Defoliation management of kleingrass (Panicum coloratum L. var coloratum) cv Verde

Carlos Ferri, VV Jouve, AM Sáenz


The defoliation frequency determines above and belowground biomass accumulation, pasture structure and nutritive value.Two defoliation experiments with Panicum coloratum were performed,from September to March. One of them was conducted inpots under greenhouse conditions, and the other one in field plots forthree growing seasons (EC) at the Faculty of Agronomy, La Pampa,Argentina (36˚ 46' S; 64˚ 16' W). Defoliation frequency treatmentswere four cutting intervals (IC; 3, 4, 6 and 8 weeks). In greenhouseexperiment, live leaf blade accumulation rates (TAL), tiller appearance(TAM) and death (TMM) rates, live leaf blade length (LL)and above and below ground dry matter (MS) accumulation weredetermined. In field plots tiller height, weight and tiller, crude protein(PB) and dry matter accumulation were determined. TAL andthe TAM were 1.28 (0.1024 vs 0.0798 cm/tiller/°Cd; P<0.01) and1.92 (0.0133 vs 0.0069 tillers/°Cd; P<0.01) times higher in the IC3 and 4 vs 6 and 8 weeks, respectively. The TMM was 1.38 (0.0087vs 0.0063 tillers/°Cd; P<0.01) times higher in the IC 8 vs 3, 4 and6 weeks. Increased IC resulted in a decrease (P<0.05) in LL andincreases (P<0.05) in above and belowground MS accumulation.Under field conditions, MS accumulation and tillers height over thegrowing seasons differed among IC (EC × IC interaction; P<0.05).Tiller weight increased (P<0.05) with higher IC and tiller densitydid not differ (P=0.13) among IC. The PB values ranged from 11.4%to 7.1% (P<0.001) with increasing IC and they were related (r =-0.89; P<0.01) with MS accumulation. In addition, the last one wasrelated to tiller weight (r = 0.81; P<0.001) and tiller height (r = 0.79;P<0.001) but not with tiller density (r = 0.05; P=0.73). The variationsfound in plant structure would indicate a compensatory capacity ofkleingrass and self-regulation of leaf area index in response to defoliation.However, these responses were smaller in magnitude under infield than under greenhouse conditions.

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Phyton. International Journal of Experimental Botany. ISSN print 0031-9457 ISSN en line 1851-5657 Fundación Rómulo Raggio Gaspar Campos 861,  Vicente López, Buenos Aires, Argentina (C.P. 1638) Tel 54 11 4791-0868 / 4796-1456