Cumulative Reference Evapotranspiration Research Articles

Modeling Yield of Irrigated and Rainfed Bean in Central and Southern Sinaloa State, Mexico, Based on Essential Climate Variables

The goal was to model irrigated (IBY) and rainfed (RBY) bean yields in central (Culiacán) and southern (Rosario) Sinaloa state as a function of the essential climate variables soil moisture, temperature, reference evapotranspiration, and precipitation. For Sinaloa, for the period 1982–2013 (October–March), the following were calculated: (a) temperatures, (b) average degree days for the bean, (c) cumulative reference evapotranspiration, and (d) cumulative effective precipitation. For essential climate variables, (e) daily soil moisture obtained from the European Space Agency and (f) IBY and RBY from the Agrifood and Fisheries Information Service were used. Multiple linear regressions were significant for predicting IBY–RBY (dependent variables) as a function of essential climate variables (independent variables). The four models obtained were significantly predictive: IBY–Culiacán (Pearson correlation (PC) = 0.590 > Pearson critical correlation (CPC) = |0.349|), RBY–Culiacán (PC = 0.734 > CPC = |0.349|), IBY–Rosario (PC = 0.621 > CPC = |0.355|), and RBY–Rosario (PC = 0.532 > CPC = |0.349|). Due to the lack of irrigation depth data, many studies only focus on modeling RBY; this study is the first in Sinaloa to predict IBY and RBY based on essential climate variables, contributing to the production of sustainable food.

Evapotranspiration from pilot-scale vertical flow subsurface constructed wetlands in arid area

This paper aims to conduct a comparative evaluation of evapotranspiration (ET) rates in two experimental pilot-scales vertical flow subsurface constructed wetlands carried out in south east of Algeria (Touggourt), planted separately with P. australis (Ph) and T. latifolia (Ty) in two different substrate types with constant hydraulic loading rate under arid climatic conditions. An estimate of crop coefficient (Kc) for the two macrophytes based on climate conditions and the plant growth was also provided. Two kinds of vertical flow subsurface systems has been tested in the hottest period of the year 2018 over five months (April-August): first with fine gravel (G) (experiment 1), and second with sand (S) (experiment 2). During this period, the cumulative ETTy-G, ETPh-G and ETNp-G in the 1st experiment were 206, 276 and 125 mm, whereas in the 2nd experiment; the cumulative ETTy-S, ETPh-S and ETNp-S were 833, 968 and 635 mm, respectively. Comparing these results with cumulative reference evapotranspiration (ET0), ET0 value (426 mm) was higher than ET in the 1st experiment, and lower than in the 2nd experiment. Cumulative ET values in planted lysimeters were found to be different and higher than unplanted ones. Moreover, the highest accumulated ET value was obtained with P. australis bed which was found to have higher accumulated ET values than T. latifolia bed. Regarding the crop coefficient (Kc), the average seasonal value of Kc in the 1st experiment was relatively smaller than 2nd experiment. The Kc Ph-S value was almost three times the Kc Ph-G, and Kc Ty-S values were also almost four times the Kc Ty-G.In general, this study demonstrated that ET and Kc are dependent on climate conditions, the macrophytes growth as well as on the type of substrate in which the macrophytes are planted.

Technical feasibility of using suboptimal irrigation in maize cropping

Maize (Zea mays L.) is one of the main cereal crops grown around the world and is widely used as food, feed and raw material in various industries. However, the crop is sensitive to weather conditions, and this causes large variations in yield between crop seasons. Suboptimal irrigation can be used to secure reasonable yields with increased water productivity. For maize grown offseason in the Cerrado biome of Brazil, there is little knowledge about the benefits of suboptimal irrigation. This study was designed to evaluate the effect of different irrigation amounts and two Brachiaria cultivars intercropped with maize on maize grain yield, biomass production for silage and water productivity in the second crop season. The study was conducted at Embrapa Milho e Sorgo Experimental Station, Sete Lagoas, MG, Brazil, in 2018 and 2019. Six irrigation levels were obtained by using a line-source sprinkler irrigation system. The irrigation levels used ranged from 94% to 11% of the cumulative reference evapotranspiration (ET0) in 2018, and from 90% to 34% of ET0 in 2019. Suboptimal irrigation above a certain level did not cause a significant decrease in silage biomass (59% and 71% of the ET0, in 2018 and 2019, respectively) and grain productivity (48% and 60% of the ET0, in 2018 and 2019, respectively). Additionally, there was an increase in crop water productivity and irrigation water productivity, for biomass of both silage and grains. The results demonstrate the potential of suboptimal irrigation as a strategy to reduce water resource usage while maintaining acceptable productivity levels.

