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1.
The accuracy of ‘available’ and ‘extractable’ soil water estimates was investigated using irrigated and unirrigated beans (Vicia faba) grown in an alluvial silt loam in Canterbury, New Zealand. Available water capacity was defined as the difference between soil water contents in the root zone at the drained upper limit (DUL) and at the lower limit (LL) as estimated by laboratory procedures. Extractable water capacity was specified as the difference between field estimates of DUL and LL for the whole profile affected by roots. DUL was estimated in the laboratory by equilibrating soil cores at matric potentials at ?10, ?20 or ?30 kPa, and in the field by neutron moderation. Laboratory estimates of LL were made from soil samples equilibrated at ?1.5 MPa matric potential. In the field LL was measured by neutron moderation on plots where evaporation had apparently ceased due to drought stress.When compared at intervals down the profile laboratory estimates of DUL and LL showed poor agreement with field observations. However, the final estimates of available and extractable water capacities were similar because of compensatory inaccuracies in the laboratory estimates. Furthermore, field measurements of evapotranspiration, using neutron moderation and tensiometry, indicated that the accuracy of the available water estimates was much reduced by upward fluxes of water into the rooting zone. These fluxes resulted in water extraction to at least 1.0 m although the apparent maximum rooting depth (measured by counting roots washed from soil cores) was only 0.7 m.Particular attention was paid to the influence of subsoil textural variability, which is pronounced in such soils. Laboratory and field estimates of the LL had to be carefully matched texturally before relevant comparisons could be made. Problems associated with subsoil textural variability affected laboratory methods of DUL estimation more than field methods. 相似文献
2.
Summary Concurrent diurnal measurements of water potential, osmotic potential and conductance were made on leaves of lucerne grown under weekly (W) and fortnightly (F) irrigation on gypsum-treated (G) and untreated soil (C). Measurements were made throughout the period of vegetative growth.Leaf water potentials were lower both at dawn and in the afternoon under fortnightly as compared to weekly irrigation. Gypsum application led to a slower decline in water potential under fortnightly irrigation, although the effect was small compared with more frequent irrigation. Stomatal conductance was reduced under treatments FG and FC during the later stages of vegetative growth, coinciding with leaf water potentials of less than c. –1.6 MPa.The relationship between leaf water potential and turgor potential changed with time such that positive turgor was maintained as leaf water potential declined. Turgor maintenance was achieved through a decrease in leaf osmotic potential. These data suggest that lucerne is capable of osmotic adjustment.Stomatal conductance declined rapidly below a leaf turgor potential of c. 0.1 MPa. It is hypothesised that osmotic adjustment enabled stomatal adjustment, which contributed to continued assimilation despite increasing soil moisture deficits. 相似文献
3.
根据宁夏地区1962—2017年11个国家级气象站的逐日气象资料,采用Penman-Monteith公式计算宁夏地区潜在蒸散发(potential evapotranspiration,ET0)日值系列,采用气候倾向率、Mann-Kendall突变检验、ArcGIS反距离权重空间插值、敏感性分析和贡献率等方法对宁夏地区... 相似文献
4.
《Agricultural Water Management》2006,83(3):261-265
In the Trás-os-Montes region, almond orchards are usually planted in the dry soils on the upper valley of the Douro river and are typically cultivated under non-irrigated conditions, leading to low yields. This study aimed to compare the physiological responses of five almond varieties (Francoli, Ferragnès, Glorieta, Lauranne and Masbovera) growing under non-irrigated and irrigated conditions. In irrigated conditions, all cultivars had higher photosynthetic rates, with maximum rates in a range of 10–12 μmol CO2 m−2 s−1. Study of daily photosynthesis (June–August) indicates that, irrigated plants showed maximal values at 11 h (32 °C), while in water stressed ones highest values were found at 9 h (28 °C). The irrigation induced an increase in photosynthesis of around 173% in Lauranne, 187% in Francoli, 204% in Glorieta, 266% in Masbovera and 331% in Ferragnès. In relation to values of water potential that allow half-rate of photosynthesis (ψw50), they were calculated as −2.95, −2.50, −3.10, −3.20 and −3.30 MPa for Ferragnès, Glorieta, Masbovera, Francoli and Lauranne, respectively. 相似文献
5.
