Search

Plant yield is strongly influenced by the amount of water used by it. In this sense, yield response factor (Ky) allows evaluating the decrease in yield as a function of the evapotranspiration that occurs, which may be an important tool for harvest forecasting. Therefore, this study aimed to determine Ky for winter corn crop grown in the region of Dourados, MS, Brazil. The yield function analysis based on the water factor, which requires actual (Ya) and maximum (Ym) yield data, as well as actual (ETa) and maximum (ETm) evapotranspiration, was used to adjust Ky. Ym was assumed to be 8,820 kg ha−1, while Ya was obtained for each season from the database SIDRA from IBGE. ETm and ETa were estimated by sequential daily water balance, considering four different sowing dates (all in the off-season). In total, seasons from 2001 to 2013 were analyzed. The high Ky value obtained (1.22) for winter corn crop showed its high sensitivity to water deficit. Its yield is strongly influenced by water availability so that for every 1% reduction in evapotranspiration, there is a 1.22% yield reduction.

Made available in DSpace on 2020-04-25T00:39:45Z (GMT). No. of bitstreams: 1 37018.pdf: 584452 bytes, checksum: 246ac392189ddc5e14ad384967239e0c (MD5) Previous issue date: 2020

In agrometeorology, reference surface consists of those traditional grass cover on weather stations. Net radiation (Rn) of this surface is an important information that has many applicability, but its measurement is rare due to the high cost of the sensor and the complexity involved on the measurement. Therefore, estimate Rn from another variable is desirable, as from solar radiation (Rs); however, standard methods used are complex, making interesting the use of simplified methodologies. Considering these aspects, the present study aimed to set two empirical methods to estimate Rn from Rs for Dourados region, located in the Mato Grosso do Sul State, Brazil. One method was set with a scientific purpose (Gauss Method) and it comprised a mathematical modeling. The other one was set with a practical purpose (Practical Method) and comprised the determination of fixed monthly conversion factors. It was used daily Rs data of a 12-years database. With these, there were estimated Rn values by the standard method recommended by FAO. Gauss Method was set using Table Curve 2D 5.01 software. Modeling consisted in defining the values of the equation parameters. On Practical Method we developed monthly coefficients of the ratio Rn/Rs. In order to validate both methods it was measured Rs and Rn during two years using high precision sensors. In addition, Rn values were estimated by both methods and then compared with those measured. Both estimating methods showed satisfactory results, with low error and low advantage for the Gauss Method.

AVALIAÇÃO DE UM CONJUNTO LISIMÉTRICO NA DETERMINAÇÃO DA DEMANDA HÍDRICA DE MILHO CULTIVADO NO OUTONO-INVERNO ÉDER COMUNELLO1; PAULO CESAR SENTELHAS2; CARLOS RICARDO FIETZ1; DANILTON LUIZ FLUMIGNAN1 E GESSI CECCON1 1Embrapa Agropecuária Oeste, Rodovia BR 163, km 253,6, Cx. Postal 449, CEP 79804-970, Dourados, MS, Brasil. Fone:(67) 3416-9700. E-mail(s): {eder.comunello, carlos.fietz, danilton.flumignan, gessi.ceccon}@embrapa.br 2Departamento de Engenharia de Biossistemas, Escola Superior de Agricultura Luiz de Queiroz (USP/Esalq), Av. Pádua Dias, 11, CEP 13418-900, Piracicaba, SP, Brasil. Fone:(19) 3429-4283. E-mail: pcsentel.esalq@usp.br 1 RESUMO O conhecimento da evapotranspiração é fundamental para a determinação da demanda hídrica dos cultivos e a lisimetria está entre os métodos mais confiáveis para sua determinação. Uma série de fatores ligados à construção e operação dos lisímetros pode interferir na confiabilidade das medidas tomadas, de modo que o presente trabalho buscou avaliar se ligeiras diferenças nesses fatores seriam suficientes para gerar diferenças estatisticamente significativas entre as séries obtidas de três lisímetros similares. O trabalho experimental foi implantado em março de 2014, em Dourados, MS, com o conjunto lisimétrico disposto em uma área de 0,49 ha, cultivada com um híbrido de milho superprecoce irrigado (125 dias). Variáveis fitotécnicas avaliadas demonstraram a homogeneidade de condições entre os lisímetros e entorno. Não havendo diferenças significativas entre séries, estabeleceu-se um coeficiente de cultivo (Kc) médio. Partindo de 0,54 na fase inicial (0-15 DAE), houve incremento linear dos valores de Kc, atingindo 1,37 no pendoamento (50 DAE). Desse ponto, houve redução gradual dos valores, chegando a 0,80 na maturação fisiológica (110 DAE) e 0,40 na colheita. A demanda hídrica calculada para todo ciclo foi de 475 mm. A análise complementar do saldo de radiação e temperatura do ar foram fundamentais para interpretação dos resultados. Palavras-chave: coeficientes de cultura, lisímetros de pesagem, milho safrinha. COMUNELLO, E.; SENTELHAS, P. C.; FIETZ, C. R.; FLUMIGNAN, D. L. E CECCON, G. EVALUATION OF A SET OF LYSIMETERS FOR DETERMINING WATER DEMAND OF AUTUMN-WINTER MAIZE CROP 2 ABSTRACT Evapotranspiration is a key variable to determine crop water demand, and lysimetry is among the most reliable methods for its determination. A number of factors related to lysimeters construction and operation can interfere with the reliability of measurements. Thus, this study aimed at assessing whether slightly differences could result in significant differences among the series of three similar lysimeters. The experiment was started in March, 2014, in Dourados county, MS, Brazil, with the lysimetric set located in an area of 0.49 ha where a short cycle maize hybrid (125 days) was cropped with irrigation. Plant measurements showed homogeneity conditions among lysimeters and their surrounding areas. With no significant differences among the series, an average crop coefficient (Kc) was used. The value of 0.54 was obtained in the initial phase (0-15 DAE). Right after, Kc values presented linear increment, reaching 1.37 in the tasseling stage (50 DAE). From this point, there was gradual decrease in values, reaching 0.80 at physiological maturity (110 DAE) and 0.40 at harvest. Water demand calculated for the entire cycle was 475 mm. A complementary analysis of net radiation and air temperature was important to evaluate the results obtained. Keywords: crop coefficients, weighing lysimeters, off-season maize.

Made available in DSpace on 2018-05-12T00:50:09Z (GMT). No. of bitstreams: 1 Irriga.pdf: 579469 bytes, checksum: 75e830942080023cadf0b07e47ea1b8f (MD5) Previous issue date: 2018-05-11