Peanut yield under irrigation levels in off-season cultivation

Water deficit is considered the most critical environmental factor for peanut production in Brazil, as it constitutes one of the major constraints to the expansion of its cultivation in the suitable crop zones of the country. Determining crop water demand is fundamental to increasing yield with lower water consumption. The present study aimed to evaluate the effects of full and deficit irrigation levels (L1 = 8%, L2 = 27%, L3 = 63%, L4 = 94% and L5 = 100% replenishment of crop evapotranspiration) on the development, growth and yield of peanut crop sown in two times, February and March. Treatments were distributed in a split-plot randomized complete block design, with four replicates, using a line-source sprinkler system. Irrigation depths from 65 to 314 mm were applied with the levels L1 to L5 during the first and second cropping cycles. Full irrigation with sowing in March was more advantageous due to yield increase of up to 30% compared to sowing in February, but crop cycle was 25 days longer. Water stress caused by deficit irrigation reduced plant height, seed mass and pod yield, while full irrigation (L5) led to yields from 4,141 to 5,102 kg ha-1 for February and March, approximately three times higher than those obtained with the lowest irrigation level (L1). Highlights Peanut has great importance in the food and industry of several countries. The results of this research apply to regions that require irrigation, which is of about 70% of the areas of the globe with this legume. This paper contributes with information that emphasizes the possibility of cultivation in the drought season, aiming at the expansion of the crop and the production of quality seeds using irrigation.Water deficit is considered the most critical environmental factor for peanut production in Brazil, as it constitutes one of the major constraints to the expansion of its cultivation in the suitable crop zones of the country. Determining crop water demand is fundamental to increasing yield with lower water consumption. The present study aimed to evaluate the effects of full and deficit irrigation levels (L1 = 8%, L2 = 27%, L3 = 63%, L4 = 94% and L5 = 100% replenishment of crop evapotranspiration) on the development, growth and yield of peanut crop sown in two times, February and March. Treatments were distributed in a split-plot randomized complete block design, with four replicates, using a line-source sprinkler system. Irrigation depths from 65 to 314 mm were applied with the levels L1 to L5 during the first and second cropping cycles. Full irrigation with sowing in March was more advantageous due to yield increase of up to 30% compared to sowing in February, but crop cycle was 25 days longer. Water stress caused by deficit irrigation reduced plant height, seed mass and pod yield, while full irrigation (L5) led to yields from 4,141 to 5,102 kg ha-1 for February and March, approximately three times higher than those obtained with the lowest irrigation level (L1). Highlights Peanut has great importance in the food and industry of several countries. The results of this research apply to regions that require irrigation, which is of about 70% of the areas of the globe with this legume. This paper contributes with information that emphasizes the possibility of cultivation in the drought season, aiming at the expansion of the crop and the production of quality seeds using irrigation

