This study was conducted to establish a simple convenient method for calculating crop coefficient, and provide a certain basis for the research of the empirical formula for calculating crop coefficient with plant heig...This study was conducted to establish a simple convenient method for calculating crop coefficient, and provide a certain basis for the research of the empirical formula for calculating crop coefficient with plant height which could be measured conveniently with regional differences, especially for the establishment of accurate irrigation schedule of potato in Yunnan. By the field experiment on potato under the condition of drip irrigation, it was found that the models of plant height with corrected FAO-56-recommended K and measured K were a quartic polynomial and a cubic polynomial, respectively, and the polynomial of potato plant height with measured crop coefficient was simpler with higher degree of fitting; and the differences between the period with the highest change rate of potato plant height and the periods with the greatest FAO-56-recommended K and measured K exhibited a differences of 3 d. In conclusion: In the future study of simple or empirical formula calculation of crop coefficient, plant height should be considered as a main dependent variable in that the calculation result would be closer to the measured crop coefficient with the problem of regional difference existing in the FAO method solved and the formula might be simpler; and the irrigation time of potato should be 3 d earlier than the irrigation time determined according to the corrected FAO-56-recommended crop coefficient, especially in the key water requirement stages of potato.展开更多
The aim of this study was to estimate the evapotranspiration of cauliflower and red cabbage crops grown under cool season semiarid climatic conditions from Class A pan evaporation. Actual evapotranspiration (ETc) of...The aim of this study was to estimate the evapotranspiration of cauliflower and red cabbage crops grown under cool season semiarid climatic conditions from Class A pan evaporation. Actual evapotranspiration (ETc) of cauliflower and red cabbage crops was calculated according to the water balance approach. Reference evapotranspiration (ETo) was calculated with FAO Penman-Monteith equation. Pan evaporation (Epan) was measured by using Class A pan. Seasonal ETc was determined as 475 mm for cauliflower and 556 nun for red cabbage. Seasonal pan coefficient (kp=ETo/Epan) was determined as 0.82, and the seasonal crop coefficient (kc=ETc/ETo) was determined as 0.84 for cauliflower and 0.83 for red cabbage. So the evapotranspiration of cauliflower and red cabbage crops was estimated as 70% Class A pan evaporation.展开更多
Maize (Zea mays L.), a staple crop grown from June to September during the rainy season on the North China Plain,is usually inter-planted in winter wheat (Triticum aestivum L.) fields about one week before harvesting ...Maize (Zea mays L.), a staple crop grown from June to September during the rainy season on the North China Plain,is usually inter-planted in winter wheat (Triticum aestivum L.) fields about one week before harvesting of the winterwheat. In order to improve irrigation efficiency in this region of serious water shortage, field studies in 1999 and 2001, twodry seasons with less than average seasonal rainfall, were conducted with up to five irrigation applications to determineevapotranspiration, calculate the crop coefficient, and optimize the irrigation schedule with maize under mulch, as well asto establish the effects of irrigation timing and the number of applications on grain yield and water use efficiency (WUE)of maize. Results showed that with grain production at about 8 000 kg ha-1 the total evapotranspiration and WUE ofirrigated maize under mulch were about 380-400 mm and 2.0-2.2 kg m-3, respectively. Also in 2001 WUE of maizewith mulch for the treatment with three irrigations was 11.8% better than that without mulch. In the 1999 and 2001seasons, maize yield significantly improved (P = 0.05) with four irrigation applications, however, further increases werenot significant. At the same time there were no significant differences for WUE with two to four irrigation applications.In the 2001 season mulch lead to a decrease of 50 mm in the total soil evaporation, and the maize crop coefficient undermulch varied between 0.3-1.3 with a seasonal average of 1.0.展开更多
The current study proposes a novel method using Excel Solver to estimate, from limited data, crop coefficient (Kc) in paddy fields under intermittent irrigation (11). The proposed method was examined in a field ex...The current study proposes a novel method using Excel Solver to estimate, from limited data, crop coefficient (Kc) in paddy fields under intermittent irrigation (11). The proposed method was examined in a field experiment conducted at Karang Sari Village, Bekasi, West Java, Indonesia during the first rice season of 2007/2008 (December 2007 to April 2008) in the rainy season. As the control, continuous flooding irrigation (CF) was applied to the conventional rice cultivation fields. Based on the observed water storage, Excel Solver was used to estimate crop evapotranspiration. Estimated crop evapotranspiration was used to compute Kc value, then the average Kc values at each growth stage were compared with that for the CF treatment. The estimation method was evaluated by comparing estimated crop evapotranspiration and the crop evapotranspiration derived by the well established FAO procedure. Excel Solver estimated crop evapotranspiration accurately with R2 values higher than 0.81. Accordingly, more than 81% of the FAO crop evapotranspiration was described by the proposed method. Thus, Kc value could be well determined from those estimated crop evapotranspiration. Under the II treatment, the average Kc values were 0.70, 1.06, 1.24 and 1:22 for the initial, crop development, reproductive and late stages, respectively. These values were lower than those under the CF treatment for initial and crop development stages because of a minimal soil evaporation and intense dryness during these stages. However, average Kc values under the II treatment were higher than those under the CF treatment at the reproductive and late stages, indicating that the II treatment promoted more plant activity particularly for dry biomass production as indicated by a greater number of tillers per hill.展开更多
