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Grapevines are extensively grown in the arid region of China, but little information is available on the diurnal, seasonal and interannual variability of vineyard evapotranspiration (ET). To address this question, two vineyards in...
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Grapevines are extensively grown in the arid region of China, but little information is available on the diurnal, seasonal and interannual variability of vineyard evapotranspiration (ET). To address this question, two vineyards in the arid region of northwest China were taken as an example to study the variation of ET using Bowen ratio-energy balance method in 2005-2008. Results indicate that the Bowen ratio method provided accurate estimate of vineyard ET as the instrument was correctly installed. Irrigation and rainfall increased daily ET by 38 and 175%, respectively, but frost decreased it by 32%. Daily ET had a maximum value of 1.6-3.5 mm/d at the berry development stage, and a minimum value of 0.8-1.7 mm/d at the early and later stages. The total ET was 226-399 mm over the growing season. The ratio of transpiration to evapotranspiration was 0.52 and the modified crop coefficient (Kcm) was 0.71-0.88 (except 2005) over the whole growing stage. Larger interannual difference of ET and Kcm mainly resulted from the difference of irrigation and rainfall between different years.
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Field experiments were conducted to study the effects of drip irrigation regimes on potato (Solanum tuberosum L.) growth, tuber yield and quality, and water use efficiency (WUE) when grown under plastic mulch in an arid area of No...
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Field experiments were conducted to study the effects of drip irrigation regimes on potato (Solanum tuberosum L.) growth, tuber yield and quality, and water use efficiency (WUE) when grown under plastic mulch in an arid area of Northwestern China in 2008, 2009 and 2010. The 2008 experiment consisted of a drip irrigation check without plastic mulch and four different drip irrigation frequency treatments with plastic mulch: once every day, once every 2 days, once every 4 days, and once every 8 days. In 2009 and 2010 the drip check treatment without mulch was irrigated at -25 kPa soil matric potential (SMP) during three potato development stages and four different SMP drip irrigation strategies were compared during the potato development stages (using plastic mulch): S1 (-25 kPa SMP during the three development stages), S2 (-25 kPa SMP during tuber initiation and bulking and -35 kPa SMP during maturation), S3 (-25 kPa SMP during tuber initiation and maturation and -35 kPa SMP during bulking), S4 (-35 kPa SMP during the three development stages). Plastic mulch negatively affected tuber yield, WUE, and tuber quality. In the presence of plastic mulch, tuber yield, specific gravity, starch content, and vitamin C content seemed to be enhanced as the irrigation frequency increased, although the differences were not statistically significant. Irrigation frequency did not affect WUE for potato grown under plastic mulch. Analysis of plant height, tuber yield and WUE showed that a drip irrigation threshold of -35 kPa SMP led to obvious water stress for potato growth in this arid area. Under plastic mulch in 2010, S2 was the optimum drip irrigation regime because of the significantly higher yield than S3 and S4, the highest WUE and significantly firmer tubers than any of the other irrigation regimes tested.
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摘要 :
Field experiments were conducted to study the effects of drip irrigation regimes on potato (Solanum tuberosum L.) growth, tuber yield and quality, and water use efficiency (WUE) when grown under plastic mulch in an arid area of No...
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Field experiments were conducted to study the effects of drip irrigation regimes on potato (Solanum tuberosum L.) growth, tuber yield and quality, and water use efficiency (WUE) when grown under plastic mulch in an arid area of Northwestern China in 2008, 2009 and 2010. The 2008 experiment consisted of a drip irrigation check without plastic mulch and four different drip irrigation frequency treatments with plastic mulch: once every day, once every 2 days, once every 4 days, and once every 8 days. In 2009 and 2010 the drip check treatment without mulch was irrigated at -25 kPa soil matric potential (SMP) during three potato development stages and four different SMP drip irrigation strategies were compared during the potato development stages (using plastic mulch): S1 (-25 kPa SMP during the three development stages), S2 (-25 kPa SMP during tuber initiation and bulking and -35 kPa SMP during maturation), S3 (-25 kPa SMP during tuber initiation and maturation and -35 kPa SMP during bulking), S4 (-35 kPa SMP during the three development stages). Plastic mulch negatively affected tuber yield, WUE, and tuber quality. In the presence of plastic mulch, tuber yield, specific gravity, starch content, and vitamin C content seemed to be enhanced as the irrigation frequency increased, although the differences were not statistically significant. Irrigation frequency did not affect WUE for potato grown under plastic mulch. Analysis of plant height, tuber yield and WUE showed that a drip irrigation threshold of -35 kPa SMP led to obvious water stress for potato growth in this arid area. Under plastic mulch in 2010, S2 was the optimum drip irrigation regime because of the significantly higher yield than S3 and S4, the highest WUE and significantly firmer tubers than any of the other irrigation regimes tested.
