The seasonal and inter-annual patterns of biomass accumulation and crude protein in kleingrass (Panicum coloratum) in the semiarid Pampean region of Argentina

Kleingrass (Panicum coloratum L. var. coloratum) is a perennial warm-season grass that begins its growing season later in the spring than does weeping lovegrass (Eragrostis curvula (Schrad.) Nees), which suggests that combining weeping lovegrass with kleingrass in a grazing sequence could increase livestock production. The objectives of this study were to determine the seasonal and inter-annual variation of the patterns of the accumulation of dry matter (DM) and the percentage of crude protein (CP) in P. coloratum, cv. Verde, in the semiarid Pampean region of Argentina. This study was performed during four growing seasons in a 3.0 ha pasture of kleingrass that was sown in the spring of 1996. The forage samples were gathered at biweekly intervals and were separated into leaf blade, stems (including sheaths and inflorescence) and senescent material. Finally, patterns of dry matter accumulation and the percentage of crude protein were evaluated in relationship to the thermal time accumulated from early October to late February. In comparison with the other growing seasons evaluated, the third growing season had less (P ≤ 0.01) accumulation of dry matter and a higher (P ≤ 0.01) proportion of green leaf blade and CP. Dry matter accumulation increased with increases in the thermal time. The CP percentage of the total biomass and of the plant parts declined as thermal time increased, and this coincided with a reduction in the proportion of green leaves and the CP percentage in each plant part. Management decisions depend on an accurate assessment of the change in sward structure and nutritive value during the growing season. The results of this study will allow selection of the appropriate grazing time and the management of sequential grazing of warm-season grasses.