Hopkins, Donald P. <br/><br/>
Chemicals, humus, and the soil : a simple presentation of contemporary knowledge and opinions about fertilizers, manures, and soil fertility  a simple presentation of contemporary knowledge and opinions about fertilizers, manures, and soil fertility 

 - vii, 358p. :   il. 
<br/><br/> Bibliogtaphy;: p.347-349 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Agronomía