A grazing height target to minimize tiller stem elongation rate in annual ryegrass swards

• Published in: Ciência rural 2016-01, Vol.46 (1), p.169-175
• Main Authors: Santos, Gabriela Trevisan, Zanini, Guilherme Doneda, Padilha, Deisy Andrade, Sbrissia, André Fischer
• Format: Article
• Language: English
• Subjects: Accumulation; AGRONOMY; altura do pasto; Competition; Design of experiments; Elongation; Experimental design; Experiments; flexibilidade de manejo; Forage crops; Grasses; Grazing; Information processing; interceptação de luz; Leaves; Light; Lolium multiflorum; manejo do pastoreio; Pasture; Pasture management; Pastures; Population density; Senescence; Sheaths; Stems; Sward; Tillers
• ISSN: 1678-4596; 0103-8478; 1678-4596
• DOI: 10.1590/0103-8478cr20141508

Italian ryegrass (Lolium multiflorum Lam) is one of the most cultivated temperate annual forage crop around the world. Despite that, there is little information about the process of stem elongation during its vegetative growth. This information would be useful for grazing management purposes. Thus, the aim of this study was to assess the herbage accumulation and stem elongation rates in annual ryegrass pastures submitted to intermittent stocking. The experimental design used was a completely randomized 2x2 factorial with three replications. The treatments were defined by the combination of two pre-grazing heights (15 and 25cm) associated with two post-grazing heights (4 and 8cm). The herbage accumulation rates were higher in pastures with 25cm pre-grazing associated with post-grazing heights of 8cm. However, leaf production rate was only affected by post-grazing height, with higher values being recorded for stubbles heights of 8cm, regardless of pre-grazing height. Stem elongation rates in annual ryegrass tillers increased rapidly when pastures reached around 18cm, a condition where there was a relatively low competition for light, suggesting that; 1) pre-grazing heights of 18 to 20cm in annual ryegrass could be used as a upper limit for grazing management purposes whether the objective is to minimize stem contribution in accumulated herbage and 2) It seems that stem elongation is as inevitable process (independently of competition for light) and that this could be related to the necessary strength of stems, pseudostems and sheaths to support larger and heavier leaves. RESUMO: O azevém anual (Lolium multuflorum Lam) é uma das plantas forrageiras de clima temperado mais cultivadas no mundo. Apesar disso, há poucas informações sobre o processo de alongamento de colmos para essa espécie durante seu crescimento vegetativo. Tal informação seria útil para o manejo mais adequado desta espécie. Assim, o objetivo do presente trabalho foi avaliar o acúmulo de forragem e as taxas de alongamento de colmos em pastos de azevém anual submetidos à lotação intermitente. O delineamento experimental foi completamente casualizado em arranjo factorial 2x2, com três repetições. Os tratamentos consistiram na combinação de duas alturas em pré-pastejo (15 e 25cm), associadas com duas alturas de resíduo (4 e 8cm). A maior taxa de acúmulo de forragem foi observada nos pastos manejadas com 25cm, associadas com alturas de resíduo de 8cm. Entretanto, a taxa de acúmulo de folhas foi sim