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1.
Establishment of shallow and restricted root systems in cotton and its impact on plant response to irrigation 总被引：1，自引：0，他引：1
Summary The effects of frequent and shallow soil wetting by surface drip irrigation on root growth, morphology, and location, and their impact on plant sensitivity to irrigation management were studied in cotton (Gossypium hirsutum L.). Daily drip irrigation, which wetted the 0 to 40-cm soil depth, encouraged root development mainly around the drippers. Water extraction took place mostly from 0 to 20 cm below the drippers, where the roots were concentrated. Shallowness of root growth was not altered by the expansion and deepening of the wetted soil zone which resulted from an increase in amount of irrigation water. The shallow and restricted root system was characterized by a high fraction of thin roots (less than 1 mm dia.) which comprised almost 90% of the root dry matter. Root proximity to the drippers and the limited amount of water in the rooted soil led to a sensitive and quick response of the plants to small amounts of irrigation. A supply of 1.0 mm H2O given at midday to 70 day-old plants resulted in a leaf water potential (L
w) increase from –1.64 to –1.32 MPa over a 20-min period. This amount of irrigation comprised 15% of the average daily quantity. A 24 h delay in irrigation to 80 dayold plants was enough to decrease L
w from –1.41 to –2.42 MPa. This decrease was caused by a soil water deficit of less than 6 mm H2O. Extending the irrigation delay to 72 h affected yield and earliness, although the deficient amount of water was supplied over the several days after the treatment. A strong response to minor, but continuous, differences in the daily irrigation amount was detected. Differences in irrigation of less than 1 mm H2O per day applied during the whole growth season substantially affected L
w, yield and earliness. It was concluded that the establishment of a shallow and restricted root system resulted in strong dependence of the plants on frequent and sufficient supply of water, and temporary minor changes in irrigation affected plant water status and productivity. 相似文献
2.
【目的】确定根际环形多点源滴灌技术的应用效果。【方法】以陕北沙地枸杞为研究对象,采用小区灌水试验,将根际环形多点源滴灌与地表滴灌、涌泉根灌下对比,研究了不同灌水方式对土壤湿润锋垂直分布范围、土壤含水率、枸杞产量的影响。【结果】地表滴灌下69%的土壤湿润体位于地表0~20cm,涌泉根灌下72.2%的土壤湿润体位于根系主要分布层,根际滴灌下土壤湿润体100%位于枸杞主要根系层;地表滴灌和涌泉根灌、根际滴灌产量比不灌溉枸杞分别增产2 075、3 145、4 150 kg/m^2,水分利用率分别提高了22.4%、41.9%、60.2%;净收入高低排序为根际滴灌>涌泉根灌>地表滴灌,分别比不灌溉处理提高了193.1%、126.3%、81.2%,单位水产值达到了15.0、13.3、11.5元/m^3。【结论】根际环形多点源滴灌的水分湿润范围更适宜于沙质土壤的经济林,是减少地表蒸发损失和深层渗漏的有效技术措施,该技术在沙地经济林生产中有广阔的推广应用前景。 相似文献
3.
为了研究干旱半干旱地区土壤剖面深层水分对冬小麦根系生长及抗旱性的影响,采用PVC管土柱法进行冬小麦生长水分调控试验,设计了4个处理,即处理Ⅰ为地面灌溉、处理Ⅱ为计划湿润层取根系分布深度的60%、处理Ⅲ为计划湿润层取根系分布深度的75%、处理Ⅳ为计划湿润层取根系分布深度的90%,测定了冬小麦各生育期根系形态指标和地上部分植株体干重的变化,结果表明:灌水总量一定,改变灌水方式、考虑计划湿润层的深层灌溉,能够促进冬小麦根系深扎,至成熟期,处理Ⅱ、Ⅲ、Ⅳ的根长比处理Ⅰ长27~37 cm,总根干重均增加,但根冠比减小,产量增加。适宜的根冠比能更好地协调冬小麦地上部分与地下部分之间生长关系,提高抗旱能力。处理Ⅱ和处理Ⅲ是冬小麦根冠层生长协调、提高抗旱能力较适宜的灌溉方案,可为我国北方地区冬小麦节水灌溉提供参考。 相似文献
4.
