Abstract:

In order to quantitatively analyze the response of main growth indexes of summer soybean canopy to nitrogen, field experiments of nitrogen application and nitrogen and potassium fertilizer management were carried out in the growing season of summer soybean by using soybean variety ‘Qihuang 34’ as the material in 2021. The response of main growth indexes of summer soybean canopy to nitrogen was clarified by the systematic analysis of the effects of different nitrogen application levels and nitrogen and potassium fertilizer management on the plant canopy nitrogen content in the key growth periods of summer soybean, and the internal relationship between the plant canopy nitrogen accumulation quantity, leaf area index, SPAD value, RVI value, NDVI value and the plant canopy nitrogen content. The results showed that nitrogen application could effectively increase the nitrogen content in the summer soybean canopy at flowering stage and early stage of grain bulging within a certain range, and the timely supply of potassium fertilizer in the early stage of grain bulging could promote the absorption of nitrogen by soybean plants. The canopy nitrogen content, canopy nitrogen accumulation, leaf area index, SPAD value, RVI value and NDVI value at early stage of grain bulging were higher than those at flowering stage. Canopy nitrogen accumulation, leaf area index and RVI value increased exponentially with canopy nitrogen content, SPAD value and NDVI value increased linearly with canopy nitrogen content at flowering stage, while SPAD value decreased linearly with canopy nitrogen content at early stage of grain bulging. Canopy growth indexes are important parameters to reflecting the growth status of summer soybean plant. To clarify the response of main growth indexes of summer soybean canopy to nitrogen is of great significance to guiding the efficient production of summer soybean and the regulation of fertilizer management.

Key words: summer soybean, canopy, growth index, nitrogen, response