Potencial de produtividade e fatores de manejo que causam a perda de produtividade da mandioca de mesa em ambiente tropical e subtropical do Brasil

Abstract

It is estimated that over the next few decades, the world population will increase from the current 7.6 billion to 9.8 billion inhabitants by 2050, increasing the demand for food by 50%. In this scenario, the importance of producing foods that make up the food base in less developed countries, such as cassava, increases. Cassava is considered a staple food for more than a billion people in 105 countries. Rich in carbohydrates, it is the third largest source of calories after rice and corn. However, cassava yield levels in Brazil are very low (14.8 t ha-1 ) compared to the yield achieved in some experiments in Brazil (33.0 t ha-1 ) or the potential reported by several authors (> 60 t ha-1 ). Therefore, the objective of this work was to determine the yield gap and identify the main management factors that limit the yield of sweet cassava in tropical and subtropical environments in Brazil, as well as evaluate different weed management in subtropical environments. The study area covers the Central-West and Southeast Regions (tropical environment) and South (subtropical environment), where 303 sweet cassava crops were evaluated. The trials to evaluate the different weed management in cassava cultivation were conducted in 5 municipalities in Rio Grande do Sul with 5 different managements, during the 2019/20 and 2020/21 harvests. The yield gap was 34.2 t ha-1 and 27.7 t ha-1 , for the tropical and subtropical environment, respectively. The main practices that limit yield in the tropical environment were: plant density, planting date, leasing and irrigation. In the subtropical environment, they were: plant density, planting date, row spacing and desiccation. The optimum plant density for the production and quality of sweet cassava roots is 13 thousand plants ha-1 in the tropical environment and 11 thousand plants ha-1 in the subtropical environment. The optimal planting date for table cassava production is until November 15th for crops without irrigation in the tropical environment and until September 27th for the subtropical environment. Keeping the crop free of weeds increased the productivity of sweet cassava by 75 to 99% in Rio Grande do Sul. Manual weeding was the management that resulted in the best yield, in terms of fresh mass of tuberous roots, number of leaves and height, especially where there was greater infestation of invasives. The use of pre-emergence associated with weeding in the post-emergence of the crop also led to satisfactory results in environments with greater weed infestation in Rio Grande do Sul.