Groundnut spectral indices and characterization in relation to crop nutrient status

Abstract

The spectral indices such as NDVI and RVI were calculated by using spectral signatures obtained through spectro-photo-sensor. The mean NDVI and RVI values were 0.71 and 6.46, respectively. Wide variation in the NDVI and RVI values were observed across the farmers’ fields revealing that crop was exposed to varied levels of nutrient deficiency. The SPAD (Indicator of chlorophyll activity) readings ranged between 25.8 and 46.8. The SPAD and the index leaf N, P, K, Ca and Fe content had positive and strong relation with both NDVI and RVI. However, NDVI registered stronger relation than RVI. Co-efficient of determination (R2) value of the multiple regressions between NDVI and index leaf nutrient content was 0.52. The mean N, P, K, Ca and S content in the index leaf were 3.9, 0.43, 3.45, 1.77 and 0.43 per cent, respectively. Similarly, Zn, Fe, Mn and Cu content in the crop index leaf tissue were 21.9, 40.6, 53.2 and 19.3 mg kg-1.