Determine Crop Evapotranspiration Research Articles

Impact Assessment of Climate Change on Water Requirements for Summer Paddy Cultivation in Raipur District, Chhattisgarh

Water is a crucial and finite resource, primarily utilized for irrigation, necessitating effective distribution for long-term sustainability. This study quantifies the water requirements for summer paddy cultivation in Raipur district, Chhattisgarh, and assesses its implications under changing climatic conditions. The FAO-CROPWAT 8.0 model was applied to assess irrigation parameters using historical meteorological data from 2000 to 2020 and projected meteorological data from 2040 to 2100. Reference evapotranspiration (ET₀) was estimated using Penman-Monteith method, incorporating crop coefficient (Kc) values to determine crop evapotranspiration (ETc). Irrigation water requirements were estimated by accounting for various losses and efficiencies of crop and field. Comprehensive water balance models were developed across the century, focusing on a 20-year average time span, including the historical period as 2000-2020 and the predicted time span from 2040 to 2100 with two socio-economic scenarios: SSP2-4.5 and SSP5-8.5, along with soil, meteorological, and phenological factors. Over the baseline period, the crop water requirement (CWR) for summer paddy was calculated as 751.4 mm, with net irrigation water requirement (NIWR) and gross irrigation water requirement (GIWR) as 1094.7 mm and 1563.8 mm, respectively. Under SSP2-4.5 scenario, the minimum and maximum temperatures are projected to rise by 1.3 °C and 1 °C respectively with rainfall increasing by 378.5 mm. This scenario anticipates a CWR increase of 32.6 mm by century's end, resulting in final values of CWR as 784 mm, NIWR as 1164.7 mm, and GIWR as 1663.9 mm. In the SSP5-8.5 scenario, temperatures are expected to rise by 4.4 °C and 3.1 °C as minimum and maximum temperature, leading to a CWR of 800.4 mm, with NIWR and GIWR as 1176.5 mm and 1680.7 mm, respectively. Overall, most parameters indicate an upward trend throughout the century. This study provides critical insights for efficient irrigation management in summer paddy cultivation and highlights the implications of future climate change on irrigation needs, promoting sustainable agricultural practices.

Water requirement and single and dual crop coefficients of sesame cultivated in the coastal tablelands of Brazil

AbstractSesame irrigation is essential in drought‐prone regions. However, information about the water needs of sesame is scarce. Therefore, the objective of this study was to determine crop evapotranspiration (ETc) and the sesame crop coefficient (Kc) during the rainy (S1) and dry (S2) seasons in the coastal tablelands of Alagoas, Brazil. The BRS Seda cultivar was grown in Rio Largo, Alagoas, Brazil, between 2021 and 2022. A system with 25 drainage lysimeters was installed to estimate the daily and cumulative ETc and the Kc for the entire crop cycle. The ETc was partitioned into transpiration (T) and evaporation (E), and the basal crop coefficients (Kcb) and soil evaporation coefficients (Ke) were subsequently estimated. The daily and cumulative ETc were 3.04 mm day−1 and 450.4 mm cycle−1, respectively, in S1 and 3.52 mm day−1 and 440.1 mm cycle−1, respectively, in S2. Regardless of the season, T was the main water flux (74%–80% of the ETc). The mean values of Kc were similar for S1 (0.79) and S2 (0.75), and Kcb and Ke followed the same trend as T and E, respectively. The accumulated ETc and Kc of sesame cultivated in the coastal tablelands of Alagoas, Northeast Brazil, are similar for the rainy and dry seasons.

Estimation of crop evapotranspiration and crop coefficient for coriander using Portable Automatic Closed Canopy Chamber

An experiment was carried out to determine crop evapotranspiration and crop coefficient of Coriander crop by using Portable Automatic Closed Canopy Chamber (PACCC), Micro-Lysimeter (MLs) and field water balance (FWB) methods. The results revealed that there was no significant difference in the coriander crop evapotranspiration measured by the MLs inside and outside the PACCC and no significant difference among the crop evapotranspiration measured by the PACCC, MLs and FWB at 95 percent confidence level was found. It is indicating that, there are no effects of the change in micro-climate for a short period of 2 minutes in the chamber and on the plant physiological processes. During validation of PACCC, the average crop coefficients measured by MLs were varied from 0.66 to 1.26 for coriander crop. However, the stage wise crop coefficients of corianders measured by FWB were varied from 0.67 to 1.28 during field testing of PACCC. The result showed that the PACCC can be used for measurement of crop evapotranspiration in the field condition.