Uniformity of water application to central pivot and to super 10 sprayer

O aumento da preocupação mundial com o aproveitamento e uso da água e a expansão da agricultura irrigada exigem otimização da eficiência de seu uso, destacando-se a sua uniformidade de aplicação, que influencia a otimização do uso da água pelas plantas. Objetivou-se, com o presente estudo, comparar a uniformidade de aplicação de água de um aspersor, obtido em condições de campo com o catálogo do fabricante, além de avaliar a uniformidade de aplicação de água de um pivô-central com aspersores novos e usados. Em condições de campo, a uniformidade de aplicação de água do aspersor SUPER 10 foi inferior à informada no catálogo do fabricante. Não se recomenda a utilização do aspersor SUPER 10 em espaçamentos iguais ou superiores a 12 x 12 m. Além disso, em culturas com alto valor agregado, como hortaliças, indica-se a utilização desse aspersor no espaçamento de 8 x 8 m. O pivô central apresenta boa uniformidade de aplicação de água, com CUH de 87,4% e CUD de 82,8%, além de aplicar uma lâmina média de 7,39 mm. The increase in global concern with the use and use of water and the expansion of irrigated agriculture require optimization of the efficiency of its use, highlighting its uniformity of application, which influences the optimization of water use by plants. The objective of this study was to compare the uniformity of water application of a sprinkler, obtained in field conditions with the manufacturer's catalog, and to evaluate the uniformity of water application of a central pivot with new and used sprinklers. Under field conditions, the water application uniformity of the SUPER 10 sprinkler was lower than that reported in the manufacturer's catalog. It is not recommended to use the SUPER 10 sprinkler in spacings equal to or greater than 12 x 12 m. In addition, in cultures with high added value, such as vegetables, the use of this sprinkler in the 8 x 8 m spacing is indicated. The central pivot shows good uniformity of water application, with CUH of 87.4% and CUD of 82.8%, besides applying a mean blade of 7.39 mm.El aumento de la preocupación mundial con el aprovechamiento y uso del agua y la expansión de la agricultura irrigada exigen optimización de la eficiencia de su uso, destacándose la uniformidad de aplicación, que influye en la optimización del uso del agua por las plantas. Se objetivó, con el presente estudio, comparar la uniformidad de aplicación de agua de un aspersor, obtenido en condiciones de campo con el catálogo del fabricante, además de evaluar la uniformidad de aplicación de agua de un pivote central con aspersores nuevos y usados. En condiciones de campo, la uniformidad de aplicación de agua del aspersor SUPER 10 fue inferior a la indicada en el catálogo del fabricante. No se recomienda el uso del aspersor SUPER 10 en espaciamientos igual o superiores a 12 x 12 m. Además, en cultivos con alto valor agregado, como hortalizas, se indica la utilización de este aspersor en el espaciado de 8 x 8 m. El pivote central presenta buena uniformidad de aplicación de agua, con CUH de 87,4% y CUD del 82,8%, además de aplicar una lámina media de 7,39 mm

Comparison of equations for the estimation of head loss in polyethylene tube

La determinación de la pérdida de carga en proyectos de riego no es utilizada por ser un método de baja practicidad. Para ello, existen ecuaciones que estiman esa variable, basándose en características de las tuberías y del proyecto, tales como material del tubo, diámetro y caudal del sistema. De esta forma, se objetivó evaluar la mejor ecuación para la estimación de la pérdida de carga en tubería de polietileno con diámetro interno de 25 mm, comparando los resultados a la pérdida de carga determinada en manómetro de mercurio. El experimento fue realizado en lo laboratorio de irrigación de la FCAV / Unesp, Jaboticabal en junio de 2017. La estimación de la pérdida de carga fue realizada por la ecuación de Hazen-Williams y de Darcy-Weisbach, siendo que para esa última el factor de fricción (f ) fue estimado por los modelos de Swamee y Jain y de Blasius. Las ecuaciones fueron comparadas con los datos determinados en columna de mercurio en 5 caudales, con valores que varían de 1,55 m3 h-1 a 5,15 m3 h-1. La estimación de la pérdida de carga por el método de Swamee y Jain sobreestimó los valores determinados en la columna de mercurio. Hasta el caudal de 5,15 m3  h-1 el método de Hazen-Williams presentó la menor variación y, consecuentemente, la mayor eficiencia de estimación de pérdida de carga en relación a los valores determinados para la tubería de polietileno de diámetro de 25 mm.A determinação da perda de carga em projetos de irrigação não é utilizada por ser um método de baixa praticidade. Para isso, existem equações que estimam essa variável, embasando-se em características das tubulações e do projeto, tais como material do tubo, diâmetro e vazão do sistema. Dessa forma, objetivou-se avaliar a melhor equação para a estimativa da perda de carga em tubulação de polietileno com diâmetro interno de 25 mm, comparando os resultados à perda de carga determinada em manômetro de mercúrio. O experimento foi realizado no laboratório de irrigação da FCAV/Unesp, Jaboticabal em junho de 2017. A estimativa da perda de carga foi realizada pela equação de Hazen-Williams e de Darcy-Weisbach, sendo que para essa última o fator de atrito (f) foi estimado pelos modelos de Swamee & Jain e de Blasius. As equações foram comparadas com os dados determinados em coluna de mercúrio em 5 vazões, com valores variando de 1,55 m3 h-1 a 5,15 m3 h-1. A estimativa da perda de carga pelo método de Swamee & Jain superestimou os valores determinados na coluna de mercúrio. Até a vazão de 5,15 m3 h-1 o método de Hazen-Williams apresentou a menor variação e, consequentemente, a maior eficiência de estimativa de perda de carga em relação aos valores determinados para a tubulação de polietileno com diâmetro de 25 mm. The determination of the head loss in irrigation projects is not used because it is a low practical method. For this, there are equations that estimate this variable, based on characteristics of the pipes material, diameter and system flow. Thus, the objective of this study was to evaluate the best equation for estimating the head loss in polyethylene tubing with internal diameter of 25 mm, comparing the results to the head loss determined in a mercury manometer. The experiment was carried out in the irrigation laboratory of the FCAV/Unesp, Jaboticabal, in June 2017. The estimation of the head loss was performed by the Hazen-Williams and Darcy-Weisbach equation, with the friction factor (f) estimated by Swamee and Jain and Blasius models. The equations were compared with the data determined in column of mercury in five flows, with values ranging from 1.55 m3 h-1 a 5.15 m3 h-1. The estimation of the head loss by Swamee and Jain method overestimated the values determined in the mercury column. Up to the 5.15 m3 h-1 flow the Hazen-Williams method presented the lowest variation and, consequently, the higher efficiency of estimated of head loss in relation to the values determined for polyethylene tubing with a diameter of 25 mm

