EVAPOTRANSPIRATION BY IRRIGATED ALFALFA AS RELATED TO SEASON AND GROWTH STAGE

1965 ◽  
Vol 45 (4) ◽  
pp. 309-313 ◽  
Author(s):  
K. K. Krogman ◽  
E. H. Hobbs
Keyword(s):  
Growth Stage ◽  
Conversion Factor ◽  
Potential Evapotranspiration ◽  
Balance Sheet ◽  
Ground Cover ◽  
Irrigation Scheduling ◽  
Evaporation Ratio ◽  
Moisture Balance ◽  
Evapotranspiration Rate ◽  
Soil Moisture Balance

The results of a plot experiment wherein three levels of irrigation were applied during three successive summers showed that the average daily rates of evapotranspiration by alfalfa ranged from 0.05 to 0.36 in. per day. The maximum evapotranspiration rate was associated with complete ground cover and at this stage equalled potential evapotranspiration. Except for early in the season the conversion factor for estimating evapotranspiration from evaporation for irrigation scheduling by the budget method or soil moisture balance sheet should approximate the potential evapotranspiration–evaporation ratio.

scholarly journals Effect of soil moisture stress on growth light azimuth and yield of dryland sorghum

MAUSAM ◽  
2022 ◽  
Vol 44 (3) ◽  
pp. 261-264
Author(s):  
H. P. DAS ◽  
A. N. KALE ◽  
A. S. PONKSHE
Keyword(s):  
Soil Moisture ◽  
Root Zone ◽  
Potential Evapotranspiration ◽  
Moisture Stress ◽  
Growth Cycle ◽  
Yield Reduction ◽  
Soil Moisture Stress ◽  
Growing Period ◽  
Moisture Balance ◽  
Soil Moisture Balance

Based on weekly data for 4 years (1986-1989) at Bellary, soil moisture balance for rabi sorghum has been worked out for both irrigated and non-irrigated conditions. These soil moisture values have been used to identify periods of water stress which the crop experienced. during the growth cycle. The extent of yield reduction due to the stress was then evaluated from the actual soil water content and total available water extent and discussed. The ratio of evapotranspiration to potential evapotranspiration and water requirement of the crop has also been worked out to assess the stress situation of the crop during its growing period. This ratio has been found to be related to moisture availability at the root zone.

scholarly journals Weighing Lysimeters for Developing Crop Coefficients and Efficient Irrigation Practices for Vegetable Crops

HortScience ◽  
2010 ◽  
Vol 45 (11) ◽  
pp. 1597-1604 ◽  
Author(s):  
David R. Bryla ◽  
Thomas J. Trout ◽  
James E. Ayars
Keyword(s):  
Potential Evapotranspiration ◽  
Irrigation Management ◽  
Quadratic Function ◽  
Ground Cover ◽  
Soil Surface ◽  
Irrigation Scheduling ◽  
Yield Potential ◽  
Vegetable Crops ◽  
Soil Water Conditions ◽  
Crop Coefficients

Large, precision weighing lysimeters are expensive but invaluable tools for measuring crop evapotranspiration and developing crop coefficients. Crop coefficients are used by both growers and researchers to estimate crop water use and accurately schedule irrigations. Two lysimeters of this type were installed in 2002 in central California to determine daily rates of crop and potential (grass) evapotranspiration and develop crop coefficients for better irrigation management of vegetable crops. From 2002 to 2006, the crop lysimeter was planted with broccoli, iceberg lettuce, bell pepper, and garlic. Basal crop coefficients, Kcb, defined as the ratio of crop to potential evapotranspiration when the soil surface is dry but transpiration in unlimited by soil water conditions, increased as a linear or quadratic function of the percentage of ground covered by vegetation. At midseason, when groundcover was greater than 70% to 90%, Kcb was ≈1.0 in broccoli, 0.95 in lettuce, and 1.1 in pepper, and Kcb of each remained the same until harvest. Garlic Kcb, in comparison, increased to 1.0 by the time the crop reached 80% ground cover, but with only 7% of additional coverage, Kcb continued to increase to 1.3, until irrigation was stopped to dry the crop for harvest. Three weeks after irrigation was cutoff, garlic Kcb declined rapidly to a value of 0.16 by harvest. Yields of each crop equaled or exceeded commercial averages for California with much less water in some cases than typically applied. The new crop coefficients will facilitate irrigation scheduling in the crops and help to achieve full yield potential without overirrigation.

