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RESUMEN El uso de los coeficientes de cultivo (Kc) en el cultivo de tomate es determinante en la procucción del cultivo permitiendo hacer uso eficiente del recurso hídrico. Esta investigación evaluó el efecto de diferentes Kc en fase de establecimiento (0,1; 0,2 y 0,3) y floración-llenado (0,6; 0,8 y 1.1) sobre dos híbridos, Pietro F1 y Mateus 7370 en invernadero. El diseño experimental desarrollado fue BCA con arreglo en franjas divididas, donde los factores fueron los coeficientes Kc y los híbridos. La evaluación de las variables se realizó en etapa vegetativa y productiva. Los resultados mostraron un comportamiento similar entre los híbridos en la época de establecimiento, caso contrario a la fase de producción ,donde existieron diferencias estadísticas, para las variables número de frutos, peso de fruto y rendimiento, donde el híbrido Pietro, bajo el coeficiente Kc: 1,1 presentó mejores rendimientos y Mateus mejoró su producción, bajo el coeficiente Kc: 0,6.
ABSTRACT The use of crop coefficients (Kc) in tomato crops is decisive in the production, improving the efficient use of water resources. This research evaluated the effect of different Kc in the establishment phase (0.1, 0.2 and 0.3) and flowering-filling (0.6, 0.8 and 1.1) on two hybrids Pietro F1 and Mateus 7370 in greenhouse. The experimental design developed was BCA with a divided strip arrangement where the factors were the Kc coefficients and the hybrids. The evaluation of the variables was carried out in the vegetative and productive stages. The results showed a similar behavior between the hybrids at the establishment time, contrary to the production phase where there were statistical differences for the variables number of fruits, fruit weight and yield, where the Pietro hybrid under Kc coefficient: 1.1 presented better yields and Mateus improved its production under the Kc coefficient: 0.6.
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During Rabi 2020-21, a field experiment was conducted at SKUAST-K, Shalimar, India, focusing on field Pea (Pisum sativum L.). The aim of this study was to determine the water requirement and single crop coefficient (Kc) of pea using a lysimeter setup. Four empirical models were employed to calculate the reference evapotranspiration and were then compared with the actual crop evapotranspiration at different growth stages. The Kc values for field pea were 0.50, 0.80, 1.15, and 1.10 during the initial, development, mid-season and late season stages, respectively. The water requirement was found as 239.9 mm for the whole cropping period of the pea. Among the models, the Penman Montieth crop evapotranspiration model exhibited the closest agreement with the corresponding values obtained in the field through water balance study, yielding RMSE, RSR, and NSE values of 0.97, 9.5, and 11.6, respectively. These findings highlight the significance of using Penman Monteith crop evapotranspiration model for estimating crop evapotranspiration in temperate regions.
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Accurate estimation of reference evapotranspiration (ET0) is crucial for a multitude of applications, encompassing drought detection, irrigation scheduling, water resource management, and disaster risk reduction. This investigation utilized the FAO-PM equation for ET0 estimation and subsequently incorporated meteorological variables as input variables with machine learning (ML) models to enhance ET0 predictions. The dataset was bifurcated into training and testing data segments. Four distinct machine learning models were deployed in this study, namely Random Forest (RF), Support Vector Machine (SVM), Gradient Boosting Machine (GBM), and Linear Regression (LR). The performance of these models was evaluated using various statistical indices, including Mean Absolute Error (MAE), Mean Sum of Error (MSE), Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), and the coefficient of determination (R2), to pinpoint the most efficacious ML algorithm. After conducting a comprehensive analysis involving both training and testing data, the results unequivocally identify GBM with MAE values of 0.054 and 0.077, MSE values of 0.005 and 0.011, MAPE values of 0.014 and 0.022, RMSE values of 0.072 and 0.107, and an R2 value of 0.096 and 0.092 during training and testing, respectively. This model has been selected as the optimal choice for precise ET0 estimation within the study region. Subsequently, SVM, RF, and LR follow as alternatives in terms of performance, in descending order.
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A field experiment was conducted on Ridge gourd during rabi season of 2021-22 and 2022-23 at the Experimental Research Plot Soil and Water Engineering, CAE, Raichur. The study aimed to assess the efficacy of a sensor and evapotranspiration based irrigation system in varying irrigation levels, comparing the performance between mulched and non-mulched conditions. The use of sensor-based irrigation at 100% field capacity under mulched has shown positive outcomes, leading to a notable enhancement in crop production by about 9.40% additionally, this approach has resulted in a significant conservation of irrigation water, with savings of approximately 12.35% compared to the treatment involving irrigation at 100% evapotranspiration under mulched, but without the use of sensors. Across the treatments, the water application efficiency ranged from 94.13 to 91.37%. The highest water use efficiency was observed in the treatment with irrigation at 100% FC under mulched condition on pooled basis (0.20 t ha-1 mm-1). The sensor based drip irrigation system under mulched is an economically viable option to be recommended among farmers in arid and semi-arid climate. Despite the higher initial setup costs, farmers can achieve significant cost savings in the long run due to lower water usage, better yields, and minimised labour requirements.