Effects of different levels of irrigation suppression and fertigation on potato yield

With the limitation in the availability of water for agriculture and the high costs of fertilizers, it is necessary to adopt strategies for water and nutritional management of agricultural crops. The objective of this study was to evaluate the morphological and physiological characteristics and productivity of potato under the influence of suppression of irrigation and fertigation in Jaboticabal, SP, Brazil. The experiment was carried out in randomized blocks, conducted in the field, using a 3 x 2 factorial scheme. Different times of irrigation suppression were studied at 80, 90 and 100 days after planting, along with forms of fertigation, following the rate of crop absorption and equivalent fertigation. The imposition of irrigation suppression at 100 days, linked to fertigation following the rate of crop absorption, showed a positive effect on the aerial fresh mass of the potato variety studied, especially promoting the increase in productivity, which was 47.82 t ha-1, and efficiency in water use, which was 10.53 kg of tubers per cubic meter of water. This observation indicates that the application of fertilizers, in sync with the needs of the crop, can improve the efficiency of water use and increase productivity. These findings highlight the importance of integrated strategies to optimize potato cultivation and make it more resistant to adversity, seeking a more sustainable and productive agriculture.With the limitation in the availability of water for agriculture and the high costs of fertilizers, it is necessary to adopt strategies for water and nutritional management of agricultural crops. The objective of this study was to evaluate the morphological and physiological characteristics and productivity of potato under the influence of suppression of irrigation and fertigation in Jaboticabal, SP, Brazil. The experiment was carried out in randomized blocks, conducted in the field, using a 3 x 2 factorial scheme. Different times of irrigation suppression were studied at 80, 90 and 100 days after planting, along with forms of fertigation, following the rate of crop absorption and equivalent fertigation. The imposition of irrigation suppression at 100 days, linked to fertigation following the rate of crop absorption, showed a positive effect on the aerial fresh mass of the potato variety studied, especially promoting the increase in productivity, which was 47.82 t ha-1, and efficiency in water use, which was 10.53 kg of tubers per cubic meter of water. This observation indicates that the application of fertilizers, in sync with the needs of the crop, can improve the efficiency of water use and increase productivity. These findings highlight the importance of integrated strategies to optimize potato cultivation and make it more resistant to adversity, seeking a more sustainable and productive agriculture

Impact of Si on C, N, and P stoichiometric homeostasis favors nutrition and stem dry mass accumulation in sugarcane cultivated in tropical soils with different water regimes

Studies with silicon (Si) in sugarcane indicate a greater response in productivity in plants under stress, and the underlying mechanisms of Si in the crop are poorly reported. In this context, the benefits of Si in the crop’s stem production are expected to occur at the C:N:P stoichiometry level in plant tissues, benefiting plants with and without stress. However, the extension of this response may vary in different soils. Thus, this research aimed to evaluate if fertigation with Si modifies the C:N:P stoichiometry and if it can increase sugarcane’s nutritional efficiency and vegetative and productive parameters. Therefore, three experiments were installed using pre-sprouted seedlings to cultivate sugarcane in tropical soils belonging to the Quartzarenic Neosol, Eutrophic Red Latosol, and Dystrophic Red Latosol classes. The treatments comprised a 2 × 2 factorial scheme in each soil. The first factor was composed without water restriction (water retention = 70%; AWD) and with water restriction (water retention = 35%; PWD). The second factor presented Si concentrations (0 mM and 1.8 mM) arranged in randomized blocks with five replications. Fertigation with Si increases the Si and P concentration, the C and N efficiency, the C:N ratio, and the dry mass production. However, it decreases the C and N concentration and the C:P, C:Si, and N:P ratios in sugarcane leaves and stems regardless of the water regime adopted in the three tropical soils. Cluster and principal components analysis indicated that the intensity of the beneficial effects of Si fertigation on sugarcane plants varies depending on the cultivation soil and water conditions. We found that Si can be used in sugarcane with and without water stress. It changes the C:N:P homeostasis enough to improve the nutritional efficiency of C, P, N, and, consequently, the dry mass accumulation on the stems, with variation in the different cultivated soils

