alkali (sodium carbonate) is commonly known as salsoda, or washing soda. It is corrosive in its action on plants, and the presence of one-tenth of one per cent, will practically prevent the cultivation of all crops, and this salt is therefore greatly dreaded by farmers. White alkali includes a group of salts, as common salt (sodium chloride), Glauber’s salt (sodium sulphate) and baking soda (sodium bicarbonate), which form a white incrustation on the surface of the soil. While white alkali is injurious to vegetation, it is not corrosive, but crops will not endure, as a rule, more than one-half of one per cent, of these salts. Thus the soils of the eastern states and the semi-arid western states differ profoundly, and there is a great difference in the native vegetation.
When irrigation is practiced the soil is very fertile and produces enormous crops. If the land has never previously been irrigated, the presence of harmful salts is seldom noticed except in low spots where water has accumulated. But after a few years of irrigation, especially in localities where water has been used excessively, alkali salts may appear at the surface of land that was formerly quite free from them. Capillary attraction draws the alkali to the surface, and in a single season has been known to transform a flourishing alfalfa field into a barren alkali flat. Probably a million acres have been lost on account of alkali.
All of the legumes are very sensitive to the presence of black alkali. Many western farmers have complained that after a few years their alfalfa deteriorated and yielded less nectar. This has resulted from a rise of alkali in the soil. If there is an appreciable quantity of black alkali in the soil the cultivation of alfalfa should not be attempted, but it has succeeded with 0.4 per cent, of white alkali present. The rise of alkali in the soil is injurious to the development of roots and their functions, causing a check in nutrition and the formation of less sugar. The roots of sugar beets are smaller and contain a smaller percentage of sugar than in soils free from alkali. Sugar cane also contains a less amount of sugar. Fruit is seriously injured in sweetness and flavor. Cotton produces a smaller number of flowers, and nectar secretion is impaired or fails. The black locust, plane tree, some species of Eucalyptus, and the golden willow will endure a moderate amount of alkali.
There are a few honey plants which are confined to soils rich in common salt, as the black mangrove, the salt-marsh goldenrod, and the sea-grape. The sea-grape grows on the beaches of southern Florida, and on many of the islands, where it is exposed to the full force of the salt spray driven by storms. It is much less valuable for nectar than the black mangrove. Asparagus also will thrive in a soil containing considerable salt. On the other band, certain families avoid saline conditions, as the rose family. The heaths, likewise, which are acid-soil plants, are absent from such localities.
The influence of lime soils on the distribution of plants has been known for centuries, but the effects of acid soils have been recognized only during the past ten years. A plant might survive in an acid soil, but in general it was supposed to be injurious to plant growth. “During the last five years, however,” said Wherry a few years ago, “newly developed methods of interpreting and determining acidity have been applied in several widely separated regions — Sweden, Denmark. the northeastern United States (and subsequently in India and England), with the same result in all cases — recognition of the great significance of the acidity of the soil in controlling the growth and distribution of native plants.”
There is an immense area of acid soils in the eastern states. For example, as the result of the study of 1474 samples of soil taken from many counties in Pennsylvania, 72 per cent, of the soil areas were found to be acid. Of the river-bottom soils, 82 per cent, were acid. In Maryland 1500 soils have been tested; 75 showed very strong acidity; 150 strong acidity; 405 medium acidity; 270 were slightly