Irrigation Scheduling Based on Evaporation and Crop Water Requirement for Summer Peanuts1

1984 ◽  
Vol 11 (1) ◽  
pp. 4-6 ◽  
Author(s):  
D. K. Pahalwan ◽  
R. S. Tripathi
Keyword(s):  
Water Use ◽  
Irrigation Water ◽  
Irrigation Scheduling ◽  
Water Requirement ◽  
Crop Water Requirement ◽  
Pan Evaporation ◽  
Crop Water ◽  
Formation Stage ◽  
Evaporation Ratio ◽  
Pod Development

Abstract Field experiment was conducted during dry season of 1981 and 1982 to determine the optimal irrigation schedule for summer peanuts (Arachis hypogaea L.) in relation to evaporative demand and crop water requirement at different growth stages. It was observed that peanut crop requires a higher irrigation frequency schedule during pegging to pod formation stage followed by pod development to maturity and planting to flowering stages. The higher pod yield and water use efficiency was obtained when irrigations were scheduled at an irrigation water to the cumulative pan evaporation ratio of 0.5 during planting to flowering, 0.9 during pegging to pod formation and 0.7 during pod development to maturity stage. The profile water contribution to total crop water use was higher under less frequent irrigation schedules particularly when the irrigations were scheduled at 0.5 irrigation water to the cumulative pan evaporation ratio up to the pod formation stage.

scholarly journals Optimisation of Irrigation Regime for Early Potatoes, Late Cauliflower, Early Cabbage and Celery

2013 ◽  
Vol 1 (No. 4) ◽  
pp. 139-152
Author(s):  
Zavadil Josef
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Field Experiments ◽  
Actual Evapotranspiration ◽  
Suction Pressure ◽  
Irrigation Regime ◽  
Marketable Yield ◽  
Moisture Balance ◽  
Seasonal Irrigation ◽  
Soil Moisture Balance

The paper deals with optimisation of threshold suction pressure of soil water on light soils for early potatoes, early cabbage, late cauliflower and celery on the basis of results of small-plot field experiments with differentiated irrigation regime. Experiments were conducted in 2003–2005. Threshold suction pressures of soil water were identical for all crops: 15 kPa in treatment I, 30 kPa in treatment II, 60 kPa in treatment III, and 120 kPa in treatment IV. Precipitation, air temperature and relative humidity, global solar radiation, wind speed and direction were measured by an automated meteorological station. Reference and actual evapotranspiration was determined for the experimental crops according to FAO Paper No. 56 and by means of a biological curve (BC) in 2003–2005. To compare these two methods of calculation of actual evapotranspiration the soil moisture balance was found out. Based on the influence on marketable yield and proportion of the crop quality grades it is possible to determine the optimum threshold suction pressure on light loamy-sand soils in early potatoes, late cauliflower and cabbage 30 kPa and in celery 15 kPa. 80% of available soil water capacity (ASWC) corresponds to the threshold suction pressure 30 kPa, and as much as 96% of ASWC corresponds to 15 kPa. The seasonal irrigation depths determined on the basis of soil moisture balance, in which the crop evapotranspiration (ETc) is calculated either according to FAO 56 or by the BC, are substantially different from the really achieved irriga­tion depths in the treatments where optimal suction pressure is maintained. For potatoes, the really achieved values of seasonal irrigation depths are nearer to the depths calculated by the BC, while for the other vegetables (cauliflower, cabbage and celery) they are more similar to the depths calculated by FAO 56 methodology. The theoretical irrigation depths calculated by the BC method sometimes differ substantially from those based on FAO 56. These differences are at maximum for cauliflower and celery and at minimum for cabbage and decrease with the decreasing irrigation depths.

scholarly journals Effect of controlled sprinkler chemigation on wheat crop in a sandy soil