The infiltration and redistribution of soil moisture under surface drip irrigation considering hysteresis were investigated in two soils (loamy sand and silt loam) of different texture. The effect of continuous versus intermittent application of 1, 2 and 4 l/h to the soils was evaluated in terms of wetting front advance patterns and deep percolation under the root zone. For this purpose, a cylindrical flow model incorporating hysteresis in the soil water retention characteristic curve, evaporation from the soil surface, and water extraction by roots was used. The results show that, compared with continuous irrigation, pulse irrigation slightly reduces the water losses under the root zone in both cases (with and without hysteresis). Also, at the total simulation time, in both types of irrigation, hysteresis reduces significantly the water losses under the root zone. Finally, the effect of hysteresis was found to be greater at higher discharge rate (4 l/h) and consequently at higher water content at the soil surface. 相似文献
5.
Intercropping, drip irrigation, and the use of plastic mulch are important management practices, which can, when utilized simultaneously, increase crop production and save irrigation water. Investigating soil water dynamics in the root zone of the intercropping field under such conditions is essential in order to understand the combined effects of these practices and to promote their wider use. However, not much work has been done to investigate soil water dynamics in the root zone of drip-irrigated, strip intercropping fields under plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate soil water contents (SWC) at different locations, for different irrigation treatments, and with respect to dripper lines and plants (corn and tomatoes). Experimental data were then used to calibrate the HYDRUS (2D/3D) model. Comparison between experimental data and model simulations showed that HYDRUS (2D/3D) described different irrigation events and SWC in the root zone well, with average relative errors of 10.8, 9.5, and 11.6 % for irrigation treatments T1, T2, and T3, respectively, and with corresponding root mean square errors of 0.043, 0.035, and 0.040 cm3 cm?3, respectively. The results showed that the SWC in the shallow root zone (0–40 cm) was lower under non-mulched locations than under mulched locations, irrespective of the irrigation treatment, while no significant differences in the SWC were observed in the deeper root zone (40–100 cm). The SWC in the shallow root zone was significantly higher for the high irrigation treatment (T1) than for the low irrigation treatment, while, again, no differences were observed in the deeper root zone. Simulations of two-dimensional SWC distributions revealed that the low irrigation treatment (T3) produced serious severe water stress (with SWCs near the wilting point) in the 30–40 cm part of the root zone, and that using separate drip emitter lines for each crop is well suited for producing the optimal soil water distribution pattern in the root zone of the intercropping field. The results of this study can be very useful in designing an optimal irrigation plan for intercropped fields. 相似文献
6.
Patterns of water withdrawal beneath an irrigated peach orchard on a red-brown earth 总被引：1，自引：0，他引：1
Summary Water withdrawal from the soil beneath an irrigated peach orchard is described over depth and time after irrigation for a red-brown earth where the hydraulic properties vary with depth. Relationships between water uptake by roots, root concentration and soil-water suction were explored over protracted drying cycles. In the early stages of drying water uptake by roots was well correlated with root concentration over the profile but, over time, water uptake was redistributed over the root system. Theoretical analysis suggests that poor utilization of water from depth on this soil was associated mainly with low root concentrations and low root (radial) conductance. Practical considerations for improved water management in the root zone of peach orchards on shallow soils are discussed. 相似文献
7.
8.
