Highest Values Of Water Use Efficiency Research Articles

石羊河流域水分利用效率及其对饱和水汽压差的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 石羊河流域水分利用效率及其对饱和水汽压差的响应 DOI: 10.5846/stxb202111243322 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学青年基金项目(41705062,32071606); 甘肃省气象局研究型业务重点项目(ZD2021-02); 云南省教育厅项目"云南省高校山地实景点云数据处理及应用重点实验室" Spatial-temporal dynamics of water use efficiency and responding to vapor pressure deficit in Shiyang River Basin, northwestern China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:水分利用效率(WUE)是叶片通过光合作用调节水分生理过程的指标,是联系生态系统碳循环与水循环关系的关键,反映了植被生态系统对立地环境快速调整和资源的变化适应策略。基于卫星遥感和地面观测数据,利用光能利用率模型和蒸散发经验估算模型,模拟石羊河流域2000-2019年植被总初级生产力(GPP)和蒸散发(ET)数据,估算2000-2019年不同植被类型的WUE空间分布特征,研究GPP/ET/WUE与饱和水汽压差(VPD)的相关性,探讨干旱区不同类型植被对水分利用及胁迫的适应策略。结果表明:(1) 2000-2019年石羊河流域植被WUE、GPP和ET的平均值分别为0.80 gC m-2 mm-1、256.52 gC/m2和302.52 mm,其三者的空间分布特征表现为"南高北低",即由流域源头至下游逐渐减少的空间分布。(2) 近20年内,流域内WUE、GPP和ET的变化率的平均值分别为0.017 gC m-2 mm-1 a-1,6.99 gC m-2 a-1和3.80 mm/a,流域总体呈现波动上升的趋势,但城区和民勤耕地-荒漠交接区呈不同程度的减少趋势。(3) 流域内不同类型植被的WUE平均值关系为:森林>农作物>草地>灌丛>荒漠植被>湿地植被,WUE增加速度的平均值关系为:农作物>森林>草地>灌丛>荒漠植被>湿地植被,与GPP基本一致,其中ET在灌丛、荒漠植被、湿地植被地区呈现降低趋势。(4) 研究区内GPP/ET/WUE与VPD相关性的空间分布特征与石羊河径流方向具有高度一致性,WUE与VPD相关性分布特征受土地利用以及径流方向影响显著。WUE与VPD呈正相关的区域主要分布在河西走廊绿洲东部和荒漠区东部,呈负相关区域主要分布在祁连山高海拔地区、河西走廊绿洲中部和荒漠区西部。因此,正确揭示内陆河植被GPP/ET/WUE的空间分异以及变化趋势及其对驱动因素VPD的响应,是了解流域尺度中干旱区植被对全球干旱加剧的适应性策略前提,进而为生态保护提供决策服务。 Abstract:Water use efficiency (WUE) is the regulation index of leaf photosynthesis on the water physiological process, as the key to link the relationship between the ecosystem carbon cycle and the water cycle, and directly reflects the rapid adjustment of the ecosystem to the site environment and the adaptation strategy of resource changes. The Gross primary production (GPP) temporal and spatial characteristics derived from the data of MODIS-NDVI by the Light Energy Utilization Model, and the Evapotranspiration (ET) temporal and spatial characteristics derived from the meteorological data by the Thornthwaite Evapotranspiration Model during 2000-2019 in Shiyang River Basin (SRB). In this research, we estimated the spatial pattern and temporal variations of the GPP, ET and WUE in different vegetation types from 2000 to 2019, investigated the co-relationship between GPP/ET/WUE and Vapor pressure deficit (VPD), and discussed the response of adaptation strategies for water utilization and stress in the arid area among the different vegetation. The results show that: (1) from 2000 to 2019, the average annual value of total WUE, GPP, and ET in SRB were 0.80 gC m-2 mm-1, 256.52 gC/m2, and 302.52 mm, respectively; The spatial patterns of average annual WUE, GPP and ET in the SRB's vegetated areas varied widely, and the values decreased from upstream on the south side of the Qilian Mountains and middle to downstream on the north side of the desert. (2) During the 20 years, the average slope of WUE, GPP, and ET showed an obvious upward trend in almost whole basin, with the rate of 0.017 gC m-2 mm-1 a-1, 6.99 gC m-2 a-1 and 3.80 mm/a. The change rates of WUE, GPP and ET within the basin exhibited an upward trend, except for Liangzhou and the areas surrounding Minqin cropland according to the urbanization and industrial adjustment. (3) The WUE, GPP and ET annual average values, and slope of trends among the different land use types also varied significantly. Among various vegetation types, the highest values of WUE, GPP and ET appeared in forests, and the lowest values presented in wetlands; the highest change rate of different vegetation was forest, and the lowest one was the wetland. (4) Correlation analysis and statistical results indicated that the correlation distribution characteristics of GPP/ET/WUE and VPD in the study area were highly consistent with the runoff direction of the SRB. As the WUE was determined by GPP and ET, the correlation distribution between WUE and VPD had obviously spatial heterogeneity with the land-use and SRB runoff direction. The positive correlation was distributed in the eastern part of the Hexi Corridor oasis and the eastern desert area, and the negative correlation was distributed in the high-altitude areas of the Qilian Mountains, the middle of the Hexi Corridor oasis and the western part of the desert area. Overall, correctly revealing the spatial differentiation and changing trend of GPP/ET/WUE of inland river vegetation and its response to the driving factor VPD was the premise of understanding the adaptive strategy of vegetation in arid areas at the watershed scale to the intensification of global drought, to provide decision-making services for ecological protection. 参考文献 相似文献 引证文献

