Want more green in your portfolio? Try fertilizer: It worked for Sam Zell, as evidenced by IMC Global's Nov. 13 deal to buy rival Vigoro Corp. for $1.2 billion in stock. A decade ago, Zell bankrolled Vigoro with a $51 million loan, repaid in 1991. He sold part of his stake for $64 million two years ago and stands to make $238 million on his remaining shares. Some analysts think IMC is overpaying, but NatWest Securities' David Nelson figures that as fertilizer demand soars, IMC will get a boost from Vigoro.