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

 - New York  Chemical  1948 
 - 358 p.  il. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>SUELO<br/>HUMUS<br/>ABONOS<br/>QUIMICA DEL SUELO<br/>FERTILIDAD DEL SUELO<br/>APLICACION DE ABONOS