Agronomic Comparison of Three Pennisetum Interspecific Hybrids and Forage Sorghum Millo Blanco in Puerto Rico

Napiergrass (Pen11isetum purpureum Schumach.) (2n=28) has proven to be an excellent male parent in crosses with cytoplasmic male-sterile lines of pearl millet (P. g/aucum (L.) K. Schum.) (2n= 14) 'for the development of superior interspecific Pen11isetum forage hybrids (IPFH). These hybrids (3x=21) are sexually propagated and combine the leafiness and forage quality of pearl millet with the high dry matter yield and perennial nature of napiergrass. Three lPFH (101, 102, and -.103 developed by W. H. Hanna) and local photoperiod-sensitive forage sorghum Millo Blanco (Sorghum bicolor (L) M~nch) were compared at cutting intervals (CI) of 45, 65, and 85 days, equivalent to seven, five, and four harvests, respectively, at two locations (Oxisol and Ultisol) in Puerto Rico. Across locations, dry forage yields (DFY) of the lPFH averaged 6.0, 10.4, and 16.0 t ha-1 at the 45-, 65-, and 85- day CI, respectively, representing 119, 79, and 127 % more DFY than that of Millo Blanco. From the data obtained, it appears that the optimum time for harvesting these grasses is 65 days. At this stage, the DFY were 5.8, 9.5, 11.4, and 10.3 t ha-I for Millo Blanco and the three IPFH, respectively. The in vitro dry matter digestibility for the same CI ranged from 42 to 52 % and 'the crude protein content from 6 to 11 % . The perennial nature of the interspecific hybrids plus their production of excellent quality forage attest to their potential as valuable new forage grasses for the tropics.