Energy balance determination of crop evapotranspiration using a wireless sensor network

Determining crop evapotranspiration (ET) is essential for managing water at various scales, from regional water accounting to farm irrigation. Quantification of ET may be carried out by several procedures, being eddy covariance and energy balance the most established methods among the research community. One major limitation is the high cost of the sensors included in the eddy covariance or energy balance systems. We report here the development of a simpler device (CORDOVA-ET: COnductance Recording Device for Observation and VAlidation of ET) to determine crop ET based on industrial-grade, commercial off-the-shelf (COTS) sensors costing far less than research-grade sensors. The CORDOVA-ET contains a sensor package that integrates the basic micrometeorological instrumentation and the infrared temperature sensors required for estimating ET over crops using the energy balance approach. One novel feature is the presence of four different nodes that allow the determination of ET in four different locations within a field or in four different fields of the same crop, thus allowing an assessment of ET spatial variability. The system was conceived as an open-source and hardware alternative to commercial devices, using a collaborative approach for the development of a regional ET network in countries of North Africa and the Near East. Comparisons of radiation, temperature, humidity, and wind against those of research-grade sensors yielded excellent results, with coefficients of correlation (R2) above 0.96. The estimated reference ET calculated from these measurements showed R2 = 0.99 and a root mean square error (RMSE) of 0.22 mm/day. The infrared temperature measurements at the four different nodes showed an RMSE below 0.56°C. The energy balance components and estimates of ET from the CORDOVA-ET were validated against an eddy-covariance system over a wheat crop. The high (R2) for net radiation (0.98), sensible heat (0.88), and latent heat (0.86) showed good agreement between the modeled energy fluxes and the field measurements. The hardware components, acquisition, and data processing software are available as open-source repositories to facilitate adoption for different applications, from water use efficiency research to irrigation management.

Quantifying the effects of advection on single crop coefficients over a humid paddy field for sustainable irrigation

Understanding the variation and magnitude of crop coefficient (Kc) is important to accurate determine crop evapotranspiration (ETc) and optimal irrigation scheduling. Sensible heat advection is expected to increase Kc by providing additional energy, while its effect on Kc over paddy field is rarely featured. A three-year experiment was conducted over a paddy field to develop local Kc using the eddy covariance technique (EC) in the Poyang River basin, southern China. The local Kc curve, the characteristics of advection and its contribution to Kc were investigated. The three-year average local Kc values during the initial, mid-season and late-season stages were 1.12, 1.29 and 1.13 for the early rice and 1.11, 1.39 and 1.02 for the late rice, respectively. The advection was more likely to occur during the late rice season than the early rice season. The three-year average advective days were 8.0 d for the early rice season and 29.7 d for the late rice season, respectively. The contribution of advection to daily Kc ranged from 0.6% to 13.2% for the early rice season and 1.1% to 37.7% for the late rice season, respectively. The upwind city was found to be a possible energy source for advection. The occurrence of advection was closely related to air temperature gradients (ΔT) between the city and paddy field and wind speed (u2). Our study indicated advection also existed in the humid paddy field and had considerable effects on Kc. These results are helpful for decision-makers to quantify crop water consumption and improve irrigation water efficiency.

Evapotranspiration, crop coefficient and water use efficiency of onion cultivated under different irrigation depths

ABSTRACT This study aimed to determine crop evapotranspiration through the soil water balance, the crop coefficient and water use efficiency of the onion (Allium cepa L.) in a system with four irrigation regimes, cultivated in the semiarid region of northeastern Brazil. Two field experiments were carried out during the rainy and dry periods of the region in 2018, using the treatments of 100% (T1), 75% (T2), 50% (T3) and 25% (T4) of the reference evapotranspiration for daily water replacement and five replicates for each treatment. It was verified that crop evapotranspiration varies according to the water availability in the soil; however, the highest water use efficiency occurred for the T3 treatment. The T1 treatment obtained the highest estimated yield, 43.86 tons ha-1, while T4 obtained 13.47 tons ha-1, the lowest estimated yield among the treatments, and this difference was statistically significant (p ≤ 0.05) by F test. The crop coefficients obtained were 0.68, 0.89, 0.99 and 0.73 for the initial, vegetative, bulbing and maturation stages, respectively.

