One Thousand Questions in California Agriculture Answered

by Edward J. Wickson

It would have a tendency to make the surface more friable and therefore better for moisture retention, and it could be used at the rate of 1000 pounds to the acre, broadcasted before plowing for grain. As our soils are, however, usually well supplied with lime, there is a question whether there would be any profit in the use of gypsum, for, aside from lime, it contains no plant food, although it does act rather energetically upon other coil contents. Gypsum is a tonic and not a fertilizer from that point of view. The best way to satisfy yourself of its effect would be to try a small area, marked so as you could note its behavior as compared with the rest of the field.

Gypsum and Alfalfa.

What is gypsum composed of? Is it detrimental to land in future years? Have the lands of California any black alkali in them? I notice my neighbors who sow gypsum on their alfalfa get a very much better yield of hay than those who do not.

Gypsum is sulphate of lime. It is not detrimental to the land in after years except that its action is to render immediately available other plant foods and this may render the land poorer - not by the addition of anything that is injurious but by the quicker using up of plant food which it already contains. Black alkali is very common in California in alkali lands. In lands which show their quality by good cropping, there is no reason to apprehend black alkali nor to use gypsum to prevent its occurrence. The use of gypsum does stimulate the growth of alfalfa and makes its product greater just as you observe in the experience of your neighbors, but the more they use up the land now the less they will have later, unless they resort to regular fertilization to restore what has been exhausted. But even that may be a good business proposition.

What Gypsum Does.

I intend to fertilize alfalfa and should like to know about gypsum. I have heard it stimulates the growth temporarily but in three or four years hurts the land. I have heavy land.

The functions of gypsum are: (a) to supply lime when the soil lacks it; (b) to make a heavy soil more mellow, and (c) to act upon other soil substances to render them more available for plant food. These are some of the soil aspects of gypsum; it may have plant aspects also. It is too much to say that gypsum hurts the land; it does, however, help the plant to more quickly exhaust its fertility, and in this respect is not like the direct plant foods which comprise the true fertilizers - one of which gypsum is not. It might be best for your pocketbook and for the mechanical condition of the soil to use it, but do not think that it is maintaining the fertility of the land (a service which we expect from the true fertilizers) except as it may supply a possible deficiency of lime.

How Much Gypsum?

How much per acre, how frequently and what seasons of the year are the best time to apply gypsum?

Of gypsum on alkali, we should begin at the rate of one ton to the acre and repeat the application as frequently as necessary to achieve the desired result. If the alkali was quite strong we would use twice as much. Without reference to an alkaline condition in the soil, and to give heavy soil a more friable character, which promotes cultivation, aeration, etc., and, therefore, ministers to more successful production, half a ton to the acre can be used, applications to be repeated as conditions seem to warrant it.