Effect of Sowing Date on Forage Yields and Quality of Italian Ryegrass in Early Spring-seeded

Abstract Text: Because Italian ryegrass (IRG) is generally cultivated by winter cropping on a drained paddy field, the harvest season is overlapped with that of rice in some cases. In addition, people may miss the adequate seedtime for IRG because of the rainy season. Therefore, this research has been performed between October, 2012 and July, 2013 in Kangjin, Korea, to examine the effect of Spring-seeding on the yields and quality of IRG, as an alternative seeding when the adequate seedtime is missed. Using Kowinearly species, 5 test groups were prepared depending on the sowing date: Control group (sowing date: October 20^th, 2012 which is an optimum seeding-time), T1 (sowing date: February 15^th, 2013), T2 (sowing date: February 25^th, 2013), T3 (sowing date: March 5^th, 2013) and T4 (sowing date: March 15^th, 2013), and the IRG was harvested in May 31^st, 2013. The lodging of vegetative period for control group, T1 and T2 was >70%, while that of T3 and T4 was approximately 50%. The plant height by harvesting for control group showed the highest value of 109.5cm, and for T1 and T2 was 102.2 and 103.0cm, while those for T3 and T4 were 98.6 and 93.3cm, respectively, whereby the difference was statistically significant (p<0.05). The fresh yield per ha was 38.0, 26.5, 21.2, 22.3 and 20.4 ton/ha for control group, T1, T2, T3 and T4, respectively, where the control group showed the highest value and the T1 was significantly larger than those for T2~T4 (p<0.05). The yield for dry matter was 31.3, 27.8, 28.8, 24.4 and 22.3% for the control group, T1, T2, T3 and T4, respectively, which is the similar to the fresh yield. On the other hand, the content of crude protein was 7.9, 8.6, 8.7, 9.4 and 12.3% for the control group, T1, T2, T3 and T4, respectively, where a shorter growing period represents the higher crude protein content. The ADF was 36% for the control group and T1 ~ T3, while that for T4 decreased to 33%. The NDF was 66% for the control group and T1 ~ T3, while that for T4 decreased to 61%. According to these findings, it can be summarized that the Spring-seeding of IRG gives <70% yield compared to that by the adequate seeding. However, the optimum seeding time to maximize the forage yield and quality would be before February 25^th.

Keywords: Italian ryegrass, Early spring-seeded, Forage yield, Forage quality