282 REPORTS ON THE STATE OF SCIENCE,—1914. 
humus under cultivation. Where legumes were grown, crop-rotations 
practised, live-stock kept, and the farm-manure used, the nitrogen 
content of the soil was maintained. This practice the dry- farmer of the 
Great Plains must eventually adopt as far as his conditions will permit, 
if a permanent agriculture is to be assured in these sections. The 
American dry- farmer has much to learn from Australian practice in 
the use of stock, especially sheep, on the dry-farm. 
The Water-requirement of Different Dry-Farm Crops. 
A word must be said in regard to the importance of considering 
the water-requirement of crops grown on the dry-farm. Other things 
being equal, those crops which are most efficient in the use of water 
are obviously best adapted to dry-land conditions. The great success 
of millet, sorghum, and maize in American dry-farming is due in part 
at least to their remarkable efficiency in the use of w ater. ‘The amount 
of water required for the production of a pound of dry matter of some 
strains of alfalfa is four times that required by millet, where the two 
crops are growing side by side. Different varieties of the same crop 
often exhibit wide differences in water-requirement. The following 
figures represent the range in water-requirement due to varietal differ 
ences as measured by Briggs and Shantz ** in the Great Plains. 
Taste IIT.— Varietal Range in the Water- pr urn ai different Crops. 
| Pea water requir oa to pr wae one pound of ay Vy 
i matter of the 
Crop | Al 
| Most efficient variety | Least efficient variety 
| lb. oz. Ib. 02. 
Millet ; ; : . 261 15 | 444 9 
Proso 4 ‘ ; A 268 1 | 341 10 
Sorghuny eo. mee 285 3 467 9 
Maize ; : ; : 315 3 413 ~ 5 
Wheat ; ; , : 473 8 5594 
13 Pia Gees Some mene Sica Be 502. 4 578 13 
Oats . ; ‘ A eas | 559 «8 622 9 
Clover ‘ é : a 7389 9 805 8 
Alfalfa : 3 : i 651 12 963 9 
These wide crop and varietal differences in water-requirement 
suggest great possibilities in the development of strains for dry-land 
conditions. In fact, the measurement of the water-requirement affords 
a novel and promising method of attack in the breeding and selection 
of dry-land crops. 
3 Jour. Agricultural Research, U.S. Department of Agriculture, 3, 58, 1914. 