Estimative of the evapotranspiration of the tomato plant in two conduction systems

Este trabalho foi desenvolvido na área experimental da empresa Agrotech, situada na cidade de Pará de Minas -MG,durante os meses de junho a novembro. A área experimental possui 2500 m 2 e foi cultivada com tomate. Foram transplantadas 1880 mudas de tomate da variedade Sheila e 1640 mudas da variedade Débora. O trabalho teve como objetivos o estudo da evapotranspiração e necessidades hídricas do tomateiro em condições de campo, utilizando-se dois sistemas de condução da cultura; Estudar a lâmina de irrigação nas variedades Sheila e Débora; Estudar a interferência da lâmina de irrigação na incidência do distúrbio fisiológico conhecido Podridão apical (“fundo preto”); Comparar dois sistemas de condução, em relação ao desenvolvimento e a produtividade: (1) espaçamento de 0,80 metros entre plantas, com duas hastes por planta; (2) espaçamento de 0,40 metros entre plantas com uma haste por planta; Determinar o coeficiente de cultura (Kc) para os sistemas de produção citados em condições de canteiros com e sem cobertura plástica; Determinar os valores de graus dias para a cultura do tomateiro. A lâmina de irrigação que proporcionou os melhores resultados de produtividade e uma menor incidência de podridão apical foi a de 696 mm para as duas variedades.A incidência de podridão apical foi maior na lâmina de 463 mm. Não houve interação significativa para a relação condução x lamina aplicada.Observou-se um maior numero de frutos totais, comerciais e não comerciais para o sistema de condução 1 em relação ao 2. Observou-se uma maior incidência de podridão apical no sistema de condução 1 em relação ao 2, fato explicado pela maior quantidade de frutos de um em relação a outro. O sistema de condução 2 apresenta frutos com maior peso em relação ao sistema de condução 1. Pode-se concluir que embora o sistema 2 apresente menos frutos que o sistema 1, a sua superioridade em relação a produtividade foi da ordem de 33 t/ha. Para adoção desse novo sistema de condução se faz necessário um estudo da relação custo beneficio levando em conta um maior custo inicial com aquisição de mudas. O ciclo total da cultura foi de 148 dias, totalizando 1548 graus dias para essas condições de cultivo, considerando uma temperatura basal de 10o C. O software IRRIGA apresentou-se como uma excelente ferramenta para a realização do manejo da irrigação propiciando um rigoroso gerenciamento da quantidade de água a ser aplicada e o momento exato da aplicação. O efeito da cobertura do solo acarretou um aumento na demanda hídrica da cultura, no vigor vegetativo e no desenvolvimento das raízes. Percebeu-se também que o sistema de condução com 0.4 metros entre plantas com uma haste/planta teve uma maior demanda hídrica, fato que pode estar relacionado com o stand de plantas/ha. Os valores de Kc encontrados para o sistema de condução 0,8 metros entre plantas com duas hastes/planta para os canteiros com cobertura plástica foram de 0,75; 1,10; 1,15 e 0,86 e 0,53; 0,80; 1,08 e 0,73 para os canteiros sem cobertura nos respectivos estádios de desenvolvimento (floração, frutificação, colheita 1 e colheita 2). Os valores de Kc encontrados para o sistema de condução 0,4 metros entre plantas com uma haste/planta para os canteiros sem cobertura plástica foram de 0,80; 1,05; 1,12 e 0,85 e 0,92; 1,17; 1,22 e 1,03 para os canteiros com cobertura plástica.This work was developed in the experimental area of the company Agrotech, located in the city of Pará de Minas - MG,during the months of June to November year 2003. The experimental area has 2500 m2 and it was cultivated with tomato. 1880 seedlings of tomato of the variety Sheila were transplanted and 1640 seedlings of the variety Débora. The work had as objectives the study of the evapotranspiration and water needs of the tomato plant in field conditions, using two conductions systems of the culture; To study the irrigation lamina in the varieties Sheila and Débora; To study the interference of the irrigation lamina in the incidence of the disturbance known physiologic blossom-end rot a ("black bottom"); to Compare two conduction systems, in relation to the development and the productivity: (1) spacing of 0,80 meters between plants, with two stems for plant; (2) spacing of 0,40 meters among plants with one stem for plant; To determine the culture coefficient (kc) for the production systems mentioned in conditions of beding with and without mulching; To determinate the values of degrees days for the culture of the tomato. The irrigation lamina that provided the best productivity results and a smaller incidence of blossom-end rot was the one of 696 mm for the two varieties. The incidence of blossom-end rot was larger in the lamina of 463 mm. There was not significant interaction for the relationship conduction x applied lamina. Was observed a larger total number of fruits , commercial and not commercials for the system of conduction 1 in comparatively to the 2. A larger incidence of blossom-end rot was observed in the system of conduction 1 in relation to the 2, fact explained by the largest amount of fruits of one in relation to other. The system of conduction 2 presents fruits with larger weight in relation to the system of conduction 1. It can be concluded that although the system 2 presents less fruits than the system 1, its superiority in relation to productivity was of the order of 33 t/ha.To adoption of that new conduction system is made necessary a study of the relationship cost by benefits taking into account a larger initial cost with acquisition of seedlings. The total cycle of the culture was of 148 days, totaling 1548 degrees days for those cultivation conditions, considering a basal temperature of 10° C. The software IRRIGA came as an excellent tool for the policy of the irrigation, providing a rigorous administration of the amount of water to be applied and the exact moment of the application. The effect of the covering of the soil brought an increase in the demand hídrica of the culture, in the vegetative vitality and in the development of the roots. It was also noticed that the transport system with 0.4 meters between plants with one stem/plant had a larger water demand , fact that can be related with the number of plants/ha. The values of kc found for the system of conduction 0,8 meters between plants with two stem/plant for the beding with mulching were of 0,75; 1,10; 1,15 and 0,86 and 0,53; 0,80; 1,08 and 0,73 for the beding without covering in the respective development stadiums (flowering, fructification, harvest 1 and harvest 2). The values of kc found for the system of conduction 0,4 meters between plants with a stems/plant for the beding without mulching were of 0,80; 1,05; 1,12 and 0,85 and 0,92; 1,17; 1,22 and 1,03 for the beding with mulching.Fundação de Amparo à Pesquisa do Estado de Minas Gerai