DEMANDA HÍDRICA E ADUBAÇÃO ORGÂNICA NO CULTIVO PROTEGIDO DE PIMENTÃO NA REGIÃO NORTE DA BAHIA

DEMANDA HÍDRICA E ADUBAÇÃO ORGÂNICA NO CULTIVO PROTEGIDO DE PIMENTÃO NA REGIÃO NORTE DA BAHIA RUANNA MATOS ALMEIDA SOUZA¹; MÁRIO DE MIRANDA VILAS BOAS RAMOS LEITÃO²; GERTRUDES MACÁRIO DE OLIVEIRA³; EMERSON DAMASCENO DE OLIVEIRA4 E LEONARDO TORRES CORREIA5 ¹ Colegiado de Engenharia Agrícola e Ambiental, Universidade Federal do Vale do São Francisco, UNIVASF, Av. Antônio C. Magalhães, 510, Country Club, Juazeiro - BA, CEP: 48902-300, ruanna.matos@outlook.com ² Colegiado de Engenharia Agrícola e Ambiental, Universidade Federal do Vale do São Francisco, UNIVASF, Av. Antônio C. Magalhães, 510, Country Club, Juazeiro - BA, CEP: 48902-300, mario.miranda@univasf;edu.br ³ Departamento de Tecnologia e Ciências Sociais, Universidade do Estado da Bahia, UNEB, Av, R. Edgar Chastinet, s/n - São Geraldo, Juazeiro - BA, CEP: 48900-000, gemoliveira@uneb.br 4 Colegiado de Engenharia Agrícola e Ambiental, Universidade Federal do Vale do São Francisco, UNIVASF, Av. Antônio C. Magalhães, 510, Country Club, Juazeiro - BA, CEP: 48902-300, emerson.oliveira@univasf.edu.br 5 Colegiado de Engenharia Agrícola e Ambiental, Universidade Federal do Vale do São Francisco, UNIVASF, Av. Antônio C. Magalhães, 510, Country Club, Juazeiro - BA, CEP: 48902-300, leonardo.torrescorreia@hotmail.com 1 RESUMO Palavras-chave: evapotranspiração, irrigação, coeficiente de cultivo. MATOS, R.M.A; LEITÃO,M.DE M.V.B.R; OLIVEIRA, G.M.DE; OLIVEIRA, E. D. DE;CORREIA, L. T. WATER DEMAND AND ORGANIC FERTILIZATION IN PROTECTED PIMENTÃO CULTIVATION IN THE NORTH REGION OF BAHIA 2 ABSTRACT The objective was to determine crop evapotranspiration (ETc), crop coefficient and water use efficiency for the production of sweet pepper (Capsicum annuum L.) cultivated under two soil compounds in a protected environment. The experiment was conducted in Juazeiro-BA, from June to October 2019. The pepper was grown in pots, the design was randomized blocks, split plots, four irrigation depths were used (95, 100, 105 and 110% of ETc) and two levels of soil fertilization: A1 (25% manure and 75% soil) and A2 (40% manure and 60% soil), which were based on studies developed by Santana (2019). ETc was determined using two sets of constant water table lysimeters and the crop coefficient was determined from ETc and reference evapotranspiration. The total water demand of the crop for the A1 fertilization level was 527.3 mm and for that A2 was 395.7 mm. The maximum and minimum crop coefficients were respectively 0.78 and 0.23 for A2; 1.02 and 0.34 for A1. The A1 level of fertilization showed higher productivity and satisfactory conversion of water into fresh fruit mass. Keywords: evapotranspiration, irrigation, crop coefficient.

