In this study, the effects of agricultural management, such as nutrient management practices and tillage, on the accumulation and consumption of some elements in the arable Andosols of Tokachi district, Hokkaido, were investigated. The researchers collected soil samples from soil profiles of Low-humic Andosols (Typic Hapludands) and Cumlic Andosols (Pachic Melanudands) and compared the vertical distribution of the total elements in uncultivated virgin soil and cultivated upland soil. The net accumulation or consumption of each element in the arable soil was calculated, while the bulk densities and the differences in the thickness of the layers between the cultivated and adjacent virgin soil were also accounted for. In the virgin soil, the amount of each element on the basis of soil mass was attributed to soil formation processes and parent materials in the virgin soil, while cultivated soil was strongly affected by physical disturbances in the plow layer and elemental inputs from fertilizers. The vertical distribution of each element indicated that the amounts of C, N, P, Ca, and Cd were large in surface soil, while the amounts of K, Mg, and Zn were large in subsoils. The net consumption of C and N in the cultivated Andosols was observed; remarkably, the consumption of C in the plow layer of the Cumulic Andosols was 124 Mg ha⁻¹. The net accumulation of P and Cd in the plow layer of cultivated soil was 3.5–4.6 Mg ha⁻¹ and 350–569 g ha⁻¹, respectively, which was remarkably large; this suggests that most of the Cd may have accumulated through heavy phosphate fertilization. The accumulation and/or consumption of K, Mg, and Ca were also observed in the cultivated Andosols, which implies that appropriate plant nutrient management is critical to avoid the exhaustion of these elements that are essential for plants.

In order to compare two types of the magnesium fertilizer (lightly-burned magnesium: including 650–800 g kg⁻¹ of citric acid soluble MgO, sarpomag: including 185 g kg⁻¹ of water soluble MgO), a laboratory elution experiment and several field experiments of spring wheat, soybean, sugar beet and potato, were conducted.

The laboratory elution experiment showed that the magnesium from sarpomag was quickly eluted in water while the magnesium in lightly-burned magnesium was never eluted in water, but slightly soluble in nitrate solution. And the elution of lightly-burned magnesium was in proportion with the concentration of nitrate solution. As seen above, the dissolubility of lightly-burned magnesium was considerably less than that of sarpomag.

Comparison of the two magnesium fertilizers by the field experiments, applied to spring wheat, soybean, sugar beet and potato, showed that there was no significant difference between the two magnesium fertilizers in crop yields, crop quality, MgO concentration of the plant body, MgO uptake, at the harvest time. Moreover, in the case of spring wheat and sugar beet, there was no significant difference between the lightly-burned magnesium plot and the sarpomag plot, in the midway of the growing.

However, in some cases of the midways of the growing of soybean and potato, MgO concentration of the leaf and MgO uptake in the lightly-burned magnesium plot were significantly lower than those in the sarpomag plot, especially the tendency was more explicit in soybean.

Even so, both of lightly-burned magnesium and sarpomag could be thought as having no problem when being used as the ordinary magnesium fertilizer, because no magnesium deficiency was observed in any experimental plots of all the studied crops, and because the fertilization effects of the two magnesium fertilizers on soybean and potato in the harvest time were observed as no difference.

On the other hand, the fact that exchangeable MgO of the soil after harvesting was significantly higher in the sarpomag plots than those in the lightly-burned magnesium plots, should be noticed carefully.