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1.
A tool named DOPIR (Dimensioning Of Pressurized IRrigation) was developed to optimize the process of water abstraction from an aquifer for pressurized irrigation systems. This tool integrates the main factors throughout the irrigation process, from the water source to the emitter. The objective is to minimize the total cost of water abstraction and application (C T) (investment (C a) + operation (C op) per unit of irrigated area according to the type of aquifer, crop water requirement and electricity rate periods. To highlight the usefulness of this tool, DOPIR has been applied to a corn crop in Spain with a permanent sprinkler irrigation system, considering two types of aquifer: confined and unconfined. The effects of parameters such as the static water table in the aquifer (SWT), irrigated area (S), number of subunits in the plot (NS), sprinkler and lateral pipe spacing, and average application rate (ARa) on C T have been analyzed. Results show that energy cost (C e) is the most important component of C T (50–72 % in the case studies). Thus, it is very important to adapt the design and management of the irrigation and pumping system throughout the irrigation season to the energy rate periods.  相似文献   

2.
The aim of this study was to present a methodology to analyse the main factors that influence annual water application costs in centre pivot irrigation systems and to determine the most cost-effective centre pivot design, given the variables of machine length, lateral pipe diameter, sprinkler type (LEPA and fixed and rotating spray plate sprinklers (FSPS and RSPS)), system capacity, application efficiency, and water and energy costs for the irrigation of crops such as maize under conditions in Spain. Annual water application costs were calculated as the sum of the investment (Ca), energy (Ce), water (Cw), and equipment maintenance costs (Cm). Parameters used to assess the influences on pivot design were system capacity S c = 1.25 L s?1 ha?1; application efficiency Ea = 80% for FSPS, Ea = 85% for RSPS, and Ea = 90% for LEPA; water price P w = 0.06 € m?3 (0.081 US dollars); energy price Ene = 0.10 € kWh?1 (0.135 US dollars); net annual crop irrigation water requirement N n = 7,000 m3 ha?1 year?1; and net daily peak crop water requirement N nmax = 7.63 mm d?1 for maize. Results indicate that for plots smaller than 30 ha, the recommended pipeline diameter is 127.0 mm (5 in); for 30–40 ha, 168.3 mm (6 5/8 in); for 40–75 ha, 219.1 mm (8 5/8 in); and for 75–100 ha, 254.0 mm (10 in). A multidiameter pipe solution only slightly reduced water application costs in most cases studied. It was also determined that water costs and irrigation efficiency have a major influence on the total annual cost of water application; however, system capacity and energy price did not strongly affect total cost. For this reason, water application uniformity is very important and can be accomplished using a proper nozzle package and regular maintenance. The paper helps farmers determine the most cost-effective centre pivot design and management.  相似文献   

3.
We studied the suitability of empirical crop water stress index (CWSI) averaged over daylight hours (CWSId) for continuous monitoring of water status in apple trees. The relationships between a midday CWSI (CWSIm) and the CWSId and stem water potential (ψ stem), and soil water deficit (SWD) were investigated. The treatments were: (1) non-stressed where the soil water was close to field capacity and (2) mildly stressed where SWD fluctuated between 0 and a maximum allowable depletion (MAD of 50 %). The linear relationship between canopy and air temperature difference (ΔT) and air vapor pressure deficit (VPD) averaged over daylight hours resulted in a non-water-stressed baseline (NWSBL) with higher correlation (?T = ?0.97 VPD – 0.46, R 2 = 0.78, p < 0.001) compared with the conventional midday approach (?T = ?0.59 VPD – 0.67, R 2 = 0.51, p < 0.001). Wind speed and solar radiation showed no significant effect on the daylight NWSBL. There was no statistically meaningful relationship between midday ψ stem and CWSIm. The CWSId agreed well with SWD (R 2 = 0.70, p < 0.001), while the correlation between SWD and CWSIm was substantially weaker (R 2 = 0.38, p = 0.033). The CWSId exhibited high sensitivity to mild variations in the soil water content, suggesting it as a promising indicator of water availability in the root zone. The CWSId is stable under transitional weather conditions as it reflects the daily activity of an apple crop.  相似文献   