Variability of Water Use Efficiency Associated with Climate Change in the Extreme West of Bahia

Water has become more important in agricultural implementations over the years, as has the need for water management. Thus, Water Use Efficiency (WUE) has been used as an alternative form of detecting the variability of water management based on the carbon–water cycle. The study aimed to map and quantify the spatio-temporal distribution of WUE based on its interactions with environmental changes. It focused on an agricultural area in the westernmost region of Bahia, Northeast Brazil (NEB). For WUE estimation, data from Collection 6 MODIS Gross Primary Productivity (GPP) and Evapotranspiration (ET) products with a spatial resolution of 0.05° × 0.05° were obtained from the Earth Explorer website. Subsequently, annual WUE anomalies were calculated based on the 2001–2019 period. The results obtained indicated that the highest values of GPP (580 gC/m2), ET (3000 mm), and WUE (3.5 gC/mm·m2) occurred in agricultural areas, associated with cultural treatments and insertion of irrigation, which helped in the higher WUE values and consequently increased agricultural productivity in the study region. In addition, there was a marked influence of the phases of the climate variability mode—El Niño-Southern Oscillation (ENSO)—on the annual variability of the WUE, with a reduction of 96% during the La Niña of 2016 (an increase of 89% during El Niño of 2005). During El Niños, vegetation had greater efficiency resulting from the adaptation of vegetation in maintaining the carbon–water balance, using water more efficiently. However, unlike Las Niñas, with excessive precipitation there is an interference in the WUE, which interferes with the absorption of radiation and nutrients for the biophysical processes of vegetation and agriculture and, consequently, agricultural production. The use of WUE for agriculture is extremely important, especially for Brazil and countries with an economy based on primary production. This information on the way vegetation (native or agricultural) responds to interactions with the environment aids in decision-making about water management, possibly lowering losses or agricultural damage caused by a lack of water.

Variation Characteristics of Ecosystem Water Use Efficiency and Its Response to Human Activity and Climate Change in Inner Mongolia

Water use efficiency (WUE) reflects the balance between carbon assimilation and water consumption in terrestrial ecosystems. Considering the fragile conditions of global water resources, the evaluation of regional WUE variation characteristics and response mechanisms is critical for promoting sustainable ecological development and water resource utilization. Based on gross primary productivity (GPP) and evapotranspiration (ET) datasets, combined with vegetation and meteorological data, this study examined the spatiotemporal variations, annual variation contribution rate, and driving mechanism of WUE in Inner Mongolia from 2001 to 2020. The main results are as follows: (1) The interannual and spatial variations of GPP, ET, and WUE all exhibited increasing trends, with WUE increasing in approximately 70% of the region and significantly increasing in 22.35% of pixels exhibiting a significant increase. Areas with the most significant increases were located in the Horqin sandy land and Mu Us sandy land. (2) The highest WUE values were observed in the summer season, followed by autumn and winter, and the lowest in spring. (3) Among all vegetation types, the typical steppe ecosystems contributed most to the interannual variability (IAV) of GPP, ET, and WUE, with values of 169.89%, 141.09%, and 193.42%, respectively. While the coniferous forest contributed least or negatively to GPP, ET, and WUE IAV, with values of −36.28%, 28.20%, and −32.86%, respectively. (4) The primary driver of WUE variation was found to be GPP, which contributed 59.36%, mainly in the central and western regions. The remaining 40.64% was attributable to ET, concentrated in the northeast region. (5) Human activities significantly affected WUE, with a contribution (about 53.52%) larger than that of climate change (nearly 46.48%). Increased precipitation improves vegetation WUE and is the most important climate factor influencing WUE variations. These findings will aid the formulation of vegetation protection and water resource management strategies in water-stressed areas.

