Abstract:

To improve the accuracy and reliability of nitrogen nutrition diagnosis in cotton, it is necessary to clarify the determination position of canopy structure characteristics that best reflect the nitrogen nutrition status of plants and the level of nitrogen fertilizer application. The field plot test method was adopted, under the condition of a certain base fertilizer, four levels of nitrogen fertilizer topdressing were set. The canopy structure characteristic values at the middle position of the wide line, middle position of the narrow line, adjacent to plant, and intermediate position of the adjacent two membranes of cotton were determined at each growth stage of cotton. The response relationship between the cotton canopy structure characteristics at different measurement positions and the nitrogen accumulation of cotton plants and the amount of nitrogen fertilizer applied were studied. The results showed that the correlation between the cotton mean leaf angle measured and the accumulation of nitrogen in the aboveground part reached an extremely significant level, with the highest correlation coefficient at the intermediate position of the adjacent two membranes in different years. Meanwhile, there was a significant positive correlation between the cotton leaf area index measured at this position and the amount of nitrogen fertilizer applied, with the highest correlation coefficient. It can be initially determined that the intermediate position of the adjacent two membranes is the optimal location for measuring the cotton canopy structure characteristics to determine the cotton nitrogen nutrition level and the level of nitrogen fertilizer application.

Key words: cotton, canopy structure characteristics, nitrogen accumulation, nitrogen application rate, correlation