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The current study was conducted at the Farming System Research Station, situated within the Department of Agronomy at the College of Agriculture, Junagadh Agricultural University in Junagadh, Gujarat, India. This research took place during the winter cycle (Rabi season) 2021 to 2022 and 2022 to 2023. In this study, the CROPWAT crop irrigation schedule provides an overall Evapotranspiration (ETc) value of 549.6 millimeters as the optimal water requirement for achieving maximum crop production with sufficient water supply. The actual water use by the crop during its growth period amounted to 544.2 millimeters and total net irrigation applied was 507.9 millimeters, while the gross irrigation amounted to 725.6 millimeters. The irrigation efficiency was 100%. Comparing this approach to irrigation scheduling based on the Irrigation Water to Crop Potential Evapotranspiration (IW/CPE) ratio, using CROPWAT enabled the precise management of irrigation water. It ensured that the alfalfa crop received the appropriate amount of water according to its specific growth stage requirements. The CROPWAT model data indicates that there was no yield reduction, even with a 100% critical depletion of available soil moisture. Additionally, the seasonal yield response factor was calculated to be 0.80%. These findings emphasize the effectiveness of the irrigation strategy employed, resulting in optimal crop yields without yield losses due to critical soil moisture depletion.
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The study conducted at the Maize Research Centre, Agriculture Research Institute, Professor Jayashankar Telangana State Agricultural University (PJTSAU), Rajendranagar, Hyderabad, from November, 2022 to March, 2023 aimed to compute the crop evapotranspiration (ETc) of maize crop under two different irrigation treatments using the weather data generated from the Eddy Covariance (EC) flux tower. The two treatments comprise of scheduling irrigation at certain Depletion of Available Soil Moisture (DASM) viz., T1: 20% DASM and T2: 40% DASM. The maize crop was sown and cultivated as per the recommended practices. The bio-physical parameters like plant height and LAI were recorded at 15 days interval. These parameters were statistically analysed by two sample T-test with equal variance. The plant height increased from 35 to 198 cm in 20% DASM and 36 to 180 cm in 40% DASM during the crop growth period (30 to 100 DAS). Similarly, LAI increased from 0.72 to 3.9 and 0.77 to 3.2 in 20 and 40 % DASM treatments till 90 DAS, respectively and later on decreased till harvest. The findings emphasize a positive influence of optimum moisture availability in the root zone on plant growth parameters. The amount of irrigation given was measured to compute ETc using Soil Water Balance (SWB) method and the crop parameters like plant height, LAI, stomatal resistance values etc., were used for computing the Penman-Monteith equation using the weather parameters generated from the EC flux tower. Seasonal ETc estimated from the Soil Water Balance (SWB) method (340 & 280 mm) and FAO Penman-Monteith method (350 & 295 mm) in 20 and 40% DASM treatments showed a deviation of +10 and +15 mm, respectively. Furthermore, the study concludes that FAO Penman-Monteith method can accurately estimate ET by using EC flux tower measured weather data, with minor deviations from the SWB method.
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The water requirement of crops in the canal command of distributaries of Gayathri Irrigation Project in Palakkad district, Kerala was estimated using GIS and CROPWAT 8 model. The geospatial data base for canal network, land use, soil and climate were prepared using Geographic Information System (GIS) tools. This data base was used as input to CROPWAT model to estimate irrigation water requirement of different distributaries of the canal command. The gross irrigation requirement was estimated for the historical climate data (2004-2018) as well as the predicted climate data for the years 2026 and 2031. The net irrigation water requirement of different crops in the distributary command was found to vary spatially depending on soil, crop and climate. The net irrigation water requirement of paddy (mundakan) in distributaries located at head to tail reaches varied from 1004.5 to 1573.6 mm. The high value of net irrigation requirement in tail reach was due to the influence of soil series with high infiltration rate compared to head reach soil. The net irrigation requirement also varied for the same crop in same soil series in different distributaries depending upon the climatic conditions. The net irrigation water requirement of paddy (mundakan) in distributaries located at head to middle reaches for the same soil series varied from 1056.5 to 1004.5 mm due to the influence of variations in rainfall. The gross estimated irrigation water requirement showed that distributaries at the middle and tail reaches required more water than the distributaries at the head end. The maximum gross irrigation water requirement of 25369.7 m3/ha was observed for Peringhotukavu distributary in tail reach and lowest of 4390.9 m3/ha for Parakkalchalla distributary in head reach. The estimation of irrigation requirement for projected climate data also showed the same trend as that of historical data.
