Effects of nitrogen management on the ratoon crop yield and head rice yield in South USA

Ratoon rice cropping has been an important component of the rice cropping system in Texas, South Louisiana, USA and expanding in Asian countries. Two field studies were conducted with widely planted rice (Oryza sativa L.) cultivars at Eagle Lake, Texas, USA to determine the effects of nitrogen (N) management in main (first) crop (MC) and ratoon (second) crop (RC) on RC yield. In 2012 and 2013, one cultivar (Presidio) was adopted to determine the effects of RC N management on ratoon yield and head rice yield. In 2016 and 2017, CL153, CL163 and CL272 in addition to Presidio were adopted to examine the effect of MC N management on ratoon yield and head rice yield. N applied at preflood after MC harvest considerably improved RC yield. Application of 99 kg N ha−1 at preflood after MC harvest was practically adequate for RC regrowth, development and approaching the yield potential for Presidio. RC could produce quite high average grain yields of 5.90 to 6.53 t ha−1 in 2012 and 2013, respectively. Main crop N rate only significantly affected MC yield; however, given N applied of 99 kg ha−1 at preflood after MC harvest, ratoon yield was not significantly affected by MC N rate. Neither the main nor ratoon crop N management had a significant effect on RC head rice yield. Considerable RC head rice yields (55–65%) were observed in all of the four cultivars and 4 years except for CL272 in 2016. These results indicat that without very high N fertilizer application, rice ratoon crop could produce a considerable grain yield and an expectative head rice yield. Rice ratooning could be a practical way to increase rice yields with the minimal input in south Texas and regions with a similar climate.