基于茎直径变化监测番茄水分状况的机理与方法

该研究以春季温室番茄为试验材料，以筒栽和小区相结合的方法探索了番茄茎直径变化的机理与规律、外界环境因素对茎直径变化的影响以及如何消除气象因子对实测日最大收缩量（MDS）数值干扰等问题，目的在于为基于茎直径变化监测作物水分状况、实现自动灌溉的技术提供理论和实践依据。试验结果表明，番茄茎直径变化落后于叶水势变化，二者存在很好的相关性。番茄茎直径收缩过程是由韧皮部及木质部收缩同步构成，而恢复过程则是不同步的，木质部恢复较快。番茄盛果期蒸腾强度大于花果期蒸腾强度，蒸腾强度越大一天中最小茎直径出现的时间越晚，而其茎直径开始恢复的临界气孔导度值越小。番茄MDS的变化趋势和日均辐射的变化趋势一致，但变化幅度由土壤水分决定。当土壤相对含水率由田间持水率降至50%时，MDS随土壤水分的下降而变大，天气晴好时MDS能够很好的反映出土壤水分的差异；而当土壤相对含水率小于50%后，MDS随土壤水分的下降而变小。通过统计分析，由实测MDS与参照MDS相比的相对日最大收缩量（RMDS）指标基本上可以消除气象因子对监测结果的影响，稳定的反映土壤水分状况。     

土壤水势对春季桃树茎干变化的影响研究

将土壤水势控制在-10~-20 kPa和-40~-60 kPa,以自然条件为对照。分析3个小区不同时段土壤水势变化对桃树茎干生长的影响,研究结果表明,在干旱半干旱气候条件下,春季桃树在不同生长时段内相对适宜土壤水势分别为-23.38,-22.16和-42.94 kPa。对不同小区春季各月份桃树茎干日变化规律进行分析,3月份茎干日变化呈台阶式上升变化趋势,4月份桃树茎干日变化呈"W"变化趋势,5月份桃树茎干日变化规律基本呈"勺状"变化趋势。对4月和5月茎干日变化曲线进行拟合,符合Guss曲线变化规律。同时分析了影响桃树茎干日最大收缩量(MDS)的主要因素,明确以MDS作为灌溉指标的适用条件,进一步分析了以MDS作为灌溉指标的缺陷。     

不同土壤水势条件下枣树的生长发育研究

通过设定4个不同的土壤水势区间,研究不同土壤水势条件对枣树生长发育的影响。结果表明,在-23～-526kPa的土壤水势范围内,较低的土壤水势条件有利于枣树日最大茎直径的增加,但会使叶面积指数减小。透光率增加;在果实膨大期,土壤水势为-526kPa（相对田间持水率的27％）时,枣果萎蔫,复水后恢复正常生长状态;土壤水势越...     

番茄茎直径MDS的通径分析与数值模拟

以春夏季温室番茄为实验材料,研究充分灌溉条件下的茎直径变化指标日最大收缩量(MDS)与气象因子(水面蒸发量Ew、日最高气温Tmax、日均气温Tm、日均空气饱和差DVPDm、正午空气饱和差DVPDmd、日总辐射Rs和日辐射峰值Rmax)的相关性。结果表明,Rmax、DVPDm和Ew与MDS的直接通径系数为正,Rmax的直接通径系数最高,其次为DVPDm,二者与MDS的相关性达显著水平,但Ew与MDS的相关性未达显著水平,表明Rmax和DVPDm为决策变量,对温室番茄茎直径变化起直接作用。而Tmax、Tm、DVPDmd、Rs与MDS的直接通径系数为负,但各自总作用又都为正,表明它们主要通过Rmax和DVPDm对番茄茎直径变化起间接作用。据此建立了MDS与Rmax和DVPDm的模拟方程,经检验此方程达显著水平,预测值能够准确地反映出MDS实测数值的变化。     