The effects of substrate depth and irrigation regime, on seeded Sedum species grown on urban extensive green roof systems under semi-arid Μediterranean climatic conditions

Green roofs constitute a promising technology for reintroducing lost flora in degraded urban environments. The present study aimed to evaluate the growth and ground coverage capacity of seeded Sedums grown on shallow extensive green roofs under semi-arid Mediterranean climatic conditions. Treatments included: a) two types of seed mixtures (M1 containing seeds from 16 different Sedum species and M2 containing seeds from 28 different Sedum species; b) two substrate depths (6 cm and 12 cm) and c) two different irrigation regimes (high and low) during the dry summer seasons of the three-year study period: i) 15% and 0% of the cumulative reference evapotranspiration (ETo) in year 2012, ii) 60% and 30% of ETo in year 2013 and iii) 30% and 0% of ETo in year 2014. Growth performance was evaluated based on the total number of the Sedum plants and their ground coverage rate over the three-year study period. Out of the 16 and 28 Sedum species contained in mixtures M1 and M2, respectively, only four species (S. acre, S. album, S. reflexum, S. sexangulare) were able to survive for the duration of the study period. The seeded Sedum plants did not provide adequate growth or ground coverage. Their plant number decreased abruptly soon after the imposition of the first water stress in 2012 and remained at low numbers throughout the study period. The ground coverage rate was extremely slow. At the end of the three-year study period, Sedum plants of the M1 seed mixture growing in both deep and shallow substrate depths and under high irrigation regimes provided ground coverage of 51.9% and 48.7%, respectively, while the same treatments of the M2 seed mixture provided ground coverage of 25.5% and 19.2%, respectively. All the remaining treatments provided minimal final coverage ranging from 3.1% to 0.5%. Although the seed mixture type exhibited minimal impact on total plant number and ground coverage, S. album and S. sexangulare were not able to grow in the M2 mixture. Overall, the seeded Sedum species exhibited reduced capacity to sustain growth under the Mediterranean climatic conditions, especially during the summer periods and under the imposition of water stress.

Performance of methods for estimation of table beet water requirement in Alagoas

ABSTRACT Optimization of water use in agriculture is fundamental, particularly in regions where water scarcity is intense, requiring the adoption of technologies that promote increased irrigation efficiency. The objective of this study was to evaluate evapotranspiration models and to estimate the crop coefficients of beet grown in a drainage lysimeter in the Agreste region of Alagoas. The experiment was conducted at the Campus of the Federal University of Alagoas - UFAL, in the municipality of Arapiraca, AL, between March and April 2014. Crop evapotranspiration (ETc) was estimated in drainage lysimeters and reference evapotranspiration (ETo) by Penman-Monteith-FAO 56 and Hargreaves-Samani methods. The Hargreaves-Samani method presented a good performance index for ETo estimation compared with the Penman-Monteith-FAO method, indicating that it is adequate for the study area. Beet ETc showed a cumulative demand of 202.11 mm for a cumulative reference evapotranspiration of 152.00 mm. Kc values determined using the Penman-Monteith-FAO 56 and Hargreaves-Samani methods were overestimated, in comparison to the Kc values of the FAO-56 standard method. With the obtained results, it is possible to correct the equations of the methods for the region, allowing for adequate irrigation management.

