Growth Inhibitory Factors of Italian Ryegrass (Lolium multiflorum Lam.) after Broadcasting under Growing Rice from 2014 to 2015

Abstract

The growth of Italian ryegrass (IRG) after wintering was very low in 2015 when IRG was broadcasted under growing rice in fall of 2014. To determine growth inhibitory factors of IRG, we examined the growth conditions of IRG in Nonsan region and meteorological conditions in Daejeon nearby Nonsan. Minimum temperature and maximum instantaneous wind speed on Feb. and of 2015 after wintering of IRG were , 10.7 m/s and , 9.6m/s, respectively. Air temperature was suddenly dropped due to strong wind with snow showers, which had unfavorable effect on root growth of IRG exposed at the soil surface. The minimum temperature and maximum instantaneous wind speed on Feb. , , and of 2015 were , 11.6 m/s, , 10.3 m/s, and , 7.5 m/s, respectively. The growth circumstance of IRG was not good because soil was dried due to drought continued from January. The minimum temperature and maximum instantaneous wind speed on Feb. , , and of 2015 were , 13.7 m/s, , 10.6 m/s, and , 6.8 m/s, respectively. The number of wilting of IRG was more than 59% until Mar. of 2015. IRG faced irreparable environment (low minimum temperatures and extreme instantaneous wind speeds) for 9 days from Mar. to Mar. of 2015. The main reason for the decrease of IRG productivity was collection delay of rice straw after rice harvest because there was continuous rain between Oct. and Nov. of 2014. For this reason, weakly grown IRG under rice straw was withered after wintering. IRG was withered by frost heaving, drought, and instantaneous wind speed in the spring. Furthermore, the root of IRG was damaged while growing in excess moisture in the surface of paddy soil during the winter season due to rain.