Determining evapotranspiration and crop coefficients of young and mature pomegranate trees under drip irrigation*

AbstractIn spite of the importance of increasing water shortages in most pomegranate production regions, there is not sufficient information about the water requirement and crop coefficients (Kc) of pomegranate trees under various conditions (e.g., plant cultivar and age and irrigation system). The aim of this study was to measure evapotranspiration during three growing seasons (2013, 2015, and 2016) and to determine Kc of young and mature pomegranate (Punica granatum L.) trees under drip irrigation in Iran. The soil water balance approach was applied to determine crop evapotranspiration (ETc) using soil water content measured during the growing seasons. The ratio of measured ETc to reference evapotranspiration calculated according to the Penman–Monteith equation provided the Kc values. According to the findings, from bud burst to peak season, daily Kc values for young pomegranate trees ranged from 0.18 to 0.70, 0.22 to 0.89, and 0.23 to 0.95 in 2013, 2015, and 2016, respectively. For mature pomegranate trees, these values varied between 0.26 to 1.15, 0.21 to 1.25, and 0.30 to 1.08 in 2013, 2015, and 2016, respectively. From bud burst to peak season, the total ETc for young pomegranate trees was 711, 905, and 934 mm and for mature pomegranate trees 1,172, 1,086, and 1,138 in 2013, 2015, and 2016, respectively. The results of this study are applicable to accurate water allocation, precision irrigation scheduling, and design of irrigation systems in pomegranate orchards.

Crop Coefficient for Potato Crop Evapotranspiration Estimation by Field Water Balance Method in Semi-Arid Region, Maharashtra, India

Crop evapotranspiration (ETc) estimation is essential for many studies such as irrigation system design and management, crop yield simulation, and water resource planning and management. Field studies were conducted at MPKV Rahuri, Maharashtra from 2015 - 2016 and 2016 - 2017 (2 years) in clay soils to determine crop evapotranspiration and crop coefficients (Kc) of the potato crop. The experimental area was cultivated with irrigation applied at 7-days interval. The irrigation scheduling was based on the field water balance approach. The crop evapotranspiration was determined by the field water balance; reference evapotranspiration (ETo) by the Penman-Monteith method and crop coefficients were computed using the standard FAO-56 methodology. The total reference evapotranspiration (ETo) and crop evapotranspiration (ETc) were 226 and 240 mm for the year 2015–2016 and 248 and 250 mm for the year 2016–2017, respectively. The 2-year average reference evapotranspiration was 237 mm and the crop evapotranspiration was 245 mm. The average estimated Kc values for the semi-arid region during the vegetative, tuber development, and maturity stages for potato are 0.55, 1.11, and 1.01, respectively. The calculated values are slightly lower than those suggested by FAO-56 for the vegetative and tuber development stages and higher for the maturity stage of potato. The estimated values of crop coefficients for potato are 11.25% higher than those suggested by FAO-56. However, observed variation between values from the FAO-Kc and Kc calculated by the field water balance is not significant. So, these values can be used for irrigation scheduling of potato in the semi-arid region.

Supply and Demand Analysis of Water Resources. Case Study: Irrigation Water Demand in a Semi-Arid Zone in Mexico

To sustainably use water resources, it is important to quantify water availability in a certain region. Due to climate change, population increase, and economic development, water demand increases continuously. Consequently, the difference between supply and demand of water becomes a significant issue, especially in arid and semi-arid regions. In this research, the Soil and Water Assessment Tool (SWAT) model has been applied to the Guadalupe river basin, to assess supply and demand analysis of water resources in this area, specifically for the irrigation of agricultural crops and municipal uses. From the land use, soil type, and terrain slope maps, 763 Hydrostatic Release Units (HRU) were estimated, distributed in the diverse relief types making up the basin, featured by mountains, hills, plateaus, plains, and valleys. For the crop area, 159 HRU were found with the three slope classification types, where 57 HRU represent 91% of the cultivated area on slopes, from 0 to 15%, located in the Ojos Negros and Guadalupe Valleys. The Soil Conservation Service method (SCS) was used to estimate the average monthly runoff and soil moisture content. As a result, water resource parameters related to the supply were determined with this, e.g., runoff, aquifer recharge, flow, infiltration, and others. Crop coefficient values (Kc) were used to determine crop evapotranspiration (ETc), to estimate the water demand of these for each month, using the multi-year monthly average reference evapotranspiration (ETo) calculated with the SWAT model. Overall good performance was obtained considering average monthly discharges data from the Agua Caliente gauging station. The model was calibrated, modifying the parameters chosen according to sensitivity analysis: SCS curve number, base-flow factor, ground-flow delay, and the threshold for return-flow occurrence. The Soil and Water Assessment Tool–Calibration and Uncertainty Programs SWAT-CUP has different goodness-of-fit indicators for the model e.g., determination coefficient (R2), standard deviation of the measured data (RSR), Nash–Sutcliffe coefficient of efficiency (NSE), and others. Multiple iterations were performed, resulting in a ratio between the root mean square error and the standard deviation of the measured data (RSR) of 0.61, a coefficient of determination (R2) of 0.70, and a Nash–Sutcliffe efficiency coefficient (NSE) of 0.63. A supply–demand analysis of the volume generated by the runoff from the basin was performed using the method of estimating useful volume for a reservoir. It is observed in these results that only positive deviations were obtained, implying that runoff in this basin is not enough to meet monthly demand. Finally, the need to establish actions to ensure water management efficiency is highlighted, both for irrigation of agricultural crops and for supply to the region population.

