Agronomic comparison of four Panicum hybrids and two cultivars at three cutting intervals in Puerto Rico

Abstract

Three of the main problems associated with breeding guineagrass (Panicum maximum Jacq.), an important tropical forage, are seed shattering; low germination rate; and reproduction, which is by apomixis. Three hybrids were developed at the Tropical Agriculture Research Station (TARS) of the USDA-ARS, from sexual female plants and apomictic selections of guineagrass. In addition, an interspecific hybrid, BPIH104, was made from a cross between Brachiaria purpurascens Raddl and Panicum coloratum L.  The four hybrids, common guineagrass, and Tobiata, an introduction from Brazil, were evaluated at 4-, 6-, and 8-wk cutting intervals (Cl) during one year in a randomized splft-plot design with four replications. Mean dry matter content (DMC), dry matter yield (DMY), crude protein yield (CPY), and plant height (PHt) increased (P < 0.01) from the 4- to the 8-wk Cl, but mean crude protein concentration (CPC) decreased (P < 0.01). In vitro dry mater digestibility (IVDMD) decreased (P < 0.01) only from the 4- to 8-wk Cl. DMC, CPY, and PHt were positively correlated, and CPC and IVDMD negatively correlated, with DMY. At the 8-wk Cl, Tobiata and BPIH104 were the top yielders with annual yields equivalent to 43 and 41 t/ha, respectively. These and the other hybrids deserve further evaluation under grazing management in Puerto Rico.