基于茎秆直径微变化的拔节期玉米水分亏缺诊断指标研究

为了探索利用茎秆直径微变化诊断玉米水分亏缺状况的最优指标,采用桶栽的方法,开展了不同水分处理条件下拔节期夏玉米茎秆直径微变化中的日最大收缩量(MDS)、日增长量(DI)和当日恢复时间(RT)3个指标的变化规律及其与土壤相对含水率之间相关关系方面的试验研究。结果表明,(1)不同处理间的MDS和DI受水分亏缺影响差异较为明显,RT对土壤相对含水率的响应较为一致;(2)玉米日最大收缩量MDS和日增长量DI受到环境因素的影响较大,与土壤相对含水率θ的相关系数较小;(3)恢复时间RT与土壤相对含水率θ的相关系数最高,且受水分亏缺处理的影响较小,可以作为诊断玉米水分亏缺状况的较好指标。综上可知,与MDS和DI相比,RT更适合诊断夏玉米水分亏缺状况。     

限量供水条件下灌溉预报增产效益分析

有限供水条件下,随着灌溉供水量和降水量的变化,作物优化的灌水时间是变化的,作物生长期优化的土壤含水率调控下限值也应该是变化的,为此,基于典型年的优化灌溉制度提出了动态灌水下限的概念及其理论分析方法。利用天津农学院灌溉试验基地2008、2009、2011和2012年4个年度试验资料对冬小麦复播玉米水模型参数及其整体合理性进行了率定和检验,由此分析提出了天津市5个典型年不同灌溉供水条件下冬小麦复播玉米的优化灌溉制度,得到了45组灌水前土壤含水率(0~60 cm平均值)和对应的灌水时间及可供水量(包括灌溉供水量和降雨量)数据,交替使用规划求解与多元回归分析的方法确定了冬小麦复播玉米动态灌水下限预测模型。利用该动态灌水下限进行灌溉预报,可明显地增加产量和效益,冬小麦复播玉米生长期灌溉4次水和3次水较现状经验灌水5年(2008-2012年)平均增加产量,冬小麦分别为8.3%和18.1%,复播玉米分别为5.8%和1.3%,增加的效益分别为10.0%和14.1%。该方法避免了单纯依靠田间试验确定灌水下限的不足,为优化灌溉制度的实施和灌溉用水计划的动态修正提供了重要的方法。     

温室作物需水信息指标及湿度控制

在温室土壤－作物－环境连续体中，作物水分损耗、吸收和水分利用一直是研究的热点。在温室内，作物精量灌溉必须要考虑何时灌和灌多少两个方面的问题。从冠层蒸腾速率、茎流、水势、叶温和作物水分胁迫系数、茎秆果的直径微变化、根源信号、作物生长器官的电特性及图像特征技术方面，回顾和评价了作物水分状况诊断方法中作物需水信息指标的研究进展及存在的问题。同时，为防止过量灌溉带来的高湿矛盾，讨论了温室湿度控制的不同策略，以指导灌溉。最后，初步提出了进一步研究的建议。     

充分灌溉和干旱胁迫对棉花茎直径变化的影响

以桶栽棉花为试验材料,采用随机区组试验设计,探讨充分灌水条件下(T0)和一个干旱周期中(TI)的茎直径变化量(RV)、最大收缩量(MDS)及每日生长量(DI)之间的差异。试验结果表明,由于受到土壤水分减少的影响,TI处理棉花的茎杆逐渐收缩得不到恢复,其RV曲线下降和T0处理RV曲线的差异逐渐变大,并且同是TI处理的植株其RV下降幅度也不同;二种条件下棉株的MDS和DI均呈负相关;水分胁迫的加剧导致棉花叶片气孔导度变小。经回归分析二处理MDS和气象因子中的有效辐射有较好的相关性,表明有效辐射是导致茎变化的主因。据此提出土壤相对含水量60%为RV产生差异的临界值,土壤相对含水量40%是棉花茎秆内可被用做蒸腾的水分被完全耗尽的临界值;同时提出标准茎变化的概念及其全回归方程。     