Effect of the water stress in the production of the orange tree in the North of the state of São Paulo

O Estado de São Paulo destaca-se no cenário citrícola mundial, respondendo por 80,50% do total produzido, com média de 25 t ha-1 ano-1 (IBGE, 2007). A floração é estimulada por baixas temperaturas e estresse hídrico que alteram o balanço hormonal da planta, tendo este último componente maior significância. Para monitoramento desse estresse, recomenda-se acompanhar o potencial de água na folha. Após o florescimento, as quedas são comuns, chegando a 98% do total de flores formadas, culminando num último surto de queda de frutos conhecido como June Drop , após o que a produção final está praticamente garantida. Observa- se, com isso, que a interação entre o ambiente-água-planta é importante para a condução da cultura. Dessa forma, buscou- se definir, pela análise do potencial de água na folha, como indicador do nível de estresse hídrico, a melhor época de quebra de estresse e a lâmina de irrigação mais adequada para a produção de frutos, em quantidade e qualidade. Para melhor entendimento dessa dinâmica, uma primeira experimentação foi realizada na Estação Experimental de Citricultura de Bebedouro (EECB/COOPERCITRUS), de 05/2006 a 09/2007, com laranjeira Pera sobre Cleópatra irrigada por microaspersão. Os tratamentos foram definidos segundo o potencial hídrico foliar (antemanhã): T1: -1,0; T2: -1,5; T3: -2,0; T4: -2,5; e T5: -3,0 MPa, com delineamento inteiramente casualizado com seis repetições desencontradas. Submeteram-se os resultados à análise de variância, comparando os valores médios pelo teste de Tukey a 10% de probabilidade e a regressões múltiplas, considerando a significância dos parâmetros da equação a 30% de probabilidade. Os dados meteorológicos diários foram obtidos in loco e utilizados pelo software IRRIPLUS® para a realização do balanço hídrico. Avaliaram-se as características vegetativas, reprodutivas e de qualidade de fruto. Foram observadas diferenças estatísticas na queda total de flores, com os maiores valores nos tratamentos mais estressados. Não foram observadas diferenças estatísticas na maioria das características de qualidade de fruto e produção total, e o modelo de regressão múltipla que mais representou as interações entre os tratamentos foi o quadrático. Numa segunda experimentação foram realizadas simulações visando comparar metodologias para estimar a evapotranspiração de referência, parâmetro fundamental para a definição do consumo de água pelas culturas para as principais regiões produtoras de citros do Estado de São Paulo. Compararam-se as estimativas de ETo, em base diária, pelos métodos propostos por Hargreaves e Samani (1985) e Blaney- Criddle FAO diante do padrão Penman-Monteith FAO. Na análise deles foram utilizados os parâmetros da equação de regressão, coeficiente de determinação (r²) e de correlação (r), estimativa do erro-padrão (EEP), estimativa ajustada (SEEa); índice de concordância (d); e índice de confiança (c). Observaram-se tendência à superestimativa dos valores de ETo por Hargreaves-Samani (1985) e subestimativa pelo de Blaney-Criddle FAO. Hargreaves-Samani (1985) mostrou maior amplitude em relação a Penman-Monteith FAO nos meses mais quentes e chuvosos do ano, para cima e Blaney- Criddle FAO para baixo. Nos meses mais frios, a amplitude diminui significativamente entre os três métodos estudados. Conclui-se que, nessas regiões, o método de Hargreaves- Samani (1985) é uma boa opção na estimativa da ETo e, por consequência, no cálculo das necessidades hídricas dos citros. De posse dessas conclusões, realizou-se um trabalho de sensibilidade do método de Hargreaves-Samani (1985), verificando o comportamento dele em relação a variações ( erros ) nas temperaturas máxima e mínima, utilizada na equação. Provocaram-se variações da ordem de 5% nas temperaturas, em diversos cenários, analisando os dados estimados, mensalmente, e dividindo-os nos meses mais frios e mais quentes do ano. Conclui-se que Hargreaves-Samani (1985) superestimou em 12,5% os valores de ETo em comparação com Penman-Monteith FAO 56, em todos os cenários avaliados. Variações de 5% nas temperaturas máximas e mínimas não inferem em erros grosseiros nas estimativas de ETo por Hargreaves-Samani (1985), e o acréscimo de 5% na temperatura máxima gera maiores discrepâncias nas estimativas diante do padrão.The Brazilian citrus industry