Determination of the water requirement and crop coefficient values of sugarcane by field water balance method in semiarid region

Sugarcane is a major agro-industrial crop in semiarid regions and generally has high evapotranspiration. Standardized reference evapotranspiration (ET) and location specific crop coefficients are used to estimate crop evapotranspiration. However, precise information on crop coefficient (Kc) is a major impediment in semiarid environments. Field studies were conducted during two seasons of 2015 and 2016 in clay soils to determine crop evapotranspiration and crop coefficients (Kc) of sugarcane for semiarid India.The experimental area was cultivated with irrigation applied at 7–10 days interval by a drip irrigation system in addition to rainfall and the irrigation scheduling was based on field water balance approach. The crop evapotranspiration was determined by field water balance, reference evapotranspiration (ETo) by the Penman-Monteith approach while crop coefficient were computed through the standard FAO-56 methodology.On an annual basis, the total reference evapotranspiration (ETo) and crop evapotranspiration (ETc) were 1318−1426 mm and 1291−1388 mm respectively. Two years average sugarcane crop evapotranspiration estimated by field water balance method was 1339 mm year−1. The irrigation water requirement andeffective rainfall was 991 mm year-1 and 424 mm year-1 respectively. Two years results showed that there was a notable symmetry between Kc obtained from field water balance measurements and FAO-56 reported Kc. The determined Kc values for tillering, grand growth and maturity stages of sugarcane were 0.70, 1.20 and 0.78, respectively. The Kc values were found 25.5 %, 4 % and 20.4 % less during the tillering, grand growth and maturity stage respectively over the FAO-56 Kc values. The 2nd order polynomial equation was fitted with crop coefficient as the dependent variables and ratio of days after transplanting to total crop period as the independent variable. The daily values of Kc from equation is very useful towards efficient management of irrigation water in terms of making a Decision Support System, Soil Moisture based Crop Yield Modeling, Crop Water Requirement based Computer programme or Mobile Application, Automation of irrigation system in the major sugarcane growing countries of semi arid regions.

Irrigation in the age of agriculture 4.0: management, monitoring and precision

Technological evolution is essential to make irrigated agriculture more efficient in the use of water. Thus, this review article aims to contextualize irrigation in the age of agriculture 4.0 in order to address how these new technologies are impacting the rational use of water. With regard to the automation of irrigated systems, irrigation efficiency with moisture sensors, applications using smartphone, controllers and fertilizer injectors, as well as how their operation can promote irrigation, was addressed. Regarding irrigation management, the use of remote sensing as an option to determine crop evapotranspiration was contextualized, listing the types of spectral bands and sensors used to collect images (orbital, aerial and terrestrial), in the monitoring of crop water status. The importance of data collection in the delineations of management zones for precision irrigation and what possible advances can still be achieved with regard to obtaining and analyzing data were also discussed. Finally, it is concluded that, despite the high efficiency of automated irrigation systems, information of soil, climate and plant attributes obtained through the range of data provided by sensors will be responsible for mitigating the global impacts caused by irrigated agriculture in the near future, since this information can enhance irrigation, with maximum efficiency, thus reducing water consumption by agriculture.

