首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 41 毫秒
1.
Determination of temporal and spatial distribution of water use (WU) within agricultural land is critical for irrigation management and could be achieved by remotely sensed data. The aim of this study was to estimate WU of dwarf green beans under excessive and limited irrigation water application conditions through indicators based on remotely sensed data. For this purpose, field experiments were conducted comprising of six different irrigation water levels. Soil water content, climatic parameters, canopy temperature and spectral reflectance were all monitored. Reference evapotranspiration (ET0), crop coefficient Kc and potential crop evapotraspiration (ETc) were calculated by means of methods described in FAO-56. In addition, WU values were determined by using soil water balance residual and various indexes were calculated. Water use fraction (WUF), which represents both excessive and limited irrigation applications, was defined through WU, ET0 and Kc. Based on the relationships between WUF and remotely sensed indexes, WU of each irrigation treatments were then estimated. According to comparisons between estimated and measured WU, in general crop water stress index (CWSI) can be offered for monitoring of irrigated land. At the same time, under water stress, correlation between measured WU and estimated WU based on CWSI was the highest too. However, canopy-air temperature difference (Tc − Ta) is more reliable than others for excessive water use conditions. Where there is no data related to canopy temperature, some of spectral vegetation indexes could be preferable in the estimation of WU.  相似文献   

2.
A sensitivity analysis of irrigation water requirements at the regional scale was conducted for the humid southeastern United States. The GIS-based water resources and agricultural permitting and planning system (GWRAPPS), a regional scale, GIS-based, crop water requirement model, was used to simulate the effect of climate, soil, and crop parameters on crop irrigation requirements. The effects of reference evapotranspiration (ETo) methods, available soil water holding capacities (ASWHC), crop coefficients (Kc), and crop root zone depths (z) were quantified for 203 ferneries and 152 potato farms. The irrigation demand exhibited a positive relationship with Kc and z, a negative relationship with ASWHC, and seasonal variations depending on the choice of ETo methods. The average irrigation demand was most sensitive to the choice of Kc with a 10% shift in Kc values resulting in approximately 15% change in irrigation requirements. Most ETo methods performed reasonably well in estimating annual irrigation requirements as compared to the FAO-56 PM method. However, large differences in monthly irrigation estimates were observed due to the effect of the seasonal variability exhibited by the methods. Our results suggested that the selection of ETo method is more critical when modeling irrigation requirements at a shorter temporal scale (daily or monthly) as necessary for many applications, such as daily irrigation scheduling, than at a longer temporal scale (seasonal or annual). The irrigation requirements were more sensitive to z when the resultant timing of irrigation coincided with rainfall events. When compared with the overall average of the irrigation requirements differences, the site-to-site variability was low for Kc values and high for the other variables. In particular, soil properties had considerable average regional differences and variability among sites. Thus, the extrapolation of site-specific sensitivity studies may not be appropriate for the determination of regional responses crop water demand.  相似文献   

3.
Consumptive water use and crop coefficients of irrigated sunflower   总被引：2，自引：1，他引：1  
In semi-arid environments, the use of irrigation is necessary for sunflower production to reach its maximum potential. The aim of this study was to quantify the consumptive water use and crop coefficients of irrigated sunflower (Helianthus annuus L.) without soil water limitations during two growing seasons. The experimental work was conducted in the lysimeter facilities located in Albacete (Central Spain). A weighing lysimeter with an overall resolution of 250 g was used to measure the daily sunflower evapotranspiration throughout the growing season under sprinkler irrigation. The lysimeter container was 2.3 m × 2.7 m × 1.7 m deep, with an approximate total weight of 14.5 Mg. Daily ET c values were calculated as the difference between lysimeter mass losses and lysimeter mass gains divided by the lysimeter area. In the lysimeter, sprinkler irrigation was applied to replace cumulative ET c, thus maintaining non-limiting soil water conditions. Seasonal lysimeter ET c was 619 mm in 2009 and 576 mm in 2011. The higher ET c value in 2009 was due to earlier planting and a longer growing season with the maximum cover coinciding with the maximum ET o period. For the two study years, maximum average K c values reached values of approximately 1.10 and 1.20, respectively, during mid-season stage and coincided with maximum ground cover values of 75 and 88 %, respectively. The dual crop coefficient approach was used to separate crop transpiration (K cb) from soil evaporation (K e). As the crop canopy expanded, K cb values increased while the K e values decreased. The seasonal evaporation component was estimated to be about 25 % of ET c. Linear relationships were found between the lysimeter K cb and the canopy ground cover (f c) for the each season, and a single relationship that related K cb to growing degree-days was established allowing extrapolation of our results to other environments.  相似文献   

