Page:Popular Science Monthly Volume 48.djvu/686

614 time most of the soil moisture was exhausted, only a moderate efflorescence of alkali was seen on this land even late in the season.

It is thus obvious that when by any means a good "stand" of a leafy perennial crop with deep roots, like alfalfa, can be obtained on alkali land, the rise of the salts resulting from irrigation is measurably checked, and may remain wholly innocuous so long as that crop occupies the soil. Experience amply confirms this conclusion; but the difficulty of obtaining such a stand is often very great, especially on "black" alkali land, which "rots" the seed as often as sown. It is then that the use of gypsum to neutralize the carbonate of soda often becomes the saving clause, enormous crops being then grown on land formerly considered worthless. Diagram No. 5 may illustrate this in the case of wheat, which was grown in 1892 at the Tulare Station on ground that, prior to the reclamation work, would hardly grow even "alkali weeds," but then yielded grain at the rate of forty-five bushels per acre.

The diagrams, however, convey unanimously the fundamentally important lesson that the amount of alkali salts in these soils is limited, and lies within such easy reach of the surface that ordinary underdrainage at the depth of from three to four feet will relieve these rich soils of their noxious surplus, once for all. Also that toward the end of the dry season the removal of a few inches of surface soil will go far toward relieving the land of the same.

A few words should be said in regard to the kind of the salts as well as their quantities. As regards the main ingredients, which may be considered as useless or harmful to vegetation, inspection of the diagrams shows that in no case is the noxious carbonate of soda as abundant near the surface as in the case of the subsoil hardpan in Diagram No. 1. Investigation has shown this to be due to the aëration which occurs near the surface; while, on the contrary, in a water-logged soil, the "black" alkali is constantly in progress of formation from the "white" or neutral salts. Hence we find the worst of the "black" cases in low or badly drained ground, and in close soils. Here, again, underdrainage affords radical relief.

But underdrainage and washing-out of the salts would in many cases be like "throwing out the child with the bath." For, as has been stated at first, not only the useless but also the useful or plant-food ingredients, which the farmer purchases in the form of fertilizers, are present in them. They not unusually contain as much as twenty per cent of salts of potash, ten to twenty per cent of saltpeter, and several per cent of soluble phosphates. In one notable case the equivalent of one ton of Chile saltpeter (worth