A Subsurface Drip Irrigation System for Weighing Lysimetry

Abstract. Large, precision weighing lysimeters can have accuracies as good as 0.04 mm equivalent depth of water, adequate for hourly and even half-hourly determinations of evapotranspiration (ET) rate from crops. Such data are important for testing and improving simulation models of the complex interactions of surface water and energy balances, soil physics, plant growth, and biophysics that determine crop ET in response to rapid microclimate dynamics. When crops are irrigated with sprinkler systems or other rapid additions of water, the irrigation event is typically short enough that not much ET data are compromised by the lysimeter mass change due to irrigation. In contrast, subsurface drip irrigation (SDI) systems may take many hours to apply an irrigation, during which time the lysimeter mass change is affected by both ET rate and irrigation application rate. Given that irrigation application rate can be affected by pressure dynamics of the irrigation system, emitter clogging and water viscosity changes with temperature over several-hour periods, it can be difficult to impossible to separate the ET signal from the interference of the irrigation application. The inaccuracies in the data can be important, particularly for comparisons of sprinkler and SDI systems, since they are of the order of 8 to 10% of daily ET. We developed an SDI irrigation system to apply irrigations of up to 50 mm to large weighing lysimeters while limiting the period of lysimeter mass change due to irrigation delivery to approximately ten minutes by storing the water needed for irrigation in tanks suspended from the lysimeter weighing system. The system applied water at the same rate as the SDI system in the surrounding field, allowed irrigation over periods of any duration, but often exceeding 12 h, without directly affecting lysimeter mass change and the accuracy of ET rate determinations, and allowed irrigation overnight without compromising lysimeter daily ET measurements. Errors in lysimeter ET measurements using the previous SDI system, which was directly connected to the field irrigation system, were up to 10% of daily ET compared with negligible error using the new system. Errors using the previous, directly connected, SDI system varied over time due to variable system pressure, and possibly due to water temperature (viscosity) changes and emitter clogging. With the new system, all of the water transferred to the lysimeter weighing system was eventually applied by the SDI system regardless of temperature, pressure, or emitter clogging. Differences between planned and applied irrigation depth were less than 2% over the irrigation season. Keywords: Evapotranspiration, ET, Subsurface drip irrigation, SDI, Weighing lysimeter.

Determination of crop evapotranspiration and partitioning of bare soil evaporation of mustard using weighing type field lysimeters

Determination of crop evapotranspiration (ETc) plays a significant role in estimating crop water requirement and subsequently irrigation scheduling of different crops leading to saving of water. Keeping this in view, the research work was undertaken to determine crop evapotranspiration (ETc)of mustard (Brassica juncea) cultivar Pusa Vijay (NPJ-93) and bare soil evaporation (E) using weighing type field lysimeters located at the research farm of Water Technology Centre, ICAR-IARI, New Delhi, India during rabi seasons of 2013–14 and 2014–15. It was observed that the average value of ETc during rabi 2013–14 season was 155.3 mm. Whereas, during rabi 2014–15 season, the value of ETc was 151.8 mm. Mean values of daily ETc were 1.23 mm/day and 1.08 mm/day during rabi seasons of 2013–14 and 2014–15, respectively. Mean monthly crop coefficient (Kc) values were estimated and relationship between Kc and Leaf Area Index (LAI) was established. The ratio of transpiration (T) to ETc was 0.70 during both the years. Nonetheless, the estimated ETc values of mustard and E can be used for judicious irrigation scheduling.

Shoot water content and reference evapotranspiration for determination of crop evapotranspiration

Determination of water requirement for crops in resource limited areas is challenging, yet worsened by the common assumption that all crop varieties within a species have similar water requirements. The objective of the study was to indirectly determine crop evapotranspiration of soybean varieties, using reference evapotranspiration and shoot water content under tillage and no tillage cultivation. The treatments were no tillage and conventional tillage as main plots, and soybean varieties Nyala, SB19, and SB20 as sub-plots, replicated three times. Crop evapotranspiration (ETC) and crop coefficient (KC) were different among varieties, and increased during growth period. SB20 had the highest KC (0.8437 at 87 days after planting - DAP); followed by SB19 (0.7888 at 70 DAP), and Nyala (0.7026 at 66 DAP). Conversely,water use efficiency (WUE) was 0.58 in SB19, 0.52 in Nyala, and 0.47 in SB20.Validation of the calculated ETC using a crop production function showed a correlation of r = 0.97 between the observed and predicted yields of the three varieties. Furthermore, the normalised root mean square error (NRMSE) and the index of agreement (d) were 0.14 and 0.87, respectively indicating accurate fit. Calculated crop coefficient strongly correlated with observed shoot water content of Nyala (R2 = 1), SB19 (R2 = 1), and SB20 (R2 = 1). Key Words : Crop coefficient, evaporation, Glycine max, shoot, soybean, transpiration

