THE EFFECT OF POTASSIUM, NITROGEN AND PHOSPHORUS FERTILIZING UPON THE CHLOROPLAST PIGMENTS, UPON THE MINERAL CONTENT OF THE LEAVES, AND UPON PRODUCTION IN CROP PLANTS

Urban (13) found evidence of a correlation between the color of the leaves of beets and the nitrogen content, the darker leaves containing the most nitrogen and the lighter the least. Also, he apparently found a relation between the highest potassium content of the leaves and the greatest sugar content of the roots. In beets the dark colored leaves contained more potassium and less sodium than did the light colored leaves. In the leaves of ripening beets the potassium rapidly increases while the sodium decreases. A great difference in the chlorophyll content of alpine and of lowland plants was observed by Henrici (2). She represented the amount of chlorophyll present in alpine plants as 100 per cent, and found that lowland plants contained 230 per cent, and ravine plants 350 per cent. She makes no reference to the soil in which these grew but it is highly probable that the soil was a very important factor in the amount of chlorophyll which was found in the plants studied. Perhaps the first real experiments on the effect of chemical fertilizers upon chlorophyll were conducted by Wlodek (16) in 1920. Green leaves of potato plants and sugar beets were studied. These were grown in soils to which various fertilizers were added: (1) without fertilizer; (2) with phosphorus, potash and nitrogen; (3) with phosphorus and nitrogen but no potash; (4) with phosphorus, nitrogen and magnesium but no potash; (5) with potash and nitrogen but no phosphorus; and (6) with potash and phosphorus but no nitrogen. After a certain period of development of the