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Drip irrigation is the most effective and reliable method for reclaimed wastewater irrigation. Emitter clogging is the major problem for extending the drip irrigation technology. The existence of suspended particulates in irrigati...
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Drip irrigation is the most effective and reliable method for reclaimed wastewater irrigation. Emitter clogging is the major problem for extending the drip irrigation technology. The existence of suspended particulates in irrigation water is the main reason for the emitter clogging. However, the reclaimed wastewater quality is extremely complex, and there is a series of physical, chemical, and biological reactions between suspended particulates and other materials contained such as microorganisms, which make the characteristics of suspended particulates in reclaimed wastewater complicated. In this paper, two types of widely used wastewaters treated with fluidized-bed reactor (FBR) and biological aerated filter (BAF) processes respectively were selected. The scanning electron microscope (SEM) technology and fractal theory were used to quantitatively describe the characteristics of the surface topography of suspended particulates. The results showed that the suspended particulates in two reclaimed wastewater were flocculent and porous. The pore system mainly consisted of solid suspended particulates, and most areas between the particulates were filled with microbes and extracellular polymers (EPS). The complex structure of biofilms was formed. That the biofilms grew and detached in irrigation system and deposited continuously at the inlet and outlet of labyrinth path was the major reason for the emitter clogging. The surface topography of suspended particulates in both reclaimed wastewaters showed fractal and multifractal characteristics, and the fractal dimension could not characterize the local and microsingularity of particulates but multifractal dimension could. The uniformity of the distribution of sediment pores increased with the size. Comparatively, the uniformity of suspended particulates in reclaimed wastewater treated by FBR was lower. With operation of reclaimed wastewater irrigation system, the average discharge of emitters decreased continuously with obvious fluctuations. The clogging degree of emitters was low during the first 256 h, and the clogging degree of the two types of reclaimed water was similar. But then, the degree of clogging increased greatly, and the FBR treatment on the emitters discharge were more obvious than BAF. It was closely related to the growth, detachments and sediment of biofilms in the irrigation system. Hence, using the reclaimed wastewater treated by BAF for drip irrigation is more suitable.
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Deficit irrigation is widely used in tomato production because of water shortage. Many studies indicate that tomato yield is reduced but the fruit quality is improved under certain degree of water deficit. In order to investigate ...
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Deficit irrigation is widely used in tomato production because of water shortage. Many studies indicate that tomato yield is reduced but the fruit quality is improved under certain degree of water deficit. In order to investigate the quantitative relationship between tomato yield, fruit quality and water deficit, two experiments with different irrigation treatments were conducted in solar greenhouse in an arid region of northwest China from winter in 2008 to spring in 2009 (2008-2009 season) and from winter in 2009 to spring in 2010 (2009-2010 season). Results showed that the application of 1/3 (T1) and 2/3 (T2) of full irrigation at seedling stage (Stage I) did not significantly influence greenhouse tomato water consumption, total yield and fruit quality. Tomato water consumption and total yield were decreased by the application of 1/3 (T3) of full irrigation at flowering and fruit development stage (Stage II), and 1/3 (T5) or 2/3 (T6) of full irrigation at fruit maturation stage (Stage III). But the fruit contents of total soluble solids (TSS), reducing sugars (RS), organic acids (OA) and vitamin C (VC) as well as fruit firmness (Fn), sugar/acid content ratio (SAR), color index (CI) and water use efficiency (WUE) were significantly increased. However, no significant effects were found on tomato yield and fruit quality in the application of 2/3 full irrigation at Stage II (T4). The relative yield (Y/Y-CK) had a significant positive correlation with relative seasonal evapotranspiration (ET/ETCK), while negative correlations were found between the relative values of fruit quality parameters and ET/ETCK. Tomato yield is sensitive to water deficit during Stage II and Stage III, but fruit quality is mainly affected by water stress during Stage III. The regression equations between tomato yield, fruit quality parameters and ET could provide important basis for making irrigation strategies with the compromise between tomato yield and fruit quality (C) 2013 Elsevier B.V. All rights reserved.
