Physiological and productive aspects of cassava under different irrigation levels

The aim of this research was to evaluate the physiological and productive aspects of irrigated cassava crop. The statistical design used was randomised blocks, with six treatments and four replications. The used treatments were irrigation levels, based on the crop evapotranspiration - ETC-(L-0 = 0% [rainfed], L-1 = 40%, L-2 = 80%, L-3 = 120%, L-4 = 160% and L-5 = 200% of the ETC) and the analysed physiological variables were: gas exchange, the quantum efficiency of photosystem II (PSII)and the soil plant analysis development (SPAD) index. The growth and crop productivity were also evaluated through of the leaf area index (LAI), the number and productivity of commercial roots and total biomass. In this research, the total irrigation depth was defined as the irrigation depth plus the effective rainfall. The estimated ETC was 1,030 mm over the 12-month production cycle and the greatest value for LAI and SPAD were 7.6 and 57.4, respectively, obtained in irrigated areas with the level of 80% of the ETC. While, in the areas irrigated with 120% of the ETC, were obtained the highest values of root productivity (93 Mg.ha(-1)), total biomass yield (149 Mg.ha(-1)) and photosynthetic rate (22.4 mmol CO2.m(-2).s(-1)). On the other hand, with irrigation equivalent at 200% of the ETC were obtained the greatest values of internal CO2 concentration (245 mmol CO2.m(- 2).s(-1)), stomatal conductance (0.35 mmol H2O.m(-2).s(-1)) and effective quantum efficiency (0.68).