In Australian irrigated citriculture, fruit yield and quality outcomes are not tightly related to levels of plant available water, which raises the possibility of using mild water stress applied to part of the root zone, i.e. partial root zone drying, to stimulate physiological mechanisms that reduce tree water use by changing the relationship between stomatal conductance and ambient evaporative conditions.The PRD technique alternates irrigation such that one side of the tree root zone is allowed to dry whilst the other side is irrigated. This significantly reduces the wetted soil volume at any point in time, whilst always maintaining a readily available water supply to part of the root zone. By adopting this irrigation strategy water use of mature Navel orange trees C. sinensis (L.) Osbeck was reduced and water use efficiency was increased. The technique did not induce excessive fruitlet drop and crop yield was unaffected. Both fruit size and juice percentage slightly decreased whereas total soluble solids percentage (TSS) and juice acid percentage increased. As water use was reduced and juice quality attributes were increased, this technique has obvious benefits for juice fruit production.PRD offers an advantage over conventional deficit irrigation strategies because it helps reduce water use by separating the biochemical signaling responses to water deficit in the dry part of the root zone from the physical effects of reduced stomatal conductance due to lower water availability, allowing developmental processes associated with plant growth to remain unperturbed. Irrigating a reduced root zone volume in this way reduces crop water requirement. However, it is also important to understand that this technique pushes the crop to its limits and should only be applied to well established healthy trees.When applying PRD irrigation, it is important that water is supplied with sufficient frequency and depth of wetting to meet the water needs of the whole plant. 相似文献
9.
The 2-year field experiments were carried out to research the effect of different irrigation methods, namely border irrigation,
sprinkler irrigation, and surface drip irrigation, on root development and profile water uptake in winter wheat. Results showed
that the main root distribution zone moved upward under sprinkler and surface drip irrigation when compared to the traditional
border irrigation. Profile root distribution pattern changed with irrigation methods. Soil profile water uptake was correlated
to the root system and soil water dynamics. Due to the appropriate soil water and higher root density in the surface soil
layer under sprinkler and surface drip irrigation, the main water uptake zone was concentrated in the upper layer. Because
of the water deficit in the surface layer under border irrigation, water uptake in 50–100 cm depth was stimulated, which caused
the main uptake zone downward. The amount and pattern of root water uptake varied with irrigation methods. This may provide
valuable information on the aspect of agricultural management. 相似文献
10.
【目的】探究冬小麦适宜的计划湿润层深度和土壤含水率控制下限的组合模式,为冬小麦田间用水管理及自动灌溉控制决策提供理论依据。【方法】以冬小麦为研究对象,采用大田试验,设置3个土壤含水率控制下限(L:40%,M:50%,H:60%)和3个计划湿润层深度(60、80、100 cm),共9个处理(T60L、T60M、T60H、T80L、T80M、T80H、T100L、T100M、T100H),研究了不同计划湿润层深度与土壤含水率控制下限对华北地区冬小麦生长发育和水分利用的影响。【结果】计划湿润层深度及土壤含水率控制下限的不同改变了处理间灌水定额及灌水次数,计划湿润层深度过高或土壤含水率控制下限过低均不利于冬小麦植株的生长发育。随着计划湿润层深度(60~100 cm)和土壤含水率控制下限(40%~60%)的增大,冬小麦花前及花后的干物质累积量呈先增大后减小的趋势。产量随土壤含水率控制下限增高呈增加趋势,当计划湿润层深度为80 cm时,产量相对最高,同时耗水量也越多,而计划湿润层深度为60 cm时耗水量最少。计划湿润层深度越低,土壤含水率控制下限越高,冬小麦水分利用效率则越高。T60H处理的水分利用效率最大,为19.96 kg/(hm2·mm),比最小值T100L大21.0%。【结论】本试验条件下,计划湿润层深度为60 cm,土壤含水率控制下限设置为土壤有效含水率的60%时,冬小麦节水高产效果相对最优。 相似文献
11.