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Accurate estimate of transpiration in greenhouses is of great importance for developing water-saving management practices. In this study, we evaluated the performance of the Penman-Monteith (P-M) model using aerodynamic resistance...
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Accurate estimate of transpiration in greenhouses is of great importance for developing water-saving management practices. In this study, we evaluated the performance of the Penman-Monteith (P-M) model using aerodynamic resistance values estimated from heat transfer coefficient (h) to predict transpiration of hot pepper grown in a solar greenhouse based on different convection types. The reference transpiration was measured by sap flow meters. Results showed that heat transfer was conducted through mixed convection in about 81% and 71% of the study period, respectively, for the 2010-2011 and 2011-2012 season, while the rest of the study period was pure free convection which occurred mainly at night and in the early morning when transpiration rates were low and no pure forced convection occurred in the study solar greenhouse. Under pure free convection, the P-M model with h calculated by the McAdams equation tends to underestimate the transpiration, and the model with h calculated by the Stanghellini equation performed similar to the one by the McAdams equation. Under mixed convection, the P-M model with h calculated by the Stanghellini equation can accurately estimate the transpiration of hot pepper. This study shows that the P-M model with h estimated by the Stanghellini equation can well predict the transpiration rates of hot peppers grown in solar greenhouses without distinguishing the convection types.
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Large areas of vineyards have been established in recent years in arid region of northwest China, despite limited water resources. Water to support these vineyards is mainly supplied by irrigation. Accurate estimation of vineyard ...
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Large areas of vineyards have been established in recent years in arid region of northwest China, despite limited water resources. Water to support these vineyards is mainly supplied by irrigation. Accurate estimation of vineyard evapotranspiration (ET) can provide a scientific basis for developing irrigation management. Transpiration and soil evaporation, as two main components of ET, were measured separately in a vineyard in this region by heat balance sap flow system and micro-lysimeters during the growing season of 2009. Diurnal and seasonal dynamics of sap flow and its environmental controls were analyzed. Daily sap flow rate (SRl) increased linearly with solar radiation (Rs), but showed an exponential increase to its maximum curve as a function of vapor pressure deficit (VPD). Residuals of the two regressions both depended on volumetric soil water content to a depth of 1.0 m (VWC). VWC also significantly influenced SRl. The relationship of them could be expressed by a piecewise regression with the turnover point of VWC=0.188 cm3 cm-3, which was 60% of the field capacity. Conversely, soil evaporation (Es) increased exponentially with VWC. Thus, we recommended keeping VWC in such vineyards slightly above 60% of the field capacity to maintain transpiration while reducing soil evaporation. Vineyard transpiration (Ts) was scaled from sap flow by using leaf area (Al) as it explained 60% of the spatial variability of sap flow. Vine transpiration was 202.0 mm during the period from April 28 to October 5; while that of Es was 181.0 mm. The sum of these two components was very close to ET estimated by the Bowen ratio energy balance method (386.9 mm), demonstrating the applicability of sap flow for measuring grape water use in this region.
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Accurate determination of evapotranspiration (ET) is useful to develop precise irrigation scheduling. Although eddy covariance (EC) is a direct method which is widely used to measure ET, its performance in arid region of northwest...