The use of midday leaf water potential for scheduling deficit irrigation in vineyards 总被引:1,自引:0,他引:1
J. Girona M. Mata J. del Campo A. Arbonés E. Bartra J. Marsal 《Irrigation Science》2006,24(2):115-127
Midday leaf water potential (Ψmd) was monitored for 3 years at a commercial vineyard (cv. Pinot Noir) under four irrigation strategies. Three treatments were
established based on irrigating vines with 4–6 mm/day, when daily measured Ψmd was more negative than the pre-defined threshold. After the first experimental year, thresholds were adjusted for each treatment
as: (1) Control (C), irrigated when Ψmd was less than −0.6 MPa at the beginning of the season and gradually fell to −0.8 MPa at about mid-June, after which the threshold
was maintained at −0.8 MPa until harvest. (2) Control–Deficit (CD), irrigated as C from bud-break to mid-June (around the
middle of Stage II of fruit growth), and from then until harvest when Ψmd decreased below −1.2 MPa. (3) Deficit–Deficit (DD), irrigated when Ψmd was less than −1.0 from bud break to mid-May (about the middle of fruit growth Stage I), and after that time the Ψmd threshold became −1.2 MPa until harvest. A fourth treatment was applied following a soil water budget approach (WB). All
treatments were replicated five times but irrigation in the Ψmd-based treatments were independently applied to each of the replicate plots, whereas irrigation for WB was applied equally
to all replications. The more site-specific information obtained from Ψmd thresholds in C provided substantial advantages for yield homogeneity and repeatability of results with respect to WB, thus
demonstrating the method’s greater ability to account for spatial variability. Average applied water for the 3 years in C,
CD, and DD was 374, 250, and 178 mm, respectively, while the yields were 11.8, 9.2, and 6.1 kg/vine, respectively. The CD
treatment produced better juice quality than C, and was superior in other quality parameters to both C and DD. However, over
the study period, an important carryover effect was observed in the yields and the grape size of CD, which tended to diminish
from year to year relative to C. 相似文献
6.
Relationship between root uptake-weighted mean soil water salinity and total leaf water potentials of alfalfa 总被引:1,自引:0,他引:1
C. Dirksen 《Irrigation Science》1985,6(1):39-50
Summary Alfalfa was grown in five laboratory soil columns and irrigated at a fixed average amount per day. One column received tapwater at 6-day intervals; the others saline water (h
o=–12 m) at intervals of 4, 6, 8, and 12 days. The alfalfa was harvested at 24-day intervals. The resulting widely varying distributions of soil water content, pressure potential and osmotic potential were measured in detail. From these data variously weighted mean soil water potentials were calculated and correlated with measured total leaf water potentials. This indicated that in the moist, saline soil columns the alfalfa plants tended to maximize the root uptake-weighted mean total soil water potential and, since the pressure potentials were generally high compared with the osmotic potentials, also the uptake-weighted mean osmotic soil water potential (minimize the uptake-weighted mean salinity). For the drier nonsaline soil column the leaf water potentials were much lower than expected from the soil water retention function. This was attributed to dominant resistance for water flow through the soil and across the soil-root interface. 相似文献
7.
A study was conducted to determine the relationship between midday measurements of vine water status and daily water use of
grapevines measured with a weighing lysimeter. Water applications to the vines were terminated on August 24th for 9 days and
again on September 14th for 22 days. Daily water use of the vines in the lysimeter (ETLYS) was approximately 40 L vine−1 (5.3 mm) prior to turning the pump off, and it decreased to 22.3 L vine−1 by September 2nd. Pre-dawn leaf water potential (ΨPD) and midday Ψl on August 24th were −0.075 and −0.76 MPa, respectively, with midday Ψl decreasing to −1.28 MPa on September 2nd. Leaf g
s decreased from ~500 to ~200 mmol m−2 s−1 during the two dry-down periods. Midday measurements of g
s and Ψl were significantly correlated with one another (r = 0.96) and both with ETLYS/ETo (r = ~0.9). The decreases in Ψl, g
s, and ETLYS/ETo in this study were also a linear function of the decrease in volumetric soil water content. The results indicate that even
modest water stress can greatly reduce grapevine water use and that short-term measures of vine water status taken at midday
are a reflection of daily grapevine water use. 相似文献
8.
