不同产量水平稻茬小麦氮素需求特征研究

Nitrogen demand characteristics with different grain yield levels for wheat after rice

It is necessary to clarify the nitrogen (N) demand characteristics with yield levels for wheat after rice in the middle and down reaches of the Yangtze River, which could provide theoretical basis for N fertilizer management. Based-on the multi-years and multi-sites wheat experiments in Jiangsu province, this study constructed the datasets of different yield levels derived from different varieties, N rates, densities, and sowing date experiments. N indicators including N requirement per ton grain (N_req), dry matter accumulation (DMA), plant N accumulation (PNA), plant N concentration (PNC), straw N concentration (SNC), grain N concentration (GNC), harvest index (HI), N harvest index (NHI) and N nutrition index (NNI) were analyzed. The results showed that there were not significant differences in N_req among the different yield levels, and the highest N_req was middle-low yield with 27.8 kg t^-1, while the lowest value was 24.8 kg t^-1for low yield level. With the increase of yield levels, DMA, PNA and PNC all showed a gradually increasing trend during maturity stage, and there were significant differences among the different yield levels. There was a significant positive correlation between grain yield and PNA, the DMA and PNA increased with the increase of yield in the sowing-jointing stage, jointing-flowering stage and flowering-maturing stage, but the DMA and PNA proportion in different growth stages showed different trends. The SNC and GNC increased with the increase of yield levels. For SNC, there was no significant difference between the high yield and middle yield level, but it was significantly higher than the low-middle and low yield level. For GNC, there were significant differences among different yield levels except for the middle and low-middle yield level. The HI increased gradually with the increase of the yield levels, and its range was 0.39-0.49. The HI for low-middle and low yields were significantly lower than that of middle and high yield levels, while there were not significant differences in NHI among different yield levels. Its variation range was 0.60-0.96. The NNI gradually increased with the increase of the yield levels, and there was significant difference between different yield levels. The NNI of the high-yield level was higher, and some of the values were greater than 1 which indicating that some experiments had excessive nitrogen fertilizer supply. With the increase of the yield level, the N_req increased first and then decreased, while the DMA, PNA, PNC, SNC, and GNC were gradual increased. The increase of SNC was higher than the GNC, therefore, the extravagant absorption of N by wheat should be avoided in field management. The variation ranges of the HI and NHI were consistent with previous studies. The higher DMA and PNA in the late growth stages were the main reasons for the high yield of wheat. The NNI could be a promising indictor in the field N management of wheat.