A field experiment was conducted throughout 2009/2010 in a sugarcane field of a commercial distillery located on the coastal area of Paraiba state, Brazil. The objectives were to determine sugarcane water requirements...A field experiment was conducted throughout 2009/2010 in a sugarcane field of a commercial distillery located on the coastal area of Paraiba state, Brazil. The objectives were to determine sugarcane water requirements and to test the single and dual crop coefficients by comparing the calculated values of ET with measured ones. Crop evapotranspiration was determined by field water balance, reference evapotranspiration (ETo) by the Penman-Monteith approach, while single and dual crop coefficients were computed through the standard FAO-56 methodology. The experimental area was cultivated with irrigation applied weekly by a centre pivot system in addition to rainfall and the irrigation scheduling was based on 100% ETo. Three statistical tests, mean bias difference (MBD), normalized root mean square difference (NRMSD) and regression analysis, were used to evaluate the performance of single and dual crop coefficients. Results showed that there was a notable symmetry between ET measured and ET calculated by Kc dual. The ET values, calculated from Kc single, underestimated those obtained from soil water balance measurements by 36%.展开更多
While the amount of water used by a crop can be measured using lysimeters or eddy covariance systems, it is more common to estimate this quantity based on weather data and crop-related factors. Among these approaches,...While the amount of water used by a crop can be measured using lysimeters or eddy covariance systems, it is more common to estimate this quantity based on weather data and crop-related factors. Among these approaches, the standard crop coefficient method has gained widespread use. A limitation of the standard crop coefficient approach is that it applies to “standard conditions” that are invariant from field to field. In this article, we describe a method for estimating daily crop water use (CWU) that is specific to individual fields. This method, the “spectral crop coefficient” approach, utilizes a crop coefficient numerically equivalent to the crop ground cover observed in a field using remote sensing. This “spectral crop coefficient” Ksp is multiplied by potential evapotranspiration determined from standard weather observations to estimate CWU. We present results from a study involving three farmers' fields in the Texas High Plains in which CWU estimated using the Ksp approach is compared to observed values obtained from eddy covariance measurements. Statistical analysis of the results suggests that the Ksp approach can produce reasonably accurate estimates of daily CWU under a variety of irrigation strategies from fully irrigated to dryland. These results suggest that the Ksp?approach could be effectively used in applications such as operational irrigation scheduling, where its field-specific nature could minimize over-irrigation and support water conservation.展开更多
To develop basis for strategic or arranged decision making towards crop yield improvement in Thailand, a new method in which crop models could be used is essential. Therefore, the objective of this study was to measur...To develop basis for strategic or arranged decision making towards crop yield improvement in Thailand, a new method in which crop models could be used is essential. Therefore, the objective of this study was to measure cultivar specific parameters by using DSSAT (v4.7) Cropping Simulation Model (CSM) with five upland rice genotypes namely Dawk Pa-yawm, Mai Tahk, Bow Leb Nahng, Dawk Kha 50 and Dawk Kahm. Experiment was laid out in a Completely Randomized Design (CRD) with split plot design. Results showed that five upland rice genotypes had significantly affected each other by different temperature treatments (28°C, 30°C, 32°C) with grain yield, tops weight, harvest index, flowering, and maturity date. At the same time, all the phenological traits had highly significant variation with the genotypes. The cultivar specific parameters obtained by using a temperature tolerant cultivar (Basmati 385) with five upland genotypes involved in the DSSAT4.7-CSM. Model evaluation results indicated that utilizing the estimated cultivar coefficient parameters, model simulated well with varying temperature treatments as indicated by the agreement index (d-statistic) closer to unity. Hence, it was estimated that model calibration and evaluation was realistic in the limits of test cropping seasons and that CSM fitted with cultivar specific parameters can be used in simulation studies for investigation, farm managing or decision making. This electronic document is a “live” template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document.展开更多
Priestley-Taylor equation(PT)and the Penman-Monteith equation(PM)are commonly used methods for regional evapotranspiration monitoring,using the PT coefficient(α_(a))and PM crop/vegetation coefficient(K_(c)).This pape...Priestley-Taylor equation(PT)and the Penman-Monteith equation(PM)are commonly used methods for regional evapotranspiration monitoring,using the PT coefficient(α_(a))and PM crop/vegetation coefficient(K_(c)).This paper investigates the seasonal changes inα_(a)and K_(c)at five sites in Australia and China,to understand the relation-ship between environmental conditions and evapotranspiration when applying different evaporation estimation methods.The research shows that higher actual evapotranspiration does not lead to higherα_(a)and K_(c)values.α_(a)and K_(c)perform similarly in cropland and forest environments in both China and Australia.Bothα_(a)and K_(c)continuously increase to a peak during the growing season and then decrease to their lowest values during the winter season.Considering K_(c)’s similar performance toα_(a)and its greater data processing requirements,K_(c)has few advantages for estimating regional evapotranspiration.Applying the Priestley-Taylor equation with a regional𝛼indicator will enhance the accuracy and reduce the workload when estimating regional evapotranspiration for similar landcover types based on remote sensing.展开更多