《Agricultural Water Management》2006,79(1):1-27
The monitoring of crop production and irrigation at a regional scale can be based on the use of ecosystem process models and remote sensing data. The former simulate the time courses of the main biophysical variables which affect crop photosynthesis and water consumption at a fine time step (hourly or daily); the latter allows to provide the spatial distribution of these variables over a region of interest at a time span from 10 days to a month. In this context, this study investigates the feasibility of using the normalised difference vegetation index (NDVI) derived from remote sensing data to provide indirect estimates of: (1) the leaf area index (LAI), which is a key-variable of many crop process models; and (2) crop coefficients, which represent the ratio of actual (AET) to reference (ET0) evapotranspiration.A first analysis is performed based on a dataset collected at field in an irrigated area of the Haouz plain (region of Marrakesh, Central Morocco) during the 2002–2003 agricultural season. The seasonal courses of NDVI, LAI, AET and ET0 have been compared, then crop coefficients have been calculated using a method that allows roughly to separate soil evaporation from plant transpiration. This allows to compute the crop basal coefficient (Kcb) restricted to the plant transpiration process. Finally, three relationships have been established. The relationships between LAI and NDVI as well as between LAI and Kcb were found both exponential, with associated errors of 30% and 15%, respectively. Because the NDVI saturates at high LAI values (>4), the use of remotely-sensed data results in poor accuracy of LAI estimates for well-developed canopies. However, this inaccuracy was not found critical for transpiration estimates since AET appears limited to ET0 for well-developed canopies. As a consequence, the relationship between NDVI and Kcb was found linear and of good accuracy (15%).Based on these relationships, maps of LAI and transpiration requirements have been derived from two Landsat7-ETM+ images acquired at the beginning and the middle of the agricultural season. These maps show the space and time variability in crop development and water requirements over a 3 km × 3 km irrigated area that surrounds the fields of study. They may give an indication on how the water should be distributed over the area of interest in order to improve the efficiency of irrigation. The availability, in the near future, of Earth Observation Systems designed to provide both high spatial resolution (10 m) and frequent revisit (day) would make it feasible to set up such approaches for the operational monitoring of crop phenology and irrigation at a regional scale. 相似文献
9.
A Landsat-based energy balance and evapotranspiration model in Western US water rights regulation and planning 总被引:5,自引:0,他引:5
Richard G. Allen M. Tasumi Anthony Morse Ricardo Trezza 《Irrigation and Drainage Systems》2005,19(3-4):251-268
The quantification of evapotranspiration (ET) from irrigated projects is important for water rights management, water resources
planning and water regulation. Traditionally, ET has been estimated by multiplying a weather-based reference ET by crop coefficients
(Kc) determined according to the crop type and the crop growth stage. However, there is typically question regarding whether
crops grown compare with the conditions represented by the Kc values, especially in water short areas. In addition, it is difficult to estimate the correct crop growth stage dates for
large populations of crops and fields.
METRIC (Mapping Evapotranspiration at high Resolution and with Internalized Calibration) is an image-processing model for
calculating ET as a residual of the surface energy balance. METRIC is a variant of SEBAL, an energy balance process developed
in the Netherlands by Bastiaanssen and was extended to provide tighter integration with ground-based reference ET. METRIC
was applied with Landsat images in southern Idaho to predict monthly and seasonal ET for water rights accounting and for operation
of ground water models. ET “maps” (i.e., images) provide the means to quantify, in terms of both the amount and spatial distribution,
the ET on a field by field basis.
The ET maps have been used in Idaho to quantify net ground-water pumpage in areas where water extraction from underground
is not measured and to estimate recharge from surface-irrigated lands. Application and testing of METRIC indicates substantial
promise as an efficient, accurate, and relatively inexpensive procedure to predict the actual evaporation fluxes from irrigated
lands throughout a growing season. 相似文献
10.
