Forage productivity of Corn and sorghum hybrids in rice black-streaked dwarf virus prevalent area

Silage productivity of 7 corn and 3 sorghum hybrids was determined at two planting dates differing in rice black-streaked dwarf virus (RBSDV) infection rates in the southern part of Korea where RBSDV is prevalent. Percent stand was similar between two planting dates, but that of corn hybrids (85.0-99.5 %) was higher compared with sorghum (59.8-82.3 %). Culm length of corn hybrids at April 23 planting was longer compared with May 20 planting, but that of sorghum hybrids was similar between two planting dates. RBSDV infection rate of corn hybrids at April 23 planting was lower compared with May 20 planting, but sorghum was not infected at both planting dates. Among corn hybrids Suwon 19 was most severely infected, but Suwon 99 was least infected at both planting dates. Percent ear bearing plants and ear/total dry matter (TDM) ratio of corn hybrids at April 23 planting was higher than those of May 20 planting. Among the corn hybrids percent ear bearing plants, ear/TDM ratio of Suwon 19 was lowest at both planting dates due to severe RBSDV infection. Ear/TDM ratio of sorghum hybrids was below 17.8 % due to sterility and partially bird damages. Silage yield at April 23 planting was higher than that at May 20 planting and sorghum hybrids outyielded corn hybrids. Silage yield of Suwon 19 and Jinjuok was lowest due to severe RBSDV infection. Crude protein was similar regardless planting dates, species, and varieties except the lowest P 931. Ether extract at April 23 planting was lower than that at May 20 and corn was lower compared with sorghum hybrids. Crude fiber and nitrogen free extracts (NFE) was similar between planting dates. Crude fiber of corn was lower, but NFE was higher compared with sorghum, but similar among hybrids in a species. In vitro dry matter digestibility (IVDMD) at May 20 planting was higher than that of April 23 planting and corn was higher than sorghum hybrids. Digestible dry matter (DDM) of both corn and sorghum at April 23 planting was higher than that of May 20 planting