Effect of Drought–Flood Abrupt Alternation on Rice Yield and Yield Components

The purpose of this paper is to clarify the compensation or reduction effect of drought-flood abrupt alternation (DFAA) events on the yield and yield components of rice (Oryza sativa L.). The experiments, conducted in 2016 and 2017, were on three different drought and flood treatments and compared with normal irrigation conditions. Compared with the normal control group, the average yield reduction of the DFAA groups was 12.98% in 2016 and 29.94% in 2017, and the combination of heavy droughts and heavy flooding was the most unfavorable for yield. The reduction in grains per panicle and the total grain number was the main reason for yield reduction under DFAA stress. The damage in terms of the total grain number amounted to 18.84 and 17.82% in 2016 and 2017, respectively. The interannual differences in the thousand-seed mass and seed setting rate increased in 2016 and decreased in 2017. Compared with the drought groups and the flood groups, the flood stress of the DFAA groups reduced the yield under drought conditions, and the decrease in the total grain number and panicles per barrel during the flood period was the main reason. The drought stress of the DFAA groups compensated the yield under flood conditions, mainly because the total grain number and seed setting rate increased during the drought period. Under long-term light drought conditions, the panicles per barrel, grains per panicle, total grain number, thousand-seed mass, and seed setting rate increased. Under long-term heavy drought conditions, the panicles per barrel mainly increased.