2d. A second class of alkalies are the sulphates and chlorides, all soluble in water. Such salts are: Magnesium chloride (bittern), magnesium sulphate (Epsom salt), calcium chloride, etc. These salts, when not present in too large quantities, are easily counteracted by lime.
3d. A third class of alkalies is composed of neutral salts, such as chloride of sodium (common salt), sulphate of sodium (Glauber salt), sulphate of potassium, all soluble in water, but not convertible into less injurious substances by lime or gypsum. These salts do not bake the soil, but rather contribute towards keeping it loose and mellow.
The remedies which are practical and not too expensive may be divided into several classes, which, if used in combination, may prove effective, while each one of them used separately would fail.
1st. Leaching with water. All soluble salts may be leached with water. The alkali land should be checked and so ditched that the water from each check can be drained into a waste ditch. But, besides these waste ditches, drain ditches should be made for the purpose of draining off the water, say to a depth of four feet below the surface. The modus operandi consists in first flooding the soil, and while the check is yet full the floodgates are opened and the water drawn off into the waste ditch, when the water will carry off the salts which have been dissolved in it. A second or third flooding should be allowed to settle in the soil and be drained off below into the drain ditches. The drawback to common leaching is that under certain circumstances the water may deposit its alkali in lower strata, especially if they are sandy, and there form hardpan or alkali accumulations. A much better method is under-drainage by means of pipes or gravel drains constructed all through the tract at certain regular distances. This under-drainage, if properly constructed under conditions favorable for its perfect working, is by far the best method of freeing alkali soils from their superfluous salts. To what extent this system is practical depends upon circumstances. To reclaim large districts by this method may not prove economical as long as good land is plentiful and cheap, but where smaller alkali tracts are surrounded by soil, and where it is of importance to get a uniform plantation, under-drainage by pipes or common drains is both the surest and most practical solution of the alkali problem. Under-drainage is strongly recommended by Prof. E. W. Hilgard, who has repeatedly pointed out its value, and who has called the author’s special attention to this as yet little understood remedy.
2d. Deep and constant plowing. Deep and frequent plowing acts in various ways. By being mixed with a larger quantity of soil, the alkali is diluted sufficiently to not cause any serious injury to the crops, the damage generally being done near the surface. Constant plowing also prevents evaporation, which carries the alkali to the surface and deposits it there. This method can only be successful when the alkali salts are limited in quantity, and no one need expect to be able to rid badly charged lands from their alkali by plowing it under.
3d. By plowing under green or dry crops. If grain can be made to grow on the alkali land at all the turning under of it, either green or dry, will in course of time greatly reduce the alkali. The turned-under stubble or straw forms in decaying an acid, which in many instances will combine with and counteract the effects of the alkali. Similarly, straw stacks spread on alkali spots and plowed under will considerably reduce the alkali. But manure containing ammonia and other salts should not be used, as it will, on the contrary, only increase the alkali by adding other or similar salts to those already in the soil.
4th. Cropping. If water, either in the form of sufficient rain or as irrigation can be had, alkali lands can be reclaimed by cropping. It is amply proved that beets and carrots, as well as other plants, such as salt-bush (Chenopodium), take up large quantities of alkali salts, and in the course of a few years render alkali soils available for grain. Wheat also extracts alkalies, and repeated croppings with grain will in the course of time prepare the soil for vines and trees. Bermuda grass will completely remove the alkali from soils to the depth at which the roots can penetrate, and must be recommended for the worst places. Afterwards, cropping with annual crops may be advisable before vines are finally planted on such reclaimed lands. The Australian salt-bushes, or Chenopodium, extract alkalies, and are besides liked by stock. They should be introduced to alkali lands and take the place of the California native salt-bushes, which are not eaten by stock. While being real desert plants, they yet require some moisture in the soil, but they could probably be grown anywhere on the alkali lands in this State where the rainfall is over three or four inches.
5th. By chemicals. The use of chemicals of various kinds in counteracting the alkali is not resorted to by our farmers as it should be. The principle upon which chemicals can be used is that obnoxious or greatly injurious alkalies may be changed into less obnoxious and less injurious salts, or even into fertilizers. The most available of these chemical compounds are gypsum (sulphate of lime) and lime (carbonate of lime). When the alkali consists mainly of carbonates, such as carbonate of sodium (sal-soda) or potassium carbonate (saleratus), in other words of the class which we have designated as class number one, the most dangerous and worst class of alkalies to combat, gypsum may be used as an antidote or rather as a means to convert these alkalies into alkalies of the second class, or the sulphates. The principle upon which this is done is to displace the sulphate in the gypsum and force it to combine with the alkali (sodium carbonate) and form sulphate of sodium (Glauber salt), an alkali belonging to the third class of alkalies, and which is twenty times less injurious to vegetation than is class number one. The change is made on the following principle, and might be thus illustrated: To the alkali in the soil (carbonate of sodium), add sulphate of lime. As soon as the mixture is made with sufficient water, a change will take place, and the substances (carbonate of sodium and sulphate of lime) will form new compounds. Thus we will get, out of those two substances, two new compounds, viz., carbonate of lime and sulphate of sodium. Of these, carbonate of lime is not injurious to vegetable life, and sulphate of sodium (Glauber salt) is only injurious when present in large quantities. The carbonate of lime is not soluble in water, but the sulphate of sodium is, and can consequently be eliminated by underdraining or by flooding, as we have previously described.
To know when gypsum can be used is not necessarily a scientific matter. Mix some of the alkali in a tumbler with water, and allow the mixture to settle. In another tumbler mix some gypsum and water, and allow it to settle. Then mix the two clear liquids, which, if gypsum is an antidote and the proper thing to use, will be turbid or milky through the chemical combinations which take place. If the water remains clear, gypsum will not prove an antidote to the alkali under consideration. The use of lime is based very much on the same principle. If the second class of alkalies are present, and lime is added, the changes that take place may be illustrated as follows: Epsom salt (magnesium sulphate) combined with calcium carbonate, will form two new compounds, viz., gypsum (calcium sulphate) and magnesium carbonate, both of which substances are less injurious to crops. But, as I have already stated, raisin-vines prefer soils which are naturally free from alkali, and should never be planted on soils which cannot readily be reclaimed. Chemical antidotes may do where the alkali occurs in a few spots mixed in among tracts of good soil, but where the whole field must be reclaimed some other crop than vines had better be first attempted. There is too much good and suitable soil in California, and until all this is occupied the alkali soils had better be given up to other crops than vines.