4.
To quantify night-time (S n) and diurnal (S d) tree water uptake, two sets of sap flow sensors (heat-pulse compensated) were installed per tree in the north-east and south-west sides of the trunk in three trees per treatment. There were two treatments: (1) control, irrigated with 100 % ETc (T100), and (2) deficit, irrigated at 60 % ETc (T60) with daily irrigations at the peak atmospheric demand (December–January). Normalised S n by trees was in the range of 15–25 % throughout the season, compared to normalised S d, for T100 and T60, respectively. Furthermore, S n was parabolically correlated to plant water status from the previous day, measured as midday stem water potential. We also found strong correlations between S n and nocturnal vapour pressure deficit for T100 and T60, indicating that nocturnal transpiration was significant for both treatments. Differences in S n were observed for the NE and SW sensors for T60, being significantly less for the NE side (sunny side) compared to the SW side (more shaded). No differences were observed for T100 regarding probe positioning.  相似文献   

5.
Use of literature crop coefficient (K c) values for quantifying evapotranspiration (ETc) under non-standard conditions such as plastic mulch, shallow water table, and sub-tropical conditions can lead to inaccurate ETc estimates. A 5-year experiment was conducted for fall crop growing seasons in south Florida to quantity bi-weekly ETc and K c for bell pepper grown under shallow water table and plastic mulch environments using large drainage lysimeters. The ETc values varied from 205 to 320 mm with a seasonal average of 267 mm. Average K c values for bell pepper for development, mid-season, and late stages were 1.05, 1.21, and 1.28, respectively. Higher than literature initial K c values were due to rainfall and use of sub-irrigation system to maintain artificially high water table which results in high soil moisture in the bare soil area—such high moisture results in high evaporation. The K c values from this study were statistically higher than literature values. Use of literature K c values resulted in underestimating ETc by 27–37%. The K c values would provide improved estimates of sub-irrigated pepper ETc in subtropical Florida and elsewhere with similar environment.  相似文献   

6.
Irrigation technologies [i.e., automatic timer, automatic timer with rain sensor, automatic timer with soil water sensor (SWS), and evapotranspiration (ET) controller] were compared in a bahiagrass plot study by measuring irrigation applied, water volumes drained, and NO3–N and NH4–N leached. All irrigation technologies were scheduled to irrigate on Sunday and Thursday. Three different irrigation depths were evaluated with the automatic timer: 15, 19, and 32 mm. SWS treatment allowed scheduled irrigation if soil water content was estimated to be below 70 % of water holding capacity, while the ET treatment allowed scheduled irrigation if soil water content was estimated to be below 50 % of plant available water. The rain sensor, SWS, and ET controller treatments applied significantly less water (p < 0.05) than the automatic timer treatment (which irrigates on specific days and times without regard to system conditions), reducing water by 17–49, 64–75, and 66–70 %, respectively. NO3–N and NH4–N were only significantly different after the second fertilizer application, which coincided with the 32 mm per event irrigation rate for the automatic timer treatment. Under these conditions, the automatic timer treatment had significantly greater NO3–N and NH4–N leachate than other treatments due to greater occurrence of soil water content exceeding water holding capacity, which resulted in drainage. Findings suggest that water can be saved using rain sensors, SWSs, or ET controllers and that leachate NO3–N and NH4–N can be reduced using rain sensors, SWSs, or ET controllers.  相似文献   