Searching for alternative methods for traditional irrigation is World trend at days due to a reduction in water and increased of drought due to climate changes therefore farmers need use modern methods of scheduling w...Searching for alternative methods for traditional irrigation is World trend at days due to a reduction in water and increased of drought due to climate changes therefore farmers need use modern methods of scheduling water and minimizing water losses while also increasing yield. To meet the future increasing demands water and food there is a need to utilize alternative methods to reduce evaporation, transpiration and deep percolation of water. Any countries use recycled water (drain and sewage) and desalination water from the sea or drains to irrigate crops plus computing actual crop evapotranspiration (ET<sub>c</sub>) so as to calculate the amount of water to apply to a crop. The paper aims to assess the actual evaporation and evaporation coefficient of carrots, by planting carrots in a field and the crop was exposed to several sources of water (DW and RW) and comparing ET<sub>c</sub>, K<sub>c</sub> and production among plots of three sites (A, B and C). The study used two types of irrigation water (drain water (DW) and river water (RW)). The results were to monthly rate and accumulated actual evapotranspiration to C (irrigation by RW only) more than A (67% RW and 33% DW) and B (17% RW and 83% DW) via 7% and 58%, respectively. The yield to C more than A and B by 17% and 75%, respectively. In conclusion the use of DW can cause a reduction in crop consumptive of carrot crops also causes a reduction in yield, crop length, root length, root size, canopy of crop, number of leaves and biomass of the plant therefore, the drainage water needs to treated before irrigating crops And making use of it to irrigate the fields and fill the shortfall in the amount of water from the river. The drain water helped on filling the water shortage due to climate changes and giving production of carrot crop but less than river water.展开更多
The aim of this study was to assess the crop water demand and deficit of spring highland barley and discuss suitable irrigation systems for different regions in Tibet, China. Long-term trends in reference crop evapotr...The aim of this study was to assess the crop water demand and deficit of spring highland barley and discuss suitable irrigation systems for different regions in Tibet, China. Long-term trends in reference crop evapotranspiration and crop water demand were analyzed in different regions, together with crop water demand and deficit of spring highland barley under different precipitation frequencies. Results showed that precipitation trends during growth stages did not benefit the growth of spring highland barley. The crop coefficient of spring highland barley in Tibet was 0.87 and crop water demand was 389.0 ram. In general, a water deficit was found in Tibet, because precipitation was lower than water consumption of spring highland barley. The most severe water deficit were in the jointing to heading stage and the heading to wax ripeness stage, which are the most important growth stages for spring highland barley; water deficit in these two stages would be harmful to the yield. Water deficit showed different characteristics in different regions. In conclusion, irrigation systems may be more successful if based on an analysis of water deficit within different growth stages and in different regions.展开更多
A non-dimensional relative sensitivity coefficient was employed to predict the responses of reference crop evapotranspiration (ET0) to perturbation of four climate variables in Tao'er River Basin of the northeaste...A non-dimensional relative sensitivity coefficient was employed to predict the responses of reference crop evapotranspiration (ET0) to perturbation of four climate variables in Tao'er River Basin of the northeastern China. Mean monthly ET0 and yearly ET0 from 1961 to 2005 were estimated with the FAO-56 Penman-Monteith Equation. A 45-year historical dataset of average monthly maximum/minimum air temperature, mean air temperature, wind speed, sunshine hours and relative humidity from 15 meteorological stations was used in the analysis. Results show that: 1) Sensitivity coefficients of wind speed, air temperature and sunshine hours were positive except for those of air tem- perature of Arxan Meteorological Station, while those of relative humidity were all negative. Relative humidity was the most sensitive variable in general for the Tao'er River Basin, followed by sunshine hours, wind speed and air tem- perature. 2) Similar to climate variable, monthly sensitivity coefficients exhibit large annual fluctuations. 3) Sensitivity coefficients for four climate variables all showed significant trends in seasonal/yearly series. Also, sensitivity coefficients of air temperature, sunshine hours and wind speed all showed significant trends in spring. 4) Among all sensitiv- ity coefficients, the average yearly sensitivity coefficient of relative humidity was highest throughout the basin and showed largest spatial variability. Longitudinal distribution of sensitivity coefficients for air temperature, relative hu- midity and sunshine hours was also found, which was similar to the distribution of the three climate variables.展开更多
The common Soil in Egypt is clay soil so common irrigation system is tradition surface irrigation with 60% irrigation efficiency. Agricultural sector consumes more than 80% of water resources under surface irrigation ...The common Soil in Egypt is clay soil so common irrigation system is tradition surface irrigation with 60% irrigation efficiency. Agricultural sector consumes more than 80% of water resources under surface irrigation (tradition methods). In arid and semi-arid regions consumptive use is the best index for irrigation requirements. A large part of the irrigation water applied to farm land is consumed by Evapotranspiration (ET). Irrigation water consumption under each of the physical and climatic conditions for large scale will be easier with remote sensing techniques. In Egypt, Agricultural cycle is often tow agricultural seasons yearly;summer and winter. Common summer crops are Maize, Rice and Cotton while common winter crops are Clover and Wheat. Landsat8 bands 4 and 5 provide Red (R) and Near Infra-Red (NIR) measurements and it used to calculate Normalized Deference Vegetation Index (NDVI) and monitoring cultivated areas. The cultivated land area was 3,277,311 ha in August 2013. In this paper Kc = 2 * NDVI ? 0.2 represents the relation between crop coefficient (Kc) and NDVI. Kc and Reference evapotranspiration (ETo) used to estimate ETc in Egypt. The main objective of this paper is studying the potential crop Evapotranspiration in Egypt using remote sensing techniques.展开更多
