1. INRA (P.H., E.B., C.P., X.T.) and Institut de Recherche pour le Développement (L.B., A.B.), UMR Eco&Sols, 34060 Montpellier, France; and Department of Plant Nutrition, China Agricultural University, Key Laboratory of Plant-Soil Interactions, Ministry of Education, Beijing 100193, People’s Republic of China (J.S., F.Z.)