30 AGRICULTURE 



now become so impoverished as to yield only a small part 

 of what the soil is capable of producing. 



Second, a one-crop system encourages the growth of 

 plant enemies in the soil. The insects that feed upon the 

 crop one season are left upon the field ready to reproduce 

 their kind and attack the next season's crop. Various 

 bacteria and fungous enemies also have a tendency to mul- 

 tiply when the same crop is produced from year to year. 

 Let the crop be changed, however, and the insects and 

 fungi, not finding the necessary food, die and the field is 

 in a measure cleared of their danger. Weed enemies dis- 

 appear in a similar way in the presence of the new crop. 



Third, a one-crop system always leaves the farmer at 

 the mercy of weather conditions. If the season turns out 

 too dry or too wet, or in any other way unfavorable so 

 that a failure of the crop results, the farmer is left with- 

 out resources and faces financial failure. If, on the other 

 hand, he has a variety of crops, seasonal troubles which 

 affect one crop may not affect others, so that the farmer 

 does not suffer an entire loss. If he raises but one crop 

 and the insect enemies or other reverses prove strong 

 enough to ruin the crop, he is left in poverty. But these 

 plant enemies require different seasonal conditions for their 

 best thriving, hence when they attack one crop they are not 

 so likely to injure others. 



Fourth, one of the most serious disadvantages of a 

 one-crop system is the changing market conditions. If for 

 any reason the market happens to fail for the par- 

 ticular crop raised, no matter how good the yield may 

 have been, the farmer is helpless with the crop left on 

 his hands. This was well illustrated when in the season 

 of 1914 the South had hundreds- of thousands of bales of 

 cotton for which there was no market because of the Euro- 

 pean war. Thousands of southern farmers found them- 



