22 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 



INJURIES FKOM DISEASE, INSECTS, AND ANIMALS. 



Injuries from disease, insects, and animals are sometimes so g^reat 

 as completely to destroy the value of a year's work. The relative 

 damage to certain plots frequently may be estimated and allowances 

 made, but where the injury is considerable, it is often wise to throw 

 out the results entirely. Hall and Russell ^ state that " the unequal 

 incidence of disease is sometimes very troublesome." It is certainly 

 rare if the various plots of an experiment field are equally affected 

 by one or more of the above injuries; so, no matter how slight the 

 damage may appear, it should be recorded and mention made of it 

 in publishing the field results. 



KIND OF CKOP GEOWN AND SELECTION OF SEED. 



Experience has shown that for trucking purposes, where the delay 

 of a week or less in the maturing of a crop will often mean the 

 difference between profit and loss to a farmer, the water soluble 

 fertilizers are much more desirable than the relatively insoluble 

 varieties. Some crops also seem better able to utilize the less soluble 

 phosphates than do other crops.^ Extensive root systems may en- 

 able certain plants to forage for their food better than those which 

 feed over a more limited area. 



The selection of uniform seed is also an important factor, particu- 

 larly when dealing witli small plots. In order to decrease the prob- 

 able variation in individual productiveness of corn grains, Lyon ^ 

 suggested the plan of planting all the plots in an experiment with 

 kernels from the same ears. While such a scheme is not possible in 

 the case of many other crops, the selection of seed either by mechani- 

 cal or other means can not be sufficiently emphasized. 



UNIFORM DISTRIBUTION OF THE FERTILIZER. 



In order to obtain the maximum benefit from an application of 

 fertilizer a thorough distribution in the soil is necessary. The root 

 systems of some plants are so extensive that they feed over a very 

 wide range, and unless the fertilizer has affected the soil in the 

 vicinity of all the root hairs, full benefit from the application can 

 not be obtained. In the case of a soluble fertilizer it is not neces- 

 sary to exercise such extreme care in application, since the distri- 

 bution is largely brought about by rain and the circulation of the soil 

 water, but with relatively insoluble fertilizers, such as basic slag, 



1 Error of Experiment in Agricultural Field Tests. Cbem. News. 102, 180 1910). 



a Me. Agr. Expt. Sta. Ann. Kept, for 1898 (1899). R. I. Expt. Sta., Bui., 163, p. 

 516-560 (1915). 



*A Test of Planting Plots With the Same Ears of Corn to Secure Greater Uniformity 

 ia Yield. Proc. Am. Soc. Agron., 2, 35-37 (1910). 