Spatial-temporal variation of vegetation water use efficiency and its relationship with climate factors over the Qinghai-Tibet Plateau, China

Water use efficiency (WUE) is an effective index to study the coupling of land carbon and water cycle. The Qinghai-Tibet Plateau is the most important ecological security barrier in China. Understanding the characteristics and mechanism of WUE is important for the carbon cycle and water resources rational utilization in the plateau. Based on MODIS data of gross primary productivity (GPP) and evapotranspiration (ET), we analyzed the spatial-temporal variations of WUE over the Qinghai-Tibet Plateau and the effects of climate factors. The results showed that WUE in the Qinghai-Tibet Plateau had an upward trend under the combined action of GPP and ET during 2001-2020. The southeast and northeast of the Plateau had the highest WUE value, while the central part had the lowest WUE value. WUE of grassland, marsh and alpine vegetation showed an increasing trend, while that of shrub land, broadleaved forest and coniferous forest showed a decreasing trend. There was a significant positive correlation between WUE and annual air temperature, and the sensitivity increased with the increases of air temperature. The relationship between WUE and annual precipitation was non-linear. When precipitation was less than 700 mm, the sensitivity of WUE to precipitation decreased with the increases of precipitation. When precipitation was more than 700 mm, the sensitivity of precipitation increased with the increases of precipitation. However, WUE was negatively correlated with precipitation in more than 75% of regions, and was affected by precipitation in a larger area. In the future, warm and humid climate would lead to a decrease in WUE.

Calcium and Potassium Nutrition Increases the Water Use Efficiency in Coffee: A Promising Strategy to Adapt to Climate Change

Coffee (Coffea spp.) represents one of the most important sources of income and goods for the agricultural sector in Central America, Colombia, and the Caribbean region. The sustainability of coffee production at the global and regional scale is under threat by climate change, with a major risk of losing near to 50% of today’s suitable area for coffee by 2050. Rain-fed coffee production dominates in the region, and under increasing climate variability and climate change impacts, these production areas are under threat due to air temperature increase and changes in rainfall patterns and volumes. Identification, evaluation, and implementation of adaptation strategies for growers to cope with climate variability and change impacts are relevant and high priority. Incremental adaptation strategies, including proper soil and water management, contribute to improved water use efficiency (WUE) and should be the first line of action to adapt the coffee crop to the changing growing conditions. This research’s objective was to evaluate at field level over five years the influence of fertilization with calcium (Ca+2) and potassium (K+) on WUE in two coffee arabica varieties: cv. Castillo and cv. Caturra. Castillo has resistance against coffee leaf rust (CLR) (Hemileia vastatrix Verkeley and Brome), while Caturra is not CLR-resistant. WUE was influenced by yield changes during the years by climate variability due to El Niño–ENSO conditions and CLR incidence. Application of Ca+2 and K+ improved the WUE under such variable conditions. The highest WUE values were obtained with an application of 100 kg CaO ha−1 year−1 and between 180 to 230 kg K2O ha−1 year−1. The results indicate that adequate nutrition with Ca+2 and K+ can improve WUE in the long-term, even underwater deficit conditions and after the substantial incidence. Hence, an optimum application of Ca+2 and K+ in rain-fed coffee plantations can be regarded as an effective strategy to adapt to climate variability and climate change.

