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13 October 2016 Sward structure and relationship between canopy height and light interception for tropical C4 grasses growing under trees
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Abstract

The canopy height (CH) at 95% light interception (LI) is a valuable defoliation frequency strategy used to handle variability in herbage accumulation throughout the year, mainly in C4 grasses. Such a strategy has been adopted as an open pasture management index, but defoliation frequency and intensity remain unsolved issues for shade-grown forages. A field experiment was conducted for 2 years to determine the influence of tree canopy (Eucalyptus dunnii) shading and nitrogen availability (0 and 300 kg N ha–1 year–1) on CH at 95% LI of six perennial tropical forage species. The plots were cut at 95% LI, and the height of the residual sward was kept at 50% of the corresponding CH at 95% LI. The shade level ranged from ∼40% at the beginning of the experiment to ∼60% at the end of summer 2013. Variations in CH at 95% LI occurred because of shading and across seasons. The range of these variations was species-dependent. Overall, species growing under trees showed higher CH, except for Paspalum notatum and Megathyrsus maximus in the first year. There was a significant increase in the length of the sheaths and leaves, as well as a decrease in tiller density and leaf : stem ratio in plants growing under trees. Nitrogen also had an impact on CH; however, its application did not compensate the shade effect on CH. Therefore, our results suggest that greater CH should be considered in case of defoliated, shade-grown plants and that such strategy might change throughout seasons.

© CSIRO 2016
Tiago Celso Baldissera, Laíse da Silveira Pontes, André Faé Giostri, Raquel Santiago Barro, Sebastião Brasil Campos Lustosa, Aníbal de Moraes, and Paulo César de Faccio Carvalho "Sward structure and relationship between canopy height and light interception for tropical C4 grasses growing under trees," Crop and Pasture Science 67(11), 1199-1207, (13 October 2016). https://doi.org/10.1071/CP16067
Received: 26 February 2016; Accepted: 1 September 2016; Published: 13 October 2016
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