Produtividade e composição bromatológica de Panicum maximum cv. Mombaça sob irrigação e adubação azotada

Abstract

R e s u m oForam avaliados os efeitos de diferentes lâminas de irrigação e doses de azoto (N) sobre a produtividade, efi ciência do uso do azoto (EUN) e composição bromatológica do Panicum maximum cv. Mombaça. O delineamento experimental foi em blocos casualizados, em esquema fatorial 2x4, com três repetições, sendo dois níveis de irrigação (50% e 80% da evaporação do Tanque Classe "A", ECA) e quatro doses de N (200, 400, 600 e 800 kg/ha/ano). As lâminas de irrigação aplicadas apresentaram comportamentos semelhantes em relação à EUN, produção de matéria seca total (PMST), de folhas (PMSF) e colmos (PMSC), e teores de fi bra em detergente neutro (FDN). A adubação azotada infl uenciou positivamente a PMST, PMSF e PMSC, no entanto, diminuiu a EUN. Os teores de proteína bruta (PB) das folhas e colmos foram infl uenciados pela interação lâminas de irrigação x adubação azotada. Houve efeito linear do N sobre os teores de PB. Os teores de fi bra em detergente ácido (FDA) apresentaram infl uência negativa da maior lâmina de irrigação e foram reduzidos pela adubação azotada. A irrigação de 50% da ECA, associada à aplicação de 800 kg de N/ha/ano, apresentou os melhores resultados, considerando-se a produtividade, composição bromatológica e economia de água.Palavras-chave: fi bra em detergente ácido, fi bra em detergente neutro, proteína bruta, tanque classe "A". A b s t r a c tThe eff ects of diff erent irrigation levels and doses of nitrogen (N) on yield, nitrogen use effi ciency (NUE) and chemical composition of Mombasa grass (Panicum maximum) were evaluated. The experimental design was randomized blocks in a 2x4 factorial, with three replicates, two water levels (50% and 80% of Class A pan evaporation, ECA) and four levels of N (200, 400, 600 and 800 kg / ha / year). The water depth applied showed similar behaviors regarding NUE, total dry matt er yield (TDMY), leaves (DMYL) and stems (DMYS), and levels of neutral detergent fi ber (NDF). The nitrogen fertilization infl uenced positively TDMY, DMYL and DMYS, however, decreased NUE. Crude protein (CP) of the leaves and stems were infl uenced by the interaction of blades irrigation x nitrogen fertilization. There was a linear eff ect of N on the PB. The levels of acid detergent fi ber (ADF) had negative infl uence of greater water depth. Concentrations of ADF were reduced by nitrogen fertilization. Irrigation of 50% of ECA, associated with application of 800 kg N / ha / year, showed the best results, considering productivity, chemical composition and water savings.Keywords: acid detergent fi ber, class A pan, crude protein, neutral detergent fi ber.

Períodos de utilização de gramíneas forrageiras diferidas implantadas sob sombreamento de coqueiro-anão

“…Utilization Periods August September October November Average --------------------GDM (t ha -1 ) -------------------- Analyzing the effect of grasses alone, marandu (6.67 t ha -1 ) and Mombasa (6.82 t ha -1 ) grasses showed higher forage yields (P<0.05) (Table 1). This situation was already expected, as these grasses have a high potential for forage production, when in favorable soil and climate conditions, and annual forage production can exceed 30 tons of GDM ha -1 , as a sum of several defoliations during growth season (Magalhães, 2010;Mochel Filho et al, 2016). Although, in this experiment, the forage production was lower than the one mentioned above.…”

Ruminal degradation of Panicum grasses in three post-regrowth ages

“…The reduction in the contents of this constituent with advancing forage age is associated with the higher complexation of nitrogen compounds with the lignocellulosic fraction of the cell wall. However, even at the highest cutting age, the CP content is above the minimum of 6-8% in DM, recommended for the maintenance of 8 mg NH 3 -N.dL -1 in the rumen fluid and for the efficient ruminal degradation, with an increase in the production of microbial protein (24) ; these values are equivalent to those obtained for tropical grasses (1,5) .…”

“…Reductions in the degradation rate of nitrogen fractions from 34 days can reduce the amount of ammonia nitrogen available to rumen microorganisms, which use it for the synthesis of amino acids, cell structures, and growth (25) , which negatively impacts the DM degradability (Table 2). In tropical grasses, a reduction in the protein degradation rate is expected with advancing age, associated with factors such as climate, water availability, and temperature, with the incorporation of this fraction in the less soluble components of the forage (1,13) .…”

“…In the current feeding systems of ruminants on pastures, information is needed regarding the nutritional value and their rates of degradation and utilization in the digestive system, in order to balance the availability of energy and nitrogen in the rumen, maximizing microbial efficiency. However, in tropical regions, due to climatic conditions, forage plants have marked seasonality, with high availability and good nutritional value only in the rainy season, a phenomenon determined mainly by the limitations of light, water availability, and temperature in the dry season (1) . Thus, the search for tropical grasses with high productivity in dry matter and adequate nutritional value is a challenge for the production of ruminants.…”

Agronomic and Bromatological Traits of Brachiaria brizantha cv. Piatã as Affected by Nitrogen Rates and Cutting Heights

“…However, due to the climatic conditions, tropical forages present a marked seasonality of production, with forage of good nutritive value and availability in the rainy season, and forage losses in quantity and quality during the dry season. In this perspective, it is fundamental to implement management practices that allow the optimization of the forage use for increasing animal production [2,3,4].…”