Effects of different irrigation methods and hormone application on water use efficiency, yield, and leaf biochemical traits in potato

Investigation of different irrigation methods on plants is necessary due to limited water resources and the increasing need for food products. The purpose of this study was to evaluate the effect of sprinkler and drip irrigation systems and hormones on morphological and physiological characteristics of potato. Treatments included sprinkler and drip irrigation systems and hormones (gibberellic acid, acetylsalicylic acid, epi-brassinolide, and no use of growth regulators) as split plot based on randomized complete block design with three replications during 2015 and 2016 growing seasons at a research farm located in Malayer. Results showed that the highest level of tuber dry matter (TDM) was related to epi-brassinolide hormone + drip irrigation after using 80% of the field capacity(FC) in 2015 and epi-brassinolide hormone + drip irrigation after using 70% of the FC in 2016. The lowest amount of water use efficiency (WUE) was seen in sprinkler irrigation + no use of regulators in both years. The highest value of WUE was seen in epi-brassinolide hormone along with drip irrigation after using 80% the FC and drip irrigation after using 70% of the FC in 2015 and also in epi-brassinolide hormone + drip irrigation after using 70% of the FC in 2016. There were high and significant correlations between water use efficiency and relative water content with morphological characteristics. In order to increase the production and potato water use efficiency in cold dry climate, drip irrigation along with epi-brassinolide hormone is recommended.

Carrot yield and water-use efficiency under different mulching, organic fertilization and irrigation levels

ABSTRACT This study was carried out to evaluate the contributions to the optimization of water use in a carrot crop under different forms of mulch using Gliricidia sepium, fertilization with castor bean cakes and irrigation water depths. The experiment was conducted in Seropédica, RJ, Brazil (22º 46’ S and 43º 41’ W), from June to September 2010. The experiment was conducted using a split-split-plot scheme (5 x 3 x 2), with four replicates. The five plots had irrigation depths corresponding to 0, 43, 72, 100 and 120% of crop evapotranspiration (ETc); the three subplots contained the different forms of mulch (whole leaves (WL) and chopped leaves and branches (CLB)) and the absence of mulch (AM); and the two sub-subplots contained either the presence (PF) or absence of fertilization (AF). Using time domain reflectometry (TDR) in the irrigation management, water depths ranging from 67.8 to 285.5 mm were applied. The use of mulch in association with fertilization led to higher yields and water-use efficiency (WUE) of the carrot plants, and the mulch composed of WL performed best. The application of irrigation depths corresponding to 97% of ETc promoted the highest carrot yields, although the highest values of WUE were observed, with irrigation depths corresponding to a range from 51 to 68% of ETc.

Gas exchange at whole plant level shows that a less conservative water use is linked to a higher performance in three ecologically distinct pine species

Increasing temperatures and decreasing precipitation in large areas of the planet as a consequence of global warming will affect plant growth and survival. However, the impact of climatic conditions will differ across species depending on their stomatal response to increasing aridity, as this will ultimately affect the balance between carbon assimilation and water loss. In this study, we monitored gas exchange, growth and survival in saplings of three widely distributed European pine species (Pinus halepensis, P. nigra and P. sylvestris) with contrasting distribution and ecological requirements in order to ascertain the relationship between stomatal control and plant performance. The experiment was conducted in a common garden environment resembling rainfall and temperature conditions that two of the three species are expected to encounter in the near future. In addition, gas exchange was monitored both at the leaf and at the whole-plant level using a transient-state closed chamber, which allowed us to model the response of the whole plant to increased air evaporative demand (AED). P. sylvestris was the species with lowest survival and performance. By contrast, P. halepensis showed no mortality, much higher growth (two orders of magnitude), carbon assimilation (ca. 14 fold higher) and stomatal conductance and water transpiration (ca. 4 fold higher) than the other two species. As a consequence, P. halepensis exhibited higher values of water-use efficiency than the rest of the species even at the highest values of AED. Overall, the results strongly support that the weaker stomatal control of P. halepensis, which is linked to lower stem water potential, enabled this species to maximize carbon uptake under drought stress and ultimately outperform the more water conservative P. nigra and P. sylvestris. These results suggest that under a hotter drought scenario P. nigra and P. sylvestris would very likely suffer increased mortality, whereas P. halepensis could maintain gas exchange and avoid water-induced growth limitation. This might ultimately foster an expansion of P. halepensis to higher latitudes and elevations.