Evapotranspiration and crop coefficients of Moringa oleifera under semi-arid conditions in Pernambuco

ABSTRACT Efficient water use in agriculture is fundamental, especially in semi-arid regions where water scarcity is intense. The aim of this study was to estimate water requirements and crop coefficients in the different phenological stages of Moringa oleifera. The experiment was carried out from February to April 2015 at the Experimental Unit for Reuse and Hydrological Management, located in Mutuca, PE (7º 15’ 18’’ S, 35º 52’’ 40’’ W, 550 m). A lysimeter was used to estimate crop evapotranspiration. Reference evapotranspiration (ETo) was estimated by indirect methods. In the lysimeter, soil salinity and leaf water potential of the crop were monitored. The direct and indirect methods presented an excellent performance compared with the standard grass-lysimeter, especially Hargreaves-Samani, which presented a remarkable result for the study area. Crop coefficients (Kc) ranged from 0.73 to 1.73 in the different phenological stages. Moringa crop evapotranspiration (ETc) exhibited temporal variations, with a cumulative rate of 139.8 mm, for a cumulative reference evapotranspiration of 130.97 mm. Moringa plants showed slight water restriction, at the times of lower solar radiation.

Determining input values for a simple parametric model to estimate evaporation from vineyard soils with special reference to clay content and trellis system

Estimating soil evaporation (Es) is an important part of modelling vineyard evapotranspiration for irrigation purposes. Furthermore, quantification of possible soil texture and trellis effects is essential. Daily Es from six topsoils packed into lysimeters was measured under grapevines on slanting and vertical trellises, respectively. Following irrigation, cumulative soil evaporation (ΣEs) from the bare, untilled soils over 14-day drying cycles was plotted against cumulative reference evapotranspiration (ΣETo) to determine Es transition from the constant rate stage (Stage 1) to the falling-rate stage (Stage 2). During Stages 1 and 2, rate of Es is determined by atmospheric conditions and soil properties, respectively. Slopes of ΣEs vs square root of ΣETo plots in Stage 2 provided the input constant (β value) for each soil. In Stage 1, ΣEs was almost equal to ΣETo but the ratio varied as grapevine canopies developed. The β values varied between 2.15 ± 0.09 mm0.5 and 4.68 ± 0.14 mm0.5. The β values were best related to clay content (R2 was 0.7861 and 0.5108 for horizontal and vertical canopies, respectively). The vertical trellis seemed to have a windbreak effect that tended to reduce Es compared to the slanting trellis. Therefore, clay content and trellis orientation effects on β need to be considered.

Interannual and seasonal variability in evapotranspiration and energy partitioning over the alpine riparian shrub Myricaria squamosa Desv. on Qinghai–Tibet Plateau

The Qinghai–Tibet Plateau is a sensitive area of global climate changes, and riparian ecosystems are thought as “hotspots” for climate change adaptation, but little work has been conducted regarding the alpine riparian ecosystems on the Qinghai–Tibet Plateau. We measured evapotranspiration (ET) and surface energy fluxes over the riparian shrub Myricaria squamosa Desv., which is widely distributed on the Qinghai–Tibet Plateau but has not been studied until now. The results indicated that annual ET was 390mm and 503mm for the period of 2010 to 2011 and 2011 to 2012, respectively, which was higher than the amount of precipitation during the same period. Cumulative ET was lower than the cumulative reference evapotranspiration during the entire experimental period, whereas ET in August was higher than reference evapotranspiration. ET in the growing season occupied over 80% of annual ET with a maximum daily ET of 7.2mmd−1, and the ET in the non-growing season was quite low because of the frozen soil. In general, temperature and net radiation were the key variables controlling daily ET rates for M. squamosa. Annual sensible heat flux (H) consumed 60% of net radiation (Rn) and latent heat flux (LE) 40% during the three years of the study. LE occupied the main part of Rn from July to September. H was the highest in May and June, then sunk in the mid-growing season, and rebounded the other peak at late September and early October. Daily ground heat flux was positive from April to mid-September, and it was an important heat source of land surface in the winter and spring. This study highlighted that as an alpine riparian ecosystem in a semiarid region, ET and surface energy partitioning of the M. squamosa community are strongly affected by the freeze–thaw cycle, groundwater fluctuation, precipitation pulses and soil water content. We speculate that climate warming has a significant impact on ET process and surface energy partitioning of the M. squamosa community by influencing the freeze–thaw cycle and soil water content.

