The Effect of Manganese on the Growth of Wheat:A Source of Manganese for Agricultural Purposes
Journal of Industrial & Engineering Chemistry
solutions. Under especially favorable conditions as regards concentration and temperature, syngenite has been observed after 3 hrs.' agitation in solution from flue dust. Continuous leaching operations have, however, been carried on with practically saturated potash solutions. where the time of contact averaged one hour, with no sign whatever, either visual or analytical, of the formation of any of t h e double salts ref erred to. From the above i t will be seen t h a t during the leaching of
... g the leaching of cement mill flue dust for the recovery of potash, the operations may be so adjusted as regards time of contact and solution concentration t h a t the formation of double salts can be avoided a t whatever temperature is chosen as being the most desirable for the leaching operation CHEMICAL LABORATORY The object of the experiments in this paper was t o demonstrate the effect of manganese on the growth of wheat under different conditions and t o point out a source of this element for agricultural purposes. I n a study of t h e work of previous investigators on the relation of manganese t o agriculture and its probable function in the vegetable economy one is impressed with the lack of agreement in the results of the several investigators and, especially, with the variety of their conclusions. I n seeking a plausible explanation of the wide variations in the conclusions reached by the many investigators on this subject one must give attention t o the object t o be attained and t o the various conditions under which the different investigations were carried on. I n regard t o the object t o be attained, one class of investigators apparently have been interested in determining whether or not manganese has any commercial value from the standpoint of a necessary fertilizer, whereas the other class have sought t o determine whether or not manganese is a n essential element in t h e vegetable economy and, if so, its functions. Since the end t o be attained b y each of these different classes of investigators was not one and the same thing it is only natural t h a t considerable contention has arisen as t o whether or not manganese plays a definite rdle in agriculture. For example, an investigator having the commercial viewpoint in mjnd may add a manganese compound t o a soil already containing enough of this element and when he observes no effect on t h e growth of the crop he arrives a t the conclusion t h a t manganese has no important function in t h e growth of crops, t h u s failing t o take into consideration the amount of this element already contained in the normal soil. T h e most productive soils of Kentucky contain as 1 Read before the Division of Agricultural and Food Chemistry, Cleve-Land Meeting, American Chemical Society, September 12, 1918. much as 0.40 per cent of manganese,l whereas some of the least productive soils contain as little as 0.005 per cent.2 I n all probability the latter soils would respond t o an application of this element, whereas preliminary experiments show t h a t the former do not. It is, therefore, evident t h a t the failure on t h e part of those having the commercial viewpoint t o recognize the importance of manganese from an agricultural standpoint is due t o the fact t h a t no consideration has been given t o the amount of this element already contained in normal soils. Apart from the work of Bertrand, very little has been done t o prove whether or not manganese is a n essential element in the vegetable economy. After extended researches on t h e effect and function of manganese in t h e vegetable economy, this investigator arrives a t the interesting conclusion3 that manganese Is, apparently, not t o be replaced by another element, not even by iron, and the small quantity of it occurring is no reason for regarding it as a secondary element in the composition of plants. As a result of his investigations on laccase, an enzyme occurring in plants, t h e activity of which seems t o be in some way associated with manganese, Bertrand concludes t h a t this element can no longer be considered as a non-essential, but t h a t it is a substance of vital necessity t o the functions of plant life. I n a more recent investigation he insists on the r8le of manganese in the functioning of t h e oxidizing enzymes, and still later investigations led him t o t h e conclusion t h a t manganese intervenes as a catalytic agent, in the material changes of which plants are the seat, and t h a t i t participates in a n indirect manner in the building up of t h e tissues and in t h e production of organic matter. An earlier investigation b y the writer,4 on the manganese content of various seeds, revealed t h e unsuspected and interesting fact t h a t the manganese was not uniformly distributed in the different parts of the seed b u t was confined almost entirely to the thin, brown seed-coat which envelops the cotyledons and forms the inside lining of the outer epidermal layer or hull of certain seeds and nuts. For example, in case of t h e almond we find the greater part of t h e manganese, not in the hard outside shell nor in t h e cotyledons, but in t h e brown seed-coat that surrounds the cotyledons. Again, in the case of the seed of wheat, we find only traces of manganese in either the chaff or t h e flour, and relatively large concentrations in t h e bran. The observation t h a t the greater part of t h e manganese contained in seeds is confined t o t h e seed-coat affords food for thought in regard t o t h e function of this element in plants and whether or not it is essential in t h e growth and normal development of their seeds. EXPERIMENTAL The following experiments suggested themselves as a possible means of throwing further light on the question whether or not manganese is an essential element in t h e 1 McHargue, unpublished results.