WATER - GRAIN AND BIOMASS YIELD RELATIONS OF WINTER WHEAT IN A SEMI-ARID CONDITIONS OF TURKEY

The aim of this study was to determine the effect of different irrigation regime on winter wheat yield and water-use efficiency (WUE). The field experiment was carried out between the year 2009 and 2011 at Murted Basin in Turkey with 4 different irrigation treatments which was Rainfed (RF), Full irrigation (FI), Moderate irrigation (MI), and Deficit irrigation (DI). Soil moisture was measured with neutron probe. According to results average wheat yield was obtained 3.35 t ha-1, 4.54 t ha-1, 4.22 t ha-1and 4.31 t ha-1 and average harvest index was 29%, 31%, 32% 31% and 32% for RI, FI, MI and DI irrigation treatments respectively. The highest WUE value with 9.1 kg m-3 was calculated at DI treatment. A significant negative correlation was found between grain yield, total harvested biomass and the WUE. The results presented in this work suggest that the amount of soil water content affects grain yield and water use efficiency. It might be recommended that irrigation concentrated in the after heading period (DI) increase WUE in semi-arid climate condition such as Central Anatolia Region of Turkey.

VERTICAL-FARMING IRRIGATION SYSTEM APPROPRIATE FOR LETTUCE AND CELERY CROPS

The current experiment was carried out in greenhouse in the Central Laboratory of Agricultural Climate, Agricultural Research Center (ARC), Dokki, Giza, Egypt, to develop proper system for a Vertical Farming Irrigation System VFS for lettuce and celery crops, to get the best vegetative growth uniformity along vertical axis of planting column (tube), maximum water use efficiency (WUE) with minimum energy consumption, and maximum fresh yield per square meter floor. The effects of plant type, nozzle type, vertical-pipe nozzle position, and number of nozzles per vertical farming tube at operating pressure range of 150 to 300 kPa, on growth uniformity, fresh yield (kg/m2). Energy consumptive use and WUE were considered. The initial and operating cost, in addition to net profit of VFSare also discussed. The main results are summarized as follows: The longest vegtative growth heights of lettuce and celery, recorded by using four nozzles along the vertical tube was 24 and 46 cm at bottom layer of the planted column of the vertical farming tube(VFT), with increased percent ratios of 37.5 and 52.3% compared with using one mini sprinkler nozzle for the two crops resp.. The highest values of WUE under different number of nozzles and positions was 11.2, 8.8, and 8 kg/m3 for lettuce crop, and 12.8, 12.4, 9.75 kg/m3 for celery crop by using four, two, and one nozzle along the VFT axis, with increasing ratios of 21.5, 28.6 % for lettuce crop, and 3, 23.8% for celery crop, compared with micro and fogger nozzles resp.. The maximum energy requirements of lettuce and celery crops were 111.1, 97.2 kj/kg/y for lettuce and celery crops, by using four nozzles (75 μm-DS) along the VFT for all tested nozzle types. The best uniformity of vegetative growth was 96% by using four mini sprinkler nozzles along the VFT axis. The maximum productivities of lettuce and celery fresh yield were recorded as 14, 11, 10 kg/m2 for lettuce crop, and 16, 12.5, 11.5 kg/m2 for celery crop, for mini sprinkler, micro sprinkler and fogger nozzles resp., The maximum consumptive use of energy was 4.32kW.h/y, when using mini sprinkler nozzle, increased by 81% compared with fogger nozzle. Meanwhile the minimum consumptive use of energy was 0.6kW.h/y, when using fogger sprinkler nozzle. The maximum net profit was 1047, 1527LE/y/column for lettuce and celery crops, by using mini sprinkler (75 μm-DS) with an increase of 42.7, 41.1% for lettuce and celery crops, compared with using fogger nozzle (45 μm-DS).

