vegetation restoration and ecological construction on the Loess Plateau of China due to the climate warming and human activities.To determine the response thresholds of Amygdalus pedunculata(AP)and Salix psammophila(SP)to soil water availability under different textural soils,we measured the changes in net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci),leaf water potential(ψw),water use efficiency(WUE)and daily transpiration rate(Td)of the two plant species during soil water content(SWC)decreased from 100%field capacity(FC)to 20%FC in the sandy and loamy soils on the Loess Plateau in the growing season from June to August in 2018.Results showed that Pn,Gs,WUE and Td of AP and SP remained relatively constant at the beginning of soil water deficit but decreased rapidly as plant available soil water content(PASWC)fell below the threshold values in both the sandy and loamy soils.The PASWC thresholds corresponding to Pn,Gs and Ci of AP in the loamy soil(0.61,0.62 and 0.70,respectively)were lower than those in the sandy soil(0.70,0.63 and 0.75,respectively),whereas the PASWC thresholds corresponding to Pn,Gs and Ci of SP in the loamy soil(0.63,0.68 and 0.78,respectively)were higher than those in the sandy soil(0.58,0.62 and 0.66,respectively).In addition,the PASWC thresholds in relation to Td and WUE of AP(0.60 and 0.58,respectively)and SP(0.62 and 0.60,respectively)in the loamy soil were higher than the corresponding PASWC thresholds of AP(0.58 and 0.52,respectively)and SP(0.55 and 0.56,respectively)in the sandy soil.Furthermore,the PASWC thresholds for the instantaneous gas exchange parameters(e.g.,Pn and Gs)at the transient scale were higher than the thresholds for the parameters(e.g.,Td)at the daily scale.Our study demonstrates that different plant species and/or different physiological parameters exhibit different thresholds of PASWC and that the thresholds are affected by soil texture.The result can provide guidance for the rational allocation and sustainable management of reforestation species under different soil conditions in the loess regions.

Response of forestland soil water content to heavy rainfall on Beijing Mountain, northern China

Continuous recording of precipitation and soil water content（SWC）, especially during long periods of torrential rainfall, has proven challenging. Over a 16 h period spanning 21-22 July, 2012, Beijing experienced historic rainfall that totaled 164.4 mm. We used large lysimeter technology in four forested plots to record precipitation and variation in SWC at 10-min intervals to quantify the response of forestland SWC to heavy rainfall in a semi-arid area. Mean,maximum and minimum rainfall intensities were 23.4, 46.8and 12.0 mm/h, respectively. Rainfall was concentrated in 2-6 mm bursts that accounted for 67.32 % of the total rainfall event. Soil moisture conditions in this region are strongly dependent on patterns of precipitation. Water infiltration into 20, 40, 60, 80, 100, 120 and 160 cm soil layers required 1, 5,20, 37, 46, 52 and 61 mm of precipitation, respectively, and to fully saturate these soil layers required 80, 120, 140, 150, 180,200 and 220 mm of precipitation, respectively.

Status and circulation characteristics of soil water in dryland field of southeast Shanxi Province

Based on the observed soil water data from experimental site located in southeast of Shanxi Province, the physical characteristics of soil water, crop effect on soil moisture, and the field water circulation pattern were studied by using the water balance method. The results suggested that soil water deficit often exists in fields of these areas. From May to June, the amount of water deficit in bare land rises to the maximum (232 8 mm) and falls to the minimum (66 6 mm) from August to September. By comparison, because of crop transpiration, both soil water deficit and dry soil layer in cultivated land are 15 1—40 4 mm more and 20—70 mm deeper respectively than those of bare land. Crops mainly planted in these areas have a relatively weak utilization ability to soil water. Winter wheat has the highest utilization ability to soil water among the crops planted in these areas. The soil water utilization ability of winter wheat is 26 2%—30 6% and winter wheat can use soil water that lies in soil layer below a depth of over 200 cm. Spring corn and millet can only consume soil water with the maximum ability of 13 4% and the deepest layer of 0—50 cm or 0—100cm, which shows that the soil water utilization ability of winter wheat is higher than that of spring crops. After crop is ripe, more than 41% of available soil water remains unused in field. So, increasing soil water storage and improving crop utilization ability to soil water by adopting efficient agrotechnique measures are the main ways for improving agricultural productivity in dry farming areas of Northern China.

