播期播量及施氮量对冬小麦生长及光谱指标的影响

Effects of sowing dates,sowing rates,and nitrogen rates on growth and spectral indices in winter wheat

为阐明播期、播量及施氮量对冬小麦生长与光谱指标的影响规律,本研究通过开展连续两年不同播期、播量及施氮量的冬小麦田间试验,系统地研究了三因素及其互作对冬小麦产量、关键生育时期叶面积指数(leaf area index,LAI)和归一化红边指数(normalized difference red edge,NDRE)的影响,并进一步分析了三因素对冬小麦冠层NDRE时序曲线的影响。另一方面建立了不同产量水平下冬小麦冠层NDRE适宜时序曲线,以便于实时监测不同产量水平下冬小麦长势动态。结果表明,冬小麦冠层NDRE与LAI随关键生育期的变化相似,且三因素对关键生育时期2个指标的影响规律基本一致。2018—2019年冬小麦产量、不同生育时期LAI和冠层NDRE均随播期推迟而下降;2019—2020年除灌浆期外,晚播冬小麦产量、LAI及冠层NDRE峰值最大。2年冬小麦不同生育时期LAI、冠层NDRE随施氮量增加而增加;而不同播量间无明显差异。三因素中播期、施氮量对冬小麦冠层NDRE时序曲线有显著影响。冬小麦冠层NDRE时序曲线随施氮量增加被纵向拉长;曲线下降部分随播期推迟向左平移,同时2018—2019年随播期推迟曲线峰值下降,2019—2020年晚播、过晚播冬小麦曲线峰值高于适播期冬小麦。将2个年份数据融合在一起建立了3个产量水平下冬小麦冠层NDRE适宜时序曲线(产量水平分别为:小于6.75、6.75~8.25、大于8.25 t hm^(-2));发现随产量水平升高,NDRE时序曲线峰值及幅宽均增大。综上所述,冬小麦应适期早播,但若冬前积温较高,应适当推迟播期;且可通过增加一定播量和施氮量来改善晚播冬小麦群体长势。研究结果可为不同播期及不同产量水平下冬小麦长势监测提供技术支撑。

To clarify the effects of sowing dates,sowing rates,and nitrogen rates on growth and spectral indices in winter wheat,a two-year winter wheat field experiment under different sowing dates,sowing rates,and nitrogen rates was conducted.We studied systematically the effects of three factors and their interactions on yield,leaf area index(LAI),and normalized difference red edge(NDRE)of winter wheat at critical growth stages.Furthermore,to facilitate real-time monitoring of winter wheat growth dynamics,we also established the appropriate time-series curves of winter wheat canopy NDRE under different yield levels.The results indicated that the change patterns of NDRE and LAI at critical growth stages were very consistent,and the response of three factors to the two indices at critical growth stages was basically the same in winter wheat.In 2018 and 2019,the yield,LAI,and NDRE of winter wheat at each growth stages decreased with the delay of sowing date.In 2019 and 2020,the yield,peaks of LAI and NDRE under late sowing date were the largest except for the filling stage.The LAI and NDRE of winter wheat at different growth stages in the two years increased with the increase of nitrogen rates.However,there was basically no significant difference among sowing rates.Among the three factors,the sowing dates and nitrogen rates had a significant influence on the time-series curves of winter wheat canopy NDRE.The NDRE time series curves of winter wheat were stretched with the increase of nitrogen rates,the descending part of NDRE time series curve shifted to the left with the delay of the sowing date.In 2018 and 2019,the peak values of NDRE time series curves of winter wheat were declined with the delay of the sowing date.In 2019 and 2020,the peak values of the NDRE time series curves of late sowing and over-late sowing winter wheat were higher than that of suitable sowing wheat.The data of two years were merged to establish suitable time-series curves of winter wheat canopy NDRE under three yield levels,and the yield levels were less than 6.75 t hm^(-2),6.75-8.25 t hm^(-2),and higher than 8.25 t hm^(-2),respectively.The peak values and width of the NDRE time-series curves increased with the increase of yield level.In summary,winter wheat should be sown early at an appropriate date,but if the accumulated temperature before winter was higher,the sowing date should be postponed appropriately.And the growth of late sowing winter wheat could be improved by increasing a certain amount of sowing rates and nitrogen rates.At the same time,these results could provide a technical support for monitoring the growth of winter wheat under different sowing dates and different yield levels.