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RESUMEN La evapotranspiración de referencia (ETo) es una variable hidrológica de gran importancia en el manejo del riego. Su estimación se realiza con la ecuación de Penman-Montieth (PM), que requiere de muchas variables meteorológicas, las cuales, a veces, no se encuentran disponibles. Dado que la ETo es una variable no lineal y compleja, en los últimos años han surgido métodos alternativos para su estimación, como las redes neuronales artificiales (RNA). El objetivo del presente trabajo fue estimar la evapotranspiración de referencia (ETo) usando la ecuación de Penman-Montieth, a fin de desarrollar modelos de redes neuronales artificiales (RNA) que permitan predecir la ETo en regiones con información climatológica limitada, y su vez comparar el desempeño de tres modelos de RNA: FFNN, ERNN y NARX. Se utilizó información diaria durante el periodo 1 de enero de 2007 al 31 de diciembre de 2018, de las estaciones meteorológicas ENP8 y ENP4 de la CDMX. Se realizó un análisis de correlación y el análisis de sensibilidad de Garson para estudiar 2 casos (red estática FFNN y redes dinámicas: ERNN y NARX) usando 3 modelos de RNA: 1) RNA con 6 entradas: radiación solar (Rad), temperatura máxima y mínima (Tmax, Tmin), humedad relativa máxima y mínima (HRmax, HRmin) y velocidad del viento (u); y 2) RNA con 2 entradas (Rad y Tmax). La variable de salida fue la ETo calculada con la ecuación de PM. En todos los casos, las 3 RNA fueron muy parecidas, la diferencia más notable es que las redes dinámicas (ERNN y NARX) requieren de menor número de iteraciones para llegar al desempeño óptimo. Las RNA entrenadas, únicamente con Rad y Tmax como entradas, fueron capaces de predecir la ETo en el largo plazo, durante 440 d, en otra estación meteorológica cercana (ENP4), con eficiencias mayores al 90 %.
ABSTRACT Reference evapotranspiration (ETo) is a hydrological variable of great importance in irrigation management. Its estimation is carried out with the Penman-Montieth (PM) equation that requires many meteorological variables and that are sometimes not available. Since ETo is a nonlinear and complex variable, in recent years alternative methods have emerged for its estimation, such as artificial neural networks (ANN). The objective of this work was to estimate the reference evapotranspiration (ETo) using the Penman-Montieth equation, in order to develop artificial neural network (ANN) models that allow ETo to be predicted in regions with limited climatological information, and in turn to compare the performance of three RNA models: FFNN, ERNN and NARX. Daily informtion was used during the January 1, 2007 to December 31, 2018 period, for the ENP8 and ENP4 meteorological stations in Mexico city. Based on the correlation analysis and the Garson sensitivity analysis, 2 cases were studied for the 3 ANN models: 1) ANN with 6 inputs: solar radiation (Rad), maximum and minimum temperature (Tmax, Tmin), maximum and minimum relative humidity (RHmax, RHmin), and wind speed (u), and 2) RNA with 2 inputs (Rad and Tmax). The output variable was the ETo, calculated with the PM equation. In all cases, the performance of the 3 ANNs was very similar. The most notable difference is that the dynamic networks (ERNN and NARX) require fewer iterations to achieve the optimum performance. ANNs trained only with radiation and maximum temperature as inputs were able to predict a long-term ETo for 440 at another nearby meteorological station (ENP4), with efficiencies greater than 90 %.
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A study was conducted to determine the water demand of wheat crops in the area around the Tonna Pumping Canal. It used 2017-2018 climate data to determine the need for wheat crops in water in CROPWAT. Reference crop evapotranspiration (ETo) was determined using the FAO Penman Monteith method. When considering wheat crops, four stages of crop growth were considered: early stage, development stage, mid-maturity, and late-maturity stages. Crops were planted in the 2017 rabi season and yields were determined for each.This study shows that baseline evapotranspiration (ETo) in the study area ranges from 1.48 to 3.98 mm/day. Crop evapotranspiration (ETc) and water demand for wheat crops ranged from 0.44 to 3.75 mm/day and 1.9 to 39.8 mm/day. The maximum water demand was 0.13 l/s/ha or 1.1 mm/day with 65% efficiency. The irrigation water demand was estimated at about 27.93 mm/day, and the actual water intake was 81,000.29 m3. The canal can therefore provide a convenient supply of the water needed to irrigate the area.
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Para realizar un manejo eficiente del agua en la agricultura es necesario conocer los requerimientos hídricos del cultivo, lo cual, se puede realizar de manera sencilla y rápida, con la ayuda de cámaras convencionales. En este estudio, se determinaron los requerimientos hídricos de un cultivo de frijol (variedad DIACOL CALIMA G4494), sembrado en CIAT, Palmira - Valle del Cauca, Colombia, mediante la estimación de la curva del coeficiente basal de cultivo (Kcb), derivada de la curva de fracción de cobertura vegetal (Fcv). Para determinar la curva de fracción de cobertura vegetal, se emplearon imágenes tomadas con una cámara digital en el espectro visible (RGB), a baja altura (menos de 3 m). Las necesidades hídricas del cultivo de frijol, se calcularon empleando los valores del coeficiente basal de cultivo derivados junto con la modelación FAO-56. Los resultados indican que la curva de Kcb ajustada por fotografía fue diferente a la curva estándar presentada en la publicación FAO-56 para frijol, mostrando, principalmente, diferencia en la duración de las etapas y los valores de Kcb, en estas etapas. En cuanto a las necesidades hídricas, al emplear la curva de Kcb ajustada por fotografías, se evidencia que el cultivo requiere más agua en las etapas media y final, para evitar estrés hídrico en las plantas.
