( ( The ( main difference ) ) ( ( is ( that ( soil ( is ( ( the ( main component ) ) ( not water ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ main) (NN difference)) (VP (VBZ is) (SBAR (IN that) (S (NP (NN soil)) (VP (VBZ is) (NP (NP (DT the) (JJ main) (NN component)) (PP (RB not) (NP (NN water)))))))) (. .)))
The main difference is that soil is the main component not water.
(ROOT (S (NP (NNP Water)) (VP (VBZ is) (NP (NP (DT the) (JJ main) (NN component)) (PP (IN of) (NP (NN milk))))) (. .)))