An efficient water use requires accurate estimations of crop ET (evapotranspiration). However, an accurate ET estimation is really difficult to achieve when big regions such as irrigation districts or complete water...An efficient water use requires accurate estimations of crop ET (evapotranspiration). However, an accurate ET estimation is really difficult to achieve when big regions such as irrigation districts or complete watersheds are involved. Satellite images are an alternative that can be used to estimate accurate crop ET for big regions. In the present study, two known methods were used to estimate crop ET, the METRIC model which was developed by the University of Idaho and a Kc-NDVI relationship. In the METRIC model, ET is estimated as a residual of the energy balance equation. The second method uses reference ET, and estimates a crop coefficient (K,.) as a linear function of the NDVI vegetation index. ET was estimated in a section of the Rio Mayo Irrigation District located in Sonora, Mexico using Landsat 7 satellite images. Crop ET of the main crops was estimated. Results show some differences between both methods. An average ET depth of 460 mm for the wheat average growing season was found when using METRIC, while an average ET depth of 421 mm was found when using the Kc-NDVI relationship. A water use total efficiency of 62% and 63% was found for METRIC and the Kc-NDVI relationship, respectively.展开更多
Efficient agricultural water use is crucial for food safety and water conservation on a global scale. To quantitatively investigate the agricultural water-use efficiency in regions exhibiting the complex agricultural ...Efficient agricultural water use is crucial for food safety and water conservation on a global scale. To quantitatively investigate the agricultural water-use efficiency in regions exhibiting the complex agricultural structure, this study developed an indicator named water footprint of crop values(WFV) that is based on the water footprint of crop production. Defined as the water volume used to produce a unit price of crop(m^3/CNY), the new indicator makes it feasible to directly compare the water footprint of different crops from an economic perspective, so as to comprehensively evaluate the water-use efficiency under the complex planting structure. On the basis of WFV, the study further proposed an indicator of structural water-use coefficient(SWUC), which is represented by the ratio of water-use efficiency for a given planting structure to the water efficiency for a reference crop and can quantitatively describe the impact of planting structure on agricultural water efficiency. Then, a case study was implemented in Xinjiang Uygur Autonomous Region of China. The temporal and spatial variations of WFV were assessed for the planting industries in 14 prefectures and cities of Xinjiang between 1991 and 2015. In addition, contribution rate analysis of WFV for different prefectures and cities was conducted to evaluate the variations of WFV caused by different influencing factors: agricultural input, climatic factors, and planting structure. Results from these analyses indicated first that the average WFV of planting industries in Xinjiang significantly decreased from 0.293 m^3/CNY in 1991 to 0.153 m^3/CNY in 2015, corresponding to an average annual change rate of –3.532%. WFV in 13 prefectures and cities(with the exception of Karamay) has declined significantly during the period of 1991–2015, indicating that agricultural water-use efficient has effectively improved. Second, the average SWUC in Xinjiang decreased from 1.17 to 1.08 m^3/CNY in the 1990 s, and then declined to 1.00 m^3/CNY in 2011–2015. The value of SWUC was highly consistent with the relative value of WFV in most prefectures and cities, showing that planting structure is one of the primary factors affecting regional agricultural water-use efficiency. Third, the contribution rate of WFV variations from human factors including agricultural input and planting structure was much more significant than that from climatic factors. However, the distribution of agricultural input and the adjustment of planting structure significantly differed among prefectures and cities, suggesting regional imbalances of agricultural development. This study indicated the feasibility and effectiveness of controlling agricultural water use through increasing technical input and rational selection of crops in the face of impending climate change. Specifically, we concluded that, the rational application of chemical fertilizers, the development of the fruit industry, and the strict restriction of the cotton industry should be implemented to improve the agricultural water-use efficiency in Xinjiang.展开更多
Livestock rearing is one of the major occupations in India and is making significant contribution to the country GDP. The regional and seasonal variations in the teperature and rainfall distribution have been the majo...Livestock rearing is one of the major occupations in India and is making significant contribution to the country GDP. The regional and seasonal variations in the teperature and rainfall distribution have been the major factors influencing the economy of a region. It is a matter of serious concern that out of 11 districts of central India, 9 districts are showing increasing trend in maximum temperature with a rate of 0.01°C to 0.15°C/year. A significant long-term decreasing trend (Slope = -4.26) was found in annual rainfall series at Jhansi. At Jhansi, moderate to severe drought occurs once in five years. But in the last decade, 7 years experienced moderate to disastrous drought in Jhansi region, wherein rainfall deficiency ranged between 40% and 60% from normal value. Of special mention was the year, 2006, which experienced a worst drought ever recorded for this region. Studies related to crop simulation model was carried out for fodder sorghum and its application for agronomic management and assessing the impact of climate change. Crop modeling studies on forage sorghum (C4) and cowpea (C3) showed increased dry matter biomass by 3% in sorghum but more prominent in cowpea by 46% under elevated CO2 from 330 ppm to 770 ppm. The interaction study of enhanced CO2 and temperature showed prominent negative impact on yields of both the crops. Evapotranspiration and crop coefficient (Kc) of several fodder crops i.e. berseem, lucerne, oat, sorghum, teosinte, maize + cowpea, guinea + berseem were worked out. In berseem, the highest Kc (1.81) was found during 2nd cutting followed by 3rd and 4th cuts. Estimates on irrigation scheduling for the guinea grass + berseem showed that the cropping system requires 7 irrigations at an interval ranging from 13 to 30 days to fulfill the 567.6 mm of water per season as net irrigation under mar soil (black) type whose actual water holding capacity (AWHC) is 175 mm. Similarly, if the cropping system is grown under kabar (AHWC = 140 mm) soil, then it requires nine irrigation with a total water requirement of 591.5 mm at an interval ranging from 10 to 24 days. For integrated pest management (IPM) scheme of lucerne, degree day based model was developed to monitor the lucerne weevil population in central region.展开更多