Precision irrigation involves the accurate and precise application of water to meet the specific requirements of individual
plants or management units and minimize adverse environmental impact. Under precision irrigation applications, water and associated
solute movement will vary spatially within the root zone and excess water application will not necessarily result in deep
drainage and leaching of salt below the root zone. This paper estimates that 10% of the irrigated land area (producing as
much as 40% of the total annual revenue from irrigated land) could be adversely affected by root zone salinity resulting from
the adoption of precision irrigation within Australia. The cost of increases in root zone salinisation due to inappropriate
irrigation management in the Murray and Murrumbidgee irrigation areas was estimated at AUD 245 million (in 2000/01) or 13.5%
of the revenue from these cropping systems. A review of soil–water and solute movement under precision irrigation systems
highlights the gaps in current knowledge including the mismatch between the data required by complex, process-based soil–water
or solute simulation models and the data that is easily available from soil survey and routine soil analyses. Other major
knowledge gaps identified include: (a) effect of root distribution, surface evaporation and plant transpiration on soil wetted
patterns, (b) accuracy and adequacy of using simple mean values of root zone soil salinity levels to estimate the effect of
salt on the plant, (c) fate of solutes during a single irrigation and during multiple irrigation cycles, and (d) effect of
soil heterogeneity on the distribution of water and solutes in relation to placement of water. Opportunities for research
investment are identified across a broad range of areas including: (a) requirements for soil characterisation, (b) irrigation
management effects, (c) agronomic responses to variable water and salt distributions in the root zone, (d) potential to scale
or evaluate impacts at various scales, (e) requirements for simplified soil–water and solute modelling tools, and (f) the
need to build skills and capacity in soil–water and solute modelling. 相似文献
12.
《Agricultural Water Management》1998,38(1):69-76
A new method of irrigation was designed and tested for its water use efficiency (WUE). Maize plants were grown in pots with their roots divided and established into two or three separated containers of which irrigation and soil drying were controlled alternately. Results showed that when the two halves of the root system were alternatively exposed to a drying soil and a soil with its water content maintained above 55% or 65% of its field capacity, water consumption was reduced by 34.4–36.8% and the total biomass production was reduced by only 6–11%, when compared to the well-irrigated plants. Significant increase in WUE, root to shoot ratio and stomatal resistance for water diffusion were observed as a result of such treatment. Leaf transpiration was reduced substantially while the rate of photosynthesis and leaf water content were not significantly altered. The results were also compared to root-divided plants of which irrigation was fixed to one container only and showed that a better WUE, root development and distribution, shoot biomass production were achieved by the alternate drying and rewetting. We conclude that the controlled alternate irrigation (CAI) is an effective and water-saving irrigation method and may have the potential to be used in the field. 相似文献
13.
葡萄分层地下滴灌滴头布设深度优化 总被引：1，自引：0，他引：1
为解决不同树龄葡萄根系的差异使得地下滴灌系统在布设应用中存在的困难,采用室内试验和HYDRUS-2D数值模拟相结合的方法,以宁夏和关中葡萄产区为例,研究了2种土质条件下分层地下滴灌土壤水分运动规律,提出了分层地下滴灌带最佳布设深度.研究结果表明,HYDRUS-2D模拟值与试验实测值具有良好的吻合度.地下滴灌带的埋深直接影响土壤水分的分布,2种土质下湿润体内部处于最佳含水率区间的土壤体积随滴头间距的增加而增大.通过适当增大浅层滴头埋深并减小深层滴头埋深可减小表层水分无效损耗.从避免水分无效消耗以及提高湿润体与根系匹配效果等角度出发,建议关中地区葡萄单滴头灌溉且适宜滴灌带布设深度为20 cm;宁夏贺兰山地区滴灌带布设深度以15 cm和45 cm为宜. 相似文献
14.
