Morfogênese do capim faixa-branca submetido à adubação nitrogenada

Abstract

RESUMO: Objetivou-se avaliar as características morfogênicas, estruturais e produtivas do capim Faixa-Branca (Digitaria eriantha) submetido à adubação nitrogenada, no período de janeiro a maio de 2014. Foram avaliadas cinco doses de nitrogênio: 0; 100; 200; 300 e 500 kg/ha. O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições. A adubação nitrogenada não influenciou o comprimento final das folhas, a taxa de senescência foliar, o número de folhas vivas por perfilho, a altura das plantas e a relação folha:colmo do capim Faixa-Branca. As taxas de aparecimento e de alongamento de folhas, a densidade populacional de perfilhos e os acúmulos de forragem, de folhas, de colmos e de material morto do capim Faixa-Branca foram influenciados pelas doses de nitrogênio, ajustando-se a uma equação quadrática pelas doses de nitrogênio, em que a maior quantidade de nitrogênio aplicada aumentou os valores destas taxas, atingindo pontos de máximo com doses entre 300 e 400 kg/ha. O filocrono e a duração de vida das folhas foram afetados de maneira quadrática negativa pelas doses de nitrogênio. De maneira semelhante, o aumento na quantidade de nitrogênio aplicada diminuiu os valores destas taxas, atingindo pontos de mínimo com doses entre 300 e 400 kg/ha, segundo as respectivas equações ajustadas. A taxa de alongamento de colmo aumentou linearmente com a dose de nitrogênio. O capim Faixa-Branca apresenta maior renovação de tecidos e produtividade quando adubado. A melhoria nas características produtivas do capim Faixa-Branca atingem valores máximos com doses de nitrogênio em torno de 300 kg/ha. Palavras-chave: Digitaria eriantha, ecofisiologia vegetal, manejo, produção de forragem. MORPHOGENESIS OF DIGIT GRASS SUBMITTED TO NITROGEN FERTILIZATIONABSTRACT: The objective of this study was to evaluate the morphogenetic, structural and productive characteristics of digit grass (Digitaria eriantha) submitted to nitrogen fertilization from January to May 2014. Five nitrogen doses were evaluated: 0, 100, 200, 300 and 500 kg/ha. A randomized block design with four replicates was used. Nitrogen fertilization did not influence the final leaf length, leaf senescence rate, number of live leaves per tiller, plant height, or leaf:stem ratio of digit grass. The leaf emergence and elongation rates, tiller population density and forage, leaf stem and dead material accumulation rates were influenced by the nitrogen doses, fitting a quadratic equation in which the highest nitrogen dose applied increased these rates, with the maximum rates being reached at doses of 300 to 400 kg/ha. The nitrogen doses exerted a negative quadratic effect on the phyllochron and leaf lifespan, in which these rates decreased with increasing nitrogen dose, reaching minimum values at doses of 300 to 400 kg/ha according to the respective equations. The stem elongation rate increased linearly with increasing nitrogen dose. Fertilization increases the tissue renewal and productivity of digit grass. The improvement in the productive characterist...

Herbage accumulation dynamics in digit grass subjected to defoliation frequencies

“…Four defoliation frequencies were tested, namely very high, high, medium, and low (cut made when the plant reached 25, 35, 45, and 55 cm, respectively). On the said occasions, the plant was lowered to a post-cutting residual height of 10 cm (SOUZA et al, 2016), at two times of the year [greater insolation (September to March) and lesser insolation (April to August)]. The defoliation frequencies were allocated to the experimental units (4.6-m 2 plots) in a randomized-block design with four replicates.…”

“…Maintenance fertilization was performed using 300 kg of N ha -1 per year, as recommended by Souza et al (2016), as ammonium sulfate, and 240 kg of K ha -1 per year as potassium chloride. Fertilizer applications were split according to the cutting interval as proposed by Sousa et al (2010), such that all plots would receive the same amount of fertilizer at the end of the experimental period.…”

“…Suvernola syn: Digitaria umfolozii) is a forage plant recommended for intensive pasture-based milk and meat production systems (ARONOVICH et al, 1996). At present, in Brazil, its use is more restricted to the northeast region, especially the states of Sergipe and Alagoas (SOUZA et al, 2016). This grass is adapted to grow in soils with low natural fertility (GARCÍA; PÉREZ, 2005), but is responsive to nitrogen fertilization (SOUZA et al, 2016).…”

“…At present, in Brazil, its use is more restricted to the northeast region, especially the states of Sergipe and Alagoas (SOUZA et al, 2016). This grass is adapted to grow in soils with low natural fertility (GARCÍA; PÉREZ, 2005), but is responsive to nitrogen fertilization (SOUZA et al, 2016). Additionally, this species has the ability to absorb water particles suspended in the air, which allows it to grow in regions with little rainfall (NAVARRO et al, 2005), making it responsive to irrigation (OLIVEIRA et al, 2015).…”

Tillering dynamics of digit grass subjected to different defoliation frequencies

“…Digit grass is a C4 plant (Gusmão Filho, 2018), more commonly grown in Northeastern Brazil, mainly in the states of Sergipe and Alagoas (Souza et al, 2016). This grass is adapted to regions of low mean temperature, low precipitation, and soils with low natural fertility (Navarro et al, 2005), although it appears to be responsive to irrigation (Oliveira et al, 2015) and nitrogen fertilization (Souza et al, 2016). The species presents crude protein content between 10 and 15% (Gusmão Filho, 2018) and 59% total digestible nutrients (Oliveira et al, 2015), indicating its potential for usage in pastures.…”