New York Agricultural Experiment Station. 83 



soil and crop may not need, for only one or two of the three chief 

 fertilizing constituents (nitrogen, potash and phosphoric acid) may 

 be needed ; and, indeed, it may be that some pliysical condition of the 

 soil is wrong and that plant-food of any kind is not really needed at all. 

 In selecting fertilizers for use, we need to consider several im- 

 portant questions, such as the following : 



1. Under what circumstances a fertilizer should be nsed. 



2. What constituents of plant-food are needed. 



3. In what forms it is best to buy such plant-food as is needed. 



4. What amount of each fertilizing constituent is needed. 



5. Specific mixtures for different crops. 



6. Which is more advantageous, to purchase complete fertilizers 

 or to purchase separate ingredients ? 



7. To what extent home-mixing is practicable. 



8. Special suggestions in connection with the purchase of separate 

 ingredients. 



9. Methods and seasons of applying fertilizers. 



10. The most advantageous methods of using farm-produced 

 manures. 



1, Under what Circumstances should a CoMiiERciAL Fer- 

 tilizer BE used. 



One must resort to the use of commercial fertilizers when he has 

 exhausted all of the resources of the farm in producing his own 

 fertilizing materials and finds that the use of commercial fertilizers 

 will result in increased crops and profit. When the farmer's crops 

 can not get from the soil as much nitrogen, potash and phosphoric 

 acid as they need, imd when the manure made on the farm can not 

 supply the constituents in sufficient quantity, then one may resort 

 successfully to the use of commercial fertilizers. 



However, one must distinguish between lack of plant-food in the 

 soil and other conditions which prevent good crops, for lack of food 

 is not the only cause that makes crops suffer. In some soils there is 

 insufficient porosity, which causes the developement of the roots to 

 be checked. Lack of moisture, caking of soil, retention of stagnant 

 water, deficiency of humus, lime, etc., unfavorable weather and 

 other conditions may interefere with the healthy growth of plants 

 and thus cause diminished crops, even when the plant has within 

 reach all the food it needs. Under such circumstances, the unfavor- 

 able coudiii.iiis must be removed to secure good crops, which, 