7.
Research was conducted in northern Colorado in 2011 to estimate the crop water stress index (CWSI) and actual transpiration (T a) of maize under a range of irrigation regimes. The main goal was to obtain these parameters with minimum instrumentation and measurements. The results confirmed that empirical baselines required for CWSI calculation are transferable within regions with similar climatic conditions, eliminating the need to develop them for each irrigation scheme. This means that maize CWSI can be determined using only two instruments: an infrared thermometer and an air temperature/relative humidity sensor. Reference evapotranspiration data obtained from a modified atmometer were similar to those estimated at a standard weather station, suggesting that maize T a can be calculated based on CWSI and by adding one additional instrument: a modified atmometer. Estimated CWSI during four hourly periods centered on solar noon was largest during the 2 h after solar noon. Hence, this time window is recommended for once-a-day data acquisition if the goal is to capture maximum stress level. Maize T a based on CWSI during the first hourly period (10:00–11:00) was closest to T a estimates from a widely used crop coefficient model. Thus, this time window is recommended if the goal is to monitor maize water use. Average CWSI over the 2 h after solar noon and during the study period (early August to late September, 2011) was 0.19, 0.57, and 0.20 for plots under full, low-frequency deficit, and high-frequency deficit irrigation regimes, respectively. During the same period (50 days), total maize T a based on the 10:00–11:00 CWSI was 218, 141, and 208 mm for the same treatments, respectively. These values were within 3 % of the results of the crop coefficient approach.  相似文献   

8.
Intercropping, drip irrigation, and the use of plastic mulch are important management practices, which can, when utilized simultaneously, increase crop production and save irrigation water. Investigating soil water dynamics in the root zone of the intercropping field under such conditions is essential in order to understand the combined effects of these practices and to promote their wider use. However, not much work has been done to investigate soil water dynamics in the root zone of drip-irrigated, strip intercropping fields under plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate soil water contents (SWC) at different locations, for different irrigation treatments, and with respect to dripper lines and plants (corn and tomatoes). Experimental data were then used to calibrate the HYDRUS (2D/3D) model. Comparison between experimental data and model simulations showed that HYDRUS (2D/3D) described different irrigation events and SWC in the root zone well, with average relative errors of 10.8, 9.5, and 11.6 % for irrigation treatments T1, T2, and T3, respectively, and with corresponding root mean square errors of 0.043, 0.035, and 0.040 cm3 cm?3, respectively. The results showed that the SWC in the shallow root zone (0–40 cm) was lower under non-mulched locations than under mulched locations, irrespective of the irrigation treatment, while no significant differences in the SWC were observed in the deeper root zone (40–100 cm). The SWC in the shallow root zone was significantly higher for the high irrigation treatment (T1) than for the low irrigation treatment, while, again, no differences were observed in the deeper root zone. Simulations of two-dimensional SWC distributions revealed that the low irrigation treatment (T3) produced serious severe water stress (with SWCs near the wilting point) in the 30–40 cm part of the root zone, and that using separate drip emitter lines for each crop is well suited for producing the optimal soil water distribution pattern in the root zone of the intercropping field. The results of this study can be very useful in designing an optimal irrigation plan for intercropped fields.  相似文献   

9.
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10.
The effect of irrigation water quality was investigated in a commercial mandarin orchard during four growing seasons using fresh water (EC ≈ 1 dS m?1), irrigators’ association water (EC = 1–3 dS m?1) and reclaimed water (RW) (EC ≈ 3 dS m?1). RW had higher concentration of macro- and micronutrients, especially potassium, and the phytotoxic elements, boron, sodium and chlorides. The microbiological load in the different irrigation water sources showed a high seasonal variability, and all water sources occasionally exceeded health standards to irrigate fruit trees. In the RW treatment, an increase in soil salinity and leaf boron concentration was observed. The nutritional contribution of RW was high, providing 24 and 15 % of the annual nitrogen and phosphorus (N and P2O5) fertilizer requirement for mandarin oranges, respectively, and RW treatment satisfied the entire potassium requirement (K2O). An important fluctuation in the crop production was observed during the 4 years in the different water quality treatments. In general, quality parameters of mandarins were not affected. The results provide additional evidence that long-term effects must be studied to test sustainability when using RW irrigation on fruit trees.  相似文献   

