Non-destructive estimation of potato leaf chlorophyll and protein contents from hyperspectral measurements using the PROSPECT radiative transfer model

Optimizing nitrogen (N) fertilization in potato (Solanum tuberosum L.) production by in-season measurements of potato N status may improve fertilizer N-use efficiency. Hyperspectral leaf reflectance and transmittance measurements can be used to assess potato N status by estimating leaf chlorophyll or N contents. This study evaluated the ability of the inverted PROSPECT radiative transfer model to predict leaf chlorophyll and N (as protein) contents. Trials were conducted with Russet Burbank and Shepody potato cultivars under different N fertility rates (0 to 300 kg N ha(-1)) in 2001 and 2002. Leaf reflectance and transmittance, leaf chlorophyll content, and leaf protein content were measured. Leaf chlorophyll and protein content correlated significantly (r = 0.16*, n = 584), but the relationship was strongly dependent on sampling date (r = 0.55* to 0.92*). Chlorophyll content was predicted with reasonable accuracy by the model, particularly in 2002. The low estimation accuracy in 2001 was probably related to sample variability induced by prolonged drought conditions. Protein content could not be predicted with any degree of accuracy by the model. The relative success of the PROSPECT model to predict chlorophyll content, and the good correlation between leaf chlorophyll and leaf N, suggests that it might be used as a component of a more complex leaf-canopy reflectance model to estimate chlorophyll content from reflectance spectra at the canopy level.