Crescimento e desempenho agroindustrial de diferentes perfis de cana em cultivo de sequeiro

Abstract

In the Northeast of Brazil, Alagoas stands out as the largest producer of sugarcane. In this region, seasonal droughts have been frequent in the last eight years, causing high water deficits in soils and drastic reductions in crop yield. Faced with these problems, sugarcane breeding programs have adopted the strategy of developing sugarcane cultivars with diferente characteristics of current cultivars, focusing mainly on increasing the production of biomass, increase in fiber content and drought tolerance. This work aimed to evaluate the growth patterns and agroindustrial yields of different cane profiles, in the environmental conditions of Alagoas, Northeast of Brazil. With the results of this work, the doctoral thesis was elaborated in four Chapters: 1) General introduction and literature review; 2) Growth analysis of different cane profiles in the plant cane cycle in Northeast of Brazil; 3) Agroindustrial yields of different cane profiles in two crop cycles in the Northeast of Brazil; and 4) RB0442: drought tolerant sugarcane cultivar. In order to meet the objectives of Chapter II and Chapter III, a field experiment was installed at the Campus of Engineering and Agrarian Sciences from the Federal University of Alagoas, Rio Largo, Alagoas, Brazil. Six genotypes of cane were evaluated. These genotypes were classified into three profiles: I – Traditional sugarcane genotypes (RB92579 and RB951541); II – Drought tolerant sugarcane genotypes (RB0442 and RB0459) and; III – Energy cane genotypes (RB11999 and RB13403). In addition, experimental data from 31 harvests (thirteen plant cane, ten first-ratoon and eight second-ratoon) from trials conducted by PMGCA/CECA/UFAL were used to evaluate the performance of cultivar RB0442 in the sugarcane regions of Alagoas (Chapter IV). The results indicated that the cane profile have different growth patterns, highlighting the energy cane that had the most intense vegetative growth, the highest accumulation of dry mass and the highest leaf area index. However, in the drought season, energy cane was the profile that had the most impaired growth, with large reductions in the relative growth rate and net assimilation rate, in addition to a greater specific leaf area. In two crop cycles, it was observed that drought tolerant sugarcane showed an agricultural yield similar to that of energy cane and superior to traditional sugarcane. Although energy cane is very productive, the quality of its raw material for sugar production is lower than that of the other two profiles. Therefore, the drought tolerant sugarcane, especially the RB0442 cultivar, is a good option for cultivation in Northeast of Brazil, especially in environments with water restriction.