Table 1. Categories of NDEI (normalized difference soil enzyme index) calculated from phosphatase activity (PA) and dehydrogenase activity (DHA)

Range	Feature	Example (PA : DHA)
NDEI = 1	No dehydrogenase activity	100 : 0
0.75 ≤ NDEI < 1	Much higher phosphatase activity	100 : 0~31
0.5 ≤ NDEI < 0.75	Higher phosphatase activity	100 : 31~72
0.25 ≤ NDEI < 0.5	A little higher phosphatase activity	100 : 72~130
0 ≤ NDEI < 0.25	A little higher dehydrogenase activity	100 : 130~215
−0.5 ≤ NDEI < 0	Higher dehydrogenase activity	100 : 215~650
NDEI < −0.5	Much higher dehydrogenase activity	100 : more than 650