Soil improvement and adaption of cultivation practices on low yielding soils

abonos abonos nitrogenados amendement organique analyse de sol aradura avena fatua chaulage clay soils cultivos de invierno cultivos de primavera culture d'hiver culture de printemps encalado engrais essai fertilidad del suelo fertilizers fosfatos labour labranza del subsuelo liming manejo del suelo mise en valeur du sol nitrogen fertilizers organic amendments perfil del suelo permeabilidad permeability phosphate phosphates pisum sativum ploughing precipitation profil du sol pruebas reclamation rendement rendimiento rotation culturale rotational cropping silty soils soil fertility soil management soil profiles soil testing soil texture sol argileux sol limoneux sous solage spring crops subsoil subsoiling subsuelo suelo arcilloso suelo limoso textura del suelo texture du sol trials triticum water holding capacity winter crops yields