To carry out efficient water management in agriculture, it is necessary to know the water requirements of the crop, which can be done easily and quickly with the help of conventional cameras. In this study, the water requirements of a bean crop (DIACOL CALIMA G4494 variety) planted in CIAT, Palmira - Valle del Cauca, Colombia, were determined by estimating the curve of the basal crop coefficient (Kcb) derived from the vegetation cover fraction curve (Fcv). To determine the vegetation cover fraction curve, images taken with a digital camera in the visible spectrum (RGB) at low height (less than 3m) were used. The water needs of the bean crop were calculated using the basal crop coefficient values derived together with the FAO-56 modelling. The results indicate that the Kcb curve adjusted by photography was different from the standard curve presented in the publication FAO-56 for beans, mainly showing a difference in the duration of the stages and the Kcb values in these stages. Regarding water needs, when using the Kcb curve adjusted by photographs, it is evident that the crop requires more water in the middle and final stages, to avoid water stress in the plants.
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Abstract The production of litterfall is essential for nutrient cycling in terrestrial ecosystems. From November 2009 to October 2011, analyzed the monthly litterfall production in two areas of Caatinga, a type of Seasonally Dry Tropical Forest located in the Cariri Paraibano, in the semiarid region of the Paraíba, Northeastern Brazil. One of the areas, Private Natural Heritage Reserve (RPPN) Fazenda Almas, is legally protected, and the other, Fazenda Moreiras, does not. The aims were to evaluate the effects of precipitation, evapotranspiration and vegetation structure on the temporal and spatial dynamics of litterfall production. Eight sampling points were randomly chosen at each site, and two 1 m2 collectors were installed 50 m apart from each other. The collected material was sorted, dried and weighed. Additionally, the characteristics (density, species richness, height and mean basal area) of the tree-shrub stratum in plots with a 10 m radius surrounding each collector. Total litterfall production was 4,500 kg ha-1 yr-1 for Fazenda Almas and 3,300 kg ha-1 yr-1 for Fazenda Moreiras; these values were within the expected range for Seasonally Dry Tropical Forests. The inter- and intra-annual variation in litterfall production was positively correlated with precipitation and evapotranspiration rates, and four months after the highest precipitation rates, there was a marked decrease in litterfall occurred during the dry season. Furthermore, the contributions of the material fractions were distinct with the leaf fraction representing for more than 60% of the litterfall, and the vegetation structure explained 75% of the variation in litterfall production. Therefore, climatic factors and vegetation structure affect the temporal and spatial dynamics of litterfall production and consequently influence nutrient dynamics in the semiarid region of Brazil.
Resumo A produção de serapilheira é essencial para a ciclagem de nutrientes em ecossistemas terrestres. De Novembro de 2009 a Outubro de 2011, foi analisada a produção de serapilheira em duas áreas de Caatinga, um tipo de Floresta Tropical sazonalmente Seca localizada no Cariri Paraibano, na região do semiárido da Paraíba, Nordeste do Brasil. Uma das áreas, Reserva Particular do Patrimônio Natural - RPPN - Fazenda Almas, é legalmente protegida, ao contrário da outra, Fazenda Moreiras. Os objetivos foram avaliar o efeito da precipitação, evapotranspiração e estrutura da vegetação sobre a dinâmica temporal e espacial da produção de serapilheira. Oito pontos de amostragem foram escolhidos aleatoriamente em cada localidade, e dois coletores de 1 m2 foram instalados a 50 m um do outro. O material coletado foi triado, secado e pesado. Adicionalmente, foram registradas as características (densidade, riqueza de espécies, altura e área basal média) das espécies arbóreo-arbustivas na parcela com um raio (r) de 10 m ao redor de cada coletor. A produção total de serapilheira foi 4,500 Kg ha-1 yr-1 para a Fazenda Almas e 3,300 kg ha-1 yr-1 para a Fazenda Moreiras; estes valores estão dentro da faixa esperada para as Florestas Tropicais sazonalmente secas. A variação inter e intranual na produção de serapilheira foi positivamente correlacionada com as taxas de precipitação e evapotranspiração, e quatro meses depois das maiores taxas de precipitação, houve uma diminuição acentuada na serapilheira coletada durante a estação seca. Além disso, as contribuições das frações de material foram distintas com a fração de folha representando mais que 60% da serapilheira, e a estrutura da vegetação explicou 75% da variação na produção de serapilheira. Portanto, os fatores climáticos e a estrutura da vegetação afetam a dinâmica temporal e espacial da produção de serapilheira e, consequentemente, influenciam a dinâmica de nutrientes na região semiárida do Brasil.
