Fresh Leaf Spectroscopy to Estimate the Crop Nutrient Status of Potato (Solanum tuberosum L.)

Estimating leaf nutrient concentration in field crops is essential to increase crop yield by optimum fertiliser application. Notably, these practices become more critical for short-cycle crops like potatoes (Solanum tuberosum L.), where conventionally, laborious in-field plant sampling and laboratory analysis take a long time. Multiple samples are frequently required to reach the field’s representation and reliability. The alternative technique of optical spectroscopy, which reports the canopy reflectance to the specific band of the electromagnetic spectrum, can be used to estimate the plant nutrient concentration. Previous studies have made such efforts using the electromagnetic spectrum’s visible to near-infrared (VNIR, 400–1100 nm) and short-wave infrared (SWIR, 1100–2400 nm) ranges. In this study, we are testing the ability of the spectroscopy with a full-range spectroradiometer (400–2400 nm) along with a comparison of VNIR and SWIR to estimate the total Kjeldahl nitrogen (TKN), phosphorus (P), potassium (K), and sulphur (S) nutrient concentration in freshly picked petiole/leaf samples of potato plants. Results show that the full-range spectrum predicted TKN with an accuracy of R² = 0.91 external validation (0.74 internal validation), followed by K, R² = 0.87 (0.69), P, R² = 0.86 (0.82), and S with R² = 0.75 (0.68). It was also reported that the maximum difference in the estimation accuracy among VNIR and SWIR was reported for K, where VNIR had R² = 0.48 (0.54) and SWIR had R² = 0.86 (0.80). This study lays a foundation for further development of models that can estimate the canopy nutrient concentration in the field with spectral reflectance and scale up these models with hyperspectral imaging.