Relationship between plant nitrogen nutrition and lodging of winter wheat

Objectives The purpose of this study was to clarify the intrinsic relationship between nitrogen nutrition and wheat lodging, and also to reveal the mechanism of how nitrogen fertilization affects wheat lodging.

Methods A field experiment was carried out in Yuzhou city, Henan province. Two wheat cultivars, Yumai49-198 (YM49-198) and Zhoumai16 (ZM16), were used with five different nitrogen levels (0, 120, 180, 240 and 360 kg/hm²) to explore the effect of nitrogen content on wheat lodging. Nitrogen concentration in wheat at different growth stages was anlyzed, the lodging situation, stem traits and grain yield of wheat were investigated at the maturity. The correlation between the lodging of wheat and the nitrogen nutrition index of the plant was also analyzed.

Results The results showed that with the increase of nitrogen application rate, the lodging rates and lodging indexes of YM49-198 and ZM16 had an increasing trend, more nitrogen rate led the lodging rates and lodging indexes of ZM16 and YM49-198 increased insignificantly when nitrogen application rates were 180 kg/hm² and 240 kg/hm², respectively, and the highest lodging rates were 23.3% and 61.8%, respectively. The plant height, stem length, ear length and the length of base internode of both cultivars also showed increasing trends. On the other hand, the nitrogen concentration and the content of basal stem nitrate-N were also increased at the returning, jointing and anthesis stages. Compared with ZM16, YM49-198 showed a higher lodging rate, lodging index and stalk parameter. After lodging, the decrease amplitude of yield and 1000 grain weight of both cultivars increased gradually as the nitrogen fertilizer rate increased, while the average decreases of 1000 grain weight were 11.3% and 6.3% for YM49-198 and ZM16, respectively. The correlation analysis indicated that lodging rates were significantly related to plant height, ear length and base internode length. Further analysis showed that the nitrogen concentrations of whole plant, stem and root, and basal stem nitrate-N of wheat at different growth stages were all significantly and positively correlated to the lodging rates.

Conclusions When nitrogen application rate was exceeded 180 kg/hm², wheat lodging resulted in more decreases of grain weight and yield. This negative effect on yield caused by lodging was far greater than the positive effect on yield increase caused by nitrogen fertilizer application. Therefore, the rate of nitrogen applied should be controlled at a proper level to ensure high and stable yield of wheat.