4.
A simple irrigation scheduling approach for pecans   总被引：1，自引：0，他引：1  
Pecans are a major crop in New Mexico's Lower Rio Grande Valley (LRGV). It is estimated that New Mexico is responsible for about 21% of the world's pecan production (Lillywhite et al., 2007). Currently, approximately 12,000 ha of pecan orchards at various stages of growth consume 45% of the area's irrigation water. Pecan evapotranspiration (ET) varies with age, canopy cover, soil type, crop density and method of water management. Intense competition for the LRGV's limited water supply has created a serious need for better water management through improved irrigation scheduling. Annual pecan ET ranges from as low as 500 mm to as high as 1400 mm. Diversity of the pecan crop coefficient (Kc) and ET makes the task of irrigation scheduling for this crop very complicated. Using remote sensing technology and field ET measurements, a simple relationship was developed to relate crop coefficient and ET to canopy cover. This relationship is then used in combination with climate data to calculate daily and weekly water requirements for each orchard. The difference between annual ET values estimated from canopy cover and values measured with an eddy covariance flux tower ranged from 2 to 5%. The average ratio of estimated monthly ET values over measured ET values was 1.03 with the standard error of the estimate ranging from 10 to 20 mm/month. This methodology provides a simple tool that farmers can use to schedule irrigation of pecan orchards. Even though the methodology was developed for irrigation scheduling in the LRGV, it can be used in other locations by transferring the reference crop coefficients using Kc-GDD relationships.  相似文献   

5.
New cultivars of sorghum for biomass energy production are currently available. This crop has a positive energy balance being irrigation water the largest energy consumer during the growing cycle. Thence, it is important to know the biomass sorghum water requirements, in order to minimize irrigation losses, thus saving water and energy. The objective of this study was to quantify the water use and crop coefficients of irrigated biomass sorghum without soil water limitations during two growing seasons. A weighing lysimeter located in Albacete (Central Spain) was used to measure the daily biomass sorghum evapotranspiration (ETc) throughout the growing season under sprinkler irrigation. Seasonal lysimeter ETc was 721 mm in 2007 and 691 mm in 2010. The 4 % higher ETc value in 2007 was due to an 8 % higher evaporative demand in that year. Maximum average K c values of 1.17 in 2007 and 1.21 in 2010 were reached during the mid-season stage. The average K c values for the 2 years of study were K c-ini: 0.64 and K c-mid: 1.19. The seasonal evaporation component was estimated to be about 18 % of ETc. The average basal K c (K cb) values for the two study years were K cb-ini: 0.11 and K cb-mid: 1.17. The good linear relationship found between K cb values and the fraction of ground cover (f c) and the excellent agreement found between Normalized Difference Vegetation Index and different biophysical parameters, such as K cb and f c, will allow monitoring and estimating the spatially distributed water requirements of biomass sorghum at field and regional scales.  相似文献   

