PACHECO, N. A.; http://lattes.cnpq.br/2377129321735194; PACHECO, Nilza Araújo.
Resumo:
The aims of this study is the identification of the most suitable areas and sowing periods for
the establishment of soybean crop in northeastern and southeastern Para State region
(Brasil). It takes into consideration the water availability for crop cycle as well as the
climatic risk for its sowing. For this, a ten-day-period-frequency analysis of the rainfall was
performed at levels of 20%, 50% and 80% for the years that were considered being of low,
medium and high climatic risk respectively. Water balance simulation for crop was
performed by using SARRA model and the SGI (Geographic Information System) for
spatial analyses. The main input data for these are: daily rainfall, reference evaporation,
duration of crop cycle and phenological phases of crop and its coefficient. The last date
input are used for determining ISNH (Fulfillment of Water Need Indexes) for the growing
phase which goes from flowering to grain filling (crop's critical phase). Water balance
simulation for soybean crop was performed by combing twelve planting periods, two
varieties and three usable soil water reserve of 25mm, 35mm and 50mm in order to obtain
the ISNH. The definition of the appropriate area for soybean cropping was based in the
spatial medium variation of ISNH for the crop critical phase. This was mapped through GIS
Agroclimatic zoning maps for soybean crop in Eastern Para. It map of this shows
differences concerning the appropriate period for cropping caused by the variations in the
rainfall regime, soybean variety cycle and soil water reserve, as well as the suitable,
intermediate suitable and unsuitable sowing periods. The study also shows that the biggest
studied area presents suitable areas for soybean-crop in the period that goes from 1 to 31 of
January. However the last 10 days of this period are the most suitable ones due to cropping
season coincide with the beginning of rainfall decreasing. Its the sowing period advances,
there's an increase in the South to North direction, of the areas which final themselves unfit
for soybean sowing the results of this work will furnish subsidy to reduce or minimize
economical damages caused by soybean crop sowing in areas and periods that are
unsuitable for such to take place.