Quantifying the impacts of soil water stress on the winter wheat growth in an arid region,Xinjiang

Wheat growth in response to soil water deficit play an important role in yield stability. A field experiment was conducted for winter wheat (Triticum aestivum L.) during the period of 2002-2005 to evaluate the effects of limited irrigation on winter wheat growth. 80%, 70%, 60%, 50% and 40% of field capacity was applied at different stages of crop growth. Photosynthetic characteristics of winter wheat, such as photosynthesis rate, transpiration rate, stomatal conductance, photosynthetically active radiation, and soil water content, root and shoot dry mass accumulation were measured, and the root water uptake and water balance in different layer were calculated. Based on the theory of unsaturated dynamic, a one-dimensional numerical model was developed to simulate the effect of soil water movement on winter wheat growth using Hydrus-1 D. The soil water content of stratified soil in the experimental plot was calculated under deficit irrigation. The results showed that, in different growing periods, evapotranspiration, grain yield, biomass, root water uptake, water use efficiency, and photosynthetic characteristics depended on the controlled ranges of soil water content. Grain yield response to irrigation varied considerably due to differences in soil moisture contents and irrigation scheduling between seasons. Evapotranspiration was largest in the high soil moisture treatment, and so was the biomass, but this treatment did not produce the highest grain yield and root water uptake was relatively low. Maximum depth of root water uptake is from the upper 80 cm in soil profile in jointing stage and dropped rapidly upper 40 cm after heading stage, and the velocity of root water uptake in latter stage was less than that in middle stage. The effect of limited irrigation treatment on photosynthesis was complex owing to microclimate. But root water uptake increased linearly with harvest yield and improvement in the latter gave better root water uptake under limited irrigation conditions. Appropriately controlled soil water contents can improve the root water uptake and grain yield. Consistently high values of root water uptake and grain yield were produced under conditions of mild water deficit at the seedling and start of regrowth to stem-elongation stages, in addition to a further soil water depletion at the physiological maturity to harvest stage. We suggest that periods of mild soil water depletion in the early vegetative growth period together with severe soil water depletion in the maturity stage of winter wheat is an optimum for limited irrigation regime in this oasis. Considerable potential for further improvement in agricultural water use efficiency in the arid zone depends on effective conservation of moisture and efficient use of the limited water.

宁南黄土区不同人工植被类型深层土壤水分亏缺评价

【目的】开展评估不同人工植被类型深层土壤水分亏缺程度,能为区域科学合理实施植被恢复策略提供理论依据。【方法】以宁夏彭阳中庄小流域5种不同植被类型(山桃林、沙棘林、柠条林、苜蓿地,农田为对照)为研究对象,采用土壤水分相对亏缺指数(CSWDI)和干燥化指数(SDI)定量评价模型,对不同植被类型下0~1 000 cm土壤水分亏缺及干燥化程度进行定量化分析与评价。【结果】不同植被类型深层土壤水分变化特征差异明显,0~1 000 cm平均土壤水分含量呈现出农地(16.29%)>山桃林(13.06%)>沙棘林(12.22%)>柠条林(9.12%)>苜蓿地(8.08%)。在垂直剖面上,土壤水分随土层深度增加总体呈现先减小后增加再逐渐稳定的趋势。在0~1 000 cm农地基本没有水分亏缺和干层发生,山桃林、柠条林、沙棘林和苜蓿地均呈现不同程度的土壤水分亏缺现象,平均土壤水分相对亏缺指数分别为0、0.22、0.62、0.35、0.79,平均土壤干燥化指数分别为185.5%、67.45%、51.55%、87.35%、36.10%,5种植被类型中苜蓿地土壤水分亏缺最严重,其次为柠条林、沙棘林、山桃林、农地。山桃林、柠条林、沙棘林、苜蓿地均有不同程度的干层分布,分别呈现中度、轻度和严重干燥化,干层厚度(DSLT)分别为890、860、800、920 cm,DSL-SWC分别为12.42%、8.14%、11.56%、7.76%。【结论】宁南黄土区不同人工植被类型对深层土壤水分亏缺具有明显影响,导致不同程度土壤干层发生,其中苜蓿地土壤水分亏缺最严重,应采取相应措施恢复土壤水分,促进区域水土资源可持续利用和生态健康发展。