6.
Vast rainfed rice area (12 million ha) of eastern India remains fallow after rainy season rice due to lack of appropriate water and crop management strategies inspite of having favourable natural resources, human labourers and good market prospects. In this study, a short duration crop, maize, was tried as test crop with different levels of irrigation during winter season after rainy season rice to increase productivity and cropping intensity of rainfed rice area of the region. Maize hybrid of 120 days duration was grown with phenology based irrigation scheduling viz., one irrigation at early vegetative stage, one irrigation at tassel initiation, two irrigation at tassel initiation + grain filling, three irrigation at early vegetative + tassel initiation + grain filling and four irrigation at early vegetative + tassel initiation + silking + grain-filling stages. Study revealed that one irrigation at tassel initiation stage was more beneficial than that of at early vegetative stage. Upto three irrigation, water use efficiency (WUE) was increased linearly with increased number of irrigation. With four irrigations, the yield was higher, but WUE was lower than that of three irrigations, which might be due to increased water application resulted in increase crop water use without a corresponding increase of yield for the crop with four irrigations. The crop coefficients (Kc) at different stages of the crop were derived after computing actual water use using field water balance approach. The crop coefficients of 0.42–0.47, 0.90–0.97, 1.25–1.33, and 0.58–0.61 were derived at initial, development, mid and late season, respectively with three to four irrigation. Study showed that leaf area index (LAI) was significantly correlated with Kc values with the R2 values of 0.93. When LAI exceeded 3.0, the Kc value was 1. Study revealed that the Kc values for the development and mid season stage were slightly higher to that obtained by the procedure proposed by FAO, which might be due to local advection.  相似文献   

7.
Crop coefficient methodologies are widely used to estimate actual crop evapotranspiration (ETc) for determining irrigation scheduling. Generalized crop coefficient curves presented in the literature are limited to providing estimates of ETc for “optimum” crop condition within a field, which often need to be modified for local conditions and cultural practices, as well as adjusted for the variations from normal crop and weather conditions that might occur during a given growing season. Consequently, the uncertainties associated with generalized crop coefficients can result in ETc estimates that are significantly different from actual ETc, which could ultimately contribute to poor irrigation water management. Some important crop properties such as percent cover and leaf area index have been modeled with various vegetation indices (VIs), providing a means to quantify real-time crop variations from remotely-sensed VI observations. Limited research has also shown that VIs can be used to estimate the basal crop coefficient (K cb) for several crops, including corn and cotton. The objective of this research was to develop a model for estimating K cb values from observations of the normalized difference vegetation index (NDVI) for spring wheat. The K cb data were derived from back-calculations of the FAO-56 dual crop coefficient procedures using field data obtained during two wheat experiments conducted during 1993–1994 and 1995–1996 in Maricopa, Arizona. The performance of the K cb model for estimating ETc was evaluated using data from a third wheat experiment in 1996–1997, also in Maricopa, Arizona. The K cb was modeled as a function of a normalized quantity for NDVI, using a third-order polynomial regression relationship (r 2=0.90, n=232). The estimated seasonal ETc for the 1996–1997 season agreed to within −33 mm (−5%) to 18 mm (3%) of measured ETc. However, the mean absolute percent difference between the estimated and measured daily ETc varied from 9% to 10%, which was similar to the 10% variation for K cb that was unexplained by NDVI. The preliminary evaluation suggests that remotely-sensed NDVI observations could provide real-time K cb estimates for determining the actual wheat ETc during the growing season.  相似文献   

8.
The methods for estimating temporal and spatial variation of crop evapotranspiration are useful tools for irrigation scheduling and regional water allocation. The purpose of this study was to develop a method for mapping spatial distribution of crop evapotranspiration and analyze the temporal and spatial variation of spring wheat evapotranspiration in the Shiyang river basin in Northwest China in the last 50 years. DEM-based methods were employed to estimate the spatial distribution of spring wheat evapotranspiration (ETc). Reference crop evapotranspiration (ET0) was calculated with the Penman–Monteith equation using meteorological data measured from eight stations in the basin. Crop coefficient (Kc) was determined from measured evapotranspiration in spring wheat season in the region. The results showed that ETc gradually increased in the upper reaches of the basin in the last 50 years, while the middle reaches showed a significant decreasing trend, and in other regions, no significant trend was found. These changes can be attributed to expansion of irrigation areas and climate change. The multiple regression analysis between ETc and altitude, latitude, and aspect were carried out for eight weather stations and the relationships were used to map ETc for the basin. The spatial variations of ETc were analyzed for three typical growing seasons based their precipitation. Results showed that long-term average ETc over cultivated land was increasing from 270 mm in southwest mountainous area to 591 mm in northeast oasis of the basin, and the relative error between the estimated ETc in spring wheat growing season by reference evapotranspiration (ET0) and crop coefficient (Kc), and the interpolated ETc was within 11.1%.  相似文献   

