The lesson then to be learned from this chapter is, that it is not aufficient for the dry-farmer to store an abundance of water in the soil and to prevent that water from evaporating directly from the soil; but the soil must be kept in such a state of high fertility that plants are enabled to utilize the stored moisture in the most economical manner.  Water storage, the prevention of evaporation, and the maintenance of soil fertility go hand in hand in the development of a successful system of farming without irrigation.

CHAPTER X

PLOWING AND FALLOWING

The soil treatment prescribed in the preceding chapters rests upon (1) deep and thorough plowing, done preferably in the fall; (2) thorough cultivation to form a mulch over the surface of the land, and (3) clean summer fallowing every other year under low rainfall or every third or fourth year under abundant rainfall.

Students of dry-farming all agree that thorough cultivation of the topsoil prevents the evaporation of soil-moisture, but some have questioned the value of deep and fall plowing and the occasional clean summer fallow.  It is the purpose of this chapter to state the findings of practical men with reference to the value of plowing and fallowing in producing large crop yields under dry-farm conditions.

It will be shown in Chapter XVIII that the first attempts to produce crops without irrigation under a limited rainfall were made independently in many diverse places.  California, Utah, and the Columbia Basin, as far as can now be learned, as well as the Great Plains area, were all independent pioneers in the art of dry-farming.  It is a most significant fact that these diverse localities, operating under different conditions as to soil and climate, have developed practically the same system of dry-farming.  In all these places the best dry-farmers practice deep plowing wherever the subsoil will permit it; fall plowing wherever the climate will permit it; the sowing of fall grain wherever the winters will permit it, and the clean summer fallow every other year, or every third or fourth year.  H. W. Campbell, who has been the leading exponent of dry-farming in the Great Plains area, began his work without the clean summer fallow as a part of his system, but has long since adopted it for that section of the country.  It is scarcely to be believed that these practices, developed laboriously through a long succession of years in widely separated localities, do not rest upon correct scientific principles.  In any case, the accumulated experience of the dry-farmers in this country confirms the doctrines of soil tillage for dry-farms laid down in the preceding chapters.