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Forests , Ecosystem , Seasons , Trees , Tropical Climate , BrazilABSTRACT
In order to achieve good yields and profitability from ginger crops, the water supply must be adequate. However, there are few studies available which have evaluated the adequate water supply to this vegetable. The objective of this study was to evaluate the effect of different irrigation depths on the development and productivity of ginger plants. The research was conducted at the "Sítio Schmidt" farm located in the municipality of Santa Maria de Jetibá, in the central mountainous region of Espírito Santo State, Brazil. The experimental design was a randomized block design with four replications, each experimental unit consisting of three rows at a spacing of 0.90 m and 0.10 m between plants of two meters extension, totaling 20 experimental units. The treatments consisted of application of five irrigation depths equivalent to: 50%, 75%, 100%, 125% and 150% of crop evapotranspiration (ETc). We evaluated the number of sprouts; average mass of export quality rhizome; the production of export, small and total rhizomes (t ha-1); and water use efficiency. The total water depth applied in the range 11001200 mm per cycle favors the development of ginger plants, providing the highest yields of total and export rhizomes, the greatest average mass of export quality rhizome and lowest production of small rhizomes.
Para que se alcance bons rendimentos e lucratividade com a cultura do gengibre o fornecimento de água deve ser adequado. Entretanto, ainda são poucos os trabalhos que avaliam o adequado fornecimento de água para esta hortaliça. Frente a isso, objetivou-se avaliar o efeito de diferentes lâminas de irrigação no desenvolvimento e na produtividade da cultura do gengibre. A pesquisa foi conduzida na propriedade "Sítio Schmidt" localizada no município de Santa Maria de Jetibá, região Central Serrana do Estado do Espírito Santo. O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições, sendo cada unidade experimental constituída por três fileiras em um espaçamento de 0,90 m e 0,10 m entre plantas de dois metros de extensão, totalizando 20 unidades experimentais. Os tratamentos consistiram na aplicação de cinco lâminas de irrigação, sendo elas: 50%, 75%, 100%, 125% e 150%. Foram avaliados o número de brotações; a massa média dos rizomas com padrão tipo exportação; as produtividades de rizomas tipo exportação, pequeno e total (t ha-1); e a eficiência do uso da água. A lâmina total aplicada na faixa de 1100-1200 mm por ciclo, ou seja, 75 a 100% da ETc favorece o desenvolvimento de plantas de gengibre, proporcionando maiores produtividades de rizoma total e tipo exportação, maior massa média de rizoma tipo exportação e menor produção de rizomas pequenos.
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Evapotranspiration , Water Use , Zingiber officinale , Dehydration , HorticultureABSTRACT
Considering the scenarios with reduction of water availability, the need to increase water use efficiency and crop yield, the objective of this study was to evaluate the effect of reducing the evapotranspiration of the main irrigated crops on productivity. Data from the years 2005 to 2016 for carrot, garlic, potato, sugarcane, bean, maize, soybean, wheat, coffee and cotton crops grown in the Brazilian states of Bahia, Minas Gerais, São Paulo, Goiás, Distrito Federal and Mato Grosso were collected. The crops were irrigated by central-pivot irrigation and drip irrigation systems, and irrigation management was performed using IRRIGER® software. With the information on potential crop evapotranspiration (ETpc) and crop evapotranspiration (ETc), it was possible to obtain a reduction of ETpc (%) for all crops. For all scenarios, these data were confronted with crop productivity and regression models were fitted. It was concluded that the maximum reductions of ETpc (%) without affecting productivity are 5% for garlic and potato, 12% for maize, 13% for bean, 15% for wheat, 20% for soybean and cotton, 25% for sugarcane and 30% for coffee.
Diante dos cenários com redução da disponibilidade hídrica, necessidade de aumento da eficiência no uso da água e da produtividade das culturas agrícolas, objetivou-se neste trabalho avaliar o efeito da redução da evapotranspiração na produtividade das principais culturas irrigadas. Informações foram coletadas nas safras dos anos de 2005 à 2016 para as culturas da cenoura, alho, batata, cana-de-açúcar, feijão, milho, soja, trigo, café e algodão cultivadas nos estados da Bahia (BA), Minas Gerais (MG), São Paulo (SP), Goiás (GO), Distrito Federal (DF) e Mato Grosso (MT). As culturas foram irrigadas por sistemas de irrigação por pivô central e gotejamento, sendo que os manejos de irrigação foram realizados por meio do software IRRIGER®. Com as informações de evapotranspiração potencial da cultura (ETpc) e evapotranspiração da cultura (ETc) foi possível obter a redução da ETpc (%) para todos os cultivos. Para todos os cenários, estes dados foram confrontados com a produtividade das culturas e modelos de regressão foram ajustados. Concluiu-se que a redução máxima de ETpc (%) sem afetar a produtividade é 5% para o alho e batata, 12% para o milho, 13% para o feijão, 15% para o trigo, 20% para a soja e algodão, 25% para a cana-de-açúcar e 30% para o café.