9.
Improved water management through precise crop water requirement determination is needed to improve the efficiency of water use in agricultural production. As a result, appropriate irrigation scheduling which can lead to water saving, improvements in the yield and income can be designed. In this study, three non-weighing lysimeters having dimensions of 2 m × 1 m × 2 m were used to determine water requirement (ETc) and crop coefficient (Kc) of onion (Bombay Red cultivar). Reference crop evapotranspiration (ETo) was determined using weather data recorded at the site. The measured ETc values were 51.3 mm, 140.5 mm, 144.8 mm, and 53.9 mm during the initial, development, mid-season and late season growth stages respectively. Crop coefficient (Kc) values, calculated as ratio of ETc to ETo, were 0.47, 0.99, and 0.46 during the initial and mid-season stages and end of late season. Furthermore, third-order polynomials were fitted well to predict the crop coefficient values as functions of growing degree-days (GDD).  相似文献   

10.
A study was conducted in the San Joaquin Valley of California on Merlot to determine the interaction of applied water amounts [at 0.4, 0.8, and 1.2 of estimated vineyard evapotranspiration (ETc)] and leaf removal (at berry set or veraison) in the fruiting zone on productivity. Shaded area was measured beneath the canopy of the 1.2 irrigation treatment at solar noon throughout the study to provide an estimate of seasonal crop coefficients (K c). Vine water status was assessed across treatments and years by measuring midday leaf water potential (Ψl). The maximum K c determined from the percent shaded area was 0.7 at the row spacing of 3.66?m and canopy type that developed a “California Sprawl.” Irrigation treatment had a significant effect on midday Ψl and no such effect for leaf removal. Clusters exposed to direct solar radiation had significantly higher temperatures and lower cluster Ψ than clusters in the shade. Irrigation treatment had a significant effect on berry weight, soluble solids, and titratable acidity. Yields of vines significantly increased as applied water amounts increased. In this wine grape production area, profitability is dependent upon yield. This study provided a reliable estimate of ETc and applied water amounts to maximize yield.  相似文献   

11.
Cotton (Gossypium hirsutum L.) is the most important industrial and summer cash crop in Syria and many other countries in the arid areas but there are concerns about future production levels, given the high water requirements and the decline in water availability. Most farmers in Syria aim to maximize yield per unit of land regardless of the quantity of water applied. Water losses can be reduced and water productivity (yield per unit of water consumed) improved by applying deficit irrigation, but this requires a better understanding of crop response to various levels of water stress. This paper presents results from a 3-year study (2004-2006) conducted in northern Syria to quantify cotton yield response to different levels of water and fertilizer. The experiment included four irrigation levels and three levels of nitrogen (N) fertilizer under drip irrigation. The overall mean cotton (lint plus seed, or lintseed) yield was 2502 kg ha−1, ranging from 1520 kg ha−1 under 40% irrigation to 3460 kg ha−1 under 100% irrigation. Mean water productivity (WPET) was 0.36 kg lintseed per m3 of crop actual evapotranspiration (ETc), ranging from 0.32 kg m−3 under 40% irrigation to 0.39 kg m−3 under the 100% treatment. Results suggest that deficit irrigation does not improve biological water productivity of drip-irrigated cotton. Water and fertilizer levels (especially the former) have significant effects on yield, crop growth and WPET. Water, but not N level, has a highly significant effect on crop ETc. The study provides production functions relating cotton yield to ETc as well as soil water content at planting. These functions are useful for irrigation optimization and for forecasting the impact of water rationing and drought on regional water budgets and agricultural economies. The WPET values obtained in this study compare well with those reported from the southwestern USA, Argentina and other developed cotton producing regions. Most importantly, these WPET values are double the current values in Syria, suggesting that improved irrigation water and system management can improve WPET, and thus enhance conservation and sustainability in this water-scarce region.  相似文献   

