Saturated Paste vs. Mehlich 3
146 soil samples were evaluated using both tests. We see a good correlation between saturated paste and Mehlich 3 tests only for dissolved salts (such as sodium) and cations that are weakly held on the soil exchange sites (top graph). However, for most nutrients, including calcium (bottom graph), the saturated paste test produces values that are much lower than they actually are. Read more here.
