Effects of nitrogen application rates on the spatio-temporal variation of leaf SPAD readings on the maize canopy

• Published in: The Journal of agricultural science Vol. 160; no. 1-2; pp. 32 - 44
• Main Authors: Li, Y. Y., Ming, B., Fan, P. P., Liu, Y., Wang, K. R., Hou, P., Li, S. K., Xie, R. Z.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.02.2022
• Subjects: Chlorophyll; Corn; Crop production; Crops and Soils Research Paper; Cultivars; Fertilization; Leaves; Monitoring; Nitrogen; Nutrient dynamics; Nutrient status; Nutritional status; Plants; Soil analysis; Temporal variations; China; nitrogen fertilizer; vertical distribution; Duration; leaf SPAD reading model; maize
• ISSN: 0021-8596; 1469-5146
• DOI: 10.1017/S0021859621001052

The spatio-temporal variation of leaf chlorophyll content is an important crop phenotypic trait that is of great significance for evaluating crop productivity. This study used a soil-plant analysis development (SPAD) chlorophyll meter for non-destructive monitoring of leaf chlorophyll dynamics to characterize the patterns of spatio-temporal variation in the nutritional status of maize (Zea mays L.) leaves under three nitrogen treatments in two cultivars. The results showed that nitrogen levels could affect the maximum leaf SPAD reading (SPADmax) and the duration of high SPAD reading. A rational model was used to measure the changes in SPAD readings over time in single leaves. This model was suitable for predicting the dynamics of the nutrient status for each leaf position under different nitrogen treatments, and model parameter values were position dependent. SPADmax at each leaf decreased with the reduction of nitrogen supply. Leaves at different positions in both cultivars responded differently to higher nitrogen rates. Lower leaves (8th–10th positions) were more sensitive than the other leaves in response to nitrogen. Monitoring the SPAD reading dynamic of lower leaves could accurately characterize and assess the nitrogen supply in plants. The lower leaves in nitrogen-deficient plants had a shorter duration of high SPAD readings compared to nitrogen-sufficient plants; this physiological mechanism should be studied further. In summary, the spatio-temporal variation of plant nitrogen status in maize was analysed to determine critical leaf positions for potentially assisting in the identification of appropriate agronomic management practices, such as the adjustment of nitrogen rates in late fertilization.