Subject(s)
Evapotranspiration , Crops, Agricultural , Grassland , DehydrationABSTRACT
The average of mean monthly ET0 estimated under polyhouse by FAO PM (benchmark) model was 39.44 mm, but that of the FAO Penman, Hargreaves Stanghellini, Priestley-Taylor and FAO Radiation models were 38.37, 18.18, 37.80, 48.17 and 53.87 mm respectively. Whereas, the average of mean monthly ETo estimated under open environment by FAO PM (benchmark) model was 116.34 mm, but that of the FAO Penman, Hargreaves Stanghellini, Priestley-Taylor and FAO Radiation models were 119.33, 133, 126.41, 113.17 and 117.37 mm respectively. The FAO Penman and Hargreaves model are found to be most and least appropriate models for estimating daily ET0 under polyhouse. Whereas, FAO Radiation and Stanghellini model observed to be most and the least appropriate models in an open environment for estimating daily ET0 under polyhouse for the Pantnagar Tarai condition of Uttarakhand.
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ABSTRACT: Determining actual crop evapotranspiration (ETa) is paramount for irrigation management. The principal measurement methods and physical models generally require crop and weather data that are not readily available. We determined the crop coefficient (Kc) of sweet oranges during the initial development stage and evaluated the performance of the Poulovassilis semi-empirical model coupled with a simple soil water balance for estimating the ETa. The ETa was inferred from the variation in the soil water content over time, measured by time-domain reflectometry. In the Poulovassilis model, the ETa is obtained by multiplying the crop evapotranspiration (ETc) by an adjustment coefficient (ca), which accounts for a reduction in the evapotranspiration caused by soil water depletion. Soil water storage was obtained using the daily and 10-day soil water balances, computed by considering inputs and outputs of water from the system. The empirical parameter, ca, was determined using inverse modeling. The optimal ca value obtained through inverse modeling was 0.05 and 0.03 for the daily and 10-day soil water balances, respectively. The model performed better for the daily soil water balance than the 10-day balance, with performance comparable with the other ETa models. Average Kc during the sweet orange initial crop stage was 0.85.
RESUMO: A determinação da evapotranspiração real da cultura (ETa) é importante para o manejo da irrigação. Os principais métodos e modelos físicos de estimativa da ETa requerem dados que não são facilmente disponíveis. Neste trabalho, obteve-se o coeficiente da cultura (Kc) da laranja lima na fase inicial de desenvolvimento e avaliou-se o desempenho do modelo semi-empírico de Poulovassilis acoplado a um balanço hídrico simplificado na estimativa da ETa. A ETa (medida) foi obtida a partir da variação temporal do conteúdo de água no solo, obtida através da reflectometria no domínio do tempo (TDR). O modelo de POULOVASSILIS et al. (2001) assume que a redução da evapotranspiração da cultura é expressa por uma função exponencial do armazenamento de água do solo e por um coeficiente de ajuste empírico (ca). O armazenamento de água do solo foi obtido através do balanço hídrico (BH), diário e decendial, contabilizando as entradas e saídas de água do sistema. O parâmetro empírico ca foi obtido por modelagem inversa. O valor ótimo de ca obtido por modelagem inversa 0,05 para o BH diário e 0,03 para o BH decendial. O modelo apresentou melhor desempenho para o BH diário, comparável a outros modelos de estimativa da ETa. O Kc médio para fase inicial da laranja lima foi igual a 0,85.
ABSTRACT
ABSTRACT The estimation of the reference evapotranspiration is an important factor for hydrological studies, design and management of irrigation systems, among others. The Penman Monteith equation presents high precision and accuracy in the estimation of this variable. However, its use becomes limited due to the large number of required meteorological data. In this context, the Hargreaves-Samani equation could be used as alternative, although, for a better performance a local calibration is required. Thus, the aim was to compare the calibration process of the Hargreaves-Samani equation by linear regression, by adjustment of the coefficients (A and B) and exponent (C) of the equation and by combinations of the two previous alternatives. Daily data from 6 weather stations, located in the state of Minas Gerais, from the period 1997 to 2016 were used. The calibration of the Hargreaves-Samani equation was performed in five ways: calibration by linear regression, adjustment of parameter "A", adjustment of parameters "A" and "C", adjustment of parameters "A", "B" and "C" and adjustment of parameters "A", "B" and "C" followed by calibration by linear regression. The performances of the models were evaluated based on the statistical indicators mean absolute error, mean bias error, Willmott's index of agreement, correlation coefficient and performance index. All the studied methodologies promoted better estimations of reference evapotranspiration. The simultaneous adjustment of the empirical parameters "A", "B" and "C" was the best alternative for calibration of the Hargreaves-Samani equation.
