Response of forage sorghums Millo Blanco and Greenleaf sudangrass and their hybrids to planting dates

Forage sorghums Millo Blanco (MB) [Sorghum bicolor (L.) Moench] and ATx623 x MB (photoperiod sensitive) (PS) and Greenleaf (GL) sudangrass [S. sudanen se (Piper) Stapf] and ATx623 x GL (photoperiod insensitive) (PI) were plant ed the 15th day of each month over a period of two years at the Isabela, P. R., USDA-ARS farm. Two consecutive 60-d harvests were made for each plantin g during a period of two years. Mean annual dry matter yield (DMY) in t/ha was 32 for ATx623 x MB, 29 for MB, 26 for ATx623 x GL, and 20 for GL. On th e average, the PS genotypes had significantly higher DMY (32%) than the PI genotypes; and produced significantly more DM (96%) when planted in June th an when planted in December. ATx623 x GL and ATx623 x MB significantly surp assed their male parents in DMY (33 and 11%). Mean forage crude protein (CP ) of the genotypes was 11%. Significantly more crude protein yield (CPY) wa s obtained when the PS genotypes were planted during long days. Genotypes p lanted during short days were shorter. In most cases, leaf area was greater for the June to August plantings. Planting date (PD) had no significant ef fect on the in vitro dry matter digestibility (IVDMD) of the genotypes; the overall mean was 56%. This research demonstrated that DMY of more than 7 t /ha with a CP of 11% and IVDMD of 56% can be obtained in a 60-day growth pe riod from a forage sorghum such as MB or ATx623 x MB planted during long da ys (June) in Puerto Rico. Results showed the advantage of planting PS lines and hybrids for forage production in Puerto Rico.