322 ELEMENTS OF FARM PRACTICE 



acre to raise a crop of oats, how much less does it cost to raise 30 acroa 

 of hay than to raise 30 acres of oats? 



3. If the rotation of crops adds 15 bus. per acre to the corn 

 crop, how much will it increase the yield on 35 acres? How much is 

 the increased yield of corn worth at 35c. per bushel? 



CLASSIFICATION OF FIELD CROPS 



Three Classes. — There are a great many different sys- 

 tems of rotation. Some are good and some are not good, 

 and it is well to study a few of the principles, that we may 

 easily know whether a certain rotation is likely to give 

 good results or not. 



We rotate crops in order to get good yields, hence we 

 must know something about the effect of each crop upon 

 the soil, so that we may know in what condition the soil 

 will be left for the next crop. 



To simplify a study of the general field crops, they may 

 all be placed in three classes, grain crops, grass crops and 

 cultivated crops, basing the classification on the effect each 

 class has on the soil. 



Grain Crops. — Under grain crops we can place wheat, 

 oats, barley, flax, speltz, millet and other crops that grow 

 but one year from one seeding and are not cultivated while 

 they are growing. This class of crops has a comparatively 

 small root "system, and, as a consequeiice, very little vege- 

 table matter is left in the soil when the crop is removed. 

 From the time they are sown until they are ripe is usually 

 long enough to allow many of the worst weeds to ripen 

 seeds, so these crops have a tendency to make land more 

 weedy year after year. Grain crops are likely to be sold 

 from the farm, thus removing a large amount of fertility. 



Grass Crops. — Under grass crops we can place timothy, 

 bromus, blue grass, redtop and all the common clovers 

 and alfalfa. From the standpoint of the botanist, the 

 clovers and alfalfa are not grass crops, but for our classifica- 

 tion we will regard them as such. Grass crops are principally 

 used for hay or pasture. They all grow two or more years, 

 and are not cultivated during their growth. They develop 

 heavy root systems, and, therefore, add much vegetable 

 matter to the soil. Grass crops are usually harvested two 

 a^ Tfiore times during the year, and each crop grows so 