基金Supported by the Scientific Research Project of Yunnan Agricultural University(A3007680)the Fund for Scientific Research of Department of Education+1 种基金Yunnan(2014y1902014y193)~~
文摘This study was conducted to establish a simple convenient method for calculating crop coefficient, and provide a certain basis for the research of the empirical formula for calculating crop coefficient with plant height which could be measured conveniently with regional differences, especially for the establishment of accurate irrigation schedule of potato in Yunnan. By the field experiment on potato under the condition of drip irrigation, it was found that the models of plant height with corrected FAO-56-recommended K and measured K were a quartic polynomial and a cubic polynomial, respectively, and the polynomial of potato plant height with measured crop coefficient was simpler with higher degree of fitting; and the differences between the period with the highest change rate of potato plant height and the periods with the greatest FAO-56-recommended K and measured K exhibited a differences of 3 d. In conclusion: In the future study of simple or empirical formula calculation of crop coefficient, plant height should be considered as a main dependent variable in that the calculation result would be closer to the measured crop coefficient with the problem of regional difference existing in the FAO method solved and the formula might be simpler; and the irrigation time of potato should be 3 d earlier than the irrigation time determined according to the corrected FAO-56-recommended crop coefficient, especially in the key water requirement stages of potato.
文摘The aim of this study was to estimate the evapotranspiration of cauliflower and red cabbage crops grown under cool season semiarid climatic conditions from Class A pan evaporation. Actual evapotranspiration (ETc) of cauliflower and red cabbage crops was calculated according to the water balance approach. Reference evapotranspiration (ETo) was calculated with FAO Penman-Monteith equation. Pan evaporation (Epan) was measured by using Class A pan. Seasonal ETc was determined as 475 mm for cauliflower and 556 nun for red cabbage. Seasonal pan coefficient (kp=ETo/Epan) was determined as 0.82, and the seasonal crop coefficient (kc=ETc/ETo) was determined as 0.84 for cauliflower and 0.83 for red cabbage. So the evapotranspiration of cauliflower and red cabbage crops was estimated as 70% Class A pan evaporation.
基金the Knowledge Innovation Project of the Chinese Academy of Sciences (No. KZCX-SW-317-02).
文摘Maize (Zea mays L.), a staple crop grown from June to September during the rainy season on the North China Plain,is usually inter-planted in winter wheat (Triticum aestivum L.) fields about one week before harvesting of the winterwheat. In order to improve irrigation efficiency in this region of serious water shortage, field studies in 1999 and 2001, twodry seasons with less than average seasonal rainfall, were conducted with up to five irrigation applications to determineevapotranspiration, calculate the crop coefficient, and optimize the irrigation schedule with maize under mulch, as well asto establish the effects of irrigation timing and the number of applications on grain yield and water use efficiency (WUE)of maize. Results showed that with grain production at about 8 000 kg ha-1 the total evapotranspiration and WUE ofirrigated maize under mulch were about 380-400 mm and 2.0-2.2 kg m-3, respectively. Also in 2001 WUE of maizewith mulch for the treatment with three irrigations was 11.8% better than that without mulch. In the 1999 and 2001seasons, maize yield significantly improved (P = 0.05) with four irrigation applications, however, further increases werenot significant. At the same time there were no significant differences for WUE with two to four irrigation applications.In the 2001 season mulch lead to a decrease of 50 mm in the total soil evaporation, and the maize crop coefficient undermulch varied between 0.3-1.3 with a seasonal average of 1.0.
文摘The current study proposes a novel method using Excel Solver to estimate, from limited data, crop coefficient (Kc) in paddy fields under intermittent irrigation (11). The proposed method was examined in a field experiment conducted at Karang Sari Village, Bekasi, West Java, Indonesia during the first rice season of 2007/2008 (December 2007 to April 2008) in the rainy season. As the control, continuous flooding irrigation (CF) was applied to the conventional rice cultivation fields. Based on the observed water storage, Excel Solver was used to estimate crop evapotranspiration. Estimated crop evapotranspiration was used to compute Kc value, then the average Kc values at each growth stage were compared with that for the CF treatment. The estimation method was evaluated by comparing estimated crop evapotranspiration and the crop evapotranspiration derived by the well established FAO procedure. Excel Solver estimated crop evapotranspiration accurately with R2 values higher than 0.81. Accordingly, more than 81% of the FAO crop evapotranspiration was described by the proposed method. Thus, Kc value could be well determined from those estimated crop evapotranspiration. Under the II treatment, the average Kc values were 0.70, 1.06, 1.24 and 1:22 for the initial, crop development, reproductive and late stages, respectively. These values were lower than those under the CF treatment for initial and crop development stages because of a minimal soil evaporation and intense dryness during these stages. However, average Kc values under the II treatment were higher than those under the CF treatment at the reproductive and late stages, indicating that the II treatment promoted more plant activity particularly for dry biomass production as indicated by a greater number of tillers per hill.