拂子茅和早熟禾的灌溉比较研究

利用土壤水势作为灌溉指标，设置-30、-40、-50、-60kPa4个水势梯度，比较研究抗旱观赏草拂子茅和冷季型草坪草早熟禾在9月、10月的灌溉规律。拂子茅在土壤水势-30～-60kPa时进行灌溉生长差异不显著．9、10两月的总灌溉量最低可达74．9mm；早熟禾适宜在土壤水势达到-30kPa时进行灌溉．9、10月的总灌溉量为161．7mm．低于-30kPa的土壤水势下生长受影响。拂子茅和早熟禾的叶片水势都随土壤水势的下降而下降，拂子茅的下降速度低于早熟禾，具有较高的叶片水势，而拂子茅在-60kPa的土壤水势处理下根冠比显著升高，说明拂子茅在干旱胁迫下具备较强的吸水和保水能力。     

温室梨枣树土壤水分和品质对调亏灌溉的响应

为探明调亏灌溉对温室梨枣树水分利用效率及梨枣品质的影响,以日光温室生长的9年生矮化密植成龄梨枣树为试材,试验设置充分供水处理(处理1(CK)),萌芽展叶期重度亏水处理(处理2),萌芽展叶期中度亏水处理(处理3)和果实膨大期中度亏水处理(处理4)。结果表明,亏水处理有利于提高梨枣树的根系吸水能力,促进根系向土壤深处生长,同时显著降低棵间蒸发;与CK相比,处理2和处理3对梨枣品质的所有指标都起到了提高和改善的作用,其中处理2最佳,处理3次之;综合考虑不同生育期调亏灌溉对梨枣树各项指标的影响,萌芽展叶期中度亏水能较好的改善果实品质,是实施调亏灌溉的最佳阶段。     

Irrigation scheduling of almond trees with trunk diameter sensors

The use of plant indicators may be the ideal method for irrigation scheduling but it is hampered by the dynamic nature of plant water status and by the lack of suitable indicators, relative to established scheduling methods based on atmospheric and soil observations. A study was conducted in an almond orchard located in the San Joaquin Valley of California during the 2001 season using trunk diameter variations as the only indicator for determining the amount of irrigation. The ratio of the maximum daily shrinkage (MDS) of tree trunks relative to a reference MDS, calculated from a relationship between MDS of fully irrigated trees and atmospheric vapor pressure deficit, was used as a signal for modifying the amount of applied irrigation water. Applied water was increased by 10% each time the MDS signal exceeded the prescribed threshold. When the MDS signal went below the threshold, applied water was reduced by 10% in an interactive manner. Two schedules were tested with signal thresholds of 1.75 and 2.75, which generated mild and moderate water stress, respectively, as indicated by their stem water potential (SWP) values. The two irrigation treatments had SWP that varied over the season from around –0.7 to –1.1 MPa and –0.8 to –1.7 MPa, respectively. The two schedules resulted in seasonal water applications of 860 mm for the 1.75 and 525 mm for the 2.75 signal threshold treatments. The grower/cooperator, who based his schedule primarily on SWP measurements but also considered the water balance, applied 900 mm. Estimated crop evapotranspiration was 1,030 mm. The mean coefficients of variation for the two irrigation treatments during the monitoring period were 0.115 and 0.031 for the MDS and SWP measurements, respectively. The stress produced by the irrigation treatments hastened fruit maturation, as evidenced by accelerated hull splitting. This resulted in lower fruit hydration just prior to harvest; 17.3% and 8.0% for the two irrigation schedules, respectively, compared with 27.3% for the grower/cooperator. Based on harvesting selected trees with the same nut load, fresh and dry nut weights in the 2.75 threshold treatment were 9.0% and 10.7% less than those of the 1.75 threshold, which were not significantly different from the results for the grower cooperator. Our results demonstrate that it is feasible to develop an irrigation schedule for almond trees based solely on MDS signals, which may be tailored to any desired stress pattern and be operated in full automation with appropriate software development.Communicated by R. Evans     

Early morning fluctuations in trunk diameter are highly sensitive to water stress in nectarine trees