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Accurate determination of evapotranspiration (ET) is useful to develop precise irrigation scheduling. Although eddy covariance (EC) is a direct method which is widely used to measure ET, its performance in arid region of northwest China is not clear. In this study, ET measured by EC (ETEC) was compared with that by large-scale weighing lysimeter (ETL) during the whole growing season of maize in 2009. Energy balance ratio was 0.84 for daytime fluxes, indicating that lack of energy balance closure occurred, so daytime ETEC was adjusted by Bowen-ratio forced closure method. Compared to the corresponding ETL, half-hourly daytime ETEC was underestimated by 21.8% without the adjustment and 4.8% with the adjustment. Furthermore, nighttime ETEC was adjusted using filtering/interpolation method. Mean error between half-hourly nighttime ETEC and ETL decreased from 30.2% without the adjustment to 10.3% with the adjustment. After such adjustment of day and night measurements, daily ETEC was underestimated by 6.2% compared to ETL. These results indicated that the adjusted ETEC well matched with the ETL. Moreover, the discrepancy of adjusted total ETEC and ETL was decreased to 3.2% after subtracting the overestimated ET by lysimeter resulting from irrigation and heavy rainfall events. Thus, after appropriate adjustments of observations, eddy covariance method is accurate in estimating maize ET in the arid region of northwest China.
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Accurate determination of evapotranspiration (ET) is useful to develop precise irrigation scheduling. Although eddy covariance (EC) is a direct method which is widely used to measure ET, its performance in arid region of northwest...
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Accurate determination of evapotranspiration (ET) is useful to develop precise irrigation scheduling. Although eddy covariance (EC) is a direct method which is widely used to measure ET, its performance in arid region of northwest China is not clear. In this study, ET measured by EC (ETEC) was compared with that by large-scale weighing lysimeter (ETL) during the whole growing season of maize in 2009. Energy balance ratio was 0.84 for daytime fluxes, indicating that lack of energy balance closure occurred, so daytime ETEC was adjusted by Bowen-ratio forced closure method. Compared to the corresponding ETL, half-hourly daytime ETEC was underestimated by 21.8% without the adjustment and 4.8% with the adjustment. Furthermore, nighttime ETEC was adjusted using filtering/interpolation method. Mean error between half-hourly nighttime ETEC and ETL decreased from 30.2% without the adjustment to 10.3% with the adjustment. After such adjustment of day and night measurements, daily ETEC was underestimated by 6.2% compared to ETL. These results indicated that the adjusted ETEC well matched with the ETL. Moreover, the discrepancy of adjusted total ETEC and ETL was decreased to 3.2% after subtracting the overestimated ET by lysimeter resulting from irrigation and heavy rainfall events. Thus, after appropriate adjustments of observations, eddy covariance method is accurate in estimating maize ET in the arid region of northwest China.
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Emitter clogging, a phenomenon commonly seen in reclaimed wastewater drip irrigation systems, is a severe obstacle to the wide applications and popularization of the irrigation technology. Some experiments showed that the emitter ...
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Emitter clogging, a phenomenon commonly seen in reclaimed wastewater drip irrigation systems, is a severe obstacle to the wide applications and popularization of the irrigation technology. Some experiments showed that the emitter clogging was tightly related to biofilms formation attached to the irrigation system. In this paper, two types of wastewaters reclaimed respectively by fluidized-bed reactor (FBR) process and biological aerated filter (BAF) process were chosen as the experiment objects and then the effects of the average velocity on the growth and topography of biofilms attached to the irrigation laterals were studied. The parameters of biofilms reached their maximal values at a critical velocity of 0.45 m/s. The formation of biofilms was primarily controlled by the transport of the nutrients and suspended particles within the laterals when the average velocity is below the critical velocity, whereas it was primarily controlled by the hydraulic shear force when above the critical velocity. The main mechanism for emitter clogging was that the biofilms detached from laterals accumulated and grew at the inlets and outlets of emitters. A similar variation pattern was observed for both reclaimed wastewaters. However, the growth of biofilms for BAF process was more affected by the shear force than that for FBR process, since the nutrients and suspended particles for BAF were larger than those for FBR.
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