204 MISCELLANEOUS FARM SUBJECTS 



haustive." No crop "restores" to the soil any considerable amount 

 of plant food unless it is plowed under for green manure or is al- 

 lowed to decay upon the surface. But, nevertheless, certain crops 

 leave the land in poorer condition for a subsequent crop of some 

 particular kind than it was 'before they were raised. These are 

 designated as "exhaustive" crops, and include wheat, oats, barley, 

 rye, and millet. Their ill effects upon subsequent crops may be 

 due to a reduction of the available plant food; to an increased 

 growth of weeds, fungi, or injurious insects; to a change in the 

 physical condition of the soil, particularly its water content; or to 

 a reduction in the quantity or activity of beneficial lower organ- 

 isms. "Restorative" crops have the opposite effect. They leave 

 the soil in better condition for certain crops than it was before. 

 Among restorative crops may he mentioned corn, potatoes, beans, 

 peas, clover, alfalfa, and perennial grasses grown for meadow or 

 pasture. "Intermediate" crops are those that have, in some respects, 

 a beneficial effect upon certain crops which follow them, while in 

 other respects their influence is detrimental. The sorghums, cane, 

 milo, and kafir belong to this class. Their beneficial effects are due 

 to the fact that, like all cultivated crops, they reduce the amount 

 of weeds in subsequent crops. 



In addition to and in a certain measure independent of the 

 above-mentioned classification is the problem of crop sequence, or 

 the relations which two crops bear to each other independent of 

 any apparent difference in the conditions of the soil brought about 

 by their growth. For instance, two crops may be equally exhausr 

 tive, but when grown consecutively, better results will be obtained 

 if they are grown in one sequence than when the opposite se- 

 quence is followed. Oats following wheat generally give better 

 results than wheat following oats. Or, again, a restorative crop 

 may have a more beneficial effect upon some certain exhaustive 

 crop which follows it than it has upon some other equally exhaus- 

 tive crop. Wheat generally responds more readily to the effects 

 of a corn crop than does oats. (Ont. Dept. Ag. B. 15'6; Bu. Pit. 

 Ind. B. 187; Univ. of Minn. B. 109.) 



Fertilizers. No system of crop rotation can be devised that 

 will prove successful without a fertilizing system. A soil that is 

 called upon year after year to produce a crop will in the end be 

 exhausted of the three principal elements of plant food, nitrogen, 

 phosphoric acid and potash. These elements of plant food must be 

 returned to the soil in some way. Rotation will not alone accom- 

 plish this. A system of fertilization must go hand-in-hand with 

 rotation if success is desired. This can be done to some extent by 

 using in the rotation some crop that being plowed under will act 

 as a fertilizer. 



Experiments. The various Experiment Stations have accom- 

 plished wonders in the way of tests of rotation. These Stations 

 discover and formulate general principles. The application of 

 those principles must be by the farmer himself. The farmer who 

 profits most by the work of the Experiment Station is he who is 



