Abstract
The objective of this work was to evaluate effects of nitrogen fertilization and plant density on morphogenesis of Tanzania guinea grass. It was used a random block design with 12 treatments and two replications in a 4 × 3 factorial arrangement, with four doses of nitrogen (N) (without N application, 80, 160 or 320 kg/ha.year) and three plant densities (9, 25 or 49 plants/m²). Harvest was performed at 25 cm from the ground when the canopy intercepted 95% of the incident light. Rates of leaf appearance and pseudostem elongation were positively and linearly influenced by nitrogen, whereas phillochron and leaf life span were influenced linearly and negatively. Leaf elongation responded positively to two factors, whereas leaf senescence rate and number of live leaves were not influenced by the factors evaluated. Number of total, basal and aerial tillers were greater at the density of 9 plants/m² and at the nitrogen dose of 320 kg/ha.year. Nitrogen increases production of leaves and tillers in Tanzania guinea grass defoliated at 95% of light interception, but high density of plants reduces the number of tiller per bunch.
Highlights
It is estimated that in Brazil, approximately 172 million of hectares are used for pastures (IBGE, 2006), which represents around 22% of the national territory, but most areas used for raising domestic herbivores present productive indexes below to what is desirable
Little is known on the impact of plant density on pasture morphogenesis, when its effect is combined with nitrogen fertilization on pastures managed on the condition of pre-defoliation referent to 95% light interception
Leaf appearance rate (LAR) could be represented by the linear regression model and it was positively influenced by nitrogen fertilization (P0.05; Table 1)
Summary
It is estimated that in Brazil, approximately 172 million of hectares are used for pastures (IBGE, 2006), which represents around 22% of the national territory, but most areas used for raising domestic herbivores present productive indexes below to what is desirable. Apart from assuring pasture sustainability, the principal objective of pasture management is to make most of the diet of the animal composed of leaves, many environmental factors (light, temperature, water and nutrients) influence photosynthesis processes, growth dynamics and plant development, and leaf formation. Under distinct conditions of use, understanding the process of forage development is the first step for defining rational strategies of pasture management (Gomide et al, 2006). This statement highlights the importance of studies on forage grass production dynamics through evaluations of its morphogenetic and structural characteristics. It is believed that plant density can influence pasture structure because of the changes on patterns of intra-specific competition for nutrients and light in the canopy
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