Yield components and morphogenesis of Aruana grass in response to nitrogen supply

Abstract

Areas with Aruana grass (Panicum maximum Jacq.) in Brazilian pastures, especially those used by sheep, have expanded due to yield and morphological characteristics of this grass that are favorable to these animals. Nevertheless, the knowledge concerning yield attributes of this grass in relation to nitrogen fertilization is very limited. The objective of this research was to evaluate yield and physiological attributes in this forage grass when grown in nutrient solutions containing N rates. The experiment was carried out in a greenhouse with plastic pots containing ground quartz as substrate, during the Spring season. Six N rates in the solution (14, 112, 210, 294, 378, and 462 mg L -1 ), with 70% N-NO 3 -and 30% N-NH 4 + were tested. Experimental units were set up in a completely randomized block design, with four replications. Plants were harvested at 35 days after the seedlings were transplanted to the pots and again at 28 days after the first harvest. After the second harvest, the roots were taken from the substrate. In both growing periods, dry matter yield for plant tops and roots, leaf area, number of expanded green leaves, number of tillers, leaf appearance rate, and phyllochron were significantly affected by the N rates, and the data were adjusted to a second-order model. Aruana grass required high rates of N to show maximum response in those variables. Key words: Panicum maximum, leaf area, phyllochron, leaves, tillering COMPONENTES DE PRODUÇÃO E MORFOGÊNESE DO CAPIM-ARUANA EM RESPOSTA AO NITROGÊNIORESUMO: No Brasil, as áreas de pastagens formadas com o capim-Aruana (Panicum maximum Jacq.), particularmente destinadas ao pastejo por ovinos, têm crescido devido às características produtivas e estruturais da gramínea, propícias à exploração destes rebanhos. Porém, o conhecimento do comportamento produtivo do capim-Aruana relacionado à adubação nitrogenada é escasso. Avaliaram-se atributos produtivos e fisiológicos desta gramínea forrageira, quando submetida a doses de N em solução nutritiva. O experimento foi conduzido em casa-de-vegetação, utilizando vasos contendo sílica como substrato, no período da primavera. Foram estudadas seis doses de N correspondentes a 14; 112; 210; 294; 378 e 462 mg L -1, mantidas na proporção constante de 70%:30% entre N-NO 3 -e N-NH 4 + . O delineamento experimental foi o de blocos ao acaso, com quatro repetições. As plantas foram colhidas aos 35 dias após o transplante das plântulas e aos 28 dias após o primeiro corte, procedendo-se nesta ocasião, a separação das raízes da sílica. A produção de massa seca da parte aérea e das raízes, a área foliar, o número de folhas verdes expandidas, o número de perfilhos, a taxa de aparecimento de folhas e filocrono no primeiro e segundo cortes, foram influenciados pelas doses de N, ajustando-se ao modelo quadrático de regressão. O capim-Aruana mostrou-se exigente ao fornecimento de N para expressar o seu máximo potencial nas variáveis analisadas.

Marandu Palisadegrass Mineral Nutrition and Production Related to Nitrogen and Potassium Supply

“…Also, increases in N concentration of 21.0 g kg −1 and 10.0 g kg −1 were observed for the first and second harvests, respectively. These results are in agreement with those of Cherney et al (2004), Fitzpatrick and Guilard (2004), Lavres et al (2004), and Megda and Monteiro (2010). For a K supply of 0.5 mmol L −1 , increasing N supply from the lowest supply (2 mmol L −1 ) to the highest supply (33 mmol L −1 ) had no significant effect on dry mass production of 'Marandu' palisadegrass shoots (Table 1).…”

Effects of nitrogen fertilization and cutting intensity on the agronomic performance of warm‐season grasses

“…This greater leaf proportion would theoretically allow the development of new tillers (Skinner and Nelson, ). Therefore, it is possible that greater tiller density may be observed following N fertilization (Lavres et al ., ) and following a decrease in cutting intensity (Portela et al ., ), allowing shorter canopies to intercept 95% LI. Under nitrogen restriction or more severe cutting intensity, plants prioritize the growth of existing tillers due to reduced concentrations of water‐soluble carbohydrates and nitrogen energy reserves (Turner et al ., ).…”

“…Consequently, each species responds differently to the intensity of defoliation because it is related to the morphological and physiological characteristics of a species (D'Angelo et al ., ). Nitrogen supply has a positive effect on the aboveground productivity of forage plants because it is a major factor responsible for increasing the tiller density, number of leaves and leaf area of forage plants (Premazzi et al ., ; Lavres et al ., ; Pitman, ). Consequently, the negative effects of increased cutting intensity on herbage accumulation, which include reduced tiller development (Portela et al ., ), could be compensated for by increasing the N fertilization rate.…”

Diagnose nutricional de nitrogênio no capim-aruana em condições controladas

“…Adotou-se o critério estabelecido por Ulrich & Hills (1973), que definiram nível crítico como a concentração do nutriente no tecido que corresponde a 90 % da produção máxima da cultura. Dessa forma, com base nos valores de concentração de N nos componentes da parte aérea e nas produções de massa seca do capim-Aruana (Lavres Jr. et al, 2004), determinou-se a concentração crítica interna de N nos vários componentes da parte aérea, que apresentaram maiores coeficientes de correlação e significância para a relação.…”