施氮时期对高产夏玉米光合特性的影响

Effects of nitrogen application stages on photosynthetic characteristics of summer maize in high yield conditions

选用登海661(DH661)和郑单958(ZD958)为试验材料,研究了高产条件下施氮时期对高产夏玉米光合特性、产量和氮素利用率的影响。结果表明,分次施氮尤其是增加花后施氮较拔节期一次性施氮可提高产量9.3%—18.2%,氮肥偏生产力提高10.9%—17.5%。拔节期、大喇叭口期、花后10 d按2∶4∶4施氮,DH661产量可达14188.9 kg/hm2;基肥、拔节期、大口期、花后10d按1∶2∶5∶2施氮,ZD958产量可达14529.6 kg/hm2。分次施氮较一次性施氮可延长灌浆期LAI高值持续期。花后施氮20%—40%较一次性施氮穗位叶Pn、ΦPSⅡ、NPQ和ETR分别提高了10.8%—24.1%,16.6%—25.1%、29.2%—45.3%和14.4%—25.8%,并保持了灌浆期RuBPCase和PEPCase较高活性,延缓了叶片衰老,提高了光能利用率。DH661较ZD958在相同的施氮方式下花后具有更高的光合性能。分次施氮及花后施氮可显著改善两个高产夏玉米品种光合特性,提高氮素利用率,提高产量。

Recently,the study of issues related to maize production such as excessive nitrogen application and ineffective application strategies have become common in the pursuit of high yield.Since high nitrogen application rates used to produce high yields wastes resources and causes pollution,nitrogen application for summer maize should be managed scientifically.We studied the effects of timing and rates of nitrogen application on the photosynthetic characteristics,grain yield and nitrogen use efficiency under super-high yield conditions using the maize cultivars Denghai661（DH661） and Zhengdan958（ZD958）.The results show the yield and nitrogen partial factor productivity of these two cultivars increased 9.3%—18.2% and 10.9%—17.5%,respectively,with an incrementally delayed timing of nitrogen application and especially when nitrogen was applied after anthesis.The yield of DH661 was 14188.9 kg/hm2,when the nitrogen fertilizers were applied with a ratio of 2 ∶4 ∶4 at the jointing,male tetrad and grain filling stages,respectively.The yield of ZD958 was 14529.6 kg/hm2,when nitrogen fertilizers were applied with a ratio of 1 ∶2 ∶5 ∶2 as the base fertilizer and at the jointing,male tetrad and grain filling stages,respectively.At times applied nitrogen could increase the total nitrogen accumulation（TNA）,nitrogen accumulation of grain（NAG）,nitrogen harvest index（NHI） and nitrogen partial factor productivity（NPFP） significantly.NAG of DH661 and ZD958 were higher than NAG levels found with other methods of supplying nitrogen when nitrogen was applied using methods the ratios of 2 ∶4 ∶4 and 3 ∶5 ∶2,as described above.NPFP increased 13.0% and 15.8% with nitrogen applied after anthesis compared to a single nitrogen application at the jointing stage for DH661 and ZD958,respectively.The functional duration of the leaf area index was prolonged with the incremental increase of nitrogen application times.After anthesis plants could retain a large photosynthetic area with this nitrogen application method.Net photosynthetic rate（Pn）,actual quantum yield of PSⅡ electron transport（ΦPSⅡ）,non-photochemical quenching（NPQ） and electron transport rate（ETR） of ear leaves increased by 10.8%—24.1%,16.6%—25.1%,29.2%—45.3% and 14.4%—25.8%,respectively,with 20%—40% of the nitrogen applied after anthesis compared to a single nitrogen application.This treatment could also keep the activities of RuBPCase and PEPCase at a high level for a longer period of time.The activities of RuBPCase and PEPCase increased by 5.8%—12.8% and 6.9%—17.8%,respectively,when 20%—40% of the nitrogen was applied after anthesis compared to a single nitrogen application at the jointing stage.Applying nitrogen after anthesis increased the solar energy utilization rate as well as protected the leaves and could prolong the functional duration of photosynthesis compared with a single nitrogen application at the jointing stage.Pn of DH661 compared to Pn of ZD958 increased 22.7% and 17.4% at 40 and 54 days after anthesis,respectively.ΦPSⅡ of DH661 compared to ΦPSⅡ of ZD958 increased by 11.3% at 40 days after anthesis.So DH661 had higher photosynthetic ability than ZD958 under the same nitrogen application method after anthesis.In conclusion,careful timing of nitrogen application and applying nitrogen after anthesis could improve the photosynthetic characteristics,increase nitrogen use efficiency and grain yield of summer maize.Under experimental field conditions,as far as grain yield and nitrogen use efficiency are concerned,the jointing stage（20%）,male tetrad stage（40%） and grain filling stage（40%） for DH661 and base fertilizer（10%）,jointing stage（20%）,male tetrad stage（50%） and grain filling stage（20%） for ZD958 are the optimal nitrogen application stages and ratios.