CHOPPING AND SUMMER TILLAGE. 19 



(2) Summer tillage will almost invariably increase the yield of 

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

 plete crop failure due to drought. It may therefore be resorted 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 harrowings, as 

 is shown by yields obtained from continuous cropping by ordinary 

 methods. Alternate cropping and summer tillage by methods used 

 in these tests require on an average two plowings, four diskings, and 

 twelve harrowings. 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. 



It frequently happens that specially favorable soil conditions 

 early in the spring induce such a rank growth of the young grain 

 plants that the injury from both late spring frosts and summer 

 drought is greatly increased. These factors were of such importance 

 as to completely reverse the results at North Platte, Nebr., in 1909. 

 The moisture-conservation plats of wheat on both continuous crop- 

 ping and alternate cropping gave lower yields than the ordinary- 

 method plats, the loss due to good tillage being 7.7 bushels per acre 

 for continuous cropping and 5 bushels per acre for alternate cropping. 

 Several other instances of the same nature are shown in Tables I, II, 

 and III. This loss on well- tilled plats may in some instances be due 

 to proximate causes other than frost or drought. It seems reason- 

 ably certain, however, that the ultimate cause is usually over- 

 stimulation of the crop at some stage in its growth. It is a well- 

 recognized fact among farmers that grain usually suffers more 

 severely from rust when the growth is very rank and succulent than 

 when it is less vigorous. A well- tilled soil may sometimes blow 

 worse than a poorly tilled one. 



(3) The result of the experiments with moisture-conservation 

 methods upon continuously cropped plats are so contradictory that 

 no definite conclusions can be arrived at. This is true not only 

 where different stations are compared, but where the same station 

 for different years, or the same stations for the same years with 

 different crops, are compared. All the evidence, however, goes to 

 show that the time and depth of plowing and seeding and the har- 

 rowing of the grain after seeding are problems that are local in their 



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