荒漠草原灌丛转变过程土壤水分亏缺空间特征及影响因素

草地灌丛化对生态系统结构、功能与服务产生重要影响,目前已经认识到其对土壤水分的负面影响,但还缺乏其在区域尺度的定量评价及其驱动机制研究。在宁夏荒漠草原选取43块成对样地(即荒漠草地和灌丛地),引入样地土壤水分相对亏缺指数(PCSWDI)评价荒漠草原向灌丛转变后土壤水分亏缺空间格局现状及其驱动因子。结果表明:荒漠草原转变为灌丛后0~100 cm和100~200 cm土壤含水量分别显著下降了27.80%和57.92%,0~100 cm灌丛地的PCSWDI显著低于荒漠草地,表明0~100 cm灌丛地目前不存在土壤水分亏缺现象。地统计学分析表明,荒漠草地和灌丛地的0~100 cm土壤水分相对亏缺指数的结构方差比分别为94.73%和95.29%,均属于强空间自相关,主要受结构性因子控制。此外,地理探测器的因子探测发现0~100 cm土壤储水量、坡向和田间持水量是影响灌丛地土壤水分相对亏缺指数的主导因子;交互探测表明,灌丛地0~100 cm土壤水分相对亏缺指数空间分异是多因子共同作用的结果。尽管分析得到0~100 cm灌丛地不存在土壤水分亏缺,但100~200 cm土壤含水量显著下降已经预示了深层土壤水分的消耗。因此,干旱半干旱地区的植被恢复必须考虑其植被承载力和水分阈值,基于自然的解决方案可能是未来植被恢复的主流思路。

黄河流域植被总初级生产力对持续性干旱水分亏缺的响应

利用植被总初级生产力和高精度分层土壤含水量数据分析了2001—2020年黄河流域生长季总初级生产力时空分布和变化特征,量化了流域不同深度土壤湿度之间的相关关系,探究了不同植被类型在生长季的总初级生产力对土壤连续水分亏缺事件的响应关系。结果表明:黄河流域总初级生产力空间上呈东高西低、南高北低的分布特征,生长季耕地累积总初级生产力最大、林地次之、草地最小,研究期内流域总初级生产力整体呈上升趋势,耕地相对增速最大、草地次之、林地最小;流域土壤湿度在空间和时间上均有显著差异,表层土壤含水量波动对深层土壤含水量的影响随深度增加而减小,林地和耕地表层与深层土壤含水量的相关性远高于草地;流域草地和耕地总初级生产力对土壤水分的深度敏感区间为0~40 cm,林地的深度敏感区间为0~100 cm,在深度敏感区间内,随着土壤连续水分亏缺天数的增加,草地和耕地总初级生产力依次经历短暂平稳、加速下降、降速趋缓的变化过程,而林地总初级生产力则表现出短暂下挫、长时间平稳、加速下降的变化特征。

Effects of soil drought stress on photosynthetic gas exchange traits and chlorophyll fluorescence in Forsythia suspensa

