Effects of nitrogen fertilization for bud initiation and tiller growth on yield and quality of rice ratoon crop in central China

Rice ratooning is an ancient technology, known as harvesting twice after one sowing. In recent years, ratoon rice has drawn much attention and been widely practiced by farmers in central China because of its advantages in saving labor and increasing profit. For ratoon crop (RC), nitrogen (N) application for promoting bud initiation (Nbud) and for promoting regenerated tiller growth (Ntiller) are two common N management practices. However, it is still obscure about their effects on grain yield and quality of RC. Field experiments were conducted to compare the effects of Nbud (75 kg N ha(-1) application at 12 days after heading of main crop, MC) and Ntiller (75 kg N ha(-1) application at 2 days after harvesting of MC) on the grain yield and quality of RC in 2018 and 2019. Compared to Nbud, Ntiller had an evident and positive effect on grain yield, head rice percentage (HRP) and chalkiness degree (CD) of RC. Averaged across years, Nbud and Ntiller increased grain yield of RC by 5.5 % and 30.5 %, respectively. Moreover, Ntiller improved grain quality with an increase of 10.5 % in HRP and a decrease of 10.2 % in CD. Ntiller significantly increased sink size like spikelets m(-2), and source ability including leaf area index, leaf N content, and crop growth rate in ratoon crop. The positive effect of Nbud on grain yield of RC was positively correlated with the increase in panicles m(-2), but negatively correlated with the panicles m(-2) of MC. Nbud has no effect on stubble dry weight, and significantly increased stubble N concentration, but significantly decreased stubble non-structural carbohydrate concentration at maturity in the main season. Overall, our results indicated that nutrient status of straw and panicle number in MC affected the roles of Nbud on RC yield, and more attention should be paid on Ntiller in future RC production.

Automated summary

Ratooning rice, a traditional practice of harvesting twice after a single seeding, has gained popularity among farmers in central China. Research shows that nitrogen application for promoting regenerated tiller growth (Ntiller) has a more significant positive effect on grain yield and quality of ratoon crop (RC) compared to nitrogen application for promoting bud initiation (Nbud). Ntiller not only increases grain yield, head rice percentage, and improves grain quality, but also enhances sink size and source ability in the ratoon crop.