Abstract

MERCHAN, HD; LUTZ, EE  and  MORANT, AE. Production of a double purpose wheat defoliated at different developmental stages of the growth apex. Phyton (B. Aires) [online]. 2007, vol.76, pp.133-142. ISSN 1851-5657.

In mixed systems (beef and grain), double purpose wheat is an alternative to reduce competition between the winter cereals for grazing and wheat for harvesting. In order to optimize grass production and avoid grain yield decreases, it is necessary to use varieties with long vegetative periods and the last defoliation should be made before the apex changes to the reproductive developmental stage. A study was conducted in the experimental field of the Asociación de Cooperativas Argentinas in Cabildo (38º 36' S, 61º 58' W) to evaluate grass and grain production of the facultative wheat variety (Triticum aestivum L) Buck Charrúa, which was defoliated at different developmental stages of the growth apex. Plots were sown on 22 March. Treatments consisted of once-a-year defoliation on 5/11, 5/18, 5/27, 6/8, 7/14 or 8/10, and an undefoliated control. Grain yield (635 kg/ha) was statistically greater (p< 0.05) in the undefoliated than in the defoliated treatments. Average grain production was reduced by 23% when plants were defoliated at the vegetative apex stage, and by 63% when the apex was removed by defoliation. The smallest dry matter accumulation (798 kg/ha on average) was obtained when defoliations were made with the apex in vegetative developmental stage. When defoliation was conducted with the apex in double ridge onwards, such dry matter accumulation increased significantly (p< 0.05), reaching 2706 kg/ha when the elongated internodes and the apexes were removed in the last defoliation. The number of spikes/m² and the weight of 1000 grains did not show definite patterns.

Keywords : Wheat; Triticum aestivum; Double purpose; Wheat defoliation.

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