Comparisons of energy balance and evapotranspiration between flooded and aerobic rice fields in the Philippines 总被引:3,自引:0,他引:3
Ma. Carmelita R. Alberto Reiner Wassmann Takashi HiranoAkira Miyata Ryusuke HatanoArvind Kumar Agnes PadreModesto Amante 《Agricultural Water Management》2011,98(9):1417-1430
The seasonal and annual variability of sensible heat flux (H), latent heat flux (LE), evapotranspiration (ET), crop coefficient (Kc) and crop water productivity (WPET) were investigated under two different rice environments, flooded and aerobic soil conditions, using the eddy covariance (EC) technique during 2008-2009 cropping periods. Since we had only one EC system for monitoring two rice environments, we had to move the system from one location to the other every week. In total, we had to gap-fill an average of 50-60% of the missing weekly data as well as those values rejected by the quality control tests in each rice field in all four cropping seasons. Although the EC method provides a direct measurement of LE, which is the energy used for ET, we needed to correct the values of H and LE to close the energy balance using the Bowen ratio closure method before we used LE to estimate ET. On average, the energy balance closure before correction was 0.72 ± 0.06 and it increased to 0.99 ± 0.01 after correction. The G in both flooded and aerobic fields was very low. Likewise, the energy involved in miscellaneous processes such as photosynthesis, respiration and heat storage in the rice canopy was not taken into consideration.Average for four cropping seasons, flooded rice fields had 19% more LE than aerobic fields whereas aerobic rice fields had 45% more H than flooded fields. This resulted in a lower Bowen ratio in flooded fields (0.14 ± 0.03) than in aerobic fields (0.24 ± 0.01). For our study sites, evapotranspiration was primarily controlled by net radiation. The aerobic rice fields had lower growing season ET rates (3.81 ± 0.21 mm d−1) than the flooded rice fields (4.29 ± 0.23 mm d−1), most probably due to the absence of ponded water and lower leaf area index of aerobic rice. Likewise, the crop coefficient, Kc, of aerobic rice was significantly lower than that of flooded rice. For aerobic rice, Kc values were 0.95 ± 0.01 for the vegetative stage, 1.00 ± 0.01 for the reproductive stage, 0.97 ± 0.04 for the ripening stage and 0.88 ± 0.03 for the fallow period, whereas, for flooded rice, Kc values were 1.04 ± 0.04 for the vegetative stage, 1.11 ± 0.05 for the reproductive stage, 1.04 ± 0.05 for the ripening stage and 0.93 ± 0.06 for the fallow period. The average annual ET was 1301 mm for aerobic rice and 1440 mm for flooded rice. This corresponds to about 11% lower total evapotranspiration in aerobic fields than in flooded fields. However, the crop water productivity (WPET) of aerobic rice (0.42 ± 0.03 g grain kg−1 water) was significantly lower than that of flooded rice (1.26 ± 0.26 g grain kg−1 water) because the grain yields of aerobic rice were very low since they were subjected to water stress.The results of this investigation showed significant differences in energy balance and evapotranspiration between flooded and aerobic rice ecosystems. Aerobic rice is one of the promising water-saving technologies being developed to lower the water requirements of the rice crop to address the issues of water scarcity. This information should be taken into consideration in evaluating alternative water-saving technologies for environmentally sustainable rice production systems. 相似文献
11.
Summary Water stress was imposed upon soybean [Glyxine max (L.) Merr. cv. Williams] and maize [Zea mays (L.) cv. Pioneer 3377] plants grown under controlled-environment conditions during a growing period of several irrigation cycles. Transpiration rates of individual plants were measured with a calibrated heat-pulse method and correlated to the rate of water loss obtained from successive weighings of the pots containing irrigated or water-stressed plants. Transpiration rate was reduced in the stressed plants of both species, but the reduction was not linear with decreasing soil matric potential. Transpiration rates declined rapidly at high soil matric potential, and dropped more slowly as the soil dried. Although measured transpiration rate declined by nearly 30% following a reduction of soil matric potential to -0.1 MPa, differences in leaf water potential and CO2 assimilation rate were small and less than the sensitivity of the measurement techniques used. Total system resistance to water flow increased as the soil dried. 相似文献
12.
黑河中游地区由于农业水资源紧缺、灌溉方式粗放及水肥的不合理调配,导致该区水土资源浪费严重,为了节约水土资源,提高当地生产水平,本文基于2021年5-9月在水资源紧缺的黑河中游地区(张掖市民乐县益民灌溉试验站)采用膜下滴灌调亏灌溉技术,通过田间试验和理论分析相结合,主要研究膜下滴灌水氮耦合下大豆干物质积累及对产量的影响,研究结果表明:灌水量一定的情况下,适量增施氮肥可以促进大豆干物质的积累,但过量的氮素会导致大豆干物质的积累程下降趋势。N2W2处理是实现大豆产量较优的水氮耦合模式,较CK(不施氮量)、N1、N3(高施氮量)处理相比显著提高大豆产量39.94%、13.11%、20.73%。 相似文献
13.