in recent years, is making a significant leap forward, currently is leading the world production, with emphasis on the state of Sao Paulo that represents 80.50% of the total produced, with an average 25 t ha-1 year1 (IBGE, 2007). Flowering is stimulated by low temperatures and water stress that changes the plant hormonal balance, having the last component greater significance. For this monitoring is recommended to monitor the potential of water on the leaf. After the flowering falls are common, reaching 98% of the total flowers formed culminating in a last outbreak of falling fruit known as "June Drop", where after that the final production is virtually guaranteed. It is observed that the interaction among the environment x water x plant is important for the conduct of culture, thus sought to define, by analyzing the potential of water on the leaf, as indicator of the water stress level, the best season of break of stress and the irrigation depth more suitable for production of fruits in quantity and quality. For a better understanding of the dynamics, a first experiment was performed at the Estação Experimental de Citricultura de Bebedouro (EECB / COOPERCITRUS), from 05/2006 to 09/2007, with orange 'Pêra' on "Cléopatra" irrigated by microsprinkler irrigation. The treatments were defined according to leaf water potential (antemanhã): T1: -1.0; T2: -1.5; T3: -2.0; T4: -2.5 and T5: -3.0 MPa, with completely randomized desing with 6 replicates. The results were submitted to the analysis of variance, comparing the average numbers by the Tukey test at 10% of probability, and multiple regressions considering the parameters significance of the equation at 30% of probability. The daily meteorological data were obtained in loco and used by software IRRIPLUS® for completion of the water balance. The vegetative, reproductive and quality characteristics of fruit were evaluated. There were statistical differences in the overall flowers fall, with the highest values in the most stressful treatments. There were no statistical differences in most of the characteristics of fruit quality and total production, and the multiple regression model that more represented the interactions between treatments was the quadratic. In a second experiment were performed simulations to compare methodologies for estimating the evapotranspiration of reference, the basic parameter to define the water consumption by crops for the main citrus producing regions of the state of Sao Paulo. The estimates of ETo were compared on a daily basis, by empirical equations proposed by Hargreaves & Samani (1985) and Blaney-Criddle FAO according to the standard of Penman-Monteith FAO. In the analysis of the same parameters of the regression equation were used, determination coefficient (r ²), correlation (r), estimate the trapping data (EEP), adjusted estimate (SEEA), coefficient of correlation (r); indice of concordance (d), indice of confidence (c). There was a tendency to overestimate the values of ETo by Hargreaves- Samani (1985) and underestimation by Blaney-Criddle FAO. Hargreaves-Samani (1985) showed bigger magnitude for PM in warmer and wet months of the year to up and Blaney-Criddle FAO to down. During the coldest months the scale diminish significantly among the three methods. It concludes that for these regions the method of Hargreaves-Samani (1985) is a good option to estimate the ETo and consequently in the calculation of the water requirements of citrus. With this conclusion, it performed a sensitivity of the Hargreaves- Samani (1985) method, checking its behavior same in relation to changes "errors" in temperatures, maximum and minimum, used in the equation. It was caused variations in the order of 5% in temperatures in various scenarios, and examined the estimated data monthly, and dividing them during the coldest and hottest months of the year. It concludes that Hargreaves - Samani (1985) overestimated in 12.5% the values compared to ETo Penman-Monteith FAO 56, in all scenarios evaluated. Variations of 5% in maximum and minimum temperatures do not infer gross errors in the estimates of ETo by Hargreaves - Samani (1985) and the increase of 5% in T max generates bigger discrepancy in the estimates due to the standard.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Análise da sensibilidade dos componentes da equação de Hargreaves - Samani para a região de Bebedouro - SP

