Avaliação das características agrotecnológicas de duas variedades de cana-de-açúcar influenciadas por diferentes épocas de supressão de irrigação e níveis de adubação

Abstract

Sugarcane (Saccharum spp.) is a species adapted to tropical climate conditions and has played key role in the economic development of the Brazil's Southeast, as assessed by analysis of growth, physiological responses and yield. Brazil stands out as main grower of that crop, having in all its territorial areas favorable conditions for its culture. However, studies show that many farmers in the North of Minas Gerais State, due to face various problems, especially the low productivity of sugarcane from the use of varieties adapted to climate, which is characterized by a high annual water deficit (over 400 mm), irregular precipitation and a lack of scientific knowledge about the crop for the region. Thus, the study aimed to evaluate the technological performance of two Sugarcane varieties influenced by different times of irrigation suppression and fertilization levels. The evaluated characteristics were: plant height (m), stem diameter (mm), number of tillers per m, Brix in juice, cane Pol, juice Pol, fiber, Purity, reducing sugar, Humidity, total reducing sugar, expected liters of alcohol and total yield. The experiment was carried out at Experimental Farm of the Unimontes in Janaúba in the North of Minas Gerais, on. Soil type Oxisol, and area of s ratoon sugarcane of 2nd cut, with plant spacing of 1.4 m. The design was in randomized blocks, with three replications in split plot (2 x 3 x 6), two sugarcane varieties, RB$5 5453 and SP8O 1816 and three times of irrigation suppression (DIAP), and the subplot factor of six levels of mineral fertilization. Data were subjected to analysis of variance and, when there was significant difference by the F test, the means were compared by the Scott Knott (p < 0,05) for all of the studied variables, by the SISVAR software. The varieties showed different behavior in maturity, since the variety RB85-5453 presented highest values in technological quality and lower rates of productivity, a variety behavior in which it is possible to anticipate its harvest and also to harvest the SP8O-1816 in a regular or delayed way. The varieties showed average of 24, 3 °Brix, 17,6 % sugarcane Pol, 21 % juice Pol %, 85,4 % in Purity, 0,6% RS, 19 %TRS, 172,4 kg TRS t-1, 66,5 % moisture, 12,2 % Fiber, 3,08 m in height, 29,2 mm, 18,9 tíllers /m, 11,1 stems /m, 159,8 t ha and 105.090 L alcohol /t. The varieties reacted to different periods of irrigation (DIAP). The level 6 of fertilization provided the best performance in the conditions of this work. The variety RB 85-5453 and SP 80-1816 are promising for the North of Minas Gerais, with good adaptation to its soil and climate conditions, but the SPS0-1816 is the most indicate for the region, since it had gotten high levels of yield and good quality of its juice besides showing resistance to water restriction in the conditions of this work, thus attending the requirements of the sugar and alcohol production in its third cycle of productivity.