Effect of Soil pH on the Availability of Magnesium to Corn (Zea mays L.) from Magnesium Sulfate and High Magnesium Liming Materials

Abstract

AbstractThe effect of soil pH on the availability of Mg to corn from magnesium sulfate and several high Mg liming materials was studied in the greenhouse using a Keyport fine sandy loam soil. The soil pH was adjusted from 4.4 to 5.3, 5.7, 6.2, and 6.7 with CaCO2 containing less than 0.005% Mg. Magnesium was applied at rates of 0, 7.5, 15, 30, and 60 ppm of Mg as magnesium sulfate (9.9% Mg), coarse dolomitic limestone (12.0% Mg, 24% through a 100‐mesh sieve), fine dolomitic limestone (12.4% Mg, 80% through a 100‐mesh sieve), hydrated lime (18.7% Mg), and burnt lime (21.0% Mg). Corn (Zea mays L.) was grown for 30 days after emergence and the dry matter yields were determined. The plant tissue was analyzed for Mg.With the exception of coarse dolomitic limestone the application of 7.5 to 15 ppm of Mg to the soil significantly (5% level) increased the dry matter yield of the corn, regardless of the Mg source of soil pH level. Higher Mg rates caused no further significant yield increase. In most cases, fine dolomitic limestone, hydrated lime, and burnt lime were as effective as magnesium sulfate for increasing corn yields, while coarse dolomitic lime‐stone was often inferior to the other sources studied.An increase in soil pH from 5.3 to 6.7 significantly decreased the uptake of Mg by corn from soil treated with coarse and fine dolomitic limestone but in most cases had no significant effect on Mg uptake from magnesium sulfate. Total Mg uptake from fine dolomitic limestone was significantly greater than from coarse dolomitic limestone applied at rates of 15, 30, and 60 ppm of Mg to soil of pH 5.3 to 6.7, but was usually significantly lower than Mg uptake from magnesium sulfate, hydrated lime, or burnt lime. Very little difference in total Mg uptake existed between magnesium sulfate and hydrated or burnt lime.