Forecasting air-drying rates of small Douglas-fir and hybrid poplar stacked logs in Oregon, USA

Managing moisture in woody biomass can lead to significant economic advantages in the woody biomass energy business. In this study, two prediction models were developed to estimate moisture content for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and hybrid poplar (Populus spp.) woody biomass in the form of small stacked logs. Experimental data were collected in Oregon over a 12-month period at two locations each for Douglas-fir and hybrid poplar. These data were used to develop linear mixed-effects multiple regression models for predicting the change in moisture content for each species separately. The major factors considered in this study for predicting woody biomass moisture-content change were cumulative precipitation, cumulative reference evapotranspiration (ET0), and biomass piece size. Use of the model was demonstrated for four of the nine climate zones in Oregon: two in which air-drying data were collected, and two in which these were not collected. Considerable differences in predicted drying times were observed, depending on the climate zone and on the season in which air-drying began.

Evapotranspiration from pilot-scale constructed wetlands planted with Phragmites australis in a Mediterranean environment

This article reports the results of evapotranspiration (ET) experiments carried out in Southern Italy (Sicily) in a pilot-scale constructed wetland (CW) made of a combination of vegetated (Phragmites australis) and unvegetated sub-surface flow beds. Domestic wastewater from a conventional wastewater treatment plant was used to fill the beds. Microclimate data was gathered from an automatic weather station close to the experimental plant. From June to November 2009 and from April to November 2010, ET values were measured as the amount of water needed to restore the initial volume in the beds after a certain period. Cumulative reference evapotranspiration (ET0) was similar to the cumulative ET measured in the beds without vegetation (ETcon), while the Phragmites ET (ET phr ) was significantly higher underlining the effect of the vegetation. The plant coefficient of P. australis (Kp) was very high (up to 8.5 in August 2009) compared to the typical Kc for agricultural crops suggesting that the wetland environment was subjected to strong “clothesline” and “oasis” effects. According to the FAO 56 approach, Kp shows different patterns and values in relation to growth stages correlating significantly to stem density, plant height and total leaves. The mean Water Use Efficiency (WUE) value of P. australis was quite low, about 2.27 g L−1, probably due to the unlimited water availability and the lack of the plant's physiological adaptations to water conservation. The results provide useful and valid information for estimating ET rates in small-scale constructed wetlands since ET is a relevant issue in arid and semiarid regions. In these areas CW feasibility for wastewater treatment and reuse should also be carefully evaluated for macrophytes in relation to their WUE values.

An analysis of yearly trends in growing degree days and the relationship between growing degree day values and reference evapotranspiration in Turpan area, China

The growth and development of crops is commonly regarded as a function of time alone. However, this approach can be inadequate due to temperatures which vary from year to year caused by global climate change. This prompted the development of the growing degree day concept, which incorporates information on both the passage of time and the temperature experienced by the crop plant during that time. Crop water requirements, which are estimated by multiplying reference evapotranspiration values by a crop-specific coefficient, play a crucial role in the management of hydrologic cycles on arable land. Consequently, it would be useful to identify the relationships between cumulative growing degree days and reference evapotranspiration, in order to develop new methods for predicting crop growth and development periods and calculating reference evapotranspiration. This paper describes annual trends in cumulative growing degree days values and their impact on grape growth. Three different methods for calculating cumulative growing degree days values were evaluated as well. Several key findings were achieved. First, for the period between 1952 and 1995, the cumulative growing degree days values for specific days of the year were normally distributed. Second, the relationship between the relative cumulative growing degree days value and the passage of time can be accurately described by using a cubic polynomial function. Third, the day-to-day change in the average relative cumulative reference evapotranspiration can be described using an exponential function of time, which can be used to calculate the relative cumulative reference evapotranspiration value for any given day of the year. Fourth, there was a significant correlation between the relative cumulative growing degree days and cumulative reference evapotranspiration values during the period between grape budding and maturity, which can be described using a cubic polynomial function. Finally, a new method for determining the ET0 value for any given day of the year was developed; this method requires only a knowledge of the CGDD-at-year-end and no sophisticated meteorological data.

