... (M3-K, M3-Ca, M3-Mg, and M3-Na, respectively) areremoved by the action of ammonium nitrate and nitric acid. The Cu, Zn, Mn, and Fe (M3-Cu,M-Zn, M3-Mn, and M3-Fe) are extracted by NH4 and the chelating ... Ensminger, and F.E. Clark, Eds. Methods of Soils Analysis. Part 2.AgronomyNo.9.American Society of Agronomy, Madison, WI,pp. 1 179 –12 37. Burt, R. (Ed.) 2004. Soil Survey Laboratory Methods Manual. Soil ... clay and lowest with aeolian sand. The findings of Doyle and Fletcher (1 977 ) pointed to the potentialusefulness of information on the Se content of soil parent materials when designing sampling programs...