396 DRY LAND FARMING 



conditions, will yield some profit to the grower, and, 

 second, the furnishing of food for animals that may be 

 kept upon the farm, such as can be obtained from no 

 other source. The bare-fallow alternating with grain 

 can only give one crop in two years, whereas by this 

 system, as intimated, a crop is obtained every year. 



The area where this system of cropping may be 

 practised covers a very large amount of the semi-arid 

 belt, but it cannot be practised everywhere, because of 

 the shortage that may be present in the moisture. This 

 system of cropping will probably conserve moisture 

 about as effectively as the bare-fallow, but it draws more 

 heavily on the moisture content in the soil, since it 

 draws on it every year, where, by the other system, it 

 is drawn upon only once in two years. It is clear, there- 

 fore, that more moisture will be used when the alterna- 

 tion in the cropping includes a cultivated crop. But how 

 much more moisture will be called for in the one rota- 

 tion as compared with the other, has not been worked 

 out as yet. It would seem safe to say, however, that 

 on average soils such a rotation could be conducted 

 where the annual rainfall was not less than, say, 12 to 

 15 inches. 



To this system two objections may be urged. First, 

 it draws heavily on the plant food and humus in the soil, 

 and, second, it draws so heavily on moisture that the 

 grain crops grown must soon suffer from a shortage in 

 plant food and also in moisture. The first objection is 

 valid. The second is only partially so. In time such a 

 rotation would deplete the plant food in the soil to 

 the extent of reducing crop yields. Whether reduction 

 would follow from a shortage in moisture will depend, 

 first, on the total amount of the precipitation, and, second, 

 on the proportion of this that it is possible to conserve. 

 A crop of corn, for instance, will use as much moisture 

 in many instances as a crop of wheat, but it does not 



