FERREIRA, J. A. S.; http://lattes.cnpq.br/6044110288375854; FERREIRA, José Alberto da Silva.
Resumo:
A field experiment was conducted during the 1993 crop season (October 22, 1993 to
January 13, 1994) in a private farm , Fazenda Sao Joao, located in the city of Mossoro-RN.
The crop under study was melon (Cucumis melo L.) cultivate Gold Mine. The main objective
of this study was to relationalize the use of water resources of this region for crop production.
The experiment was divided into four plots, each plot measuring 8m x 100m. Each plot
received a different irrigation treatment. The plot PN received the irrigation treatment identical
to that adapted by the farm (which is based on the evaporation measurements of a Class A pan
evaporimeter) and the other three plots received 90, 80 and 70%, respectively, of the irrigation
amount applied to the plot PN. Canopy (Tc), dry (Ta) and wet bulb (Tw) temperatures;
atmospheric pressure (Po); global (Rg), reflected (Rr) and net (Rn) radiations; crop ( r c ) and
aerodynamic Oa) resistances and wind velocity ( W ) data were collected during the growing
season of the melon crop. The canopy temperature was monitored by an infrared thermometer
and a steady state porometer was used to measure the crop resistance. The soil humidity was
monitored by using a neutron probe and also by the use of tensiometers. The water deficit was
analyzed using different moisture stress indices such as the stress degree day (SDD), the crop
water stress index (CWSIi) proposed by IDSO et al. (1981) and the CWSIj proposed by
JACKSON et al. (1981). The values of the SDD index for the plot P3 were higher than those
of plot PN, particularly at the end of the experimental season. The values of the CWSIi
presented a large variability during the season due to variations in the global solar radiation and
the wind velocity. The results suggest that the irrigation of the melon crop should be
administered when the index reaches a value of 0.3 for the prevailing local climatic conditions.
The morphological analysis presented higher values of fresh and dry biomasses and leaf area
for plot PN compared to those of plot P3. The fruit production of plot PN was also higher than
that of plot P3, but the productivity of plot PI was the highest. It is concluded that a decrease
of 30% of irrigated water was sufficient to change the morphological development and crop
productivity.