Physiological and productive aspects of cassava under different irrigation levels

ABSTRACT

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 – ET_C – (L₀ = 0% [rainfed], L₁ = 40%, L₂ = 80%, L₃ = 120%, L₄ = 160% and L₅ = 200% of the ET_C) 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 ET_C 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 ET_C. While, in the areas irrigated with 120% of the ET_C, were obtained the highest values of root productivity (93 Mg·ha^–1), total biomass yield (149 Mg·ha^–1) and photosynthetic rate (22.4 μmol 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 μmol CO₂·m^–2·s^–1), stomatal conductance (0.35 μmol H₂O·m^–2·s^–1) and effective quantum efficiency (0.68).

Key words
Manihot esculenta Crantz ; net photosynthesis; stomatal conductance; SPAD index; quantum yield; agricultural productivity