12.
Intensification of olive cultivation by shifting a tree crop that was traditionally rain fed to irrigated conditions, calls for improved knowledge of tree water requirements as an input for precise irrigation scheduling. Because olive is an evergreen tree crop grown in areas of substantial rainfall, the estimation of crop evapotranspiration (ET) of orchards that vary widely in canopy cover, should be preferably partitioned into its evaporation and transpiration components. A simple, functional method to estimate olive ET using crop coefficients (K c=ET/ET0) based on a minimum of parameters is preferred for practical purposes. We developed functional relationships for calculating the crop coefficient, K c, for a given month of the year in any type of olive orchard, and thus its water requirements once the reference ET (ET0) is known. The method calculates the monthly K c as the sum of four components: tree transpiration (K p), direct evaporation of the water intercepted by the canopy (K pd), evaporation from the soil (K s1) and evaporation from the areas wetted by the emitters (K s2). The expression used to calculate K p requires knowledge of tree density and canopy volume. Other parameters needed for the calculation of the K c’s include the ET0, the fraction of the soil surface wetted by the emitters and irrigation interval. The functional equations for K p, K pd, K s1 and K s2 were fitted to mean monthly values obtained by averaging 20-year outputs of the daily time step model of Testi et al. (this issue), that was used to simulate 124 different orchard scenarios.  相似文献   

13.
Water requirements of subsurface drip-irrigated faba bean in California   总被引：1，自引：0，他引：1  
A 3-year study was done in central California to determine the water requirements for growing faba bean (Vicia faba L.) as a winter cover crop using subsurface drip irrigation (SDI). Water was applied at 0, 50, and 100% of the estimated crop evapotranspiration (ETc) the first 2 years and 50, 100, and 150% ETc the third year, with drip laterals installed 0.30, 0.45, or 0.60 m deep. Rainfall was above normal the first year (>330 mm) and irrigation had no effect on crop production. Irrigation improved production and water-use efficiency the following years, however. Production was higher when drip laterals were located at 0.30 or 0.45 m than at 0.60 m depth, even though roots tended to be concentrated near the laterals (later in the season) regardless of depth. Overall, well-irrigated faba bean required 231-297 mm of water to produce 3.0-4.4 t haу of dry vegetative biomass.  相似文献   

14.
Florida ranks first in citrus production, with nearly 68% of all U.S. citrus growing in the season 2005-2006. Most of the citrus groves are located from central to south Florida, and agricultural irrigation permitting is regulated by three of Florida's five water management districts. Most of the permitting for citrus production in Highlands, Polk and Hillsborough counties is conducted by the Southwest Florida Water Management District (SWFWMD), and quantities are based on the District's AGMOD computer program. In 2003, the SWFWMD implemented new permit criteria so that permitted amounts were more representative of actual water use. This paper compares grower reported citrus irrigation water use in Highlands, Polk and Hillsborough counties from 1994 through 2005 with permitted and theoretical irrigation requirements calculated by a daily water balance. Two different sets of crop coefficients (Kc's) developed for citrus in Florida were compared in the daily soil water balance calculation of theoretical irrigation requirements. The percentage of irrigated area considered in this study ranged from 40 to 60% to simulate a range of grower practices. Meteorological data from two weather stations and additional rainfall information from 50 locations within the three counties was used in the water balance. Missing and error values in the meteorological historical record data were filled with weather generators. The multiannual average water consumption (including cold protection water use) from growers ranged from 243 (Hillsborough) to 406 mm (Highlands) and the multiannual average permitted irrigation requirement (without cold protection) ranged from 295 to 557 mm. The simulated gross irrigation requirements under different scenarios of location-Kc-wetted area were variable but mostly lower than the limits established by the district, except for some scenarios in Polk County, whose maximum simulated irrigation value reached 578 mm year−1. In general, permitted limits recommended by the SWFWMD seem to be reasonable for the actual water use by growers in these counties.  相似文献   

