Relations between relative evapotranspiration and predawn leaf water potential in soybean grown in several locations     

B. Itier  D. Flura  K. Belabbes  P. Kosuth  G. Rana  L. Figueiredo 《Irrigation Science》1992,13(3):109-114

Summary The measurement of water consumption in the field is normally restricted to research purposes, although the development of practical field criteria for timing water application is required to improve crop productivity. To develop such criteria irrigation experiments on Soybean were conducted from flowering to grain filling at four locations which differed in their soil properties and the convective contribution of their climates to potential evapotranspiration. The energy balance, predawn leaf water potential (PLWP), soil moisture depletion, and a crop water stress index (CWSI) based on foliage temperature were measured. The range of soil, atmospheric, phenological and irrigation conditions, produced a common, linear relation between relative evapotranspiration (rET) and the logarithm of -PLWP. Correlation with the temperature based CWSI was weak. A similar relation with PLWP for other C₃ plants was also derived from data in the literature. This relation could be helpful for irrigation scheduling once the critical values of rET for crop productivity are known.  相似文献   

Photosynthesis,plant growth and dry matter distribution in kiwifruit as influenced by water deficits   总被引：1，自引：0，他引：1  

K. Chartzoulakis  B. Noitsakis  I. Therios 《Irrigation Science》1993,14(1):1-5

The effects of water deficits on photosynthesis, plant growth and dry matter accumulation and distribution in the kiwifruit, cv Hayward, grown under controlled conditions in the glasshouse were studied. Water stress was imposed by irrigating the plants with 100%, 85%, 65% and 40% of water needed to reach pot capacity in the soil. Water deficits reduced the rate of photosynthesis by up to 53–64% in relation to the control. This decline was attributed to stomatal closure, since stomatal conductance was reduced significantly, or/and to inhibition of photosynthesis at chloroplast level. Severe water stress reduced plant height by 78–84%, total dry weight by 58–66% and total leaf area by 72–77%. The root to shoot ratio was 3.5 times higher in water-stressed plants, showing that water stress in kiwifruit alters the pattern of dry matter distribution favouring the roots. The decrease in growth induced by water deficits was a consequence of a reduction in both photosynthesis and photosynthates partitioning, which adversely affects leaf area development.  相似文献   

Use of stem diameter variations to detect plant water stress in tomato   总被引：3，自引：0，他引：3  

M. Gallardo  R. B. Thompson  L. C. Valdez  M. D. Fernández 《Irrigation Science》2006,24(4):241-255

The sensitivity of stem diameter variations (SDV) measured with linear variable transducer (LVDT) sensors as indicators of plant water status in tomato was evaluated. Two tomato crops were grown sequentially in a sandy loam soil in an unheated plastic greenhouse. These were an autumn–winter tomato crop (autumn crop) and a spring–summer tomato crop (spring crop). One drying cycle of 61 days was imposed to the autumn crop in winter at 92 days after transplanting (DAT). Two drying cycles, each of 29 days, were applied to the spring crop, to young (58 DAT) and mature plants (121 DAT). For each drying cycle, four replicate plots did not receive irrigation, and four were well watered. During each drying cycle, LVDT sensors continuously measured SDV, and daily measurements were made of leaf (Ψ _leaf) and stem water potential (Ψ _stem). SDV data was interpreted using the SDV-derived indices, maximum daily shrinkage (MDS) and stem growth rate (SGR). The response of SDV-derived indices to water deficit differed with (1) climatic conditions during stress imposition and (2) crop age. In the winter drying cycle of the autumn crop, the responses of the SDV-derived indices to soil drying were relatively small and slower than Ψ _leaf and Ψ _stem. Under warmer conditions, the SDV-derived indices were much more responsive to soil drying. In rapidly growing young plants, where SDV was characterized by high SGR and small MDS, SGR was the most sensitive SDV-derived index. In more mature plants with little stem growth, MDS was the most sensitive SDV-derived index. In mature plants grown in warm to hot conditions, MDS (1) responded at a similar time or earlier than Ψ _leaf and Ψ _stem and (2) had larger “signal” values (ratio of values from unwatered to control plants) than Ψ _leaf and Ψ _stem. However, there was appreciably more “noise” (coefficient of variation, CV) associated with the SDV-derived indices, giving lower “sensitivity” values, determined from “signal” to “noise” ratios, than for Ψ _leaf and Ψ _stem. Regression analysis between MDS of well-watered plants and climatic variables gave best results for a linear relationship between MDS and daily maximum vapor pressure deficit. There were strong linear relationships between MDS and Ψ _leaf for each drying cycle. The slopes of these relationships differed with crop age indicating that there was no constant relationship between MDS and Ψ _leaf for a whole season. Overall these results demonstrated that MDS and SGR can be sensitive indicators of the water status of tomato crops under conditions of moderate to high evaporative demand. However, the variability associated with the SDV-derived indices and the changing MDS–Ψ _leaf relationship with crop age represent major issues regarding the development of irrigation scheduling protocols for tomato.  相似文献   