To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa（Thunb.） Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate（PN）, stomatal conductance（gs）, and water-use efficiency（WUE） in the seedlings exhibited a clear threshold response to the relative soil water content（RSWC）. The highest PNand WUEoccurred at RSWCof51.84 and 64.10%, respectively. Both PNand WUEwere higher than the average levels at 39.79% B RSWCB 73.04%. When RSWCdecreased from 51.84 to 37.52%,PN, gs, and the intercellular CO2 concentration（Ci）markedly decreased with increasing drought stress; the corresponding stomatal limitation（Ls） substantially increased, and nonphotochemical quenching（NPQ） also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II（PSII） in the form of heat, and the reduction in PNwas primarily due to stomatal limitation.While RSWCdecreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry（Fv/Fm） and the effective quantum yield of PSII photochemistry（UPSII）, photochemical quenching（qP）, and NPQ; in contrast, minimal fluorescence yield of the dark-adapted state（F0） increased markedly. Thus,the major limiting factor for the PNreduction changed to a nonstomatal limitation due to PSII damage. Therefore, an RSWCof 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% B RSWCB 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F.suspensa.

Transpiration and growth responses by Eucalyptus species to progressive soil drying

The regulation of plant transpiration is a key factor affecting transpiration efficiency, growth and adaptation of Eucalyptus species to limited water availability in tropical and subtropical environments. However, few studies have related this trait to the performance of Eucalyptus seedlings and none have investigated the influence of vapor pressure deficit (VPD) on transpiration rates and growth. In this study, the transpiration and growth responses of seedlings of Eucalyptus urophylla (S.T. Blake) and Eucalyptus cloeziana (F. Muell.) to progressive soil water deficits were evaluated under semi-controlled conditions using the fraction of transpirable soil water (FTSW) method. In addition, the influence of VPD on seedling transpiration, development and growth was also investigated. The FTSW threshold ranged from 0.40 to 0.99 for the transpiration rate and from 0.32 to 0.97 for the development and growth variables. Little or no changes in the FTSW threshold were detected in response to changes in atmospheric VPD. Both Eucalyptus species presented a conservation strategy under drought stress. In addition, water-conserving mechanisms during the seedling phase were related to rapid stomatal closure, reduced leaf area, and number of leaves.

Study on the Characteristics of Soil Moisture of Artificial Robinia pseudoacacia Forest Land in Different Latitudinal Zones of Northern Shaanxi

This article studies the soil moisture conditions of 30 years artificial Robinia pseudoacacia in the north of Shaanxi under different climate conditions in order to explore the relationship between soil moisture and impact factor of Robinia pseudoacacia in this area,and variation characteristics of soil moisture in the Loess Plateau region. The results show that soil moisture content decreases with increase of soil depth, and in 40- 50 cm depth the jump point of moisture reduction appears significantly. Soil moisture was lower than the growth critical moisture in 5 samples to the north of Chunhua,and has different degrees of deficit. Soil moisture deficit degree was more than 50% in sandy loam and light loam soils such as Yulin,Shenmu and Suide. With the increasing of latitude,both of soil accumulative storage and net rainfall tends to decrease,but the relationship between them is significant correlation,indicating that that climate conditions are the major factors causing significant difference of soil moisture.

覆土浅埋滴灌玉米分阶段亏水条件下AquaCrop与Dual Crop Coefficient模型精度对比研究

近年来,西辽河流域地下水超采问题日益突出,改进灌溉技术降低农业用水可有效解决这一问题,但该技术缺乏科学的水分管理方法及适宜的理论模型。基于单阶段及多阶段亏水情形试验,对比同类农田水分模型精度,优选阶段性亏水管理辅助模型。研究设置7个玉米分阶段亏水调控处理,于2018、2019年进行田间小区试验,取得2个同类模型的本地化参数并比较其模拟精度。结果表明,AquaCrop和双作物系数模型可相近表达玉米冠层发育到最大而未开始衰减期间土壤水分的消耗过程,而对快速生长期与后期1m土层贮水量的模拟差异大。AquaCrop模型在土壤贮水量偏低时高估其实测值,其他情形正负偏差分布相对均匀,双作物系数模型多数情形低估其实测值。AquaCrop模型描述玉米各阶段蒸散量因亏水情形而变化能力优于双作物系数模型。AquaCrop模型和双作物系数模型的标准均方根误差平均值在模拟1 m土层贮水量时分别为4.494%~8.443%、6.017%~8.626%,在模拟蒸散量时分别为8.158%~9.510%、5.980%~15.022%。综合来看,AquaCrop模型表现更好,推荐作为适宜西辽河流域覆土浅埋滴灌玉米水分管理模型。研究可为该区域覆土浅埋滴灌种植玉米选出适宜的水分管理模型,理解新技术条件下玉米分阶段亏水调控机制及田间灌溉管理优化提供参考。

