Wheat Evapotranspiration Research Articles

The water-use efficiency of winter wheat and maize on a salt-affected soil in the Huang Huai Hai river plain of China

This paper deals with the water-use efficiency of winter wheat ( Triticum aestivum L.) and maize ( Zea mays L.) on a salt-affected soil in the Huang Huai Hai river plain of China. A strong linear relationship was found between the dry above ground biomass and evapotranspiration (ET) for winter wheat (48 kg ha −1 mm −1) and maize (38 kg ha −1 mm −1). A similar result was obtained for the grain yield of winter wheat (10 kg ha −1 mm −1). The harvest index of winter wheat decreases at increasing evapotranspiration: i.e. from about 0.4 down to 0.3 when evapotranspiration increases from 200 to 380 mm. Application of the yield-decrease — evapotranspiration-decrease model of Stewart et al. (1977) to divide evapotranspiration in soil evaporation and transpiration resulted for winter wheat in a total soil evaporation of 9 mm (3% of total evapotranspiration) and for maize of 62 mm (17.5% of total evapotranspiration). The relationship between grain yield of winter wheat and irrigation depth could be approached by a quadratic curve indicating that with increasing amount of irrigation water yield increase becomes less. Soil salinity increased during the dry season mainly due to capillary rise and decreased during the rainy season in summer by leaching. The capillary rise during the dry season was estimated from the chloride concentration of the soil water at a depth of 2 m and the increase of the chloride content in the layer 0–2 m and amounted to about 55 mm. The decrease in chloride content in the layer 0–2 m during the rainy season counterbalances the chloride increase in the dry season.

Effect of irrigation scheduling on growth, yield and evapotranspiration of wheat in sodic soils

To evaluate the critical growth stage for irrigation scheduling of wheat ( Triticum aestivum L.), a field experiment was conducted at Karnal, India during the winter season of 1986–87 and 1987–88 in a sodic soil with pH 9.2, and exchangeable sodium percent ( esp) 38. An increase in the irrigation frequency resulted in greater relative growth rate, rooting density, productive tiller per meter and grain yield of wheat. The three irrigations given at crown root initiation, tillering and milk stage gave significantly higher grain yield as compared to other treatment with three irrigations. The evapotranspiration ( et) of the crop increased as the crop season advanced and reached its peak from 60 to 90 days after sowing ( das). Maximum water use efficiency ( wue) was recorded when three irrigations were given at crown root initiation, tillering and milk stage rather than at other growth stages. Most of the et occurred from the 0–15 cm soil layer and increased from lower layers (15–30, 30–60, and 60–90 cm soil depth) with an increase in the irrigation frequency, however the total amount of et from all the layers was always greater under higher irrigation frequency.

POTENTIAL EVAPOTRANSPIRATION IN THE SOUTHERN ALBERTA CHINOOK REGION

Several methods and equations exist in the literature for predicting potential evapotranspiration (PE), but the use of most of these equations is limited by the amount of climatic input data they require. The Jense-Haise equation requires only mean air temperature and solar radiation data but it appears to yield low estimates for the southern Alberta chinook region where the prevailing weather factor is wind. An empirical method was developed to modify the Jensen-Haise equation to account for the wind variable. The PE estimations obtained by the modified Jensen-Haise equation were evaluated by some widely known methods. An average of 20% improvement in seasonal PE was obtained. The modified equation was used as a driving function to estimate evapotranspiration and soil moisture for wheat, barley, and canola crops grown in 1987. The statistical analyses conducted on the measured and calculated soil moisture data indicated that soil moistures computed with the modified equation were not significantly differ...

Evapotranspiration, pan evaporation and soil water relationships for wheat ( Triticum aestivum)

Controlled irrigation experiments were conducted for wheat grown in lysimeters having undisturbed soil profiles and protected from rainfall with transparent plexiglass roofs. Crop evapotranspiration during different crop growth stages and its relationships with Class A pan evaporation and soil water parameters were studied. The actual evapotranspiration during different crop growth stages was greatly influenced by amount and time of irrigation. The ratio of the maximum evapotranspiration and Class A pan evaporation increased linearly from germination to 46 days after sowing and remained constant at 1.45 from 46 to 76 days. Then the ratio decreased linearly towards the crop ripening. The actual evapotranspiration was equal to the maximum evapotranspiration up to the critical value of relative soil water, and then the actual evapotranspiration decreased at a very fast rate with further decrease in relative soil water. The critical value of the relative soil water varied from 0.65 to 0.84 during the crop growth-stage periods late tillering-heading and dough ripe-ripe, respectively.

Evaluation of evapotranspiration and crop coefficient values for Sonalika wheat (HD 15 53 )

For evaluation or evapotranspiration and crop coefficient values for Sonalika wheat, ly-simeter study was done for three years at Jabalpur. The average evapotranspiration of Sonahka wheat was found to be 410.58mm and the range was 3.53. 51mm to 488.51 mm. The crop coefficient values as evaluated from the three years data were found quite suitable for estimating the evapotranspiration of Sonahka wheat at Jabalpur and it is suggested, can be used for other wheat varieties having the same growth season, at Jabalpur and nearby areas.

