A THIRTY-YEAR FERTILIZER TEST. 149 



same length of time. In both cases the crop was fairly satisfactory. On 

 the other hand, nitrogen and phosphoric acid without lime gave an im- 

 mensely larger crop than did nitrogen and potash without lime, — once 

 again indicating that under certain conditions phosphorus functions in 

 reducing need for lime, or in neutralizing the effects of soil acidity. It is 

 also of interest to note that the yield of cabbages classified as "poor" is 

 less absolutely, and very much less relatively, on the high-yielding plots 

 than on the low-yielding plots. 



General Summary. 



The more important conclusions which may be drawn from this work, 

 in their apphcation to the fertility practice of Massachusetts farmers, 

 are as follows : — 



1. The kind of crop being grown and the cropping system followed 

 determine the fertilizer needs of crops fully as much as does the soil type. 



2. Where the soil is farmed without live stock, and no manure returned 

 to the land, a complete fertilizer is more certain to bring satisfactory 

 results than is any other fertilizer treatment. 



3. The nitrogen response of crops is affected by nearness in the rotation 

 to a legume crop, and likewise by the kind of crop. The tests indicate 

 that where corn is grown either the first or second year following a legume, 

 the use of fertilizer nitrogen does not bring anything more than a moderate 

 return. The character of the season does not seem to have a dominant 

 influence on the functioning of tliis plant food when applied in artificial 

 form. 



4. Where the whole crop is removed and manure not returned to the 

 soil, large returns from the use of potash may be expected. As a corollary, 

 the greater the extent to which crops are removed, the greater relatively 

 will be the need for fertilizer potash; and on the other hand, the greater 

 the extent to which crops produced are fed on the farm and manure re- 

 turned, the lower will be the need for this plant food. The lesson there- 

 fore applies most particularly to farms where the supply of manure is 

 deficient, and particularly to those where hay is cut for market, or where 

 tobacco, onions or other money crops are raised continuously on the same 

 land. 



5. The use of lime in the cropping system followed has increased very 

 significantly the size of crops. Apparently, however, it has had no effect 

 on the availability of soil potash. 



6. The tests show the great dependence of clover on a generous supply 

 of lime, potash and phosphoric acid. They demonstrate a principle which 

 is believed to be of almost universal application. 



7. Soluble phosphates function in reducing, although not in eliminating, 

 the crop damage caused by "acidity" or lack of Hme. 



8. Crops vary enormously in their response to the different plant foods. 

 Except for corn and for grass and clover, however, the number of tests on 

 individual crops is too small to permit of safe generaUzation. 



