Dissertação
Análise númerica de risco de ocorrência das manchas de alternária e septória em girassol para diferentes datas de semeadura, em Santa Maria - RS
Fecha
2014-01-24Registro en:
HINNAH, Fernando Dill. NUMERICAL RISK ANALYSIS OF ALTERNARIA AND SEPTORIA LEAF SPOTS
OCCURRENCE IN SUNFLOWER FOR DIFFERENT SEEDING DATES IN SANTA MARIA RS. 2014. 84 f. Dissertação (Mestrado em Engenharia Agrícola) - Universidade Federal de Santa Maria, Santa Maria, 2014.
Autor
Hinnah, Fernando Dill
Institución
Resumen
Sunflower is an alternative specie to the system of no-tillage and crop rotation. His inclusion
in this system provides soil improvements and interruption on cycle of pests and diseases,
which are responsible for losses of productivity of the mainly sown crops. In addition to these
benefits this specie has characteristics of increased tolerance to drought than traditional crops
such as soybean and corn, maintaining satisfactory yields even in dry years considereds. For
inclusion in the rotation and maintaining satisfactory yields the knowledge of the best sowing
dates is necessary. As the weather has interannual variability, the risk analysis for the sowing
dates is required, through a study of probability with a long series of weather data for better
definition. This study aims to determine the sowing date of sunflower in which lower severity
of alternaria and septoria leaf spots in the RS Central Region occurs. For it has adapted and
calibrated an algorithm providing a forecasting system diseases, based on data from leaf
wetness duration, air temperature during the leaf wetness period and rain, calculating the
accumulated severity values (VSCA) throughout the cycle. In this adaptation and calibration
data from six experiments performed at the Department of Plant Science since 2007. Hourly
values of weather data from 1968 to 2011 was estimated from the default readings, and use
this algorithm were simulated for 14 different dates of sowing spaced in 15 days, beginning
on August 1 and ending on February 16 of each year. Due to the interannual variability of
ENSO and their influence on weather conditions, crop seasons years was apart in Neutral, La
Niña and El Niño. The data generated from the analysis of variance and the means of Scott-
Knott test at 5% probability of error was taken. In addition, the VSCA were subjected to
analysis of probability distribution, verifying that the Weibull, lognormal and normal
distributions has the best represent the distribution of values of severity of leaf spots on
sunflower, both for the entire cycle and for the subperiods emergency-end of anthesis and
early reproductive-final stage of anthesis sunflower. It was also found that the period between
early February and late April is more favorable to leaf spots, while sowing dates from August
1 to October 16, resulting in lower severity values, differing significantly from later sowings.
In El Niño years suffer the greatest severities of disease, followed by La Niña years, and
finally with the lowest values of VSCA for Neutrals years.