Nitrogen nutrition index and morphogenesis in Alexandergrass of the Central Depression of Rio Grande do Sul/Indice de nutricao nitrogenada e morfogenese em papua na Depressao Central do Rio Grande do Sul

• Published in: Ciência rural 2023-12, Vol.53 (12), p.1
• Main Authors: Salvador, Paulo Roberto, Rocha, Marta Gomes da, Machado, Juliana Medianeira, Bergoli, Tuani Lopes, Machado, Juliana Missio, Tiecher, Diego Daniel, Hoerbe, Juliana Brendler, Potter, Luciana
• Format: Article
• Language: English
• ISSN: 0103-8478
• DOI: 10.1590/0103-8478cr20210783

This study assessed the nitrogen nutrition index, morphogenic characteristics and tiller structure of Alexandergrass (Urochloa plantaginea (LINK) Hitch) pasture submitted to different nitrogen (N) levels (zero, 150 or 300 kg ha (1) of N). The experimental design was entirely randomized with repeated measures arrangement. The experimental animals were Angus heifers under rotational stocking grazing method. The number of animals was variable to keep 30[+ or -]5 cm post-grazing sward height. Nitrogen nutrition index increased linearly according N levels (Y = 59.8 + 0.1216N; P < 0.0001; [r.sup.2] =0.53). The leaf appearance rate adjusted to a positive linear regression model according the thermal sum (TS) with zero of N (Y0N = 0.0077 + 0.0000087TS; P = 0.0308; [r.sup.2] = 0.72) and 150 kg h[a.sup.-1] of N (Y150N = 0.0020 + 0.000021 TS; P = 0.0022; [r.sup.2] = 0.92). The use of 300 kg h[a.sup.-1] of N did not alter the leaf appearance rate (0.0124 leaf degree-[days.sup.-1]). The use of up to 300 kg h[a.sup.-1] of N increases the Alexandergrass nitrogen content. The leaf appearance rate in Alexandergrass is modified using N while the morphogenic characteristics leaf expansion, stem expansion, phyllochron, leaf lifespan, leaf elongation duration and tiller structure are not altered by N utilization. Key words: Leaf appearance, leaf expansion, phyllochron, nitrogen fertilization, Urochloa plantaginea. Este trabalho teve como objetivo avaliar o indice de nutricao nitrogenada, as caracteristicas morfogenicas e a estrutura dos perfilhos de papua (Urochloa plantaginea (LINK) Hitch) submetidos a diferentes niveis de nitrogenio (N) (zero, 150 ou 300 kg h[a.sup.-1] de N). O delineamento experimental foi inteiramente casualizado com medidas repetidas no tempo. Os animais experimentais foram novilhas Angus em regime de pastejo rotacionado. O numero de animais foi variavel para manter 30 [+ or -] 5 cm de altura do pasto pos-pastejo. O indice de nutricao com nitrogenio aumentou linearmente de acordo com os niveis de N (Y = 59,8 + 0,1216N; P < 0,0001; [r.sup.2] = 0,53). A taxa de aparecimento de folhas ajustou-se ao modelo de regressao linear positiva de acordo com a soma termica (TS) com zero de N (Y0N = 0,0077 + 0,0000087TS; P = 0,0308; [r.sup.2] = 0,72) e 150 kg h[a.sup.-1] de N (Y150N = 0,0020 +0,000021 TS; P = 0,0022; [r.sup.2] = 0,92). O uso de 300 kg h[a.sup.-1] de N nao alterou a taxa de aparecimento de folhas (0,0124 folha grau-[dia.sup.-1]). O uso de ate 300 kg h[a.