THE ROLE OF MANGANESE IN AGRICULTURE

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Abstract
The theory that only 10 of the chemical elements are essential in the economy of plants and animals has been shown to be erroneous. Mn is an essential element in the economy of soils, plants, and animals. Some areas of soil are deficient in Mn and therefore produce crops inferior in quantity as well as in food quality. Mn may be made unavailable in some soils by the application of an excess of basic materials, including CaCO3, in the form of ground limestone, marl, hydrated lime, or burned lime. When some soils are made alkaline with a basic material. the active compounds of Mn are rendered so inactive or unavailable that growth of the crop is retarded, yields are diminished, and the quality of the harvested product is inferior. The condition on oats known as "grey speck" is due to Mn deficiency or unavailability in the soil. When different spp. of plants are grown on the same type of soil they show a considerable range in Mn content. The leguminous plants usually contain the least amt. of Mn. and the grasses the greatest amt. When soybean plants were grown for 18 days in water culture expts. controlled near pH 4.8, it was indicated that high concs. of soluble Mn in the plant tissues were associated with low concs. of soluble Fe and vice versa. Other minor elements, including Cu, Ni, and Co have similar effects on the conc. of Fe in the tissues of plants. Mn is an essential element in the metabolism of small animals, including mice, rats, and poultry. The Mn content of cow''s milk can be doubled by adding about 50 gm. of MnSO4 to the daily ration of the cows. Since the Mn content of normal cows'' milk is usually rather low, the question may be asked: Is the increased Mn content of the cows'' milk due to feeding in-organic MnSO4 as effective as it would be if the cow had increased the Mn content of her milk from eating luxuriant pasture grass, hay, or some normal palatable plant material containing a relatively large amt. of Mn? Is it possible to double the Mn content of milk from feeding cows on pasture, hay, and grain rich in Mn? There is increasing evidence that Mn is associated with the vital organs in which enzymes, hormones, and vitamins are produced and secreted. It is suggested that Mn in some way acts as a catalyst in the production and secretion of these highly essential products.