Irrigation management of greenhouse zucchini with different soil matric potential level. Agronomic and environmental effects

Greenhouse horticultural crops are characterized by high levels of efficiency and productivity of irrigation water. But they still can and must be improved, especially in arid areas. The objective of this research was to study the effect of the soil matric potential level on the bio-productivity of zucchini crop, the water use efficiency (WUE) and nutrients use efficiency by changing the threshold of soil matric potential. An experiment was conducted in greenhouse-grown zucchini on a sand-mulched soil and fertigation with inorganic fertilizer. Automatic activation of irrigation through an electronic tensiometer and three treatments were applied: Activation of irrigation to −10kPa and application of volume of 1.5Lm−2 (T1), activation of irrigation to −25kPa and application of volume of 2.0Lm−2 (T2) and activation of irrigation to −40kPa and application of volume of 3.0Lm−2 (T3). Yield, leaf area, biomass, water consumption, WUE and nutrients, drainage volume and physical-chemical parameters of the soil were determined. The results show that T2 slightly reduced the weight of the fruit with respect to T1, but not the number of fruit, obtaining a significantly lower consumption of water. Lower weight fruits and less number of fruits were obtained by T3. Reducing the soil moisture tension level increased substantially water consumption as a result of the differences in vegetative growth (leaf area and biomass) in plants. Highest values of WUE and nutrients use efficiency were registered by T2 and T3. In none of the treatments, drainage was obtained. Soil physical-chemical parameters were not affected by treatments. Independently of soil matric potential, increased soil salinity occurred after the growing season. The soil matric potential of −25kPa was the best considering agronomic and environmental aspects, as the most efficient use of water and nutrients obtaining a commercial production of 15kgm−2.

Physiological response of juvenile hop plants to water deficit

This paper evaluates the response on the rate of photosynthesis (Pn), transpiration (E), stomatal conductance (gs) and water use efficiency (WUE) in 15 genotypes of young hop plants (19 BBCH) grown in greenhouses in the conditions of water deficit for the period of 9 days. On the 9th day, the relative content of water in the experimental plants fluctuated between 70.14-75.20%. The levels of Pn and gs evidently dropped in the monitored species as a result of the water deficit. The decrease of Pn in the experimental plants compared with the control group was largest in the Saaz Os. cl. 72 (by 77.5%), Magnum (by 73.3%) and Columbus (by 62.3%). To the contrary, the lowest Pn decrease was noted in the case of genotypes Saaz Late (by 15.7%), Vital (by 23.9%) and Premiant (by 24.2%). All genotypes except for cv. H16 showed an evident decrease of E. Judging by the highest values of WUE, the most effective water management was shown by Premiant, Vital and Saaz Late genotypes. A significant stomatal limitation of photosynthesis due to water stress was identified in the most widely used Czech cultivar, Saaz Os. cl. 72, with low values of stomatal conductance, photosynthetic rate and transpiration.

High water-use efficiency and growth contribute to success of non-native Erodium cicutarium in a Sonoran Desert winter annual community.

The success of non-native, invasive species may be due to release from natural enemies, superior competitive abilities, or both. In the Sonoran Desert, Erodium cicutarium has increased in abundance over the last 30 years. While native species in this flora exhibit a strong among-species trade-off between relative growth rate and water-use efficiency, E. cicutarium seems to have a higher relative growth rate for its water-use efficiency value relative to the pattern across native species. This novel trait combination could provide the non-native species with a competitive advantage in this water-limited environment. To test the hypothesis that E. cicutarium is able to achieve high growth rates due to release from native herbivores, we compared the effects of herbivory on E. cicutarium and its native congener, Erodium texanum. We also compared these two species across a range of environmental conditions, both in a common garden and in two distinct seasons in the field, using growth analysis, isotopic compositions and leaf-level gas exchange. Additionally, we compared the competitive abilities of the two Erodium species in a greenhouse experiment. We found no evidence of herbivory to either species. Physiological measurements in a common environment revealed that E. cicutarium was able to achieve high growth rates while simultaneously controlling leaf-level water loss. Non-native E. cicutarium responded to favourable conditions in the field with greater specific leaf area and leaf area ratio than native E. texanum. The non-native Erodium was a stronger competitor than its native congener in a greenhouse competition experiment. The ability to maintain relatively higher values of water-use efficiency:relative growth rate in comparison to the native flora may be what enables E. cictarium to outcompete native species in both wet and dry years, resulting in an increase in abundance in the highly variable Sonoran Desert.