《Agricultural Water Management》2004,70(1):67-81
Rice (Oryza sativa L.) root systems play an important role in uptake of water and nutrients from soil. A 4-year field experiment was conducted to determine the effects of different nutrient and water regimes on root growth by measuring the root diameter, root density, and root activity. Three nutrient regimes were used: (i) combined application of chemical fertilizers with farmyard manure (CM), (ii) integrated use of chemical fertilizers and wheat straw (CS), (iii) chemical fertilizers only (CK). Two soil moisture regimes included continuous waterlogging (CWL) and alternate wetting and drying (AWD). Incorporation of organic sources into paddy soil markedly improved root morphological characteristics of rice plant. In the alternate wetting and drying (AWD), root length density (RLD), and root weight density (RWD) for organic fertilization treatments (CS and CM) increased by 30 and 40%, respectively, as compared with the sole chemical fertilization (CF). Relative to root activity, CWL had adverse effects on root active absorption area (AAA), root oxidation ability of alpha-naphthylamine (α-NA) (ROA), and root surface phosphatase (RSP) of rice plants treated by integrated application of organic and inorganic fertilizers. In particular for the CM treatment, the AAA, ROA, and RSP of rice plants by the continuous flooding decreased by 22, 28, and 35%, respectively, compared to the alternately flooded regime. In the water regime of AWD, incorporation of organic manure significantly increased N, P, and K uptake by rice plants and facilitated the allocation and transfer of nutrient elements, especially P to rice ears and grains. This resulted in significant increases in the filled grains panicle−1, 1000-grain weight and grain yield. The beneficial effects of integrated use of organic and mineral fertilizers on grain yield were significantly (P < 0.05) decreased by the water regime of CWL. 相似文献
15.
An index of soil drought intensity and degree: An application on corn and a comparison with CWSI 总被引：2，自引：0，他引：2
A variety of indices have been used to measure soil and crop drought for irrigation scheduling. However, simple indices with physiological mechanisms from soil water content are still expected. Based on the water flow and supply in a soil-plant continuum, we examined the concepts of soil drought intensity and drought degree and found an empirical correlation between soil water storage and depletion in a given layer. Accordingly, an index of soil drought intensity (I) and degree (D) was established using the soil water data obtained from a field experiment conducted in Xianning, Hubei, China. Corn plants (Zea mays L., Yedan 13) were grown at field plots under a movable rain shelter. From the V6 stage to R1 stage, the corn plants were grown under seven soil water deficit levels, by no irrigation applied for 0-36 days in 2005 and 0-32 days in 2006. At the end of the irrigation withholding period, it was found that soil water below 70 cm still remained at high level, but the soil water was not easily transported to the root zone in the upper layer. The daily values of I in different soil layers reflected the soil water depletion rates in the drying course. The values of D in different soil layers, which were calculated from I, increased with the progressive soil drying course. The D index in different soil layers not only revealed the drought severity of the layer, but it was also inversely correlated with corn yields when D was less than the threshold values. When D went beyond the thresholds, for example 0.68 in 2005 (soil dried 25 days) and 0.70 in 2006 (soil dried 17 days) in the 0-10 cm soil layer, the corn yield was reduced significantly. Based on soil water changes, index D is the comprehensive result of antecedent soil water condition, crop growth and root development, soil properties, and potential atmospheric evaporation. It is also comparable to the development of drought hazard on a crop. The results suggest that soil drought degree D, together with I, can be an index for monitoring and evaluating soil-crop drought, as well as complementing the crop water stress index (CWSI) in irrigation scheduling. 相似文献
16.
Huiqun Wang Fulai Liu Mathias N. Andersen Christian R. Jensen 《Irrigation Science》2009,27(6):443-448
The effects of partial root-zone drying (PRD) as compared with deficit irrigation (DI) and full irrigation (FI) on nitrogen
(N) uptake and partitioning in potato (Solanum tuberosum L.) were investigated. Potato plants were grown in split-root pots and were exposed to FI, PRD, and DI treatments at tuber
bulking stage. Just before onset of the irrigation treatment, each plant received 0.6 g N (in the form of urea) with 5% of
which was 15N-labeled. After 4 weeks of irrigation treatments (i.e., one drying/wetting cycles completed in the PRD treatment), the plants
were harvested and plant dry mass and N content were determined. The results showed that although the plant dry mass was not
affected by the irrigation treatments, due to a reduced water use by the plant, both the PRD and DI treatments significantly
increased crop water use efficiency. Compared with the FI and DI plants, PRD plants had significantly higher N contents in
the leaves, stems and tubers; whereas, the 15N content in the plant organs was similar for the FI, PRD, and DI plants. It is suggested that not the root N uptake efficiency
but the soil N availability was enhanced by the PRD treatment. 相似文献
17.