11.
Water and fertilizer applications should be limited due to scarce resources and environmental protection aspects. An analysis of crop yield production and profit maximization was conducted to determine the optimal water and nitrogen allocation. In this analysis based on crop production and cost functions, a series of equations for determination of applied water and nitrogen for three conditions of maximum yield (wm and Nm, respectively), maximum profit under limited land (wl and Nl, respectively) and maximum profit under limited water (ww and Nw, respectively) were derived. The associated crop production function was determined from the results of a corn experiment with four levels of nitrogen fertilization and varying amounts of applied water via a line source of sprinkler irrigation. The previously derived equations were also applied to the experimental field data and finally the optimum amounts of applied water and nitrogen were determined at different conditions (wm, wl, and ww for water and Nm, Nl, and Nw for nitrogen, respectively). At present market value (15.55 Rls/m3 for water and 652 Rls/kg for nitrogen) the amounts of wm, wl, and ww were 1.0, 0.99, and 0.74 m, respectively, and the amounts of Nm, Nl, and Nw were 212, 212, and 206 kg N/ha, respectively. Because of the low price of nitrogen, the optimum amounts of nitrogen at three mentioned conditions were similar. But if the price of nitrogen and water are increased (i.e. 50000 Rls/kg N and 100 Rls/m3 water), then the amounts of applied nitrogen and water at the mentioned three conditions would be 212, 67, and 61 kg N/ha, and 1.00, 0.93, 0.84 m, respectively. When water is limiting, the optimum amount of applied water would not be different by changing the water price, however, it may be increased by a little amount when the nitrogen price is increased.  相似文献   

12.
Reliable estimation of actual evapotranspiration rates (ET) may be achieved if extensive information on the soil–plant–atmosphere system is available. Agricultural and irrigation engineers facing the problem of rational irrigation planning, rarely have at their disposal such information. Therefore, there is a demand for simpler approaches to estimate actual evapotranspiration. In this paper, a semi-empirical approach is proposed for estimating actual water losses from crops. It is assumed that the ratio of actual to maximum evapotranspiration (ET/ETm) is an exponential function of the water content w in the root-zone, of the form: ET/ETm=exp[c(w−wfc)/(w−wwp)], where c is a constant introduced to adjust the decrease of the ratio ET/ETm according to what is observed for the climatic conditions, soils and crops of Greece, wfc the water content at field capacity and wwp denotes the water content at wilting point. Verification of the above approach for estimating actual evapotranspiration was achieved by comparing ET-values obtained by the soil moisture profile changes and the ET-values obtained by the above equation. Meteorological, crop and soil data required were collected from experimental fields of the Agricultural University of Athens (38°23′N, 23°6′E). The agreement of actual versus computed ET-values for three widely grown crops in Greece (cotton, wheat and maize) may be considered as satisfactory.  相似文献   

13.
Improving irrigation water management is becoming important to produce a profitable crop in South Texas as the water supplies shrink. This study was conducted to investigate grain yield responses of corn (Zea mays) under irrigation management based on crop evapotranspiration (ETC) as well as a possibility to monitor plant water deficiencies using some of physiological and environmental factors. Three commercial corn cultivars were grown in a center-pivot-irrigated field with low energy precision application (LEPA) at Texas AgriLife Research Center in Uvalde, TX from 2002 to 2004. The field was treated with conventional and reduced tillage practices and irrigation regimes of 100%, 75%, and 50% ETC. Grain yield was increased as irrigation increased. There were significant differences between 100% and 50% ETC in volumetric water content (θ), leaf relative water content (RWC), and canopy temperature (TC). It is considered that irrigation management of corn at 75% ETC is feasible with 10% reduction of grain yield and with increased water use efficiency (WUE). The greatest WUE (1.6 g m−2 mm−1) achieved at 456 mm of water input while grain yield plateaued at less than 600 mm. The result demonstrates that ETC-based irrigation can be one of the efficient water delivery schemes. The results also demonstrate that grain yield reduction of corn is qualitatively describable using the variables of RWC and TC. Therefore, it appears that water status can be monitored with measurement of the variables, promising future development of real-time irrigation scheduling.  相似文献   

