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Master's Dissertation
DOI
https://doi.org/10.11606/D.11.1982.tde-20220208-030435
Document
Author
Full name
Silvia Maria Costa Nicola
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 1982
Supervisor
Title in Portuguese
Efeito de dias de vegetação e data de corte sobre a digestibilidade in vitro e o teor de N, P e K do capim Andropogon (Andropogon gayanus Kunth) var. bisquamulatus
Keywords in Portuguese
CAPIM ANDROPOGON
CORTE
DIGESTIBILIDADE IN VITRO
FÓSFORO
NITROGÊNIO
POTÁSSIO
Abstract in Portuguese
O presente trabalho teve como objetivo determinar os efeitos dos períodos de corte e da maturidade sobre a qualidade do capim Andropogon (Andropogon gayanus, Kunth) var. bisquamulatus, durante o período quente e úmido de 1980 a 1981. O experimento de campo foi conduzido, junto ao Departamento de Zootecnia da Escola Superior de Agricultura "Luiz de Queiroz" em solo mapeado como terra roxa estruturada e classificado como série Luiz de Queiroz. O delineamento experimental foi o inteiramente casualizado, e os tratamentos, com quatro repetições, consistiam nos cortes efetuados a cada sete dias durante 49 dias, em quatro períodos (22/10/81 a 09/12/81, 18/11/81 a 06/01/82, 16/12/81 a 03/02/82, 13/01/82 a 03/03/82). A área experimental foi dividida em quatro sub-áreas com 120 m2 cada, sendo que cada sub-área correspondeu crescimento de um período. Efetuou-se o corte de uniformização no dia 22/10/1981 em todas as sub-áreas iniciando-se na sub-área correspondente ao período, cortes em intervalos semanais enquanto que, para os demais períodos, as plantas cresciam livremente. O mesmo procedimento foi seguido para todos os períodos. As quatro sub-áreas, representando os períodos, receberam 120 kg P2O5 e 60 kg K2O/ha no plantio e, 80 kg N, 20 kg P2O5 e 90 kg K2O /ha, após cada corte de uniformização. Observou-se que na estação quente e úmida (outubro-março) o capim Andropogon deve ser colhido entre três a quatro semanas de crescimento para possibilitar digestibilidade de matéria seca ao redor de 60%. A digestibilidade in vitro da matéria seca e graus-dia foram negativamente correlacionados. O R2 foi de 86%, 74%, 79% e 94% para os períodos I, II, III e IV, respectivamente. A porcentagem de nitrogênio, fósforo e potássio decresceu com a maturidade da planta forrageira. O intervalo de variação foi de 2,91 a 1,60%; 0,35 a 0,18% e de 2,48 a 2,01%, respectivamente, para aqueles valores. O capim Andropogon até a sétima semana de crescimento apresentou mais de 8% de proteína bruta e até a quinta semana 0,2% de fósforo, que são necessários para preencher os requerimentos de manutenção de animais adultos. O início da estação de crescimento não foi o período mais adequado para obtenção de forragem de melhor qualidade, fato este que deve ser analisado com certo cuidado visto os problemas ocorridos no decorrer das avaliações.
Title in English
Effect of maturity on in vitro dry matter digestibility and mineral absorption by Andropogon grass (Andropogon gayanus Kunth) var. bisquamulatus
Abstract in English
The effect of growth stages and date of cuttings on in vitro dry matter digestibility and mineral composition was studied with Andropogon gayanus, Kunth, var. bisquamulatus. Trials were conducted in the field during the growth period (October-March) during 1981-1982 at Piracicaba, SP, in the Central part of Brazil. The experiment was established on a fertil tropudalf soil known as "terra roxa estruturada". The grass was established with an application of 120 kg P2O5 and 60 kg K2O/ha. Twenty eight treatments (four dates of growth combined to seven weekly cutting intervals) and four replicates were used in a completely randomized design. Four plots, each representing a date of growth were cut for uniformization at 25 days intervals. Plots were fertilized after each cut with 80 kg N, 20 kg P2O5 and 90 kg K2O/ha, then it was established in one plot the date of cutting and the weekly harvesting intervals up to seven weeks. Meanwhile other plots grew up to the next uniformization cut when a new fertilization and date of cutting was set. The results of this experiment allow the following conclusions: Andropogon gayanus var. bisquamulatus has to be harvested at three or four weeks of growing period during the "summer" (October-March) to have a dry matter digestibility around 60%. However this cutting frequency requires special attention to management practices to preserve the stand from degradation. It is possible to estimate the Andropogon grass dry matter digestibility in vitro by correlation with degree days (r2 = 86%; 74%; 79% and 94% for the growing periods initiated in October-December, November-January, December-February, January-March. Dry matter composition in nitrogen, phosphorus and potash decreased with maturity, however these nutrients were not limiting up to seven weeks of growth period to attend the nutritional requirement of animals in maintenance. The range of variation in dry matter composition was 2.91 to 1.60%; 0.35 to 0.18% and 2.48 to 2.01% to nitrogen, phosphorus and potash, respectively. Dray matter digestibility was lower at the beginning of the growth season but this results may be influenced by sampling problems when at the first harvesting a lot more of dead material was collected than in the following cuttings.
 
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Publishing Date
2022-02-08
 
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