Impact of crop rotation and minimum tillage on water use efficiency of irrigated cotton in a Vertisol     

S. B. Tennakoon  N. R. Hulugalle 《Irrigation Science》2006,25(1):45-52

Crop water use efficiency of irrigated cotton was hypothesized to be improved by a combination of minimum tillage and sowing a wheat (Triticum aestivum L.) rotation crop. This hypothesis was evaluated in a Vertisol near Narrabri, Australia from 1997 to 2003. The experimental treatments were: continuous cotton sown after conventional or minimum tillage and minimum-tilled cotton–wheat. Soil water content was measured with a neutron moisture meter, and runoff with trapezoidal flumes. Application efficiency of irrigation water was estimated as the amount of infiltrated water/total amount applied. Plant available water was estimated using the maximum and minimum soil water storage during the growing season. Evapotranspiration was estimated with the water balance method using measured and simulated soil water data. Seasonal evapotranspiration was partitioned into that coming from rainfall, irrigation and stored soil water. Crop water use efficiency was calculated as cotton lint yield per hectare/seasonal evapotranspiration. Rotation of cotton with wheat and minimum tillage improved water use efficiency in some years and application efficiency in all years. Average seasonal evapotranspiration was higher with minimum tillage than with conventional tillage. In years when cotton was sown in all plots, average cotton crop water use efficiencies were 0.23, 0.23 and 0.22 kg (lint)/m³ for minimum-tilled cotton–wheat and continuous cotton, and conventionally tilled continuous cotton, respectively. In-season rainfall efficiency, transpiration and soil evaporation were unaffected by cropping system.  相似文献   

The feasibility of using variable rate water application under a central pivot irrigation system     

S. A. Al-Kufaishi  B. S. Blackmore  H. Sourell 《Irrigation and Drainage Systems》2006,20(2-3):317-327

The purpose of this paper was to assess the feasibility and significance of applying spatially variable irrigation under a central pivot system at the Federal German Agricultural Research Center, Braunschweig, Germany. The assessment was based on soil moisture holding capacity, soil depth variation and root development. Soil texture analysis was carried out by sampling on a 60 meter grid. The German Agro-Meteorological Model was applied to simulate the water balance in the crop-soil-atmosphere system for the growing season 2003/4. The research findings are presented in terms of six scenarios: 20, 30, 40 mm water application depths per irrigation under both variable rate application and uniform application. The comparison revealed that the loss of water was higher for the uniform application scenarios than that for the variable rate application (VRA) scenarios for the applications of 20 and 30 mm. The VRA scenario of 20 mm water application was found out to be the best option for water conservation.  相似文献   

A model of decision-making and information flows for information-intensive agriculture     

S. Fountas  D. Wulfsohn  B.S. Blackmore  H.L. Jacobsen  S.M. Pedersen 《Agricultural Systems》2006

This paper describes the development of a systems based model to characterise farmers’ decision-making process in information-intensive practices, and its evaluation in the context of Precision Agriculture (PA). A participative methodology was developed in which farm managers decomposed their process of decision-making into brief decision statements along with associated information requirements. The methodology was first developed on a university research farm in Denmark and further revised during testing on a number of research and commercial farms in Indiana, USA. Twenty-one decision-analysis factors were identified to characterise a farm manager’s decision-making process. Then, a general data flow diagram (DFD) was constructed that describes the information flows “from data to decision”. Illustrative examples of the model in the form of DFDs are presented for a strategic, a tactical and an operational decision. The model was validated for a range of decisions related to operations by three university farm managers and by five commercial farmers practicing PA for cereal, corn and soybean production in Denmark and in Indiana, USA.  相似文献   

