Effects of Split Application of Nitrogen Fertilizer on Yield, Quality and Nitrogen Use Efficiency of Sweet Potato.

To explore the optimal split nitrogen fertilizer application methods for high yield and quality sweet potato production in intercropping, we conducted a field experiment using two sweet potato cultivars Yuzi 7 and Wanshu 10 with single N application, 2-split and 3-split N application, and measured the yield, quality, and nitrogen use efficiency in monocropping and interplanting in 2015-2016. The yield, single storage root weight, soluble protein content, soluble sugar content of storage root, apparent nitrogen use efficiency and partial nitrogen productivity were significantly increased in the two tested cultivars under 2-split and 3-split N application in monocropping and interplanting. Under interplanting, commodity rate was not significantly different in the two cultivars among the three N application treatments, however, the highest commodity rate was obtained under 3-split N application in monocropping. The highest content of β-carotene in the storage root was obtained when 3-split N application was used in Wanshu 10, and the highest content of anthocyanin in the storage root was obtained when 2-split N application was used in Yuzi 7, but the highest starch content of storage root was obtained when non-split N application was used in the two cultivars. All of the quality traits except soluble protein content of storage root, and yield and nitrogen use efficiency reduced in intercropping, but these traits were equal or better in 2 or 3-split N application when compared to those in monocropping. In conclusion, non-split N application could be used to increase the starch content of storage root, and 2 or 3-split N application could be used to increase other quality traits, yield and nitrogen efficiency of sweet potato. [ABSTRACT FROM AUTHOR]