RESUMO A estimativa da evapotranspiração de referência é um importante fator para estudos hidrológicos, projeto e manejo de sistemas de irrigação, dentre outros. A equação de Penman Monteith apresenta elevada precisão e acurácia na estimativa desta variável. No entanto, o uso desta se torna limitado devido ao grande número de dados meteorológicos requeridos. Neste contexto, a equação de Hargreaves-Samani pode ser utilizada como alternativa, contudo, requer uma calibração local para a obtenção de melhores performances. Assim, objetivou-se comparar o processo de calibração da equação de Hargreaves-Samani via regressão linear, via ajuste dos coeficientes (A e B) e expoente (C) da equação e via combinações das duas alternativas anteriores. Foram utilizados dados diários de 6 estações meteorológicas, situadas no estado de Minas Gerais, do período de 1997 a 2016. A calibração da equação de Hargreaves-Samani foi realizada de cinco formas: calibração via regressão linear, ajuste do parâmetro "A", ajuste dos parâmetros "A" e "C", ajuste dos parâmetros "A", "B" e "C" e ajuste dos parâmetros "A", "B" e "C" seguido de calibração por regressão linear. As performances dos modelos foram avaliadas com base nos indicadores estatísticos erro absoluto médio, erro de viés médio, índice de concordância de Willmott, coeficiente de correlação e índice de desempenho. Todas as metodologias estudadas promoveram melhores estimativas da evapotranspiração de referência. O ajuste simultâneo dos parâmetros empíricos "A", "B" e "C" foi a melhor alternativa para calibração da equação de Hargreaves-Samani.
ABSTRACT
ABSTRACT: The water-driven AquaCrop model to simulate yield response has been calibrated and validated for soybean cultivated under different water levels irrigation in Matopiba region, Brazil. The crop was submitted to seven irrigation treatments during the dry season and a dry treatment in the rainy season. The model was parameterized and calibrated by using soybean yield data collected at field level. Model performance was evaluated by using the following statistical parameters: prediction error (Pe), Nash-Sutcliffe efficiency index (E), coefficient of determination (R2), mean absolute error (MAE), root mean square error normalized (RMSEN) and Willmott's index (d). The statistical analyses of the AquaCrop model calibrated for the Matopiba region disclosed error acceptable for yield prediction of soybean grown under tropical climate conditions. Results also indicated that the C2 soybean cultivar is more resistant to water stress than the C1 soybean grown in the Matopiba region, Brazil. In the treatments when the crop was well supplied with water, at least in one phase, the yield was greater than those with drought stress at last in one phase.
RESUMO: O modelo AquaCrop foi calibrado e validado para simular a produtividade da soja cultivada sob diferentes lâminas de irrigação na região de Matopiba, Brasil. A cultura foi submetida a sete tratamentos de irrigação durante a estação seca e um tratamento de sequeiro na estação chuvosa. O modelo foi parametrizado e calibrado utilizando dados de produtividade de soja coletados diretamente em campo. O desempenho do modelo foi avaliado utilizando os seguintes parâmetros estatísticos: erro de predição (Pe), índice de eficiência de Nash-Sutcliffe (E), coeficiente de determinação (R2), erro médio absoluto (EMA), raiz quadrática do erro médio normalizado (EQEMN) e índice de Willmott (d). As análises estatísticas do modelo AquaCrop calibrado para a região de Matopiba apresentaram erros aceitáveis na predição da produtividade de soja cultivada sob condições climáticas tropicais. Os resultados também indicaram que a cultivar de soja C2 é mais resistente ao estresse hídrico do que a soja C1 cultivada na região de Matopiba, Brasil. Nos tratamentos durante os quais a cultura foi bem abastecida com água, em pelo menos em uma fase, a produtividade foi maior, em vista do estresse hídrico que ocorre em uma fase.
ABSTRACT
ABSTRACT: The objective of this study was to simulate the variation of the available soil water during maize crop growth, in two different sowing times (first and second growing season), using a drip irrigation system. The treatments consisted of different irrigation strategies (full to deficit). The SIMDualKc simulation model was used to determine the daily soil water balance and crop evapotranspiration using the dual crop coefficient approach. Soil, climate, crop and irrigation parameters were used as input data. Two experiments were carried out in a rainout shelter composed of two metallic structures (16x10m) in the city of Santa Maria, Rio Grande do Sul, Brazil, during 2010/11 (second crop, season 1) and 2011/12 (first crop, season 2) growing seasons, under no-tillage system. The simulations showed that all the irrigation management strategies used in season 2 resulted in soil water deficit, while only two strategies showed deficit in season 1. Results showed good agreement between observed and simulated soil water data, with an R2 ranging from 0.86 to 0.99 and the root mean square error ranging from 2.7 to 5.6% of the total available water for seasons 1 and 2, respectively. The observed results of water balance showed that maize grown in season 2 presented higher water consumption compared to season 1, due to the higher atmospheric demand of season 2. The SIMDualKc model allowed the partitioning of crop evapotranspiration into soil evaporation and crop transpiration, demonstrating that the vegetative growth subperiod presented the greatest differences between the two seasons compared to the others growth phases.
