Effects of Different Nitrogen and Potassium Application Levels on Yield and Its Components of Ratoon Rice

The effects of different nitrogen (N) and potassium (K) application levels on yield and its components of ratoon rice were studied using a two-line hybrid rice combination Guangliangyou 676. The results indicated that N and K application levels of obtaining the highest yield in the first crop were 23.27 g·m^-2 and 22.99 g·m^-2 respectively, and reached the yield of 1 152.9 g·m^-2 and 1 159.0 g·m^-2 respectively. N and K application levels of achieving the best economic benefit in the first crop were 21.86 g·m^-2and 19.54 g m^-2 respectively. N application level of obtaining the highest yield and the best economic benefit in the second crop was 20.48 g·m^-2 and 18.42 g·m^-2 respectively. These results showed that ratoon rice was more sensitive to nitrogen, and the lack of nitrogen would reduce more yield than that of potassium. Moreover, in the first crop, the number of effective panicle and plant height both increased with the increase of N and K application levels, the exhibited a bell-shaped curve correlation with N application level and a linear correlation with potassium application level. The seed setting rate decreased with the increase of N application level in the first crop. With the increase of nitrogen application level of promoting axillary buds in the second crop, the number of effective panicle significantly increased and the spikelets per panicle appeared a trend of first increasing and then reduction. Under the high nitrogen application level in the second crop, the seed setting rate slightly reduced and the difference of 1 000-grain weight was less.