滴灌模式和土壤水分对冬小麦土壤水提取量和水分利用的影响

为探索高效的灌溉策略以减少灌水量并提高作物水分利用效率以缓解黄淮海冬麦区水资源短缺。采用田间裂区试验设计,探究地表滴灌(DI)和地下滴灌(SDI)条件下不同土壤水分状况(分别为田间持水量的50%~60%,60%~70%,70%~80%,记为W_(50)、W_(60)和W_(70))对冬小麦产量、土壤水提取量、蒸散量和水分利用效率的影响。结果表明,对于整个生长季,与DI处理相比,SDI处理降低0~0.8 m土层土壤水提取比降低11.8%~21.8%,但SDI处理0.8~1.6 m土层土壤水提取量增加28.4%~29.8%。SDI处理的平均土面蒸发量和灌溉量分别比DI处理减少23.1%,8.9%。虽然花后SDI和DI处理间蒸腾速率的差异不显著,但在W_(50)和W_(60)条件下(亏缺灌溉),SDI处理的净光合速率和叶面积指数均高于DI处理。与DI处理相比,在亏缺灌溉条件下,SDI处理的产量增加14.5%~29.3%,水分利用效率增加13.9%~25.9%。与DI处理相比,在W_(70)条件下,SDI处理更多灌溉水下渗到0.8 m以下土层,从而显著降低上层土壤的土壤水提取量及叶片的净光合速率,导致产量降低4.1%~8.9%。SDI处理在W_(60)条件下能够从深层土壤提取更多水分,并调控冬小麦的光合特性,从而提高冬小麦的产量和水分利用效率。

黄土旱塬区苹果园生草覆盖对深层土壤水分和根系分布特征的影响

研究苹果园长期生草覆盖后深层土壤水分及果树根系的分布规律,以期阐明旱作条件下果园根水互作关系,为黄土旱塬区果园生草覆盖实践的优化提供依据。试验于甘肃庆阳草地农业生态系统国家野外科学观测研究站苹果园中进行,设置果园生草覆盖(生草为鸭茅草,2014年建植)和清耕处理,以一年生作物田为对照;连续两年夏季测定果树行上和行间距离树干100和200 cm共4个位置0~500 cm土层的土壤水分和果树细根长密度,分析生草覆盖对果园深层水分亏缺及细根长密度的影响。清耕果园0~300 cm土壤水分较对照农田下降了6.7%~8.3%(P<0.01),而300~500 cm土层土壤水分与对照农田差异不显著(P>0.05);生草覆盖果园0~500 cm整个剖面的土壤水分均低于清耕果园,平均下降了11.5%~12.3%。果园生草覆盖6~7年后0~500 cm土层土壤较对照农田水分亏缺量为163.9~172.1 mm,是清耕果园水分亏缺量的3.2~4.2倍。果树根系在0~100 cm土层的细根长密度最高,平均密度为0.187 cm·cm^(-3),生草覆盖促进了0~100 cm土层果树根系的分布,对深层根系影响不显著。清耕果园和生草覆盖果园0~500 cm土层土壤水分的含量随果树细根长密度的增加而降低,二者呈线性负相关关系,生草覆盖后二者相关性提高,干旱年份二者相关性更高。黄土旱塬区苹果园长期生草可促进果树根系生长,降低深层土壤水分,加剧土壤干燥化,对苹果树的利用年限和农田水分循环具有负面效应。旱作条件下应加强果园生草覆盖管理以保障水分的可持续性。