CROP COEFFICIENT AND WATER PRODUCTIVITY IN CONVENTIONAL AND SYSTEM OF RICE INTENSIFICATION (SRI) IRRIGATION REGIMES OF TERRACE RICE FIELDS IN INDONESIA

The current study initiated to investigate crop coefficient (Kc) and water productivity between conventional and System of Rice Intensification (SRI) irrigation regimes of terrace rice fields in Indonesia. Kc value represents plant responses to available water in the fields and its information is very important to determine crop evapotranspiration. The field experiments were conducted in the terrace rice fields belong to the local farmer located in Wonogiri, Central Java (S 7o47’18.66”, E 111o5’51.26”) during 21 July – 7 November 2014 in the dry season. Here, there were two irrigation regimes with three replications, i.e. conventional flooding (FL) regime and SRI with intermittent irrigation (II) regime. Water level in each regime was measured by pressure sensor, while weather parameters such as solar radiation, air temperature, precipitation, etc were measured by particular sensors and connected to the developed field monitoring system. Based on weather and water level data, we estimated the average Kc values for FL regime were 1.01, 1.02, 1.09 and 1.05 in the initial, crop development, reproductive and late growth stages, respectively. Meanwhile, the average Kc values under SRI regime were a little bit lower than that FL regime. Their values were 1.00, 0.96, 1.02 and 1.04 for the initial, crop development, reproductive and late growth stages, respectively. The reason was probably due to minimum soil evaporation under the drier soil condition. However, lower Kc values were not corresponded to the production of grain yield. Although it was not significant difference, we recorded that SRI regime produced 8.05 ton/ha grain yield, while FL regime was 7.63 ton/ha. Accordingly, with less irrigation water, SRI regime has higher water productivity than that FL regime.

Water balances and evapotranspiration in water- and dry-seeded rice systems

Rice is a crop that is usually grown under flooded conditions and can require large amounts of water. The objective of this 3-year study was to quantify water use in water- (WS) and dry-seeded (DS) systems. In WS systems, the field is continuously flooded, while in DS systems the field is flush irrigated for the first month and then flooded. Research was conducted on commercial rice fields where the residual of the energy balance method using a sonic anemometer and the eddy covariance method were used to determine crop evapotranspiration (ETc) and crop coefficient (K c) values. In addition, inlet irrigation water and tailwater drainage were determined. Across years, there was no difference in ETc (averaged 862 mm), seasonal K c (averaged 1.07), irrigation water delivery (averaged 1839 mm) and calculated percolation and seepage losses (averaged 269 mm) between systems. An analysis of the first month of the season, when the water management between these two practices was different, indicated that K c and water use were lower in DS systems relative to WS systems when there was only one irrigation flush during this period, while two or three irrigation flushes resulted in similar values between the two systems.

DEVELOPMENT AND EVALUATION OF A WEIGHABLE LYSIMETER TO DETERMINE CROP EVAPOTRANSPIRATION

The development and evaluation of a weighable lysimeter to determine crop evapotranspiration is presented. A weighable lysimeter with a diameter of 31 cm and a depth of 37 cm was constructed. The lysimeter was evaluated by using it to estimate the crop evapotranspiration of waterleaf in Umudike in Southeastern Nigeria. The evapotranspiration (ETc) estimates by Pan Evapotranspiration, Blaney – Morin Nigeria, Blaney – Criddle and Modified Hargreaves – Samani methods were compared with the estimation of the weighable lysimeter which provides the most reasonable estimation of ETc and is one of the most reliable methods. The crop was irrigated daily and the daily data generated from the lysimeter were used to calculate the crop evapotranspiration (ETc Lysimeter) between the months of July/ August, 2013. Climatic data obtained for the same period were used to determine the crop evapotranspiration (ETc) using the Pan Evapotranspiration, Blaney – Morin Nigeria, Blaney – Criddle and Modified Hargreaves – Samani methods. The total crop evapotranspiration from the Lysimeter between July and August was 141.32 mm, while that of Pan Evapotranspiration (PE), Blaney – Morin Nigeria (BMN), Blaney – Criddle (BC) and Modified Hargreaves – Samani (MHS) were 147.72 mm, 136.81 mm, 131.61 mm and 132.52 mm, respectively. Test of hypothesis using z-Test indicates that there was no significant difference between the means of the ET by lysimeter and each of the other methods (Blaney Criddle, Pan Evapotranspiration, Modified Hargreaves Samani and Blaney Morin Nigeria) for a 5% level of significance as z-cal < z-critical for the growth period of 15 July to 18 August, 2013.

