AbstractThis paper reports the procedures followed for the chemical determinations of exchangeable calcium, magnesium, and manganese; and available phosphorus and iron in soils; and for the total amount in plants of each of those minerals mentioned. Spectrophotometric methods are given for magnesium and manganese in soils and plants; and for phosphorus and iron in plants including the transmittance-concentration and spectral-transmittance curves for each of these elements. Photocolorimetric methods are also given for available iron and phosphorus in soils with their corresponding curves. This paper reports also changes of the minerals calcium, magnesium, manganese, phosphorus and iron in an acid soil, 15 and 23 months after liming. It also reports changes of these minerals in each of five crops of a mixture of Para grass Panicum purpurascens, and Carib grass Eriochloa polystachya, grown in the unlimed and limed soil. The yield of green grass is also reported for each crop.
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