Tese
Risco de ocorrência de excesso hídrico para a cultura do girassol na região central do Rio Grande do Sul
Fecha
2014-02-21Registro en:
LUCAS, Dioneia Daiane Pitol. Risk of water excess in sunflower crop in the central region of Rio Grande do Sul. 2014. 101 f. Tese (Doutorado em Agronomia) - Universidade Federal de Santa Maria, Santa Maria, 2014.
Autor
Lucas, Dioneia Daiane Pitol
Institución
Resumen
The approach to knowledge about the probabilities of water excess occurrence enables
the planning sunflower crop management, mainly about the sowing period. The objective of
this study was quantify and analyze the occurrence of water excess through numerical study
for sunflower crop sown on different dates, considering the storage capacity of water in
different soils of the Central Region of Rio Grande do Sul and determine the probability
distribution functions that better represent the water excess occurrence. Mathematical
modeling was used to simulate the sunflower development, considering a medium maturity
genotype. The simulation was done for 14 sowing dates in each year of the time series of 43
years of diary weather data from 1968 to 2011 of Main Climatological Station of Santa Maria
(ECPSM). The number of days with water excess in different development stages of culture
was determined for main soils of the region covered by the ECPSM. Capacity values of
available water storage (CAD) were considered according soil and culture characteristics,
being the water excess calculated using the Dialy Water Balance, represented by accumulated
water in the soil exceeding the CAD. The distribution probability functions tested for the
number of days with water excess were Normal, Exponential, Gamma, Lognormal and
Weibull, and the Kolmogorov-Smirnov and Chi-square tests were used to check the fit of
functions. The weather conditions were different for the different sowing dates simulated in
43 years, so that differentiate the simulations of the development cycle of the sunflower.
Thus, difference was observed in the number of days with water excess between sowing dates
for all sub-periods analyzed. In terms of functions, there was at least one function that is fitted
in most of the cases, and when there was no possible fit, the empirical frequency was used to
analyze the risk. The Weibull had the greatest number of adjustments for developmental cycle
as well as for subperiods. Early August until mid-September sowing dates are those with the
greatest number of days with water excess, considering the whole development cycle of
sunflower, regardless of the soil CAD.