4.7 Article

Evaluating the role of solar-induced fluorescence (SIF) and plant physiological traits for leaf nitrogen assessment in almond using airborne hyperspectral imagery

Journal

REMOTE SENSING OF ENVIRONMENT
Volume 279, Issue -, Pages -

Publisher

ELSEVIER SCIENCE INC
DOI: 10.1016/j.rse.2022.113141

Keywords

Chlorophyll fluorescence; SIF; Nitrogen; Chlorophyll; FluSAIL RTM; Hyperspectral; Gaussian process regression; Random Forest; Almond; Tree orchard

Funding

  1. McPherson Family
  2. Inver- gowrie Foundation

Ask authors/readers for more resources

This study investigated the combination of different hyperspectrally derived proxies for leaf nitrogen (N) to assess N status in a 1200-ha almond orchard across two growing seasons. The results showed that the RTM-based chlorophyll a + b content and solar-induced fluorescence (SIF) were the most important and consistent predictors for leaf N compared to other leaf biochemical and biophysical traits. The combination of non-collinear SIF and chlorophyll a + b content significantly improved the predictions of leaf N variability.
Accurate, spatially extensive, and frequent assessments of plant nitrogen (N) enabled by remote sensing allow growers to optimize fertilizer applications and reduce environmental impacts. Standard remote sensing methods for N assessment typically involve the use of chlorophyll-sensitive vegetation indices calculated from multi -spectral or hyperspectral reflectance data. However, the chlorophyll a + b derived from spectral indices is indirectly related to leaf N and saturates at high leaf N levels, dramatically reducing the sensitivity with leaf N under these conditions. Furthermore, these relationships are heavily influenced by canopy structure, variability in leaf area density, proportion of sunlit-shaded tree-crown components, soil background, and understory. Recent studies in uniform crops have demonstrated that estimation of plant N can be improved by considering leaf biochemical constituents derived from radiative transfer model (RTM) and solar-induced fluorescence (SIF). However, it is unclear whether these methods are transferable to tree crops due to their intrinsic physiological differences, structural complexity, and within-tree crown heterogeneity. We investigated how various hyper -spectrally derived proxies for leaf N, including RTM-based traits and SIF, could be combined to assess N status on a 1200-ha almond orchard across two growing seasons. RTM-based chlorophyll a + b content (C-ab) and SIF were found to be the most important and consistent predictors for leaf N compared to other leaf biochemical and biophysical traits. C-ab alone was a modest predictor of leaf N variability (r(2) = 0.49, RMSE = 0.16%, p-value < 0.001), but when the non-collinear SIF and C-ab traits were coupled together, predictions improved dramatically (r(2) = 0.95, RMSE = 0.05%, p-value < 0.001). Leaf area index (LAI) was poorly associated with leaf N, suggesting that leaf physiological traits may be more important than structural traits in quantifying leaf N in well-managed orchards characterized by high N levels. Consistent results across the 2 years suggests the importance of airborne SIF coupled with Cab for precision agriculture and leaf N status assessment in almond orchards.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.7
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available