Update magic.R
Update magic.R

Code changed in lines 296-301 to change the fraction biomass cover calculation. Calculation changed to use equation from Gregory 1982 paper, which requires residue mass in units of lbs/acre. Line 298 changed to make conversion from units of t/acre to lbs/acre. Line 299 changed to reflect coefficient from Gregory paper for corn.
akrherz/dep,akrherz/dep,akrherz/dep,akrherz/dep,akrherz/dep