The sensitivity to water stress of different plant water status indicators was evaluated during two consecutive years in early nectarine trees grown in a semi-arid region. Measurements were made post-harvest and two irrigation treatments were applied: a control treatment (CTL), irrigated at 120 % of crop evapotranspiration demand to achieve non-limiting water conditions, and a deficit irrigation treatment, that applied around 37 % less water than CTL during late postharvest. The plant water status indicators evaluated were midday stem water potential (Ψ _stem) and indices derived from trunk diameter fluctuations: maximum daily shrinkage (MDS), trunk daily growth rate, early daily shrinkage measured between 0900 and 1200 hours solar time (EDS), and late daily shrinkage that occurred between 1200 hours solar time and the moment that minimum trunk diameter was reached (typically 1600 hours solar time). The most sensitive [highest ratio of signal intensity (SI) to noise] indices to water stress were Ψ _stem and EDS. The SI of EDS was greater than that of Ψ _stem, although with greater variability. EDS was a better index than MDS, with higher SI and similar variability. Although MDS was linearly related to Ψ _stem down to ?1.5 MPa, it decreased thereafter with increasing water stress. In contrast, EDS was linearly related to Ψ _stem, although the slope of the regression decreased as the season progressed, as in the case of MDS. Further studies are needed to determine whether EDS is a sensitive index of water stress in a range of species.     

沟灌方式与灌水量对温室番茄生长指标的影响

采用温室内田间试验,设置常规沟灌(CFI)和交替隔沟灌溉(AFI)两种沟灌方式,依据Φ20cm标准蒸发皿的水面蒸发量,通过选取0.6(K1)、0.8(K2)、1.0(K3)、1.2(K4)4个作物-皿系数Kcp,设置4个灌水量梯度,共8个处理,比较不同处理对番茄株高、茎粗、叶面积指数和根冠比的影响。结果表明,AFI相较于CFI会抑制番茄植株的株高,但会增加茎粗;灌水量对株高呈显著的正效应,CFI、AFI下拉秧前的最大株高(148.40、144.80cm)均在最大灌水量(K4)下获得;茎粗随灌水量的增加呈先增后减的趋势,在K2灌水量下CFI、AFI处理分别获得拉秧前的最大茎粗13.93和14.74mm;沟灌方式和灌水量的耦合效应对株高、茎粗的影响始终不显著(P0.05)。叶面积指数(LAI)受沟灌方式的影响不显著,但是会随着灌水量的提高而明显增大,两种沟灌方式均在最大灌水量(K4)下取得最大LAI。根冠比在AFI处理下明显大于相同灌水量下的CFI处理,随灌水量的增加呈先增后减的趋势,CFI下在K3灌水量时达到最大值0.070 6,AFI下在K2灌水量下达到最大值0.073 4。通过综合分析沟灌方式和灌水量对番茄株高、茎粗、叶面积指数以及根冠比的影响表明,交替隔沟灌溉相较于常规沟灌更有利于番茄植株的生长;过高(Kcp取1.2)或过低(Kcp取0.6)的灌水量均不利于番茄植株的生长,适中的灌水量(Kcp取0.8或1.0)不仅会使番茄植株健壮,同时也会使LAI处于一个较为合理的大小。     

Could trunk diameter sensors be used in woody crops for irrigation scheduling? A review of current knowledge and future perspectives

The use of trunk diameter fluctuations and their derived parameters for irrigation scheduling in woody crops is reviewed. The strengths and weaknesses of these continuously measured plant-based water stress indicators compared with other discretely measured indicators for diagnosing plant water status in young and mature trees are discussed. Aspects such as sensor reading variability, signal intensity and the relationship between trunk diameter fluctuations and plant water status are analyzed in order to assess their usefulness as water stress indicators. The physiological significance of maximum and minimum daily trunk diameter and maximum daily trunk shrinkage (MDS) are also considered. Current knowledge of irrigation protocols and baselines for obtaining maximum daily trunk shrinkage reference values is discussed and new research objectives are proposed. We analyze the response of woody crops to continuous deficit irrigation scheduled by maintaining MDS signal intensity at threshold values to generate mild, moderate and severe water stress and assess the possibility of using linear variable displacement transducer (LVDT) sensors in trunk as a precision tool for regulated deficit irrigation scheduling. Finally, the possibility of using MDS signal intensity as a tool to match the irrigation regime to tree water requirements is also reviewed.     

