International tillage research organization :  12th international conference Ibadan, Nigeria 8-12th July 1991. 

 - Ibadan, Nigeria :  ISTRO,  c1991. 
 - 687 p. : ill. ; 24 cm. 
<br/><br/> Includes bibliographical references. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Tillage--Congresses.<br/>Soil management--Congresses.<br/>Sustainable agriculture--Congresses.