Rice growth, yield and water productivity responses to irrigation scheduling prior to the delayed application of continuous flooding in south-east Australia

Abstract The majority of rice grown in south-east Australia is continuously flooded for much of its growing season, but reduced irrigation water availability brought about by a combination of drought and environmental flow legislation has presented a need to maintain (or even increase) rice production with less irrigation water. Delaying the application of continuous flooding until prior to panicle initiation can increase input water productivity by reducing non-beneficial evaporation losses from free water and the soil. A field experiment was conducted over two growing seasons, 2008/9 and 2009/10, comparing a conventional dry seeded treatment (the control – continuous flooding from the 3 leaf stage) with delayed continuous flooding (10–20 days prior to panicle initiation) with several irrigation scheduling treatments prior to flooding commencement. In the first year, the delayed water treatments were irrigated at intervals of 40, 80 and 160 mm of cumulative reference evapotranspiration (ETo) prior to delayed continuous flooding, thereby imposing differing degrees of crop water stress. In year 2, the 80 and 160 mm treatments were modified by use of a crop factor (Kc) when the plants were small and the 40 mm treatment was replaced with a continuously flooded treatment throughout the crop duration. Decreases in net water input (irrigation + rain − surface drainage) and increases in input water productivity were achieved by reducing the flush irrigation frequency during the pre-flood period. Savings of 150 and 230 mm (10 and 15%) were achieved in Year 1 from the 80 and 160 mm cumulative ETo irrigation frequency treatments, respectively, in comparison to the control. In the second year, net water input savings of 230 and 330 mm (15 and 22%) were achieved with the 80/Kc and 160/Kc mm treatments, respectively. Input water productivity of the 160 mm treatment was 0.06 kg/m 3 (8%) higher than the control in Year 1, while in Year 2 a 0.15 kg/m 3 (17%) increase in input water productivity above the control was achieved by the 160/Kc mm treatment. Delaying the application of continuous flooding in the second year greatly extended the period of crop growth suggesting the need for earlier sowing (by 7–10 days) to ensure pollen microspore still occurs at the best time to minimise yield loss due to cold damage. Nitrogen fertiliser management is an important issue when delaying continuous flooding, and nitrogen losses appeared to increase with the frequency of irrigation prior to continuous flooding. This was likely due to increased denitrification from alternate wetting and drying of the soil. Further research is required to determine the most appropriate nitrogen management strategies, and to also better define the optimal pre-flood irrigation frequency.

Evaluation of Phragmites australis (Cav.) Trin. evapotranspiration in Northern and Southern Italy

The design, operation, pollutant removal as well as hydraulic modeling of wetland systems for wastewater treatment can be improved by better understanding and simulating the evapotranspiration process. To this purpose, two experiments were carried out in Northern (Veneto region) and Southern (Sicily region) Italy to measure evapotranspiration (ET) and determine the crop coefficient of Phragmites australis (Cav.) Trin. using the FAO 56 approach. The experimental set-up consisted of a combination of vegetated and unvegetated plastic tanks (Veneto) or pilot sub-surface flow beds (Sicily). The ET values were obtained by measuring the amount of water needed to restore the initial volume in the tanks and in the beds after a certain period. All the needed climatic variables were measured and taken into account in the ET measurements. In the two experimental sites cumulative reference evapotranspiration (ET 0) was similar to the cumulative ET measured in the control tanks and beds (without vegetation, ET con), while ET measured for P. australis (ET phr) was significantly higher, underlining the strong effect of vegetation. From June 2009 to September 2009 the cumulative ET 0, ET con and ET phr in Veneto were 455, 424 and 3048 mm, in Sicily 653, 556 and 3899 mm, respectively. The plant coefficient trend of P. australis ( K p) estimated in Veneto was similar to that in Sicily, suggesting that the role of the plant in dispersing water is similar under different environmental conditions. Additional measurements made in the Veneto plant showed that K p assumes different patterns and values in relation to plant age and growth stage. These results highlight the importance of the plants in regulating water losses from a wetland system, above all from small-scale constructed wetlands where the effect of the advection in ET rates is evident.

