THE TEXTURE OF THE SOIL 41 



chemical fertilizers are both amendments and 

 direct fertilizers, since they modify the structure 

 of the soil as well as add plant- food to it. 



59. The extraneous or supplementary ma- 

 terials (54) which directly modify the structure 

 of soils are those that make humus (33), 

 as green-manures, farm-manures, and the like. 

 Stable-manure is usually more important in im- 

 proving soil structure than in directly supplying 

 plant-food. 



4. Structure and Manures 



60. We have now seen that the farmer 

 should give attention to the structure of his soil 

 before he worries about its richness. The con- 

 ditions must first be made fit or comfortable 

 tor the growing of plants: then the stimulus 

 of special or high feeding may be applied. 

 But manures and fertilizers may aid in secur- 

 ing this good structure at the same time that 

 they add plant-food. Yet fertilizer, however 

 rich, may be applied to soils wholly without 

 avail; and the best results from condensed 

 or chemical fertilizers are usually secured on 

 soils that are in the best tilth. That is, it is 

 almost useless to apply commercial fertilizers 

 to lands that are not in proper physical con- 

 dition for the best growth of crops. 



