Hopkins, Donald Percy,  1909-, <br/><br/>
Chemicals humus, and the soil :  A simple presentation of contemporary knowledge and opinions about fertilizers, manures, and soil fertility. 

 - 288 páginas 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Humus<br/>Fertilizantes
<br/><br/><label>LC Class. No.: </label>S633  / H762