Daily Patterns of Apparent Photosynthesis and Evapotranspiration in a Developing Winter Wheat Crop1

AbstractHigh temperatures strongly influence apparent photosynthesis (AP), evapotranspiration (ET), and leaf area index (LAI) of winter wheat (Triticum aestivum L.) in semi‐arid regions. Our objectives were to relate temperature and short‐wave solar radiation (SR) to crop AP, ET, and LAI in a field environment. Two aluminum frame chambers covered with mylar plastic and occupying 0.74 m2 of soil surface area were used with infrared gas analyzers to measure AP and ET on ‘Wanser’ winter wheat grown in Ritzville silt loam (Mesic Calciorthidic Haploxerolls). Calculations of AP and ET were made from the respective differences between chamber intake and exhaust CO2 and H2O concentrations.On clear, high SR days, maximum AP declined from 4.2 to 2.9 g CO2m−2hour−1 from stem extension through the watery ripe developmental stage. During that same period, maximum daily ET ranged between 440 and 600 g H2O m−2 hour−1, but did not decline as LAI declined from 2.0 to 1.1. A midday reduction in AP was observed when leaf temperatures (TL) approached 25 C corresponding to high daily values of ET and SR at anthesis, water ripe, and milky ripe stages. Since measurements of ET were over dry soil and assumed to represent plant transpiration, substantial stomatal closure was apparently not responsible for the decline in AP on those days because a concomitant reduction in ET was not always observed. Temperatures that were above optimal for AP most likely caused the midday decline in AP. This interpretation was consistent with water use efficiency (WUE) values, expressed as AP/ET, which were lowest at midday and generally declined as the crop matured.Total daily AP from heading through anthesis (15 days) on clear and partly cloudy days did not decline appreciably (ranging from 30.5 to 32.4 g CO2 m−21 day−1) even though LAI declined 17% during that period. On clear days, high ET was associated with high SR and high temperatures. Temperatures tended to depress AP so that WUE was greater on partly cloudy and overcast days than on clear days at a given developmental stage. Under the climatic conditions of this study, WUE could be increased with early maturing cultivars that avoid the high late season heat load commonly associated with wheat production in this region.

Practical prediction of actual evapotranspiration

A simplified method of estimating actual evapotranspiration of crops during an irrigation interval in which soil-moisture deficits occur is presented. With some simplifying assumptions, a relation is developed between a crop-dependent critical leaf water potential, potential evapotranspiration rates, and the fraction of available soil-moisture at which reduction in evapotranspiration occurs (Fig. 1). This relation was tested by comparing calculated and measured rates of actual evapotranspiration for maize, alfalfa, sorghum, wheat, potato, and sorghum crops (Fig. 2, A through F). Calculated values of actual crop water use were close to measured ones, except for the potato crop. Sensitivity tests indicated that, for crops with a critical leaf water potential above −7.5 bars, i.e. −0.75 MPa, errors exceeding 10 per cent were made in estimating the fraction of available soil moisture at which reduction in evapotranspiration occurs.

Studies on the rates of water use of dwarf wheat and their relationship with potential values based on the climatological approach

Field studies were conducted to assess the field evapotranspiration of dwarf wheat under semi-arid conditions of Hissar (India), and to compare the same with the values obtained by various formulae using meteorological parameters. First irrigation to the crop was given three weeks after sowing and subsequent irrigations when about 50% of the available soil moisture was depleted from the root zone. Measured quantity of water was applied according to the soil moisture deficit in the root zone.

Predicting Water Needs of Wheat from U.S. Class A Pan Evaporimeter at Pantnagar, India

SUMMARYIn field experiments at Pantnagar, India during 1968–70, evapo-transpiration (ET) in wheat was significantly correlated with U.S.W.B. class A pan evaporation (E0) when the crop was in an active stage of growth and moisture was non-limiting (50 or 25% depletion of available moisture). The estimated ET was higher than E0, probably due to ‘oasis’ and ‘clothesline’ effects. When ET measurements were made at varying distances from the upwind side during the subsequent three years, it was found that ET decreased with increasing distance downwind with a conspicuous border effect up to about 25 m distance. In the absence of advective heating, i.e. in extreme downwind locations, the actual ET was 480, 533 and 530 mm during 1970–71, 1971–72 and 1972–73 respectively.

Simulation Model for Evapotranspiration of Wheat: Effect of Evaporative Conditions

A simulation model for tracing soil moisture fluctuations under irrigated wheat in a semi-arid climate is presented. The model is based on a function relating evapotranspiration to soil moisture and evaporative conditions as measured by means of Class A pan. The reliability of the model is presented with respect to experimental data, and its performance is examined.