Efecto de la Salinidad por NaCl en Híbridos de Tomate. (Lycopersicon esculentum Miller)

Soil salinity represents one of the greatest abiotic environmental stresses affecting tomato production around the world. Colombian tomato production has been affected by this problem in the Alto Ricaurte region of the Boyaca department due to fertilisers having been applied via fertigation, leading to long-term negative consequences, particularly salt accumulation. A bi-factor study was carried out in greenhouse conditions near Tunja, Boyaca, for investigating the comparative tolerance capacity of four tomato hybrids exposed to increasing salinity levels. Supermagnate, Astona, Marimba and Gloria hybrid tomato seedlings were sown in 3.5 kg pots containing soil. They were exposed to 0, 20, 40, 60 and/or 80 mmol NaCl. These treatments' electrical conductivity was 1.8, 3.6, 5.2, 7.2 and 8.8dS m-1, respectively. Water consumption, water-use efficiency (WUE), dry weight and leaf area were determined. There sults revealed statistically significant differences between hybrid sand salinity level; however, there were no differences regarding hybrid interaction x salinity. The Astona hybrid had the highest WUE value, leaf area and dry mass production whilst Marimba had the lowest WUE and dry mass value. Water consumption, WUE, total dry weight and leaf area were most severely affected when salinity was above 40 mmol NaCl. The region's tomato growers should take precautions for limiting such effects when growing these hybrids due to the salinity response of the hybrids evaluated here and should also evaluate salinity tolerance in other vegetable materials.

Assessment of yield and water use efficiency of drip-irrigated cotton (Gossypium hirsutum L.) as affected by deficit irrigation

A field experiment was conducted for 2 consecutive years to evaluate the response of cotton crop to deficit irrigation under drip irrigation conditions. Water use efficiency (WUE), seed cotton yield, and fiber quality parameters were assessed at various irrigation levels. The experiment was set up to apply water at 4 different application rates: 50%, 65%, 80%, and 100% of the soil water depletion. These were abbreviated as DI50, DI65, DI80, and FI, respectively. The total amounts of irrigation water applied were 408 and 773 mm and the average seed cotton yields were 2909 and 5090 kg ha^{-1} for the DI50 and FI treatments, respectively. The highest seed cotton yield was obtained with full irrigation treatment in both years. Values of WUE were 0.65 and 0.70 kg m^{-3} for the FI and DI80 treatments, respectively, in the 2007 season. In the 2008 season, WUE values were 0.65 and 0.72 kg m^{-3} for the FI and DI80 treatments, respectively. The highest values of WUE and irrigation water use efficiency (IWUE) were observed in DI80 (0.71 and 0.75 kg m^{-3}, respectively), and the lowest IWUE in both years was seen with the FI treatment (0.66 kg m^{-3}). The yield response factor (ky) was 1.00 during the entire growing season, based on averages of the 2 years. No significant differences in fiber length, strength, uniformity, elongation, or fineness were observed between the FI and DI80 treatments in the 2008 season. The DI80 treatment showed significant benefits in terms of irrigation water savings and better WUE, indicating an attainable advantage of deficit irrigation employment under water shortage conditions.

Changes of the photosynthetic behaviour in annual C<sub>3</sub> species at late successional stage under environmental drought conditions

Differences in structural, physiological, and biochemical features between C3 and C4 species resulted in different wateruse efficiencies and different adaptations to climate. This paper aimed at investigating, at a late successional stage, the water-use efficiency of two forage species, Dichanthium ischaemum and Dasypyrum villosum, which exhibit different growth forms (perenial, annual) and photosynthetic mechanisms (C4 and C3, respectively). The annual C3 species Avena fatua, at an early successional stage, was included in our experiments to contrast its behaviour against D. villosum. The experiment was conducted during the growing season in low-elevation grasslands of North Greece. Midday leaf water potential, net photosynthetic rate, transpiration rate and stomatal conductance were measured. Instantaneous water-use efficiency (WUE) and intrinsic water-use efficiency (WUEi) were calculated in D. ischaemum, D. villosum, and A. fatua. The results suggest that, under natural rainfall conditions, the annual C3 grass species D. villosum exhibits a similar WUE with higher values of WUEi than the perennial C4 species D. ischaemum at late stage of succession on the low elevation Mediterranean grasslands. Moreover, A. fatua at an early successional stage, exhibited different photosynthetic behaviour than D. villosum at a late successional stage. These findings indicate that the annual C3 species D. villosum under drought and at a late successional stage seems to modify the WUE obtaining values similar to those of C4 species. The extent to which the ecophysiological characteristics of D. villosum are environmentally or intrinsically determined remains to be answered.