文摘A field experiment was conducted throughout 2009/2010 in a sugarcane field of a commercial distillery located on the coastal area of Paraiba state, Brazil. The objectives were to determine sugarcane water requirements and to test the single and dual crop coefficients by comparing the calculated values of ET with measured ones. Crop evapotranspiration was determined by field water balance, reference evapotranspiration (ETo) by the Penman-Monteith approach, while single and dual crop coefficients were computed through the standard FAO-56 methodology. The experimental area was cultivated with irrigation applied weekly by a centre pivot system in addition to rainfall and the irrigation scheduling was based on 100% ETo. Three statistical tests, mean bias difference (MBD), normalized root mean square difference (NRMSD) and regression analysis, were used to evaluate the performance of single and dual crop coefficients. Results showed that there was a notable symmetry between ET measured and ET calculated by Kc dual. The ET values, calculated from Kc single, underestimated those obtained from soil water balance measurements by 36%.
文摘While the amount of water used by a crop can be measured using lysimeters or eddy covariance systems, it is more common to estimate this quantity based on weather data and crop-related factors. Among these approaches, the standard crop coefficient method has gained widespread use. A limitation of the standard crop coefficient approach is that it applies to “standard conditions” that are invariant from field to field. In this article, we describe a method for estimating daily crop water use (CWU) that is specific to individual fields. This method, the “spectral crop coefficient” approach, utilizes a crop coefficient numerically equivalent to the crop ground cover observed in a field using remote sensing. This “spectral crop coefficient” Ksp is multiplied by potential evapotranspiration determined from standard weather observations to estimate CWU. We present results from a study involving three farmers' fields in the Texas High Plains in which CWU estimated using the Ksp approach is compared to observed values obtained from eddy covariance measurements. Statistical analysis of the results suggests that the Ksp approach can produce reasonably accurate estimates of daily CWU under a variety of irrigation strategies from fully irrigated to dryland. These results suggest that the Ksp?approach could be effectively used in applications such as operational irrigation scheduling, where its field-specific nature could minimize over-irrigation and support water conservation.
文摘To develop basis for strategic or arranged decision making towards crop yield improvement in Thailand, a new method in which crop models could be used is essential. Therefore, the objective of this study was to measure cultivar specific parameters by using DSSAT (v4.7) Cropping Simulation Model (CSM) with five upland rice genotypes namely Dawk Pa-yawm, Mai Tahk, Bow Leb Nahng, Dawk Kha 50 and Dawk Kahm. Experiment was laid out in a Completely Randomized Design (CRD) with split plot design. Results showed that five upland rice genotypes had significantly affected each other by different temperature treatments (28°C, 30°C, 32°C) with grain yield, tops weight, harvest index, flowering, and maturity date. At the same time, all the phenological traits had highly significant variation with the genotypes. The cultivar specific parameters obtained by using a temperature tolerant cultivar (Basmati 385) with five upland genotypes involved in the DSSAT4.7-CSM. Model evaluation results indicated that utilizing the estimated cultivar coefficient parameters, model simulated well with varying temperature treatments as indicated by the agreement index (d-statistic) closer to unity. Hence, it was estimated that model calibration and evaluation was realistic in the limits of test cropping seasons and that CSM fitted with cultivar specific parameters can be used in simulation studies for investigation, farm managing or decision making. This electronic document is a “live” template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document.
基金This work was supported by the open Fund of State Key Laboratory of Remote Sensing Science(Grant No.PFSLRSS202023)the Qinghai Science and Technology Plan(Grant No.2019-SF-155)the National Natural Scientific Foundations of China(Grant No.41701403).
文摘Priestley-Taylor equation(PT)and the Penman-Monteith equation(PM)are commonly used methods for regional evapotranspiration monitoring,using the PT coefficient(α_(a))and PM crop/vegetation coefficient(K_(c)).This paper investigates the seasonal changes inα_(a)and K_(c)at five sites in Australia and China,to understand the relation-ship between environmental conditions and evapotranspiration when applying different evaporation estimation methods.The research shows that higher actual evapotranspiration does not lead to higherα_(a)and K_(c)values.α_(a)and K_(c)perform similarly in cropland and forest environments in both China and Australia.Bothα_(a)and K_(c)continuously increase to a peak during the growing season and then decrease to their lowest values during the winter season.Considering K_(c)’s similar performance toα_(a)and its greater data processing requirements,K_(c)has few advantages for estimating regional evapotranspiration.Applying the Priestley-Taylor equation with a regional𝛼indicator will enhance the accuracy and reduce the workload when estimating regional evapotranspiration for similar landcover types based on remote sensing.