14.
Saline water has been included as an important substitutable resource for fresh water in agricultural irrigation in many fresh water scarce regions. In order to make good use of saline water for agricultural irrigation in North China, a semi-humid area, a 3-year field experiment was carried out to study the possibility of using saline water for supplement irrigation of cucumber. Saline water was applied via mulched drip irrigation. The average electrical conductivity of irrigation water (ECiw) was 1.1, 2.2, 2.9, 3.5 and 4.2 dS/m in 2003 and 2004, and 1.1, 2.2, 3.5, 4.2 and 4.9 dS/m in 2005. Throughout cucumber-growing season, the soil matric potential at 0.2 m depth immediately under drip emitter was kept higher than −20 kPa and saline water was applied after cucumber seedling stage. The experimental results revealed that cucumber fruit number per plant and yield decreased by 5.7% per unit increase in ECiw. The maximum yield loss was around 25% for ECiw of 4.9 dS/m, compared with 1.1 dS/m. Cucumber seasonal accumulative water use decreased linearly over the range of 1.5-6.9% per unit increase in ECiw. As to the average root zone ECe (electrical conductivity of saturated paste extract), cucumber yield and water use decreased by 10.8 and 10.3% for each unit of ECe increase in the root zone (within 40 cm away from emitter and 40 cm depths), respectively. After 3 years irrigation with saline water, there was no obvious tendency for ECe to increase in the soil profile of 0-90 cm depths. So in North China, or similar semi-humid area, when there is no enough fresh water for irrigation, saline water up to 4.9 dS/m can be used to irrigate field culture cucumbers at the expense of some yield loss.  相似文献   

15.
A laboratory experiment was carried out to study the emitter performance of three commonly used emitter types with the application of freshwater and treated sewage effluent (TSE). The three emitter types are the inline-labyrinth types of emitters with a turbulent flow (E1) and a laminar flow (E2) and the online pressure-compensation type of emitters (E3). The qualities of freshwater and TSE were measured, and the emitter performance was evaluated, using the relative emitter discharge, the reduction of emitter discharge (qreduction), the coefficient of variation of emitter discharge (CV), the emission uniformity (EU), Christiansen uniformity coefficient (CU), and the percentage of emitter clogging (Pclog). Results showed that all indices were affected by water quality, emitter type and time of operation. The values of qreduction, CV and Pclog for the TSE treatments were greater than those for the freshwater treatments. The values of EU and CU for the TSE treatment were lower than those for the freshwater treatments. The qreduction, CV and Pclog increased and the EU and CU decreased as operational time increasing for the TSE treatment. For both freshwater and TSE treatments, the emitter clogging was more severe, the CV was greater, and the EU and CU were smaller for emitter type E2 than those for emitter types E1 and E3. Thus a more severe clogging was found for emitter type E2 due to its smaller flow-path dimension and higher manufacturing coefficient of variation in addition to the high pH values and relatively high total dissolved solids (TDS) values of the used water. Analyses of water quality and the precipitation components inside and at the outlet of emitters revealed that chemical precipitation was the main reason for emitter clogging due to high pH and ions’ concentration, especially in the TSE. Flushing emitters and drip pipes did not efficiently alleviate emitter clogging caused by chemical precipitation. In a conclusion, emitter type E3 showed a better anti-clogging function than emitter types E1 and E2 and was recommended for irrigation with TSE in the Beijing area of China.  相似文献   

16.
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17.
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   