15.
A 3-year study was conducted in the eastern Mediterranean region of northern Syria to develop crop coefficient, K c, for drip-irrigated short-season cotton (Gossypium hirsutum L.). Two sets of K c curves were determined, the generalized K c published by the UN’s Food and Agriculture Organization (FAO) that was adjusted for local climate, and the locally developed K c as the ratio of measured cotton evapotranspiration to calculated reference evapotranspiration. The adjusted FAO K c curves were the same for the 3 years. However, the locally developed K c curves not only differed among the 3 years, but also from the adjusted FAO K c. During the mid-season stage, the adjusted FAO K c was 24% higher than the locally developed value of 1.05. Variations in locally developed K c values were caused by normal year-to-year variations in irrigation timing and amount, suggesting sensitivity of K c that cautions against the use of locally developed K c based on limited data (i.e., a single season). On the season, the overestimation of crop evapotranspiration by using adjusted FAO K c was substantial and equivalent to 150 mm water or about two additional irrigations per season. Results caution against blind application of published FAO K c curve, suggesting some local or regional calibration for increased accuracy.  相似文献   

16.
Crop coefficients are a widely used and universally accepted method for estimating the crop evapotranspiration (ETc) component in irrigation scheduling programs. However, uncertainties of generalized basal crop coefficient (Kcb) curves can contribute to ETc estimates that are substantially different from actual ETc. Limited research with corn has shown improvements to irrigation scheduling due to better water-use estimation and more appropriate timing of irrigations when Kcb estimates derived from remotely sensed multispectral vegetation indices (VIs) were incorporated into irrigation-scheduling algorithms. The purpose of this article was to develop and evaluate a Kcb estimation model based on observations of the normalized difference vegetation index (NDVI) for a full-season cotton grown in the desert southwestern USA. The Kcb data used in developing the relationship with NDVI were derived from back-calculations of the FAO-56 dual crop coefficient procedures using field data obtained during two cotton experiments conducted during 1990 and 1991 at a site in central Arizona. The estimation model consisted of two regression relations: a linear function of Kcb versus NDVI (r2=0.97, n=68) used to estimate Kcb from early vegetative growth to effective full cover, and a multiple regression of Kcb as a function of NDVI and cumulative growing-degree-days (GDD) (r2=0.82, n=64) used to estimate Kcb after effective full cover was attained. The NDVI for cotton at effective full cover was ~0.80; this value was used to mark the point at which the model transferred from the linear to the multiple regression function. An initial evaluation of the performance of the model was made by incorporating Kcb estimates, based on NDVI measurements and the developed regression functions, within the FAO-56 dual procedures and comparing the estimated ETc with field observations from two cotton plots collected during an experiment in central Arizona in 1998. Preliminary results indicate that the ETc based on the NDVI-Kcb model provided close estimates of actual ETc.Communicated by R. Evans  相似文献   

17.
An accurate estimation of crop evapotranspiration (ET c) is very useful for appropriate water management; hence, an accurate and user-friendly model is needed to support related irrigation decisions. In this view, a study was developed aimed at estimating the ET c of winter wheat–summer maize crop sequence in the North China through eddy covariance measurements, to calibrate and validate the SIMDualKc model, to estimate the basal crop coefficients (K cb) for both crops and to partition ET c into soil evaporation and crop transpiration. Two years of field experimentation of that crop sequence were used to calibrate and validate the SIMDualKc model and to derive K cb using eddy covariance measurements. Various indicators have shown the goodness of fit of the model, with estimated values very close to the observed ones and estimate errors close to 0.5 mm d?1. The initial, mid-season and end basal crop coefficients for wheat were 0.25, 1.15 and 0.30, respectively, and those for maize were 0.15, 1.15 and 0.45, thus close to those proposed in FAO56 guidelines. The soil evaporation represented near 80 % of ET c for the initial stages of winter wheat and summer maize and decreased to only 5–6 % during the mid-season period. Evaporation during the full crop season averaged 28 % for winter wheat and 40 % for summer maize. The importance of wetting frequency and crop ground coverage in controlling soil evaporation was evidenced.  相似文献   