California Simulation of Evapotranspiration of Applied Water and Agricultural Energy Use in California

The California Simulation of Evapotranspiration of Applied Water (Cal-SIMETAW) model is a new tool developed by the California Department of Water Resources and the University of California, Davis to perform daily soil water balance and determine crop evapotranspiration (ETc), evapotranspiration of applied water (ETaw), and applied water (AW) for use in California water resources planning. ETaw is a seasonal estimate of the water needed to irrigate a crop assuming 100% irrigation efficiency. The model accounts for soils, crop coefficients, rooting depths, seepage, etc. that influence crop water balance. It provides spatial soil and climate information and it uses historical crop and land-use category information to provide seasonal water balance estimates by combinations of detailed analysis unit and county (DAU/County) over California. The result is a large data base of ETc and ETaw that will be used to update information in the new California Water Plan (CWP). The application uses the daily climate data, i.e., maximum (Tx) and minimum (Tn) temperature and precipitation (Pcp), which were derived from monthly USDA-NRCS PRISM data (PRISM Group 2011) and daily US National Climate Data Center (NCDC) climate station data to cover California on a 4 km×4 km change grid spacing. The application uses daily weather data to determine reference evapotranspiration (ETo), using the Hargreaves-Samani (HS) equation (Hargreaves and Samani 1982, 1985). Because the HS equation is based on temperature only, ETo from the HS equation were compared with CIMIS ETo at the same locations using available CIMIS data to determine correction factors to estimate CIMIS ETo from the HS ETo to account for spatial climate differences. Cal-SIMETAW also employs near real-time reference evapotranspiration (ETo) information from Spatial CIMIS, which is a model that combines weather station data and remote sensing to provide a grid of ETo information. A second database containing the available soil water holding capacity and soil depth information for all of California was also developed from the USDA-NRCS SSURGO database. The Cal-SIMETAW program also has the ability to generate daily weather data from monthly mean values for use in studying climate change scenarios and their possible impacts on water demand in the state. The key objective of this project is to improve the accuracy of water use estimates for the California Water Plan (CWP), which provides a comprehensive report on water supply, demand, and management in California. In this paper, we will discuss the model and how it determines ETaw for use in water resources planning.

Determination of evapotranspiration and crop coefficients for bush okra (Corchorus olitorius) in a sub-humid area of Nigeria

A two-year field experiment was carried out to determine crop evapotranspiration (ETc) and crop coefficients (Kc) for irrigated bush okra (Corchorus olitorius) at Minna in a tropical sub-humid area of Nigeria between February and April of 2008 and 2009. Eight 4 x 1 m check basins were laid out in a randomized complete block design with two treatments and four replications. The two common local varieties of C. olitorius(Amugbadu and Oniyaya) constituted the treatments. The soil moisture depletion method was used to determine ETc while potential evapotranspiration (ETp) was calculated on a daily basis using Blaney-Morin-Nigeria (BMN) evapotranspiration model developed for Nigerian environmental conditions. Kc values were derived as dimensionless ratios of ETc to ETp on a weekly basis. Across varieties and cropping periods, average weekly ETc ranged from 2.0 to 6.8 mm day-1 while seasonal ETc ranged from 326 to 374 mm, withAmugbadu having significantly higher seasonal ETc (P≤0.01) in each cropping period, presumably because of its spreading growth habit. Weekly Kc values rose from a minimum of 0.38 at the initial stage of crop growth to a peak value of 1.05 at the mid-season stage and dropped to 0.40 at the end of the late season stage. Closer spacing of Oniyaya, which has an erect growth habit, is recommended in order to increase its ground coverage, ETc and fresh leaf yield, under sole cropping system. Key words: Corchorus olitorius, Amugbadu, Oniyaya, evapotranspiration, crop coefficients.