Water requirements of pineapple crop grown in a tropical environment, Brazil

This research was conducted to determine the water requirements of the pineapple crop ( Ananas comosus L.), cv. “Pérola” grown in the Coastal table lands of Paraíba state, Brazil, using a sprinkler irrigation system as complementary water supply. A micrometeorological tower was mounted in a 90 m × 90 m experimental area for determining energy fluxes in the interface plant/soil-atmosphere. Crop evapotranspiration (ET c) was estimated by the Bowen ratio-energy balance and reference evapotranspiration (ET o) by the Penman-Monteith method. The mean daily crop evapotranspiration was too variable throughout the pineapple crop development cycle, with values decreasing from (ET c = 4.6 mm day −1) in the vegetative growth to 3.5 mm day −1 in the fruits harvesting phenological stage. On the overall, ET c was lower in the beginning of the vegetative growth and fruits harvest and higher in the middle of the productive cycle. The cumulative water used during the crop growing cycle was 1421 mm while the cumulative reference evapotranspiration was 1614.9 mm. Lower values of the crop coefficient ( K c) were observed during the vegetative growth (phase II) stage while for the whole crop cycle, K c = 0.88 ± 0.06. This result can be used for a most efficient water use and to optimize production of the pineapple crop grown in tropical environments, particularly in Coastal table lands of Paraíba state, Brazil.

CROP EVAPOTRANSPIRATION AND CROP COEFFICIENTS OF VIBURNUM ODORATISSIMUM (KER.-GAWL)

Determination of irrigation requirements of nursery plants is becoming more important as the nursery growersare being challenged to conserve water and minimize runoff while meeting plant water needs. Historically, not enoughattention has been given to the measurement of crop evapotranspiration (ETc) and crop coefficients (Kc) of ornamental plantsfor irrigation scheduling, water management, and allocation. Since measurement of Kc is a difficult and time consuming task,especially for the container-grown ornamentals, there is a need to develop methods for estimating Kc from more easilyobtainable variables. The ETc and Kc values of Viburnum odoratissimum (Ker.-gawl) grown in white and black Multi-Pot BoxSystem (MPBS) were measured in two growing seasons (summer and fall). The relationship between the Kc and week aftertransplanting (WAT), growth index (GI), cumulative reference evapotranspiration (ETo), and fraction of thermal units (FTU)were developed and analyzed to find out whether these parameters could be used as the base scales to estimate Kc values.The measured ETc ranged from 308 mm for the black MPBS plants in summer to 351 mm for the white MPBS plants in fall.Good relationships between Kc versus WAT, GI, cumulative ETo, and FTU were observed in both seasons (r2 . 0.93). Theserelationships were explained by third order polynomial equations in both growing seasons. Specifically, GI and FTU valueswere found to be very useful, practical, and effective base scales in estimating Kc from transplanting to physiological maturity(marketable size) of V. odoratissimum. The relationships between the Kc versus base scale variables were significantlyaffected by the season. Thus, the equations developed are season-specific and should be used accordingly. The season-specificcharacteristic of the equations was attributed to the differences in growth rates (exponential in summer and linear in fall)of the plants grown in the white and black MPBS in the summer and fall seasons. Equations developed to estimate Kc wouldhave advantages over the traditional method of estimating Kc from measured ETc and ETo for nursery crops since, in practice,measuring and/or estimating WAT, GI, ETo, and FTU are easier than measuring ETc and Kc. Experimentally derived Kc valuesand relationships developed in this study add useful information to the nursery growers, researchers and water managementdistricts in terms of collection of ETc and Kc data that can be utilized for irrigation scheduling and water resources planningand management, and are among the first ETc and Kc data for the V. odoratissimum.