TWENTY-EIGHTH CHAPTER 



TESTS OF SOIL FERTILITY. 



In many cases, ^^ the farmer can not easily get at 

 the record of the crops that have been taken off the 

 fields, nor of the treatment given to them since they 

 were put under cultivation, and consequently he 

 has no data upon which to base his estimate of the 

 probable condition of the soil. In such cases, plants 

 may be utilized as soil analyzers. The great diffi- 

 culties we meet with in this matter are the variety 

 of soils found on every farm, and the fact that there 

 are seldom two fields alike, and each may have to 

 be examined for itself, making this task of plat 

 testing rather complicated and laborious. On the 

 whole, however, such plat tests are easily made. 

 First, divide the piece for each test in strips of equal 

 uniform width, and then apply the various simple 

 plant foods, one kind to a strip. To the first one 

 for instance, we may apply a simple superphosphate 

 (dissolved bone-black or South Carolina rock), or 

 perhaps Thomas' slag; to the second, nitrate of soda 

 or sulphate of ammonia; to the third, sulphate of 



