Effect of nitrogen on yield related traits and nitrogen utilization efficiency in Zhongmai 175 and Jingdong 17
The objective of this study was to understand the effects of different nitrogen (N) application amounts and split ratios on high efficiency of N uptake and utilization, as well as the response to different N treatments of Zhongmai 175 and Jingdong 17 planted in Wuqiao, Hebei, and Shunyi, Beijing in 2013-2014 and 2014-2015 cropping seasons. Nitrogen fertilizer was applied in different total and split (basal + jointing stage) amounts, namely 0, 60+0, 120+0, 120+60, 120+120, and 120+180 kg ha?1. In the N range of 0-240 kg ha?1 in Wuqiao and 0-180 kg ha?1 in Shunyi, the canopy temperature depression (CTD), normalized difference vegetation index (NDVI), biomass of wheat population, and population spikelets increased with the increase of N application amount, as a result, higher yield at maturity was obtained; however, further more N application had a negative effect, showing decreased thousand-kernel weight (TKW), translocation amount (TA) and efficiency (TE) of dry matter accumulated before flowering to grain, contribution efficiency (CE), harvest index (HI), partial factor productivity from applied N (PFPN), N uptake efficiency (NUpE) and N utilization efficiency (NUtE). Zhongmai 175 had higher yield and yield stability than Jingdong 17 in different N application treatments, showing higher levels of spike number (SN), stability of kernel number per spike (KNS), kernel weight, population vitality, biomass, HI, dry matter accumulation before flowering, TA, and NUpE. These characters might be the physiological basis of high yield and high efficiency in Zhongmai 175. Considering the return from yield and economic benefits, we suggest that the recommended N application amounts for Zhongmai 175 and Jingdong 17 should be 180-240 kg ha?1 in the northern part of Huang-Huai Rivers Valley Wheat Zone and 120-180 kg ha?1 in the Northern Winter Wheat Zone. NDVI and CTD at middle to late grain filling stage can be used for rapid evaluation of varietal sensitivity to nitrogen because they are highly correlated with SN, yield, and biomass of wheat.