Kati W. Migliaccio Bruce Schaffer Frederick S. Davies 《Agricultural Water Management》2010,97(10):1452-1460
An irrigation study was conducted to determine the effects of implementing different irrigation practices on growth and yields of papaya plants in south Florida. Treatments included using automated switching tensiometers based on soil water status, irrigation based on ET calculated from historic weather data and a set schedule irrigation regime. The study consisted of two trials (2006-2007 and 2008-2009). Water volumes applied, plant height and diameter, leaf gas exchange, leaf petiole nutrient levels, fruit yields and fruit total soluble solids were measured throughout the study. For both trials, significantly more water was applied in the set schedule irrigation treatment than in all other treatments; historic ET and soil water based treatments received only about 31-36% of the water applied in the set schedule irrigation. Trunk diameter and plant height per unit water volume applied values for the set schedule treatment were significantly lower than those from all other treatments during both trials. The set schedule treatment in both trials also had the lowest crop production water use efficiency (CP-WUE); CP-WUE values among all other treatments were generally not significantly different from each other. Soil water and historic ET-based irrigation methods were identified as more sustainable practices compared to set schedule irrigation due to the lower water volumes applied while maintaining plant nutrient content, growth, photosynthetic rates, and fruit yields for this production system. 相似文献
14.
Summary The growth response of kenaf (Hibiscus cannabinus L.) to four irrigation schedules based on leaf water potential l was evaluated in a semi-arid tropical environment. Total dry matter production was unaffected by regimes in which the mean value of leaf water potential l (mean of solar noon and dawn value) did not fall below –1.26 MPa. Stem elongation was more sensitive than dry matter accumulation to plant water stress. — The economic yield for paper pulp production (i. e. total plant dry matter production minus that of the foliage and upper 60 cm of stem) increased with the frequency of irrigation. — Growth recovery by kenaf following a period of water stress was examined. Alleviation of water stress 10 weeks after irrigation, when l was –1.60 MPa, produced stem elongation rates that were greater than those of plants previously receiving irrigation. This ability to withstand water stress and partially compensate in growth following alleviation of the stress indicates that the kenaf crop has stress response features suitable for rainfall only production under semi-arid tropical conditions. — Irrigation schedules based on l resulted in water applications tailored to crop requirements in that water use increased, and the time interval between irrigation decreased, with increasing canopy development as well as with increasing evaporative demand. However, erratic fluctuations in l between irrigations make scheduling by this method difficult and the use of daily mean, dawn or noon values of l for scheduling irrigation of kenaf cannot be recommended in environments of high evaporative demand. The factors contributing to these fluctuations in (l) are discussed. 相似文献
15.
贵州省黔东南苗族侗族自治州地处少数民族贫困山区,农村户用沼气建设发展到一定时期,受场地、牲畜养殖量和农户自投能力等条件的限制,造成建设难度加大,发展速度放慢,制约了农村沼气建设的整体推进。正确处理好建设与条件的矛盾,对农村沼气建设的健康发展具有重要现实意义。 相似文献
16.
17.
