ROTATION OF CROPS 479 



others thrive under totally different conditions. The smah 

 grains offer particularly favorable conditions for the growth 

 of many weeds. The spring grains are sown before many of 

 the weed seeds germinate, and ordinarily no effort is made to 

 control weeds which come up in them, so that they are allowed 

 to grow unmolested till harvest. Even less opportunity is 

 afforded to combat weeds in fall grain, except that the grain 

 begins growth earlier in the spring than many of the weeds 

 and is harvested earlier than some of them mature their 

 seed. By harvest, most of the annual weeds have ripened 

 their seeds and have thus had every chance to increase. 

 Meadows and pastures offer less favorable conditions for 

 annual weeds, as the crops and weeds are cut or eaten off by 

 stock, and when a good sod is established it affords little 

 opportunity for weeds to get a start. Biennial and peren- 

 nial weeds, however, often thrive in meadows and pastures, 

 if the field is left undisturbed for several years and there is 

 no chance to destroy them by stirring the soil. Cultivated 

 crops offer opportunities for the destruction of weeds of all 

 classes. In other words, weeds increase rapidly in grain 

 crops, some classes decrease while others may increase in 

 meadows and pastures, and all classes decrease in fields on 

 which cultivated crops are grown and given proper attention. 

 656. Rotations Insure Returns. A rotation of crops, 

 with the diversification which it necessarily implies, insures 

 some return for the season's labor. Seasonal conditions may 

 be such as to cause the total failure of one crop, but it is very 

 seldom, at least east of the 100th meridian, that all the crops 

 on the farm fail to yield a profitable return. Conditions 

 that are unfavorable to oats or wheat may be quite suitable 

 for corn or hay, so that if one has several crops he is much 

 surer of some return for his labor than if he depends entirely 

 on one. The old caution, ^'Do not put all your eggs in one 

 basket," applies as well to crops as to anything else. Plant 

 diseases or insect pests may destroy one crop, but they are 



