FERTILIZERS FOR GRAPES 105 



Only vineyards in good condition respond to fertilizers. 



It is usually waste to make applications of fertilizers in 

 poorly drained vineyards, in such as suffer from winter cold 

 or spring frosts, where insect pests are epidemic and uncon- 

 trolled or where good care is lacking. The experiments fur- 

 nish several examples of inertness, ineffectiveness or failure to 

 produce profit when the fertilizers were applied under any of 

 the conditions named. They emphasize the importance of pay- 

 ing attention to all of the factors on which plant growth is de- 

 pendent. Moisture, soil temperature, aeration, the texture of 

 the soil, freedom from pests, cold and frosts, as well as the 

 supply of food may limit the yield of grapes. 



A vineyard soil may have a one-sided wear. 



It is certain in some of the experiments and strongly indi- 

 cated in others that the soil is having a one-sided wear that 

 only one or a very few of the elements of fertility are lacking. 

 The element most frequently lacking is nitrogen. Exception 

 will probably be found in very light sands or gravels which 

 are often deficient in potash and the phosphates; or on soils 

 so shallow or of such mechanical texture that the root range of 

 the vine is limited ; or in soils so wet or so dry as to limit the 

 root range or prevent biological activities. These exceptions 

 mean, as a rule, that the soils possessing the unfavorable qual- 

 ities are unfitted for grape-growing. The grape-grower should 

 try to discover which of the fertilizing elements his soil lacks 

 and not waste by using elements not needed. 



Grape soils are often uneven. 



The marked unevenness of the soil in the seven vineyards 

 in which these experiments were carried on, as indicated by the 

 crops and the effects of the fertilizers, furnishes food for thought 

 to grape-growers. Maximum profits cannot be approached 



