248 Bureau of Farmers' Institutes. 



9. The most advantageous methods of using farm-produced 

 manures. 



10. The use of green manures. 



11. Rotation of crops. 



12. The use of lime on soils. 



13. Plant-food mixtures for different crops. 



1. Under What Circumstances Should a Commercial 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 fer- 

 tilizers will result in increased crops and profit. When the far- 

 mers' crops cannot get from the soil as much nitrogen, potash and 

 phosphoric acid as they need, and when the manure made on the 

 farm cannot supply the constituents in sufficient quantity, then 

 one may resort successfully to the use of commercial fertilizers. 

 One must secure an increase of crop sufficient to pay for the fer- 

 tilizer used and for the cost of labor in applying it, and have some- 

 thing in addition in order to make the use of commercial fertilizer 

 a paying operation. 



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, for example, a tendency to harden, causing lack of 

 porosity, which prevents the development of roots and thus limits 

 the feeding power of the plant Such condition may be overcome 

 by adding humus to the soil, together with proper tillage. Other 

 unfavorable conditions may be lack of moisture, retention of stag- 

 nant water, deficiency of lime, acidity of soil, climatic influences, 

 etc., which may interfere 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 unfavorable 

 conditions must, if possible, be removed to secure good crops; and 

 this, according to the demands of special cases, may be done by 

 irrigating, draining, deep culture, better plowing, harrowing, hoe- 

 ing, marling, liming, mucking, etc. 



It often happens that a soil contains an abundance of plant food, 

 most of which is in unavailable forms. Under such circumstances 

 an effort should be made to bring this food into an available con- 

 dition as rapidly as plants can use it. Briefly stated, this can be 



