The Thorough Tillage System for the Plains 
of Colorado. 
BY W. H. OLIN. 
I. THE PRINCIPLES OF SEMI-ARID FARMING. 
Regions having an annual rainfall of less than twenty and 
more than eight inches are usually considered as semi-aricl. To 
successfully grow crops in such regions requires a careful study of 
soil and climatic conditions, with a selection of crops as nearly ad¬ 
apted to these conditions as possible. Even when all requirements are 
seemingly met, a failure is sometimes the only result. Experience, 
and experiments already conducted in many parts of our nation’s 
semiarid belt, demonstrate that the preparation of a soil reservoir of 
good depth several months before seeding, the thorough culture of 
this ground before and after seeding, the selection of suitable vari¬ 
eties of crops, the seed of which is grown under dry farming con¬ 
ditions, are essentials which very largely determine success in farm¬ 
ing lands in Colorado where irrigation can not be practiced. 
The preparation of the soil reservoir and seed bed calls for 
careful plowing, harrowing and sub-surface packing. 
i. Plowing.— Jethro Tull nearly two centuries ago said “Til¬ 
lage is manure.” Roberts’ Fertility says that stirring and mixing 
the soil is the one fundamental labor of agriculture. The object of 
plowing should be to pulverize the soil, making it possible to pre¬ 
pare a good seed bed for the reception of the various farm seeds. 
The depth to plow must depend upon the time of plowing, the 
character of the soil and the crop to be grown. 
Shallow plowing is preferred for shallow soils underlaid by an 
inferior sub-soil lacking in plant food. Spring plowing for early 
crops should not be as deep as fall plowing for the same crops. Ex¬ 
periments have shown that deep plowing of stiff or clayey, adobe 
land in the spring turns up unworked or new soil in which most of 
the plant food is not available, on account of the mechanical con¬ 
dition of the ground. Crops on lands thus plowed often make an 
unfavorable growth. It is nearly always desirable to plow sandy 
and sandy loam soils deep, since the plant food contained in these 
soils is easily available and the deep plowing brings more plant food 
to the surface for the tender young plant to feed upon, giving it a 
sturdy growth at the start. 
