26 BULLETIN 157, U. S. DEPARTMENT OF AGRICULTURE. 



not later than October 1. When seeding is delayed until very late 

 in the fall there is great danger of injury to the young plants if 

 germination occurs, from what may be termed "fall killing." They 

 are in a very critical condition when freezing weather arrives. An 

 open winter following this injury results in almost total failure of 

 the crop, regardless of the tillage methods used in preparing the 

 land and of the amount of moisture stored in it. 



As practical examples of the points brought out in the preceding 

 discussion, the past four seasons, 1909-10 to 1912-13, are worthy 

 of consideration. The seedings on August 15 and September 1, 

 1909, were made when, owing to recent rains, there was plenty of 

 moisture in the first foot to cause good growth. The yields of these 

 plats in 1910 were high in comparison with those of the plats sown 

 later, when the weather was dry and cold. The seedings on Sep- 

 tember 15, 1910, were made under conditions similar to those in 

 August, 1909. The yields on these plats were higher than those 

 seeded "in the dust" in August and those sown late in October. 

 In the fall of 1911 and again in 1912 the weather was dry until 

 early October, after which time there was plenty of moisture, but 

 the weather was cold. As a result of these conditions the yields 

 of both early-sown and late-sown crops were low. Figure 15 shows 

 the relation of precipitation to yield in this instance. The black- 

 ened portions of the figure illustrate the daily precipitation from 

 August 1 to November 30, inclusive, and the curves represent the 

 yields in bushels per acre of the two varieties of wheat seeded on 

 different dates during these months. 



It will be seen that early seeding if done in wet weather gave 

 high yields, while it gave low yields, and sometimes almost failures, 

 when done in dry weather. It is also shown that late seeding, even 

 when there was plenty of moisture, often resulted in serious loss 

 because of injury to the tender plants by freezing. There seems 

 to have been some difference in the effect of these climatic condi- 

 tions on the two varieties. This may have been due to a difference 

 in the time of germination between the hard (Turkey) variety and 

 the soft (Koffoid) variety. The writer is of the opinion that this 

 difference in germination is largely responsible for the differences in 

 yield. The soft wheat seems to germinate more rapidly than the 

 hard wheat, and for this reason it is more advanced on a given date 

 than the latter variety. This may not always be advantageous to 

 it, as it may be in a tender stage of growth when drought or cold 

 weather strikes it, and thus it may be injured more than the un- 

 germinated seed of the hard variety. On the other hand, the soft 

 wheat may be sufficiently far advanced to protect it from injury, 

 while the slower germinating Turkey wheat may be still in a tender 

 stage of growth. 



