Comportamento fisiológico e consumo hídrico da cultura de soja (Glycine max (L.) Merill) irrigada, nas condições semiáridas do Nordeste brasileiro.

Abstract

This research was conducted in the experimental station of the CPATSA/EMBRAPA at Juazeiro-Ba, with the objective of studying the water requirement of an irrigated Soybean crop (Glycine, max (L.) merrill), variety tropical, grown from September to December of 1987. Measurements of dry and wet matters production and leaf area index (LAI) were taken at a weekly basis while the crop height (h) was measured at a three days interval. Hourly measurements of the climatic parameters were made with instruments installed above the crop canopy and at the meteorological station contiguous to the experimental area. Similarly, canopy temperature was measured with an infrared thermometer. The physiological parameters were measure three times a day (09:00, 12:00 and 15:00 hours) employing a diffusion porometer. Crop maximum evapotranspiration (ETm) was measured at two constant water level evapotranspirometers and reference evapotranspiration (ETo) was estimated by the methods of Penman, "class A" pan, Penman-Monteith, Priestley & Taylor, Doorenbos & Pruitt and Jury & Tanner. Values of ETm and ETo were used to calculate crop coefficient (Kc). LAI and h reached maximum values of 8.5 and 89.2 cm, respectively. Stomatal and crop resistances showed increasing values from morning (09:00) t o afternoon (15:00) observation hours. Measured évapotranspiration was better estimated by the Penman-Monteith and " class A" pan methods for the whole crop season and full soil cover periods, respectively, showing also a better statistical significance. The statistical analysis revealled no significant differences between FA0 suggested and estimated by different methods Kc values, at a 1% level.