间接地下滴灌下灌水量对枣树生理特征及果实品质的影响

通过小区试验,以地表滴灌为对照,探究红枣间接地下滴灌模式下水分的分布特征及不同灌水量对枣树生理生态指标、产量、品质的影响。间接地下滴灌下,最大的含水率出现在15~30cm土层处;而地表滴灌下,最大的含水率出现0~10cm土层处。枣树各生理生态指标,随灌水次数的增加,各处理性状差异逐渐增大,间接滴灌下中供水和高等供水枣树长势较好,低供水处理下红枣的糖分含量高,中供水处理下红枣的有机酸和VC含量高;地表滴灌处理枣树的平均单株产量高,但水分利用率最低,中供水处理不明显降低红枣单果质量和平均单株产量的前提下可以提高水分利用率;综合考虑枣树长势、产量、果实品质及水分利用率,中供水是间接地下滴灌下最佳的灌水量。     

Assessment of trunk diameter variation derived indices as water stress indicators in mature olive trees

Plant age and size, seasonal growth patters and crop load, among other factors, have been reported to decrease the usefulness of trunk diameter variation (TDV) derived indices as water stress indicators in olive trees. Our hypothesis, however, is that indices derived from TDV records in old, big olive trees are sensitive enough to detect levels of water stress in trees of orchards under deficit irrigation that, although severe, are below the threshold for fruit shrivelling. This is of importance for the production of good quality oils, since fruit shrivelling may affect oil quality. The aim of this work was to assess different TDV-derived indices as water stress indicators in 40-year-old ‘Manzanilla’ olive trees with heavy crop load. We derived the maximum daily shrinkage (MDS), daily growth (DG) and daily recovery (DR) from TDV records taken during the 2008 dry season both in well-irrigated FAO trees and in deficit-irrigated RI trees. Measurements of volumetric soil water content (θ_v), leaf water potential (Ψ_l), stomatal conductance (g_s), net CO₂ assimilation rate (A), water and oil accumulation in the fruits and yield parameters were made for both treatments. The trunks did not grow during the experimental season, either in the FAO or RI trees, likely because of the heavy crop load. Therefore, DG was useless as water stress indicator. For MDS and DR, which were responsive to the increase of the trees’ water stress, we calculated the variability, quantified by the coefficient of variation (CV), the signal intensity (S_I) and the sensitivity (S_I/CV) values. In addition, we derived reference equations for irrigation scheduling from the relationships between MDS values in the FAO trees and main meteorological variables. Values both of S_I-MDS and S_I-DR were steady until September 9, despite of increasing differences in θ_v between treatments from early in the dry season. The Ψ_l vs θ_v values showed an outstanding capacity of the RI trees to take up water from the drying soil, and the Ψ_l vs g_s values showed a near-isohydric behaviour of those deficit-irrigated trees. These results explain, at least in part, the lack of response of MDS and DR on that period. Both S_I-MDS and S_I-DR peaked for the first time on September 9, 16 days before the appearance of fruit shrivelling. Our results suggest that using TDV-derived indices as water stress indicators for irrigation scheduling in old olive orchards with medium to low plant densities, i.e. with large root zones, may be useless in case the irrigation strategy is aimed at keeping the soil close to field capacity. Nevertheless, the MDS and DR indices may be useful indicators for the avoidance of fruit shrivelling in deficit irrigated olive orchards for the production of good quality oil. Reliable reference equations for scheduling irrigation with the signal intensity approach were obtained from the regression of MDS values vs the daily maximum values of both the air temperature and the vapour pressure deficit of the air.     

