MSAVI for Corn
(shown to be better index than NDVI, SAVI, TSAVI, or PVI for corn LAI detection)
MSAVI2 (Equation 19 from Qi et al., 1994)
Atmospherically corrected Landsat imagery can be applied to map MSAVI. Wu et al. (2007; pdf) studied MSAVI, NDVI, SAVI, TSAVI, and PVI and determined (based on Quickbird imagery which has much finer resolution than Landsat) that MSAVI was the superior index to detect leaf area index (LAI) for corn and potatoes. NDVI showed the lowest correlation to LAI for both crops. Additionally, Wu et al. (2007) found "the parameters in the MSAVI–LAI relationships were relatively consistent for both crops, suggesting it (MSAVI) might be advantageous for other crops". A plot from Wu et al. (2007) is shown below.
Reference
Qi, J., Chehbouni, A., Huete, A. R., Kerr, Y.H., and S. Sorooshian. 1994. A Modified Soil Adjusted Vegetation Index. Remote Sensing of Environment 48: 119-126.
Wu, J., Wang, D, and M.E. Bauer. 2007. Assessing broadband vegetation indices and QuickBird data in estimating leaf area index of corn and potato canopies. Field Crops Research 102: pp. 33–42.