文摘Searching for alternative methods for traditional irrigation is World trend at days due to a reduction in water and increased of drought due to climate changes therefore farmers need use modern methods of scheduling water and minimizing water losses while also increasing yield. To meet the future increasing demands water and food there is a need to utilize alternative methods to reduce evaporation, transpiration and deep percolation of water. Any countries use recycled water (drain and sewage) and desalination water from the sea or drains to irrigate crops plus computing actual crop evapotranspiration (ET<sub>c</sub>) so as to calculate the amount of water to apply to a crop. The paper aims to assess the actual evaporation and evaporation coefficient of carrots, by planting carrots in a field and the crop was exposed to several sources of water (DW and RW) and comparing ET<sub>c</sub>, K<sub>c</sub> and production among plots of three sites (A, B and C). The study used two types of irrigation water (drain water (DW) and river water (RW)). The results were to monthly rate and accumulated actual evapotranspiration to C (irrigation by RW only) more than A (67% RW and 33% DW) and B (17% RW and 83% DW) via 7% and 58%, respectively. The yield to C more than A and B by 17% and 75%, respectively. In conclusion the use of DW can cause a reduction in crop consumptive of carrot crops also causes a reduction in yield, crop length, root length, root size, canopy of crop, number of leaves and biomass of the plant therefore, the drainage water needs to treated before irrigating crops And making use of it to irrigate the fields and fill the shortfall in the amount of water from the river. The drain water helped on filling the water shortage due to climate changes and giving production of carrot crop but less than river water.
基金supported by the Innovation Program of Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (201003013)the National Basic Research Program of China(2010CB951702)
文摘The aim of this study was to assess the crop water demand and deficit of spring highland barley and discuss suitable irrigation systems for different regions in Tibet, China. Long-term trends in reference crop evapotranspiration and crop water demand were analyzed in different regions, together with crop water demand and deficit of spring highland barley under different precipitation frequencies. Results showed that precipitation trends during growth stages did not benefit the growth of spring highland barley. The crop coefficient of spring highland barley in Tibet was 0.87 and crop water demand was 389.0 ram. In general, a water deficit was found in Tibet, because precipitation was lower than water consumption of spring highland barley. The most severe water deficit were in the jointing to heading stage and the heading to wax ripeness stage, which are the most important growth stages for spring highland barley; water deficit in these two stages would be harmful to the yield. Water deficit showed different characteristics in different regions. In conclusion, irrigation systems may be more successful if based on an analysis of water deficit within different growth stages and in different regions.
基金Under the auspices of National Natural Science Foundation of China (No. 40571029)
文摘A non-dimensional relative sensitivity coefficient was employed to predict the responses of reference crop evapotranspiration (ET0) to perturbation of four climate variables in Tao'er River Basin of the northeastern China. Mean monthly ET0 and yearly ET0 from 1961 to 2005 were estimated with the FAO-56 Penman-Monteith Equation. A 45-year historical dataset of average monthly maximum/minimum air temperature, mean air temperature, wind speed, sunshine hours and relative humidity from 15 meteorological stations was used in the analysis. Results show that: 1) Sensitivity coefficients of wind speed, air temperature and sunshine hours were positive except for those of air tem- perature of Arxan Meteorological Station, while those of relative humidity were all negative. Relative humidity was the most sensitive variable in general for the Tao'er River Basin, followed by sunshine hours, wind speed and air tem- perature. 2) Similar to climate variable, monthly sensitivity coefficients exhibit large annual fluctuations. 3) Sensitivity coefficients for four climate variables all showed significant trends in seasonal/yearly series. Also, sensitivity coefficients of air temperature, sunshine hours and wind speed all showed significant trends in spring. 4) Among all sensitiv- ity coefficients, the average yearly sensitivity coefficient of relative humidity was highest throughout the basin and showed largest spatial variability. Longitudinal distribution of sensitivity coefficients for air temperature, relative hu- midity and sunshine hours was also found, which was similar to the distribution of the three climate variables.
文摘The common Soil in Egypt is clay soil so common irrigation system is tradition surface irrigation with 60% irrigation efficiency. Agricultural sector consumes more than 80% of water resources under surface irrigation (tradition methods). In arid and semi-arid regions consumptive use is the best index for irrigation requirements. A large part of the irrigation water applied to farm land is consumed by Evapotranspiration (ET). Irrigation water consumption under each of the physical and climatic conditions for large scale will be easier with remote sensing techniques. In Egypt, Agricultural cycle is often tow agricultural seasons yearly;summer and winter. Common summer crops are Maize, Rice and Cotton while common winter crops are Clover and Wheat. Landsat8 bands 4 and 5 provide Red (R) and Near Infra-Red (NIR) measurements and it used to calculate Normalized Deference Vegetation Index (NDVI) and monitoring cultivated areas. The cultivated land area was 3,277,311 ha in August 2013. In this paper Kc = 2 * NDVI ? 0.2 represents the relation between crop coefficient (Kc) and NDVI. Kc and Reference evapotranspiration (ETo) used to estimate ETc in Egypt. The main objective of this paper is studying the potential crop Evapotranspiration in Egypt using remote sensing techniques.