RESUMO: O objetivo deste estudo foi simular a variação da água disponível no solo durante o desenvolvimento da cultura do milho, em duas épocas de semeadura diferentes (primeira e segunda safra), utilizando sistema de irrigação por gotejamento. Os tratamentos consistiram em diferentes estratégias de irrigação (plena e deficitária). O modelo de simulação SIMDualKc foi utilizado para determinar o balanço hídrico diário do solo e a evapotranspiração da cultura usando a abordagem do coeficiente cultura dual. Os parâmetros de solo, clima, cultura e irrigação foram utilizados como dados de entrada. Dois experimentos foram realizados em uma cobertura móvel composta por duas estruturas metálicas (16x10m) na cidade de Santa Maria, Rio Grande do Sul, Brasil, nas safras 2010/11 (segunda safra, época 1) e 2011/12 (primeira safra, época 2), sob sistema de plantio direto. As simulações mostraram que todas as estratégias de manejo de irrigação usadas na época 2 resultaram em déficit hídrico, enquanto que apenas duas estratégias apresentaram déficit na época 1. Os resultados mostraram boa concordância entre os dados de água no solo observados e simulados, com um R2 variando de 0.86 a 0.99 e raiz quadrada do erro médio variando de 2,7 a 5,6% da água total disponível para as épocas 1 e 2, respectivamente. Os resultados observados do balanço hídrico mostraram que o milho cultivado na época 2 apresentou maior consumo de água em comparação com a época 1, devido à maior demanda atmosférica da época 2. O modelo SIMDualKc permitiu a partição da evapotranspiração da cultura em evaporação do solo e transpiração da cultura, demonstrando que o subperíodo de crescimento vegetativo apresentou as maiores diferenças entre as duas épocas em relação às demais fases de crescimento.
ABSTRACT
The great challenge of breeding programs focused on tolerance to water stress is the precise, in large scale, and automated phenotyping. Therefore, the objective of this study was to assess whether the controlled conditions of SITIS Automated Phenotyping Platform and the protocol used are suitable for discriminating cultivars of common bean and soybean for tolerance to this stress. Two experiments were carried out in randomized block design, in a split plot scheme, with four replications. The main plots had five water regimes, applied after flowering: daily replacement of 100 (control), 80, 60, 40, and 20% of water evapotranspired in control. The subplots consisted of two common bean cultivars (BRS Pontal and BRS Pérola) in the 1st experiment, and two soybean cultivars (MG/BR 46 Conquista and BR- 16) in the 2nd one. In each species, the first cultivar is more tolerant to water stress, and the second one is more susceptible. It is possible to use the SITIS Platform and the proposed protocol to evaluate common bean and soybean cultivars for tolerance to water stress. The common bean cultivars evaluated were more sensitive to this stress than soybeans. The best water status of cultivars BRS Pontal and MG/BR 46 Conquista under water stress confirmed their greater tolerance.
O grande desafio dos programas de melhoramento com foco na tolerância à deficiência hídrica é a fenotipagem precisa, em larga escala e automatizada. Assim, objetivou-se avaliar se as condições controladas da Plataforma Automatizada de Fenotipagem SITIS e o protocolo utilizado são adequados para discriminar cultivares de feijão e soja quanto à tolerância a esse estresse. Foram conduzidos dois experimentos em blocos ao acaso, em parcelas subdivididas, com quatro repetições. Nas parcelas foram conduzidos cinco regimes hídricos, aplicados após a floração: reposição diária de 100 (controle), 80, 60, 40 e 20% da água evapotranspirada no controle. As subparcelas consistiram de duas cultivares de feijão (BRS Pontal e BRS Pérola), no 1º experimento, e duas de soja (MG/BR 46 Conquista e BR-16), no 2º. Em cada espécie, a primeira cultivar é mais tolerante à deficiência hídrica e a segunda é mais suscetível. É possível usar a Plataforma SITIS e o protocolo proposto para avaliar cultivares de feijão e soja quanto à tolerância à deficiência hídrica. As cultivares de feijão foram mais sensíveis a esse estresse do que as de soja. O melhor status hídrico das cultivares BRS Pontal e MG/BR 46 Conquista sob deficiência hídrica confirmou sua maior tolerância a esse estresse.
Subject(s)
Glycine max , Evapotranspiration , Phaseolus , Plant BreedingABSTRACT
ABSTRACT This study estimated the reference evapotranspiration rate (ETo) for the Itacaiúnas River Watershed (IRW), Eastern Amazonia, and measured the accuracy of eight empirical equations: Penman-Monteith (PM), Priestley-Taylor (PT), Hargreaves and Samani (HS), Camargo (CAM), Thornthwaite (TH), Hamon (HM), Kharrufa (KF) and Turc (TC) using monthly data from 1980 to 2013. In addition, it verifies the regional applicability to the IRW using a for the Marabá-PA station. The methods TC and PM (FAO56) presented the best results, which demonstrate that radiation and higher temperatures are the dominant drivers in the Evapotranspiration process, while relative humidity and wind speed have a much smaller impact. The temporal and spatial variability of ETo for IRW show has strong seasonality, increasing during the dry season and decreasing during the rainy season. The statistical analyses at 1% level of significance, indicates that there is no correlation of the residuals between the dry and rainy seasons, and test of the physical parameters such as mean temperature, solar radiation and relative air humidity explains the variations of ETo.