242 TwENTY-FlEST BiBNNIAL RePOET 



haust the nitrogen already in soils exactly as do th.e 

 grasses and other plants. 



In this brief explanation yon have the important 

 part taken by the clovers in the rotation of crops. By 

 systematic rotation, including some clover crop, prac- 

 ticed steadily all the time, land can be kept from wear- 

 ing out, and good crops be harvested every year. In 

 some European countries where farms have been tilled 

 for centuries, better average yields of wheat and oats 

 are now harvested than we get. "When we obtain an 

 average of 16 bushels or less, they get an average of 

 25 to 30. But it would be difficult to plan a rotation 

 worth adopting that did not include both a grass and a 

 clover, the grass to supply vegetable matter, and put the 

 soil in a good physical condition, the clover to supply 

 the most costly, the most quickly removed, the most 

 fugitive, of the necessary fertilizing materials. 



We have not yet learned everywhere in Kentucky the 

 supreme importance of forage plants in rotation. Even 

 if we wish to grow tobacco all the time, we cannot 

 afford to do it because of its destructive effect on our 

 land. We cannot grow tobacco without vegetable mat- 

 ter tri the soil. In the Burley growing section of the 

 State, we grow the crop now by plowing up pasture, 

 and following it with two tobacco crops. But by a prop- 

 erly managed rotation, a farmer may, if he likes, grow 

 a crop of tobacco on his place every year without pas- 

 ture of any sort. We have now on the Experiment 

 Farm a series of plots on which we are, in co-operation 

 with the United States Department of Agriculture, prac- 

 ticing different systems of rotation. On one we grow 

 com every year, adding nothing to the soil. On another 

 we grow com every year, but fertilize with manure. On 

 others we grow grass and clover, wheat, tobacco; in 

 others, oats, soy beans and tobacco, in many of them 

 depending entirely on the rotations to keep the soil in 

 good condition. These plots have been kept in these 

 different rotations for a good many years, and if there 

 was a decline in fertility it would now be apparent. As 

 a matter of fact, the soil is in good condition, and ex- 

 ceUent crops of all sorts are obtained from the land, 



