Effects of Nitrogen Application Rate and Leaf Age on the Distribution Pattern of Leaf SPAD Readings in the Rice Canopy

Abstract

A Soil-Plant Analysis Development (SPAD) chlorophyll meter can be used as a simple tool for evaluating N concentration of the leaf and investigating the combined effects of nitrogen rate and leaf age on N distribution. We conducted experiments in a paddy field over two consecutive years (2008–2009) using rice plants treated with six different N application levels. N distribution pattern was determined by SPAD readings based on the temporal dynamics of N concentrations in individual leaves. At 62 days after transplantation (DAT) in 2008 and DAT 60 in 2009, leaf SPAD readings increased from the upper to lower in the rice canopy that received N levels of 150 to 375 kg ha−1The differences in SPAD readings between the upper and lower leaf were larger under higher N application rates. However, as plants grew, this atypical distribution of SPAD readings in canopy leaf quickly reversed to the general order. In addition, temporal dynamics of the leaf SPAD readings (N concentrations) were fitted to a piecewise function. In our model, changes in leaf SPAD readings were divided into three stages: growth, functioning, and senescence periods. The leaf growth period lasted approximately 6 days, and cumulative growing days were not affected by N application rates. The leaf functioning period was represented with a relatively stable SPAD reading related to N application rate, and cumulative growing days were extended with increasing N application rates. A quadratic equation was utilized to describe the relationship between SPAD readings and leaf age during the leaf senescence period. The rate of decrease in SPAD readings increased with the age of leaves, but the rate was slowed by N application. As leaves in the lower canopy were physiologically older than leaves in the upper canopy, the rate of decrease in SPAD readings was faster in the lower leaves.

Development of non-destructive methods to estimate functional traits and field evaluation in tea plantations using a smartphone

“…Similarly, the regression analysis of the SPAD readings and N demonstrated a significant linear relationships R² = 0.7103; y = 0.1868x -7.8051 (Fig.-4b). Similar results were arrived by Yang et al (2014), Ramesh et al (2002) and Swain & Sandip (2010) who established the linear relationships between leaf N content and SPAD readings and highly significant correlations of SPAD readings with the yield in various crops.…”

Evaluating Hyperspectral Vegetation Indices for Leaf Area Index Estimation of Oryza sativa L. at Diverse Phenological Stages

“…During rice canopy development, a photosynthetic photon flux density (PPFD) gradient can provide accurate description of the physiological relationship between nitrogen content and leaf area distribution vertically in canopy (Yang et al, 2014). But the construction of PPFD is time-costing and difficult to measure parameters.…”

Effects of different methods to control the parasitic weed Phelipanche ramosa (L.) Pomel in processing tomato crops

“…Throughout the tomato crop cycle, P. ramosa infestation was assessed according to the number of emerged shoots (branched plants) in each pot at 70, 75, 81 and 88 DAT. Moreover, considering that part of the water and mineral nutrients move from the host to the parasite, a chlorophyll meter [soil-plant-analysis-development (SPAD); Minolta Camera Co. Ltd., Osaka, Japan] was used to estimate the nutritional status of the tomato plants (Yang et al, 2014). The SPAD values were read at the centre of each leaflet of the third fully expanded leaf blade of the tomato plants, at 53 DAT and 76 DAT, for all of the treatments that were compared.…”