Sustainability of bean production systems on steep lands in Costa Rica     

B.C. Bellows  P.E. Hildebrand  D.H. Hubbell 《Agricultural Systems》1996,50(4):391-410

Responding to changes in rural-urban linkages and government policies, bean (Phaseolus vulgaris L.) production systems in Costa Rica are undergoing transitions. Impacts of changes in bean production systems on environmental and economic sustainability were analysed at the field, farm and policy levels. A combination of interviews, agronomic surveys, on-farm experiments, and secondary information was used. Changes in agronomic and economic conditions over time were assessed by conducting agronomic surveys and experiments on farms representing a range of land-use intensities. Trade-offs between productivity and stability were quantified using Modified Stability Analysis. The adoption of land and agrochemical-intensive methods by resource-poor farmers cultivating steep lands resulted in decreased environmented and economic sustainability. Farmers with adequate resources were able to maintain economic viability by transferring land out of beans and into other commodities, particularly cattle. However, this shift in resource use decreased social equity by decreasing farm labour opportunities for smallholders and landless farmers and diminishing land available for tenants. These studies indicate that the impact of technology introduction on farming system sustainability can be assessed effectively by conducting integrated socioeconomic and agronomic analyses across farms representing various land-use practices and intensities.  相似文献   

Farmers' perception on self created water management rules in a pioneer scheme: The mula irrigation scheme, India     

Jennifer McKay  Ganesh B. Keremane 《Irrigation and Drainage Systems》2006,20(2-3):205-223

During the past two decades with farmer participation in irrigation management moving to center stage, the traditional view of having a centralized control over the water resources for better management has changed. Nevertheless, success of irrigation management transfer depend on a whole set of institutional arrangements or the rules-in-use and the willingness of the users to comply and enforce and/or change the rules in the light of changing circumstances. There are many institutional analyses of water sector, much of them touch on law, policy and administration, and characteristics of the users. The present paper is based on the study carried out to examine the institutional arrangements in one of the water users association that was first in the Maharashtra state. It focuses on the institutional arrangements governing water use and distribution and attempts to elicit the perceptions of the members regarding the rules-in-use. The findings reveal that the WUA has been successful in devising and enforcing the rules for water distribution, fee collection and conflict resolution for over a decade. However, current socio-economic developments such as political heterogeneity have required explicit conflict resolution mechanisms. These issues have now become issues demanding immediate attention and may be use of existing courts or legal institutions to help the WUA sustain in future.  相似文献   

华南地区覆盖旱种水稻节水及其水分利用效率研究   总被引：3，自引：0，他引：3  

汪强  樊小林  D.Klaus  B.Sattemacher 《灌溉排水学报》2007,26(4):89-92

大田试验条件下设置常规水稻(T11)、覆膜旱作水稻(T12)、覆草旱作水稻(T13)和裸地旱作水稻(T14)4个处理,研究旱作水稻的节水效率及水分利用效率。水稻本田期T11用水总量545.40 mm,显著高于各旱作处理水稻,以此为参照,T12、T13和T14节水效率分别为35.1%、22.8%和21.2%。以裸地旱作处理T14为参照,T12节水率17.7%,而T13无明显节水效果。旱作水稻的节水效果主要发生在水稻移栽后前2个月,之后无明显节水效果。各处理以籽粒产量/耗水量为基础计算的水分利用效率(WUE),T12、T13、T14和T11处理分别为1.47、1.31、1.21和1.05 g/kg,以干物质量/耗水量为基础计算的WUE各处理之间的趋势与以籽粒产量/耗水量计算的WUE基本一致。  相似文献   

沙棘油脂     

B. Dave Oomah  土小宁  陆海 《国际沙棘研究与开发》2005,3(3):1-10,14

果实 沙棘果实由果肉（68%）、种子（23%）和果皮（7.75%）组成（Zadernowski et al.,1997）.Yang和Kallio（2001）最近发现,从中国、芬兰和前苏联（FSU）等地大量选择后采集的沙棘果实中23%～28%是种子,72%～77%是柔软的果肉/果皮.沙棘果实可提取3种油：种子油、果肉油和果皮油.不同于其他植物,沙棘果实的各部分都能合成并积累脂肪.有时果肉油和果皮油没有区别,因此统称为果实油或果肉油.沙棘叶也含油,这部分内容将在稍后部分进一步说明.  相似文献