Saturday, 15 July 2006

Sugarcane Productivity in Acrustox under Different Water Availability Conditions.

Hélio do Prado1, Antônio Carlos Machado Vasconcelos1, Marcos Guimarães de Andrade Landell1, Dilermando Perecin2, Quirijn Jong Van Lier3, and Mauro Alexandre Xavier1. (1) Centro de Cana IAC, Rodovia Anel Viário, km 321, Ribeirão Preto, 14032-800, Brazil, (2) FCAV UNESP, Rod Paulo Donato Castelani, Jaboticabal, 14870-000, Brazil, (3) Escola Superior de Agricultura Luiz de Queiroz, USP, Av Pádua Dias, sn, Piracicaba, 13417-655, Brazil

When characterizing sugarcane production environments, one must consider water availability in addition to the chemical subsurface conditions of soils. According to LANDELL et al. (2003), these chemical conditions determine productivity values in sugarcane cuts over time. This work's objective is to compare sugarcane production environments based on different water availabilities under the same soil class.

In the production environment considered by PRADO et al. (2005), acric soils conform to environment D1 under low water availability, and to environment E2 under very low availability.

Production environments and productivities were studied at two locations with the same pedological conditions (Rhodic Acrustox), but different climatic conditions: Goianésia (GO), located at latitude 15°10'S and longitude 49°15'W, in a savanna tropical climate with a rainy summer and dry winter, and Ribeirão Preto (SP), located at latitude 21°13'S and longitude 47°43'W in a tropical climate with a rainy summer and dry winter. The water balance was calculated for 75 mm, according to THORNTHWAITE & MATTER (1955).

The annual precipitation is similar in both locations (1435 mm). However, in the Goianésia region distribution over the year is more irregular (Figure 1), with a longer and more defined deficit period than in Ribeirão Preto. In addition, a higher evapotranspiration rate is verified in the Goianésia region, resulting in greater soil water loss.

The means of 15 variety competition experiments in Goianésia and 30 experiments in Ribeirão Preto were compiled; the experiments were carried out by Instituto Agronômico on a very clayed Rhodic Acrustox with a moderate A horizon (LVwf), a very representative soil class in the Central-Southern region of Brazil. Five varieties were evaluated in both locations studied (IAC87-3396, RB72454, RB855486, SP80-1816, and SP80-1842) at three sugarcane harvests (cuts). Statistical analysis was performed by cut, and a linear response model (TSH) was adopted as a function of region, varieties, and the region × varieties interaction. We also analyzed region contrasts for each variety, by extracting the means and F values for the contrast between both regional means. All analyses were performed using SAS.

The more remarkable water deficit in the Goianésia region is responsible for lower sugarcane productivity, when compared with the Ribeirão Preto (SP) region. In the average of the three cuts evaluated, this reduction reached 16.8% in stalk productivity. Although soil class is the same for both locations, their production environment classifications are different. The greater climatic restriction in Goianésia displaces the production environment classification, qualified in Ribeirão Preto as D1, to E2 in Goianésia.

Among the five varieties tested, RB72454 shows interaction with the production environment, demonstrating that its productivity was the most affected by the water deficit condition in Goianésia (GO). There was no interaction in the other varieties (IAC87-3396, RB835486, SP80-1842, and SP80-1816), indicating stability in this group of varieties tested.

LANDELL, M.G.A.; PRADO, H.; VASCONCELOS, A.C.M.; PERECIN, D.; ROSSETTO, R.; BID"IA, M.A.P.; SILVA, M.A.; XAVIER, M.A. Oxisol subsurface chemical attributes related to sugarcane productivity. Scientia Agricola, 60:741-745, 2003.

PRADO, H. Ambientes de produção de cana-de-açúcar na região Centro-Sul do Brasil. Potafós, Piracicaba. Informações Agronômicas, 110:13-17, 2005.

THORNTHWAITE, C.W. & MATTER J.R. The water balance. Centerton, N.J.; Drexel Institute of Tecnology.104p. 1955. 8(1):104.

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