The estimation of reference evapotranspiration (ETo) subsidizes the calculations of water consumption in irrigated agriculture. The use of simpler methodologies are common however should be carefully studied. The present study evaluated the sensitivity of the Hargreaves -Samani equation compared to the standard Penman-Monteith -FAO to estimate ETo for the climatic conditions of the Bebedouro-SP region, simulating the effects of increasing and decreasing 5 % in the temperatures, resulting in ten different scenarios (PM -Penman-Montheit -FAO; S0 -original Hargreaves Samani; S1 to S8 -modified Hargreaves Samani). The obtained results of sensitivity, linear regression, accuracy and concordance index, were compared. We concluded that the Hargreaves -Samani equation overestimates the monthly values of the ETo in 13% compared to the standard method. A variation of 5% in maximum and minimum temperatures resulted in errors of up to 1 mm day-1 (monthly average) and this increase is more expressive in maximum temperature.A estimativa da evapotranspiração de referência (ETo) subsidia os cálculos de consumo de água na agricultura irrigada. O uso de metodologias mais simples são comuns, porém devem ser criteriosamente estudadas. No presente estudo avaliou-se a sensibilidade da equação de Hargreaves - Samani frente ao padrão Penman-Monteith - FAO, na estimativa da ETo, para as condições climáticas da região de Bebedouro-SP, simulando os efeitos de acréscimos e decréscimos de 5% nas temperaturas, resultando em dez cenários distintos (PM - Penman-Montheit - FAO; S0 - Hargreaves Samani original; S1 à S8 - Hargreaves Samani - com alterações). Os resultados foram comparados em sensibilidade, por regressão linear, precisão e o índice de concordância. Conclui-se que a equação de Hargreaves - Samani superestima valores mensais de ETo em 13% comparado ao método padrão. Uma variação de 5% nas temperaturas máximas e mínimas resultaram em erros de até 1 mm dia-1, sendo o acréscimo mais expressivo na temperatura máxima