Evaluation of grapevine water status from trunk diameter variations

We evaluated the usefulness of short-term trunk diameter variations (TDV) as water stress indicator in field-grown grapevines cv. Tempranillo. Two indices were calculated from TDV, maximum daily trunk shrinkage (MDS), and trunk growth rate (TGR). The seasonal evolution of both indicators was compared with occasional determinations of pre-dawn leaf water potential and stem water potential, measured at early morning (Ψ_s^em) and at midday (Ψ_s^md) in irrigated and non-irrigated vines. In the second season, the effect of crop load on the vine water status indicators was also studied. Crop load did not affect either the vine water relations or the TDV. All water potential determinations had much lower variability and were more sensitive than both MDS and TGR to water restrictions. The ability of both indices to detect plant water stress varied largely depending upon the phenological period. In fact, MDS and TGR were only able to detect vine water stress during a short period of time before veraison. During this period, TGR was linearly related to both Ψ_s^em and Ψ_s^md, while for MDS a curvilinear, quadratic equation, better described the relationship with plant water status. After veraison no apparent relationship existed between plant water status and MDS or TGR. Hence, our results question the practical use of both MDS and TGR as variables to automate irrigation scheduling for grapevine.     

Evaluation of plant-based water status indicators in mature apple trees under field conditions

The performance of different indicators of plant water status as a tool for irrigation management was evaluated in mature field grown ‘Golden Delicious’ apple trees during the late summer of 1998. Control (C) and stress (S) treatments were studied. In the C treatment trees were irrigated daily at 100% ET_c whereas in the S treatment water was withheld during 31 days (DOY’s 236–266). Predawn water potential (Ψ_pd) and midday stem water potential (Ψ_stem) were measured several times a week during the experimental period. Three daily measurements of stomatal conductance (g_s) and stem water potential were made during five consecutive days in mid-September. Trunk diameter changes (TDC) were recorded by LVDT sensors, and from these measurements, maximum daily shrinkage (MDS), daily growth (DG), and cumulative growth (CG) were calculated. Midday Ψ_stem showed the best ratio between the response to moderate water stress and tree variability (“signal/noise” ratio) among the indicators studied here, followed closely by Ψ_pd. On the other hand, the poorest water status indicator was g_s. Due to the low trunk growth rate of the trees, and its high variability, DG and CG were not adequate indicators. MDS showed a lower sensitivity to water stress and a higher variability (CV = 0.19) than midday Ψ_stem (CV = 0.08) and Ψ_pd (CV = 0.10). However, MDS correlated well with ET₀ and with midday Ψ_stem (R ² = 0.79) thus, making this parameter an interesting and promising tool for irrigation management in apple orchards. More research needs to be done in order to define reference values for MDS and plant water potential indicators, in relation to evaporative conditions and in different phenological periods, and to quantify the relationship between water status indicators values and apple tree yield and fruit quality.     

涌泉根灌技术研究与应用

提出了一种新型涌泉根灌灌水方法,研究设计了一种灌水器,实现了直接将灌溉水输送到植物根系部位的研究目标,研制的涌泉根灌灌水器流态指数小于0.5,属紊流范畴.为了测得不同节水灌溉方式的应用效果,在陕北山地5年生枣树实施了管灌、滴灌和涌泉根灌等工程38.67hm^2,对3种不同灌水方法的经济效益作了分析.结果表明,与不灌溉相比,管灌、滴灌和涌泉根灌的净增收入分别为4707.70,8446.00和10926.00元/hm^2;管灌、滴灌和涌泉根灌每方灌溉水产值分别为1.90,11.30和14.60元/m3.涌泉根灌与滴灌相比,年成本降低2030元/hm^2,净收入增加2480元/hm^2,每方灌溉水产值提高3.30元/m3;涌泉根灌与管灌相比,年成本降低743.30元/hm^2,净收入增加6218.30元/hm^2,每方灌溉水产值提高12.70元/m3.不同节水灌溉方式均使得枣园净收入大幅度提高,尤其是涌泉根灌方式,净增值率高达235.0%.建议在山地经济林果中大面积推广应用涌泉根灌技术.