Water availability to soybean crop as a function of the least limiting water range and evapotranspiration

Irrigation management aimed at optimal production has been based only on the water factor. However, in addition to the water potential of the soil, factors such as soil penetration resistance and soil O2 diffusion rate also affect plant growth and interfere with water absorption, even if moisture is within the available water range. This study aimed at quantifying the least limiting water range and demonstrating its potential in soil and water management in irrigated agriculture. In order to determine the least limiting water range, soil water retention curves and soil resistance to penetration were determined from undisturbed soil samples. The sequential water balance and the reference, crop and real evapotranspiration were determined for a soybean crop season. Soil aeration was the least limiting water range upper limit for soils with bulk density greater than 1.33 Mg m-3, whereas soil resistance to penetration was the lower limit for bulk density higher than 1.43 Mg m-3. The bulk density of the soil studied was 1.35 Mg m-3, indicating 0.37 m3 m-3 of water availability, based on the least limiting water range, which is sufficient to supply the crop evapotranspiration. Irrigation management based on the least limiting water range is more efficient and complete than that based only on available water

Padrões de Chuva e de Evapotranspiração em Goiânia, GO

Resumo A chuva (P) e a evapotranspiração potencial (ETP) são variáveis climáticas relevantes para diferentes áreas do conhecimento, tais como: agricultura, manejo de bacias, previsões de tempo e drenagem urbana. O objetivo deste trabalho foi caracterizar os padrões de chuva e de ETP para o município de Goiânia, GO. Foram utilizados dados de 36 anos para chuva e de 21 anos para ETP. A precipitação foi de 1.494,66 mm, com tendência de redução a uma taxa de 3,7 mm ano-1. Observou-se que 99% das precipitações diárias são p ≤ 50 mm dia-1. Registraram-se 292 dias sem chuva e 72 dias chuvosos, com tendência de redução dos dias chuvosos e aumento de dias secos. A ETP foi de 1.380,57 mm, sendo a maior e a menor média registrada no 3° (139,02 mm) e 35° (55,36 mm) quinquídios. Há tendência de aumento na ETP (6,37 mm ano-1). Registrou-se excedente hídrico de 607 mm ano-1 e déficit 471 mm ano-1. ETR/ETP X ¯ ) e 31% ( E T P > X ¯ ), com periodicidades 4,0 (P) e 3,2 (ETP) anos. Observou-se r = 0,68 entre a temperatura média do ar e as taxas de desmatamento

Rainfall and Evapotranspiration Patterns in Goiânia, GO

<p></p><p>Abstract Rainfall (P) and potential evapotranspiration (ETP) are climatic variables relevant to different areas of knowledge, such as: agriculture, watershed management, weather forecasts and urban drainage. The aim of this work was to characterize the rainfall and ETP patterns for the Goiânia, GO city. Data of 36 years for rainfall and 21 years for ETP were used. The precipitation was 1,494.66 mm, with a trend of reduction at a rate of 3.7 mm year-1. It was observed that 99% of the daily precipitations are p ≤ 50 mm day-1. We recorded 292 days without rain and 72 rainy days, with a tendency to reduce rainy days and increase dry days. The ETP was 1,380.57 mm, with the highest and the lowest mean recorded in the 3rd (139.02 mm) and 35th (55.36 mm) quinquides. There is a tendency to increase in ETP (6.37 mm year-1). A water surplus of 607 mm year-1 and a deficit of 471 mm year-1 were recorded. ETR/ETP <0.8 between the months of April and October. Predominant frequencies of P and ETP were 38% ( P > X ¯ ) and 31% ( E T P > X ¯ ), with periodicities 4.0 (P) and 3.2 (ETP) years. Correlation of 0.68 between the mean air temperature and Goiás deforestation rates was observed.</p><p></p