Soil Adjusted Vegetation Index
The soil adjusted vegetation index can suppress the effects of soil pixels in the final output. It does this by using a factor to account for the canopy background in the source data (L). This L value is a function of vegetation density. For this reason, you select the growth stage of your crop when you are applying the SAVI algorithm. You will have Early or Mid growth stage options in this, each option will change the L value in used in the equation.
Early Growth Stage- L= 0.1
Mid Growth Stage- L= 0.25
The index is best used in areas with relatively sparse vegetation where soil is visible through the canopy.
Reference: Huete, A. "A Soil-Adjusted Vegetation Index (SAVI)." Remote Sensing of Environment 25 (1988): 295-309.