《Agricultural Water Management》2001,52(1):53-71
The influences of water quantity and quality on young lemon trees (Eureka) were studied at the University of Jordan Research Station at the Jordan Valley for 5 years (1996–2000). Five water levels and three water qualities were imposed via trickle irrigation system on clay loam soil. The primary effect of excess salinity is that it renders less water available to plants although some is still present in the root zone. Lemon trees water requirements should be modified year by year since planting according to the percentage shaded area, and this will lead into substantial water saving. Both evaporation from class A pan and the percentage shaded area can be used to give a satisfactory estimate of the lemon trees water requirement at the different growth stages. The highest lemon fruit yield was at irrigation water depth equal to evaporation depth from class A pan when corrected for tree canopy percentage area. Increasing irrigation water salinity 3.7 times increased average crop root zone salinity by about 3.8–4.1 times.The high salt concentration at the soil surface is due to high evaporation rate from wetted areas and the nature of soil water distribution associated with drip irrigation system. Then, the salt concentration decreased until the second depth, thereafter, salt concentration followed the bulb shape of the wetted soil volume under trickle irrigation. Irrigation water salinity is very important factor that should be managed with limited (deficit) irrigation. But increasing amount of applied saline water could result in a negative effect on crop yield and environment such as increasing average crop root zone salinity, nutrient leaching, water logging, increasing the drainage water load of salinity which might pollute ground water and other water sources. 相似文献
18.
多点源滴灌条件下土壤水分运移模拟试验研究 总被引：3，自引：0，他引：3
为了指导密植作物的滴灌系统合理设计,通过室内物理试验模拟了多点源滴灌条件下土壤水分运移过程,重点研究了不同滴头流量下交汇湿润体内的土壤水分时空动态分布规律．多点源滴灌条件下土壤水分运动遵循先点源入渗、再湿润锋交汇和最后形成湿润带的规律．灌水结束时,土壤水分分布呈现湿润体上部复杂、下部相对简单的特征．湿润体上部,在滴头下方存在土壤含水率相对较高的区域,2个滴头之间近地表处存在土壤含水率相对较低的区域;湿润体下部同一深度土层上的含水率有趋于一致的趋势．灌水结束后,由于土壤水分再分布,同一深度土层上含水率差异逐渐减小．灌水量相同条件下,灌水结束时,滴头流量小的入渗深度较大,湿润体内土壤平均含水率较低;灌水结束后,受土壤水分再分配的作用,不同滴头流量下入渗深度的差异较灌水结束时有所减小． 相似文献
19.
20.
R. J. Stirzaker 《Irrigation Science》2003,22(3-4):177-185
The science of irrigation scheduling is well advanced, but the field application of this knowledge among irrigators is limited. Case studies are presented to show why irrigators may fail to adopt or persevere with traditional irrigation scheduling methods. This paper describes a funnel-shaped wetting front detector that is buried at an appropriate depth in the root zone. As a wetting front moves into the funnel of the detector, the water content increases due to convergence, so that the water content at the base of the funnel reaches saturation. The free water produced is detected electronically and this provides the signal to stop irrigation. Since the philosophy of drip irrigation in most cases is to supply water little and often, the "when to turn the water on" question becomes redundant and knowing when to turn the water off is more useful. Two further case studies demonstrate the benefits of scheduling micro-irrigation using wetting front detectors. The detectors retain a water sample from each irrigation event and this was used to monitor nitrate movement in and below the root zone.Communicated by P. Thorburn 相似文献