花石崖不同植被类型土壤水分特征

为充分了解黄土高原不同植被类型与土壤水分之间的关系,选择陕西省神木市花石崖镇5种典型植被类型刺槐、木枣、侧柏、柠条和草地为研究对象,采用单因素方差分析法比较不同样地间土壤水分的差异性。结果表明:在0~100 cm土层,研究区不同植被类型间土壤含水量和土壤蓄水量均存在显著性差异(P<0.05),均表现为草地>柠条>木枣>侧柏>刺槐。不同植被类型平均土壤水分亏缺度表现为刺槐>柠条>侧柏>木枣>草地,其中只有草地土壤水分不存在亏缺。综上,处于自然恢复状态下的草地对研究区土壤水分的维持具有相对积极的意义。

淮北地区干旱胁迫对冬小麦不同土壤中生长及水分利用效率影响与差异性分析

为探究不同干旱胁迫在各生育期中对冬小麦在砂姜黑土和黄潮土中生长发育的影响与差异,基于2022年五道沟水文实验站桶栽干旱试验,在冬小麦返青-拔节、拔节-抽穗、抽穗-乳熟期进行水分控制,设置轻旱、中旱、重旱3个胁迫水平及全生育期无旱对照(CK),分析各生育阶段不同干旱胁迫对冬小麦在砂姜黑土和黄潮土中株高、耗水量、产量、水分利用效率(WUE)的影响与差异。结果表明:①两种土壤冬小麦各生育阶段受旱影响下,株高小于对照组,重旱对株高的抑制最显著,拔节-抽穗期受旱对株高造成持续抑制影响;收获时黄潮土各处理株高均低于砂姜黑土,但干旱影响下,黄潮土各生育阶段受旱组株高抑制水平均小于砂姜黑土。②两种土壤各生育阶段耗水量随干旱加重而减少,重旱减少趋势最显著,且耗水量减少均会使总耗水量低于对照组,但黄潮土各受旱组基于对照减少水平均小于砂姜黑土。③两种土壤随干旱加重减产加剧,砂姜黑土各处理组产量均大于黄潮土,但黄潮土返青-拔节期、拔节-抽穗期相比砂姜黑土有一定抗旱能力;抽穗-乳熟期,砂姜黑土抗旱能力优于黄潮土。④各处理砂姜黑土WUE均高于黄潮土,抽穗-乳熟期差距最显著,该生育阶段受旱对黄潮土冬小麦的影响比砂姜黑土更大。

半干旱黄土丘陵区不同人工植被恢复土壤水分的相对亏缺

土壤水分是制约半干旱黄土丘陵区植被恢复和生态建设的关键因子。而缺乏科学指导的人工植被恢复会加剧土壤水分耗竭,造成土壤水分亏缺,从而严重阻碍该区生态系统恢复和脆弱生境的有效改善。以典型半干旱黄土丘陵区甘肃定西龙滩流域为例,对比不同植被恢复模式下土壤储水状况,并通过构建土壤水分相对亏缺指数CSWDI(Compared Soil Water Deficit Index)和样地土壤水分相对亏缺指数PCSWDI(Plot Compared Soil Water Deficit Index)进行定量化分析与评价,发现各人工植被均存在不同程度的土壤水分亏缺。其中,柠条、油松、山杏林地PCSWDI分别达到0.65、0.62、0.62,土壤水分亏缺严重,尤其是100 cm以下土层;山毛桃林地和苜蓿草地PCSWDI分别为0.38和0.17,在100—200 cm土层有一定程度的水分亏缺,但相对较轻;侧柏林地土壤水分的亏缺主要集中在20—100 cm这一层次,100 cm以下则随深度增加而降低;0—200 cm土层内,杨树林地、撂荒草地和马铃薯农地无显著水分亏缺,且在0—100 cm内土壤水分有一定的补充。CSWDI和PCSWDI能有效反映不同层次和样地土壤水分相对亏缺状况,可用于同一地区不同植被恢复模式土壤水分响应的定量化分析与评估。