12 MASS. EXPERIMENT STATION BULLETIN 374 



IL THE ABSORPTION BY FOOD PLANTS OF CERTAIN 



CHEMICAL ELEMENTS IMPORTANT IN HUMAN 



PHYSIOLOGY AND NUTRITION 



By Walter S. Eisenmenger and Karol J. Kucinski 

 Department of Agronomy 



The object of this part of the investigation was to determine the extent 

 to which plants will absorb mineral elements important in human nutrition 

 from soil treated with salts of the elements. It was the hope that the 

 information obtained would aid in the production of crops richer in min- 

 erals, to the end that human and animal nutrition might be improved. 

 The three specific objects of the study were: to determine the general 

 principles underlying the question of the absorption by food plants of 

 mineral elements from the soil; to determine the extent to which plants 

 will tolerate salts of the minerals; and to determine the effects of the 

 mineral salts on the soil itself. 



The procedure was to grow vegetable plants on plots of land treated 

 with compounds containing the minerals to be investigated. Observations 

 as to the effects of the minerals on plant growth were made throughout 

 the growing season. After the plants had been harvested and dried, 

 parts of them were analyzed to determine their content of the minerals 

 studied, as well as of others, the absorption of which might have been in- 

 fluenced by the soil treatment. 



Experiment 1. — Salts of iron, copper, and manganese were supplied to plots 

 of soil in which onions, beets, swiss chard, spinach, and carrots were 

 grown. The beets, swiss chard, and spinach contained more iron than 

 the onions and carrots, but treatment of the soil with iron salts did not 

 produce a greater iron content in any of the plants than was obtained 

 when they were grown on soil without added iron. The hydrogen-ion 

 concentration of the soil is probably a more important factor in absorption 

 of iron by the plant than the amount of iron salt supplied. 



When copper salts were applied to soil, the plants contained more 

 copper than those grown on soil without copper treatment. However, 

 when copper sulfate was applied to soil in concentrations of 160 pounds 

 or more per acre, there was some toxic effect on the plants. Lime added 

 to the soil reduced this toxicity somewhat, but it is not known whether 

 the protective action was due to some chemical action of the lime with 

 the copper or to increased tolerance of the plants induced by the lime. 



Analysis of plants for manganese showed inconsistent results from 

 plants grown on manganese-treated plots and on other plots as well. There 

 was, however, some evidence to indicate that the application of manganese 

 to soil may increase the amount of phosphorus in crops. 



Experiment 2. — Soils known to be lacking in iron, and growing forage de- 

 ficient in that element, were treated with soluble organic iron compounds. 

 The average iron content of hay grown on four untreated plots was 0.0273 

 percent. Hay grown on the same plots treated with iron had an average 

 iron content of 0.0431 percent, an average increase of 57.9 percent in the 

 iron content. The available iron in the soils showed increases varying 

 from 27.4 to 378.9 percent. 



Experiment 3. — An area known to be deficient in magnesium was divided 