18.
This study was conducted to determine the effect of different supplemental irrigation rates on chickpea grown under semiarid climatic conditions. Chickpea plots were irrigated with drip irrigation system and irrigation rates included the applications of 0 (I 0) 25 (I 25), 50 (I 50), 75 (I 75), 100 (I 100), and 125 % (I 125) of gravimetrically measured soil water deficit. Plant height, 1,000 seed weight, yield, biomass, and harvest index (HI) parameters were determined in addition to yield-water functions, evapotranspiration (ET), water use efficiency (WUE), and irrigation water use efficiency (IWUE). Significant differences were noted for plant height (ranging from 24.0 to 37.5 cm), 1,000 seed weight (ranging from 192.0 to 428.7 g), and aboveground biomass (ranging from 2,722 to 6,083 kg ha?1) for water applications of I 0 and I 125. Statistical analysis indicated a strong relationship between the amount of irrigation and yield, which ranged from 256.5 to 1,957.3 kg ha?1. Harvest index values ranged between 0.092 and 0.325, while WUE and IWUE values ranged between 1.15–4.55 and 1.34–8.36 (kg ha?1 mm?1), respectively.  相似文献   

19.
Camelina sativa (L.) Crantz is a promising, biodiesel-producing oilseed that could potentially be implemented as a low-input alternative crop for production in the arid southwestern USA. However, little is known about camelina’s water use, irrigation management, and agronomic characteristics in this arid environment. Camelina experiments were conducted for 2 years (January to May in 2008 and 2010) in Maricopa, Arizona, to evaluate the effectiveness of previously developed heat unit and remote sensing basal crop coefficient (K cb ) methods for predicting camelina crop evapotranspiration (ET) and irrigation scheduling. Besides K cb methods, additional treatment factors included two different irrigation scheduling soil water depletion (SWD) levels (45 and 65 %) and two levels of seasonal N applications within a randomized complete block design with 4 blocks. Soil water content measurements taken in all treatment plots and applied in soil water balance calculations were used to evaluate the predicted ET. The heat-unit K cb method was updated and validated during the second experiment to predict ET to within 12–13 % of the ET calculated by the soil water balance. The remote sensing K cb method predicted ET within 7–10 % of the soil water balance. Seasonal ET from the soil water balance was significantly greater for the remote sensing than heat-unit K cb method and significantly greater for the 45 than 65 % SWD level. However, final seed yield means, which varied from 1,500 to 1,640 kg ha?1 for treatments, were not significantly different between treatments or years. Seed oil contents averaged 45 % in both years. Seed yield was found to be linearly related to seasonal ET with maximum yield occurring at about 470–490 mm of seasonal ET. Differences in camelina seed yields due to seasonal N applications (69–144 kg N ha?1 over the 2 years) were not significant. Further investigations are needed to characterize camelina yield response over a wider range of irrigation and N inputs.  相似文献   

20.
As sources of irrigation water are decreasing, efficient use of surface irrigation is essential. The purpose of this study is to determine if partially-wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation in an alluvial clay soil under cultivated grape production. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water was applied when available soil water reached 65 % and 50 %, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. Coefficient of variation (CV) was 5.2 and 9.5 % for WT and DT under furrow irrigation system comparing with 7.8 % in border, respectively. Water was deeply percolated as 11.9 and 19.2 % for wet and dry furrow treatments respectively, compared with 12.8 % for control, with no deficit in the irrigated area. Partially-wetted furrow irrigation had greater water-efficiency and grape yield than dry furrow and traditional border irrigation, where application efficiency achieved as 88.1 % for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg /ha). The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (t 0 ) in minute for WT and DT treatments as: Z WT ?=?0.528?t 0 0.6, Z DT ?=?1.2?t 0 0.501, I WT ?=?19?t 0 ?0.4, I DT ?=?36?t 0 ?0.498. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The irrigation parameters and coefficients, and soil water distribution have been also evaluated.  相似文献   

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