The aim of this study was to investigate the effect of nitrogen (N) concentration during the establishment period of Mombasa grass (Panicum maximum Jacq.). The experiment was conducted using four different N concentrations (0, 30, 60 and 90 kg N/ha) during the establishment period in order to evaluate the effect of nitrogen on the plant. These effects were assessed using different indexes, including the efficiency of nitrogen use and agricultural, physiological and nutritional efficiencies. We also determined the total dry matter and nitrogen accumulation in the plant. The recovery of applied N and the agronomic efficiency of Mombasa grass were found to be greater with increasing N concentrations, and all indexes tested were found to be affected by the concentration of applied N. Based on the indexes studied, 90 kg N/ha was found to be most suitable for Mombasa grass during the establishment period. Key words: Agronomic efficiency. Nitrogen fertilizer. Panicum maximum Jacq. Nitrogen recovery. ResumoO presente trabalho teve como objetivo estudar o efeito de doses de nitrogênio (N) em pasto de capimMombaça (Panicum maximum Jacq.) durante o período de estabelecimento. Foi realizado experimento com quatro doses de N (0, 30, 60, 90 kg.ha -1 ), durante o período de estabelecimento, para avaliação do efeito do nitrogênio na planta, através de índices de eficiência de utilização, eficiência agronômica, fisiológica e nutricional, avaliou-se ainda a matéria seca total e o acúmulo de nitrogênio na planta. Concluiu-se que a recuperação do N aplicado e a eficiência agronômica pelo capim Mombaça aumentou com o incremento das doses. Sendo que, para todos os índices ocorreu influência das doses aplicadas. A dose de 90 kg de N.ha -1 , com base nos índices estudados, é a mais indicada para o período de estabelecimento do capim-Mombaça. Palavras-chave: Eficiência agronômica. Adubo nitrogenado. (Panicum maximum Jacq.). Recuperação do N aplicado.
In recent years, agroforestry and silvopastoral systems have been gaining ground in rural areas, especially due to great acceptance by the population of products from locations that preserve the environment, being able to produce food and preserve the natural resources. This study aimed to evaluate the temporal variation of the chemical attributes of the soil in pasture areas managed with silvopastoral system and full sun (monoculture). The areas were evaluated in 2011, 2014 and 2017. Soil samples were collected at depths of 0-10 cm and 10-20 cm. Both systems presented reductions in the levels of organic matter over the evaluated period, reflecting the degradability of the material deposited in the soil. Nevertheless, it is worth mentioning that the silvopastoral system (SPS) was more efficient in maintaining the organic component when compared with monoculture, despite not maintaining regularity in the levels of organic matter in the soil. As for the other chemical parameters, there were also changes, especially related to phosphorus (P) and potassium (K). For P, low replacement via organic material from the pasture and/or native trees in the SSP system were observed, resulting in a marked reduction over time. As for K, the presence of the nutrient was critical in both studied systems and depths, showing low replacement through litter.
This study aimed to evaluate the effect of nitrogen (N) fertilizer doses on morphogenic and structural characteristics of mombassa grass (Panicum maximum Jacq.) at three different periods of the lifespan of tillers. The experiment was conducted in Araguaína-TO, Brazil, from December 2014 to February 2015. It was installed in split plots in a randomized block design with four replications. The doses of N-fertilizer (0, 30, 60, 90 kg N.ha -1 ) were the plots and the periods evaluated (1PER -first period from day 16 to 30; 2PER from day 31 to 45 and 3PER from day 46 to 60 after germination) were the subplots. The evaluated variables consisted of leaf appearance rate (LAR), leaf elongation rate (LER), stem elongation rate (SER), leaf senescence rate (LSR), phyllochron, tiller number, leaf emergence, and total leaf number. A Pearson correlation analysis was used to morphogenic and structural characteristics along with a regression analysis for all the variables. Overall, increasing N-fertilizer doses positively influenced the leaf appearance and leaf elongation rates, tiller density, and the number of live leaves per tiller. The 90-kg N.ha -1 dose enabled the best morphogenic and structural responses of the forage when compared to the other rates. Each period featured differently, with higher values of LSR, SER, and LER in 3PER when compared to those in 2PER and in 1PER. Therefore, the nutritional supply over the first weeks of tiller lives was defining to an increase in forage production in the remaining periods. In light of this, we observed that as LAR raise in the first days after germination, nutritional supplies are required from day 15 on, mainly nitrogen, so plants could continue their development since initial plant growth determines pasture productive vigor and longevity. Key words: leaf appearance; tiller; (Panicum maximum Jacq.); growth period. ResumoObjetivou-se avaliar o efeito de doses de N-fertilizante sobre as características morfogênicas e estruturais no período de estabelecimento do capim-mombaça (Panicum maximum Jacq.) em três períodos da vida do perfilho. O experimento conduzido em Araguaína-TO de dezembro de 2014 a fevereiro de 2015, foi instalado em parcelas subdivididas em um delineamento de blocos casualizados, com quatro repetições, sendo as doses de N-fertilizante (0, 30, 60 e 90 kg N.ha -1 ) a parcela e os períodos avaliados (1°PER-primeiro período do 16º ao 30º; 2°PER-segundo período do 31º ao 45º e 3°PER-terceiro período do 46º ao 60º dia pós germinação) a subparcela. Avaliou-se a taxa de aparecimento foliar (TApF), taxa de alongamento foliar (TAlF) e colmo (TAlC), taxa de senescência foliar (TSF), filocrono, número de perfilhos, surgimento de folhas e o número de folhas totais. Foi utilizada uma análise de correlação de Pearson entre as características morfogênicas e estruturais e, também, análise de regressão para todas as variáveis avaliadas. O incremento das doses de nitrogênio influenciou positivamente as taxas de aparecimento foliar, alongamento foliar, densidade de perfi...
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