Changes in productivity of exposed alluvial soil by removal of surface volcanic ash soil

abonos agricultural chemicals amendement du sol andosol andosoles andosols biogeografia biogeographie biogeography biota biote chemistry chimie chimie du sol engrais engrais organique enmiendas del suelo environment environnement estructura del suelo farmyard manure fertilizantes fosfatados fertilizers flora flora del suelo flore flore du sol fosfatos genetic soil types geografia geographie geography inorganic compounds manejo del suelo medio ambiente mise en valeur du sol phosphate phosphate fertilizers phosphates produit agrochimique sales salts sel site factors soil amendments soil chemistry soil flora soil management soil morphological features soil structure soil types structure du sol trait morphologique du sol type de sol