Effect of Carbon Dioxide on Availability of Manganese in Soil Producing Manganese Deficiency

Abstract

A SERIES of experiments, extending over several years, in which potato plants were grown both in pots and in the field, in soil producing manganese deficiency, from the recently drained lake-bed at East Mailing Research Station, has led us to suspect the presence of some hitherto unexplained factor influencing manganese availability. The soil in question is an alluvial deposit containing a large amount of calcium carbonate and organic matter and has a pH of 8·0–8·5. The soil contains ample manganese, as simple extractions in Morgan‘s solution yield considerably more than 50 p.p.m. of manganese on a dry soil basis. This, however, is only a small fraction of the total, as is shown by extractions with strong acid. The amount of manganese available to the plant is, on the other hand, very small, since plants containing less than 1 p.p.m. on a fresh weight basis and showing acute deficiency symptoms are of common occurrence in certain areas of the lake-bed. Attempts to reproduce these conditions using the same soil in pot culture never succeeded in producing plants showing such marked symptoms or low manganese contents, although the soil pH was maintained between 8·0 and 8·5 by irrigating with water saturated with calcium carbonate. Water extracts of soil taken either from pots or the lake-bed itself showed negligible amounts of extractable manganese, although the plants grown in pot culture in the summer of 1948 showed no manganese deficiency, while those grown in 1947 Were much less deficient than those growing on the lake-bed.