Water pillow irrigation compared to furrow irrigation for soybean production in a semi-arid area

Field studies were done in 2003 and 2006 to evaluate the performance of water pillow (WP) irrigation as an alternative to furrow irrigation (FI) for soybean growth in semi-arid climatic conditions. There were four irrigation treatments: two of which (FI and WP 1.0) were full irrigation, in that the water deficit in the soil profile (0.9 m) was brought to field capacity in 10-day intervals. The other two treatments (WP 0.75 and WP 0.50) were deficit irrigation treatments, and received 75% and 50% of WP 1.0 irrigation amount. The highest seed yield was achieved with the WP 1.0 treatment. Irrigation water use efficiency (IWUE) and water use efficiency (WUE) were influenced significantly by the irrigation methods and levels ( P ≤ 0.05). The highest values of WUE and IWUE were obtained by the WP 0.75 and WP 0.50 treatment, respectively, in both study years. However, the smallest irrigation amount resulted in lower total yield for the WP 0.50 treatment, and is not recommended. In conclusion, the WP 0.75 treatment is recommended for soybean production in order to attain higher values of IWUE and WUE, and to conserve water and maximize yield with the same volume of water.

Comparative ecophysiology of five species of Sedum (Crassulaceae) under well-watered and drought-stressed conditions.

Gas exchange patterns, diurnal malic acid fluctuations, and stable carbon isotope ratios of five species of Sedum were investigated to assess the ecophysiological characteristics of three different photosynthetic pathways under well-watered and drought-stressed conditions. All five species have succulent leaves and stems and were examined under identical environmental conditions. When well-watered, Sedum integrifolium (Raf.) Nels. and S. ternatum Michx. displayed C3 photosynthesis, S. telephioides Michx. and S. nuttallianum Raf. exhibited CAM-cycling, and S. wrightii A. Gray showed CAM. When grown under a less frequent watering regime, S. integrifolium and S. ternatum exhibited CAM-cycling, whereas S. telephioides and S. nuttallianum displayed CAM-cycling simultaneously with low-level CAM. Sedum wrightii retained its CAM mode of photosynthesis. In general, leaf δ13C values reflected these variations in photosynthetic pathways. While all values of water-use efficiency (WUE) were greater than those reported for most C3 and C4 species, no correlation of malic acid accumulation in the CAM and CAM-cycling (including low-level CAM) species with increased WUE was found. Sedum wrightii (CAM) had the highest WUE value at night, yet its 24-h WUE was not different from S. ternatum when the latter was in the C3 mode. Thus, relative water-use efficiencies of these species of Sedum were not predictable based on photosynthetic pathways alone.

Seasonal patterns of daily net photosynthesis, transpiration and net primary productivity of Juncus roemerianus and Spartina alterniflora in a Georgia salt marsh.

Studies of the seasonal CO2 and water vapor exchange patterns of Juncus roemerianus and Spartina alterniflora were conducted in an undisturbed marsh community on Sapelo Island, Georgia. Daily patterns of net photosynthesis, transpiration, leaf diffusive conductance and water-use efficiency in response to ambient conditions were monitored on intact, in situ plants. Net primary productivity was calculated from the daytime CO2 fixation totals, nighttime CO2 loss, leaf standing stock and aboveground to belowground biomass ratios for each plant type.The tall form of S. alterniflora had higher rates of photosynthesis and higher water-use efficiency values which, in conjunction with low respiratory losses and large leaf standing crop, results in high values of net primary productivity. The environmental factors in the marsh which permit these physiological responses occur in less than 10% of the marsh. Overall, the physiological capabilities of the short form of S. alterniflora were reduced in comparison to the tall form, but the combination of environmental factors which determine the physiological responses of this form occur in a much greater portion of the marsh, and the short form of S. alterniflora dominates the Sapelo Island marshes.The response patterns of the C3 species, J. roemerianus, differed somewhat from the height forms of S. alterniflora. A large, seasonally constant leaf standing crop coupled with moderate rates of photosynthesis resulted in a net primary productivity value which was between the tall and short height forms of S. alterniflora. However, as with the tall S. alterniflora, the environmental conditions under which this high productivity and high water loss rate can be sustained are restricted to specific regions of the environmental gradient in the marsh.