SPECIAL FARM TOPICS 211 



There is another method, however, of eliminating the toxic or pois- 

 onous effects of these excreta. Whatever they may be, it appears 

 that those cast off by one variety of plant are not, as a rule, in- 

 jurious to another variety, hence the possibility of rotation of crops. 

 By the time the first crop comes round again, the intervening culti- 

 vations having stirred up the soil, exposed it to the weathering proc- 

 esses, allowed the air to enter inland permitted the humus to do 

 its work, all the excretions injurious to that crop have been removed 

 or neutralized, and a yield equal to the last one is secured. Hence 

 it is that by proper rotation a farmer may go on cropping his fields 

 from year to year, cropping them indefinitely, without any apparent 

 exhaustion, and indeed by wise rotation even increasing the yield. 

 (Ont. Dept. Agr. B. 156.) 



Among the most important considerations that should enter 

 into any discussion of crop rotation must be the following: 1. Cli- 

 matic conditions; precipitation, annual and seasonal; temperature, 

 annual and seasonal; length of growing season, winds, frosts, etc. 

 2. Soil conditions; chemical, and physical or mechanical; effects 

 of tillage upon soil water ; effects of the growth of various crops upon 

 the crop-producing powers of the soil, either by depleting the soil of 

 its fertility, or changing its mechanical condition. 3. The relation 

 that various crops bear to each other when grown in succession. 4. 

 Effects of the application of manure in various ways and at different 

 times. 5. Effects of summer fallowing. 6. Effects of plowing un- 

 der green crops for manure. (S. Dak. Ag. Col. B. 79.) 



Summer Tillage. This will almost invariably increase the 

 yield of wheat, oats, or barley and will materially reduce the danger 

 of complete crop failure due to drought. It may therefore be re- 

 sorted to as a safeguard or temporary expedient to meet a possible 

 emergency, but it can not be depended upon to produce as profitable 

 spring-sown crops as may be produced by other methods. Very good 

 crops can usually be raised by one plowing and one or two harrow- 

 ings, as is shown by yields obtained from continuous cropping by 

 ordinary methods. Each farmer must decide for himself whether 

 he can afford to perform this additional amount of labor in order 

 to secure an increase in yield, which if the season proves favorable 

 may be small, and to materially reduce the danger of total failure 

 if the season proves unfavorable. He should, however, remember 

 that summer tillage will in no way reduce the many dangers other 

 than drought, such as unseasonable frosts and high winds, to which 

 crops are subject. In fact, these dangers may be materially increased 

 under a system of summer tillage. (Bu. Pit. Ind. B. 187.) In 

 planning a system of rotation it is well to observe the following 

 rules : 



(1) Select as large a number of restorative and as small a 

 number of exhaustive crops as is consistent with the general plan of 

 farm organization. 



(2) Arrange the crops in the rotation so as to have the ex- 

 haustive and restorative crops alternate as far as possible. 