2011 ◽  
Vol 6 (No. 2) ◽  
pp. 61-72
Author(s):  
M.A. Sayed ◽  
M.N.A. Bedaiwy
Keyword(s):  
Grain Yield ◽  
Irrigation Water ◽  
Root Zone ◽  
Nile Delta ◽  
Potential Evapotranspiration ◽  
Irrigation Treatment ◽  
Sprinkler Irrigation ◽  
Wheat Crop ◽  
Evapotranspiration Rate ◽  
Safe Limits

A two-year experiment was conducted in the desert west of the Nile Delta to study the effect of applying fertilizers and other agronomic chemicals through sprinkler irrigation water (a technique referred to as chemigation) on wheat grain yield. Experiment included three levels of irrigation inputs, namely: I<sub>1</sub> = potential evapotranspiration rate (ET<sub>p</sub>), I<sub>2</sub> = 0.8 ETp and I<sub>3</sub> = 0.6 ET<sub>p</sub>, and included two application method of fertilizers and herbicide (chemication and traditional). Applying chemigation resulted in significant increase in grain yield, ranging between 9.9% and 50.0% with averages of 43.2% and 14.5% over the first and second seasons, respectively. Irrigation treatment I<sub>1</sub> produced higher grain yield than the other two irrigation treatments both under traditional and chemigation methods as a result of better fertilizer distribution in the root zone. Grain yield associated with combined I<sub>1</sub> and chemigation was highest of all treatments and was greater than Egypt's national average by 14% and 9% for seasons 1 and 2, respectively. Chemigation resulted in more uniform distribution of nitrate-nitrogen throughout the root zone with nitrate levels falling within safe limits. Concentrations under traditional application resulted in lower levels in upper soil and greater levels at deeper soil of the root zone exceeding safe limits and subjecting the soil and groundwater to contamination hazards. For both N and K fertilizers, fertilizer use efficiency was greater under chemigation than under traditional application. Efficiencies increased with increasing irrigation water, apparently due to better fertilizer distribution. Applying herbicides with sprinkler irrigation water reduced weed infestation from 48% to 6.5%. As a result of improved yield under chemigation, an increase in revenue per hectare of 112.6% was achieved.

scholarly journals Evaluation and Bias Correction in WRF Model Forecasting of Precipitation and Potential Evapotranspiration

2019 ◽  
Vol 20 (5) ◽  
pp. 965-983 ◽  
Author(s):  
Theodor Bughici ◽  
Naftali Lazarovitch ◽  
Erick Fredj ◽  
Eran Tas
Keyword(s):  
Bias Correction ◽  
Potential Evapotranspiration ◽  
Irrigation Management ◽  
Hybrid Approach ◽  
Wrf Model ◽  
Irrigation Scheduling ◽  
Weather Research And Forecasting ◽  
Forecast Bias ◽  
Synoptic Conditions ◽  
High Bias

Abstract A reliable forecast of potential evapotranspiration (ET0) is key to precise irrigation scheduling toward reducing water and agrochemical use while optimizing crop yield. In this study, we examine the benefits of using the Weather Research and Forecasting (WRF) Model for ET0 and precipitation forecasts with simulations at a 3-km grid spatial resolution and an hourly temporal resolution output over Israel. The simulated parameters needed to calculate ET0 using the Penman–Monteith (PM) approach, as well as calculated ET0 and precipitation, were compared to observations from a network of meteorological stations. WRF forecasts of all PM meteorological parameters, except wind speed Ws, were significantly sensitive to seasonality and synoptic conditions, whereas forecasts of Ws consistently showed high bias associated with strong local effects, leading to high bias in the evaluated PM–ET0. Local Ws bias correction using observations on days preceding the forecast and interpolation of the resulting PM–ET0 to other locations led to significant improvement in ET0 forecasts over the investigated area. By using this hybrid forecast approach (WRFBC) that combines WRF numerical simulations with statistical bias corrections, daily ET0 forecast bias was reduced from an annual mean of 13% with WRF to 3% with WRFBC, while maintaining a high model–observation correlation. WRF was successful in predicting precipitation events on a daily event basis for all four forecast lead days. Considering the benefit of the hybrid approach for forecasting ET0, the WRF Model was found to be a high-potential tool for improving crop irrigation management.

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