166 Missouri Agricultural Report. 



Rotation. 



Plot 1 Corn, 17 years 



Plot 2 Corn, wheat, clover, 17 years 



Plot 3 Corn, oats, clover, wheat, timothy, 17 years 

 Plot 4 Corn, wheat, clover (manured) 17 years. . . . 



Yield in Bu. 

 per acre 1905. 



11.8 

 50.7 

 54.2 

 77.6 



These plots lie side by side, the only difference being in the 

 system of cropping, and, in the case of plot 4, to the addition 

 of manure. 



The benefits of a rotation arise mainly from a better main- 

 tenance of the humus supply, and not to a saving of plant food. 

 As a matter of fact, a rotation of crops is usually more exhaustive 

 of phosphorus and potassium, especially, than is straight grain 

 farming, but the nitrogen that is added through the legume crops 

 introduced, such as clover and cowpeas, tends to maintain the 

 nitrogen supply somewhat, and the larger amount of humus main- 

 tained tends to keep available larger amounts of plant food of all 

 kinds. It should be remembered, however, that no crop rotation 

 will maintain fertility indefinitely if the crops are continually 

 removed. It is, however, the first method we usually adopt in 

 the building up of our lands, and many farmers, seeing the imme- 

 diate benefits that are derived, conclude that a "change of crops" 

 is the only essential to a permanent productiveness. This is far 

 from true, and there are thousands of farmers in the east who 

 can testify most truthfully to this fact. A crop rotation is only 

 the first essential to the maintenance of the fertility of our lands. 



THE USE OF LEGUMES. 



No rotation is complete unless it contains a legume crop, 

 such as clover or cowpeas, once in three to six years, and the more 

 often such crops occur the better, providing they are put to the 

 proper use. The immediate effect of the legume is to set free 

 available, soluble nitrogen as its roots decay in the soil, and thus 

 supply to a considerable extent the crops which follow. Hence 

 we get the great benefit of a clover crop preceding corn or a cow- 

 pea crop preceding wheat. Analyses show, however, that the 

 large portion of nitrogen in all legumes is in the tops, rather than 

 in the roots, and that a certain share of the nitrogen even of 

 legumes comes from the soil; hence the growing of legumes and 

 the constant removal of the crop as hay does not tend to build up 