文摘An efficient water use requires accurate estimations of crop ET (evapotranspiration). However, an accurate ET estimation is really difficult to achieve when big regions such as irrigation districts or complete watersheds are involved. Satellite images are an alternative that can be used to estimate accurate crop ET for big regions. In the present study, two known methods were used to estimate crop ET, the METRIC model which was developed by the University of Idaho and a Kc-NDVI relationship. In the METRIC model, ET is estimated as a residual of the energy balance equation. The second method uses reference ET, and estimates a crop coefficient (K,.) as a linear function of the NDVI vegetation index. ET was estimated in a section of the Rio Mayo Irrigation District located in Sonora, Mexico using Landsat 7 satellite images. Crop ET of the main crops was estimated. Results show some differences between both methods. An average ET depth of 460 mm for the wheat average growing season was found when using METRIC, while an average ET depth of 421 mm was found when using the Kc-NDVI relationship. A water use total efficiency of 62% and 63% was found for METRIC and the Kc-NDVI relationship, respectively.
基金supported by the National Key Technology Research and Development Program of China (2017YFC0404301, 2016YFA0601602)the National Natural Science Foundation of China (51479209)+1 种基金the Application Foundation Research Project of Xinjiang Production and Construction Corps (2016AG003)the Talent Initiate Scientific Research Project (RCZX2015027)。
文摘Efficient agricultural water use is crucial for food safety and water conservation on a global scale. To quantitatively investigate the agricultural water-use efficiency in regions exhibiting the complex agricultural structure, this study developed an indicator named water footprint of crop values(WFV) that is based on the water footprint of crop production. Defined as the water volume used to produce a unit price of crop(m^3/CNY), the new indicator makes it feasible to directly compare the water footprint of different crops from an economic perspective, so as to comprehensively evaluate the water-use efficiency under the complex planting structure. On the basis of WFV, the study further proposed an indicator of structural water-use coefficient(SWUC), which is represented by the ratio of water-use efficiency for a given planting structure to the water efficiency for a reference crop and can quantitatively describe the impact of planting structure on agricultural water efficiency. Then, a case study was implemented in Xinjiang Uygur Autonomous Region of China. The temporal and spatial variations of WFV were assessed for the planting industries in 14 prefectures and cities of Xinjiang between 1991 and 2015. In addition, contribution rate analysis of WFV for different prefectures and cities was conducted to evaluate the variations of WFV caused by different influencing factors: agricultural input, climatic factors, and planting structure. Results from these analyses indicated first that the average WFV of planting industries in Xinjiang significantly decreased from 0.293 m^3/CNY in 1991 to 0.153 m^3/CNY in 2015, corresponding to an average annual change rate of –3.532%. WFV in 13 prefectures and cities(with the exception of Karamay) has declined significantly during the period of 1991–2015, indicating that agricultural water-use efficient has effectively improved. Second, the average SWUC in Xinjiang decreased from 1.17 to 1.08 m^3/CNY in the 1990 s, and then declined to 1.00 m^3/CNY in 2011–2015. The value of SWUC was highly consistent with the relative value of WFV in most prefectures and cities, showing that planting structure is one of the primary factors affecting regional agricultural water-use efficiency. Third, the contribution rate of WFV variations from human factors including agricultural input and planting structure was much more significant than that from climatic factors. However, the distribution of agricultural input and the adjustment of planting structure significantly differed among prefectures and cities, suggesting regional imbalances of agricultural development. This study indicated the feasibility and effectiveness of controlling agricultural water use through increasing technical input and rational selection of crops in the face of impending climate change. Specifically, we concluded that, the rational application of chemical fertilizers, the development of the fruit industry, and the strict restriction of the cotton industry should be implemented to improve the agricultural water-use efficiency in Xinjiang.
文摘Livestock rearing is one of the major occupations in India and is making significant contribution to the country GDP. The regional and seasonal variations in the teperature and rainfall distribution have been the major factors influencing the economy of a region. It is a matter of serious concern that out of 11 districts of central India, 9 districts are showing increasing trend in maximum temperature with a rate of 0.01°C to 0.15°C/year. A significant long-term decreasing trend (Slope = -4.26) was found in annual rainfall series at Jhansi. At Jhansi, moderate to severe drought occurs once in five years. But in the last decade, 7 years experienced moderate to disastrous drought in Jhansi region, wherein rainfall deficiency ranged between 40% and 60% from normal value. Of special mention was the year, 2006, which experienced a worst drought ever recorded for this region. Studies related to crop simulation model was carried out for fodder sorghum and its application for agronomic management and assessing the impact of climate change. Crop modeling studies on forage sorghum (C4) and cowpea (C3) showed increased dry matter biomass by 3% in sorghum but more prominent in cowpea by 46% under elevated CO2 from 330 ppm to 770 ppm. The interaction study of enhanced CO2 and temperature showed prominent negative impact on yields of both the crops. Evapotranspiration and crop coefficient (Kc) of several fodder crops i.e. berseem, lucerne, oat, sorghum, teosinte, maize + cowpea, guinea + berseem were worked out. In berseem, the highest Kc (1.81) was found during 2nd cutting followed by 3rd and 4th cuts. Estimates on irrigation scheduling for the guinea grass + berseem showed that the cropping system requires 7 irrigations at an interval ranging from 13 to 30 days to fulfill the 567.6 mm of water per season as net irrigation under mar soil (black) type whose actual water holding capacity (AWHC) is 175 mm. Similarly, if the cropping system is grown under kabar (AHWC = 140 mm) soil, then it requires nine irrigation with a total water requirement of 591.5 mm at an interval ranging from 10 to 24 days. For integrated pest management (IPM) scheme of lucerne, degree day based model was developed to monitor the lucerne weevil population in central region.