Yield Estimation and Quality Evaluation of Sweet Potato Using Spectral Reflectance

1. Yield Estimation and Quality Evaluation of Sweet Potato Using Spectral Reflectance SATO Muneharu, ISHIGURO Etsuji, ISHIKAWA Daitaro, and SEKIOKA Shin-ichi Faculty of Agriculture, Kagoshima University, Japan Question: Can we estimate yield & quality of sweet potato before harvest remotely? Answer: Yes. Observe spectral reflectance signatures and use our model! The total leaf areas, the numbers of leaves, the nitrogen contents of leaves, and the root yields of sweet potato plants were observed periodically throughout their cultivation period. And before digging up them, the spectral properties of their canopies were measured with a handheld spectroradiometer. Then the relationships among these traits were analyzed. Some of the NDVI models we had tried showed the close relation with total leaf area, the amount of yield, and the nitrogen content of leaves as well. This result opens up the way for the practical use of the spectral reflectance data in crop production. Fig.1 Changes of the number of leaves of sweet potato. Fig.2. Relationship between the total leaf area and the number of leaves. Fig.3 Relationship between the total leaf area and the yield. NIVI Model: ND520,710 = (R520－R710) /(R520+R710) Fig.4 Changes of spectral reflectance on the leaves of sweet potato. Fig.7. Relationship between the yield and ND520,710 index Fig.8. Relationship between the total leaf area and ND520,710 index Fig.5 First differential curves on spectral reflectance. Fig.9 Relationship between the nitrogen content in leaf and ND770,660. Fig.10 Relationship between the phosphorus content in leaf and ND550,660. Fig.11 Relationship between the potassium content in leaf and ND740,660. Fig.6 Secondary differential curves on spectral reflectance.