Growth, productivity and viability of irrigation in cassava crop in the Alagoas Coastal Plateaus

Crescimento, produtividade e viabilidade da irrigação na cultura da mandioca nos Tabuleiros Costeiros de Alagoas

ABSTRACT:

This research evaluated the effects of the irrigation on growth and productivity of irrigated cassava in the Coastal Plateaus of Alagoas. The planting was done in randomized blocks, with six treatments and four replications. The treatments were irrigation levels in function of crop evapotranspiration - ET_C (L₀ = 0% (rainfed), L₁ = 40%, L₂ = 80%, L₃ = 120%, L₄ = 160% and L₅ = 200% of ET_C). The total water applied was defined as the total irrigation plus the effective rain. The annual evapotranspiration of the cassava plantations in the Costal Plateaus of Alagoas, was 1,030 mm. Plant growth increased significantly with irrigation and the maximum values of the following variables are: leaf area index = 7.6, length of commercial roots = 49 cm, maximum productivity (physical and economic) of commercial roots = 94 Mg ha^-1 and total biomass = 149 Mg ha^-1 and the harvest index = 0.66, all obtained with total irrigation depths (effective rain plus irrigation) between 817 and 963 mm. Finally, it is ratified that understanding the growth, the agricultural and economically viable productivity of irrigated cassava, is an indispensable factor for good management of the crop, especially in regions with irregular rainfall such as the Northeast of Brazil.

Key words:
Manihot esculenta Crantz; leaf area index; total biomass; dry matter; harvest index