18.
In cold, semi-arid areas, the options for crop diversification are limited by climate and by the water supply available. Growing irrigated crops outside the main season is not easy, because of climatic and market constraints. We carried out an experiment in Albacete, Central Spain, to measure the water use (evapotranspiration, ET) of broccoli (Brassica oleracea L. var. italica Plenck) planted in late summer and harvested at the end of fall. A weighing lysimeter was used to measure the seasonal ET under sprinkler irrigation. Consumptive use reached 359 mm for a period of 109 days after transplanting. The crop coefficient (Kc) for broccoli was obtained and compared to the standard recommendations for normal planting dates. Dual crop coefficient computations of the lysimeter ET data indicated that evaporation represented 31% of seasonal ET. An analysis of the variation in daily Kc values at a time of full cover suggested that the use of a grass lysimeter as a reference ET (ETo) was superior to using the ASCE Penman-Monteith (ASCE PM) equation at hourly time steps, which in turn caused less variability in Kc than when using the FAO-56 Penman-Monteith (FAO-56 PM) equation at daily time steps for the ETo calculation. An additional experiment aimed at evaluating the yield response to applied irrigation water by the drip method (seven treatments, from 59 to 108% of ETc) generated a production function that gave maximum yields of near 12 t ha−1 at an irrigation level of 345 mm, and a water use efficiency of 3.37 kg m−3. It is concluded that growing broccoli in the fall season is a viable alternative for crop diversification, as the lower yields obtained here may be more than compensated for by the higher produce prices in autumn, at a time of the year where irrigation water demand for other crops is very low.  相似文献   

19.
Accurate prediction of crop coefficient (K c) is necessary for proper irrigation management. We explored CropSyst for determining irrigation requirements of apple trees and for accuracy of K c prediction. Values of K c were compared to those obtained, over 2002–2010, from lysimeter-grown trees. Over these years, trees had different ratios of height (H) to width (W). CropSyst predicted irrigation requirements using tree light interception and water uptake sub-model components. Parameters of the model were adjusted using data obtained from the lysimeter in 2010. Tree light interception sub-model was verified by 2007 data. After parameterization, good agreement was found between simulated and measured K c over different seasons. The porosity coefficient of the canopy was related to changes in tree’s H/W ratio and leaf overlapping. Accordingly, different porosity values could be estimated for each year. When yearly changes in canopy porosity was considered, CropSyst improved K c prediction and generated relevant information for managing irrigation under changing canopy shape for apple trees.  相似文献   

20.
Irrigation scheduling based on the daily historical crop evapotranspiration (ETh) data was theoretically and experimentally assessed for the major soil-grown greenhouse horticultural crops on the Almería coast in order to improve irrigation efficiency. Overall, the simulated seasonal ETh values for different crop cycles from 41 greenhouses were not significantly different from the corresponding values of real-time crop evapotranspiration (ETc). Additionally, for the main greenhouse crops on the Almería coast, the simulated values of the maximum cumulative soil water deficit in each of the 15 consecutive growth cycles (1988–2002) were determined using simple soil-water balances comparing daily ETh and ETc values to schedule irrigation. In most cases, no soil-water deficits affecting greenhouse crop productivity were detected, but the few cases found led us to also assess experimentally the use of ETh for irrigation scheduling of greenhouse horticultural crops. The response of five greenhouse crops to water applications scheduled with daily estimates of ETh and ETc was evaluated in a typical enarenado soil. In tomato, fruit yield did not differ statistically between irrigation treatments, but the spring green bean irrigated using the ETh data presented lower yield than that irrigated using the ETc data. In the remaining experiments, the irrigation-management method based on ETh data was modified to consider the standard deviation of the inter-annual greenhouse reference ET. No differences between irrigation treatments were found for productivity of pepper, zucchini and melon crops.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号