Using radiation thermography and thermometry to evaluate crop water stress in soybean and cotton 总被引:2,自引:0,他引:2
S.A. O'Shaughnessy S.R. EvettP.D. Colaizzi T.A. Howell 《Agricultural Water Management》2011,98(10):1523-1535
The use of digital infrared thermography and thermometry to investigate early crop water stress offers a producer improved management tools to avoid yield declines or to deal with variability in crop water status. This study used canopy temperature data to investigate whether an empirical crop water stress index could be used to monitor spatial and temporal crop water stress. Different irrigation treatment amounts (100%, 67%, 33%, and 0% of full replenishment of soil water to field capacity to a depth of 1.5 m) were applied by a center pivot system to soybean (Glycine max L.) in 2004 and 2005, and to cotton (Gossypium hirsutum L.) in 2007 and 2008. Canopy temperature data from infrared thermography were used to benchmark the relationship between an empirical crop water stress index (CWSIe) and leaf water potential (ΨL) across a block of eight treatment plots (of two replications). There was a significant negative linear correlation between midday ΨL measurements and the CWSIe after soil water differences due to irrigation treatments were well established and during the absence of heavy rainfall. Average seasonal CWSIe values calculated for each plot from temperature measurements made by infrared thermometer thermocouples mounted on a center pivot lateral were inversely related to crop water use with r2 values >0.89 and 0.55 for soybean and cotton, respectively. There was also a significant inverse relationship between the CWSIe and soybean yields in 2004 (r2 = 0.88) and 2005 (r2 = 0.83), and cotton in 2007 (r2 = 0.78). The correlations were not significant in 2008 for cotton. Contour plots of the CWSIe may be used as maps to indicate the spatial variability of within-field crop water stress. These maps may be useful for irrigation scheduling or identifying areas within a field where water stress may impact crop water use and yield. 相似文献
18.
C. R. Jensen 《Irrigation Science》1982,3(2):111-121
Summary Barley plants (Hordeum distichum, L., cv. Zita) grown in a sandy soil in pots were adjusted during a pretreatment period of 5 days to three levels of soil water osmotic potential by percolating 61 of a nutrient solution with additional 0, 22.3 and 44.6 mM KCl. A drying cycle was then started and the plants were harvested when the soil water matric potential had decreased to –1.4 MPa, respectively 6, 7 and 8 days later.No significant differences in dry matter yields, transpiration coefficients and wilting percentages were found between treatments.During the drying cycle leaf water potential (
l
) decreased concomitantly with decrease in soil water potential (
s
) with almost constant and similar differences (
l
–
s
) for all treatments despite differences in levels of potentials. The concomitant decrease in leaf osmotic potential () was due partly to dehydration (58%) and partly to increase in leaf solute content (42%) independent of treatment. The part of total osmotic solutes due to K decreased relatively during the drying cycle.Close relationships were found between and
l
as functions of relative water content (RWC). Identical curves for the two levels of salt treatment agree with similar concentrations of K, Cl, and ash found for salt treated plants indicating that maximum uptake of macro nutrients may have been reached.During the main part of the drying cycle the turgor potential as function of RWC was higher and decreased less steeply with decreasing RWC in the salt treated than in the non-salt treated plants.In the beginning of the drying cycle additions of KCI lowered the transpiration rates of the salt treated plants resulting in a slower desiccation of the soil and hence an increased growth period. A delay in uptake from a limited soil water supply may be advantageous during intermittent periods of drought. 相似文献
19.
Summary A new model for transpiration of a soybean crop is formulated and solved numerically: the model specifically includes the water stored in the plant. It describes the changes in the daily course of transpiration, stomatal behaviour, leaf water potential and leaf temperature as water deficits develop. The calculated values of leaf water potential (Fig. 3) and transpiration (Fig. 5) compared well with measured values observed during the development of water deficits in a soybean crop growing on a grey cracking clay soil. 相似文献
20.
Larry E. Williams 《Irrigation Science》2012,30(5):363-375
A study was conducted in the San Joaquin Valley of California on Merlot to determine the interaction of applied water amounts [at 0.4, 0.8, and 1.2 of estimated vineyard evapotranspiration (ETc)] and leaf removal (at berry set or veraison) in the fruiting zone on productivity. Shaded area was measured beneath the canopy of the 1.2 irrigation treatment at solar noon throughout the study to provide an estimate of seasonal crop coefficients (K c). Vine water status was assessed across treatments and years by measuring midday leaf water potential (Ψl). The maximum K c determined from the percent shaded area was 0.7 at the row spacing of 3.66?m and canopy type that developed a “California Sprawl.” Irrigation treatment had a significant effect on midday Ψl and no such effect for leaf removal. Clusters exposed to direct solar radiation had significantly higher temperatures and lower cluster Ψ than clusters in the shade. Irrigation treatment had a significant effect on berry weight, soluble solids, and titratable acidity. Yields of vines significantly increased as applied water amounts increased. In this wine grape production area, profitability is dependent upon yield. This study provided a reliable estimate of ETc and applied water amounts to maximize yield. 相似文献