Produtividade de variedades de mandioca em diferentes arranjos de plantio, épocas de colheita, fisiologia do estresse e déficit hídrico

Abstract

The objective of this study was to generate important information on cassava varieties cultivated in irrigated and rainfed conditions, for in natura and industrial consumption. Experiment I: The experimental design was randomized blocks (DBC), in a 2 x 2 x factorial scheme 12, two cultivation conditions:irrigated (Precipitation + irrigation) and non irrigated (precipitation only); two experimental rows:double rows (1,5 x 0,6 x 0,6 m) and single rows (0,9 x 0,6 m) and twelve varieties: Rosinha, Saracura, Eucalipto, Dona Rosa, Dourada, Neilton, Branca, Amarelo I,Talo Branco, Kiriris, Gema de Ovo and Imbé. The following variables were analyzed after harvesting at twelve months after planting: Root production (kg plant- 1); total yield of fresh roots (t ha-1);number of reserve roots; fresh shoot weight (kg plant-1) and harvest index (%). There was interaction of the management system (experimental arrangements and water management) with varieties, influencing the agronomic characteristics of cassava. The arrangement in double rows (1,5 x 0,6 x 0,6 m),independent of the water regime, was more productive; therefore the most recommended for the production of cassava reserve roots. It is possible to recommend plant densities based on the availability of water. As variedades Rosinha, Branca, Talo branco and Kiriris can maintain high translocation rates of photoassimilates of the aerial part to the reserve roots. Experiment II: The study was performed under irrigated conditions. Two experimental arrangements were studied: Cassava in single row (1,0 x 0,6 m) with or without Caupi beans;Cassava in double row (2,0 x 0,6 x 0,6 m) with or without bean. The single cowpea (0,5 x 0,3m) was also evaluated. The variety of cassava used was Salongor Preta and cowpea (BRS Guariba). The evaluated variables were: shoot dry mass, leaf area and yield. Irrigated double-row cultivation proved to be more conducive to the consortium with Caupi beans. In irrigated cultivation cassava yield increased, maximizing yields rapidly and allowing harvesting at 8 months after planting, regardless of the arrangement. There was an increase in yield of cassava in a consortium, regardless of the spacing adopted. Experiment III:Seven varieties of cassava were evaluated: Saracura, Dona Rosa, Dourada, Neilton, Branca, Gema de Ovo and Imbé, under two water conditions: Irrigated (Precipitation + irrigation) and non irrigated (maintenance irrigation in the two first months after planting + precipitation).Collections were made at 6, 8 and 10 months after planting. Variables analyzed:shoot yield;total and commercial productivity; harvest index; foliar water potential; stomatal conductance;relative water content. At six months after planting (MAP) only the Saracura, Neilton and Imbé varieties presented satisfactory yield of reserve roots (above 15 t ha-1). Varieties such as Saracura can be harvested at eight MAP without significant losses in yield reserve roots.