title: Symbiotic N 2 -Fixation Estimated by the (15) N Tracer Technique and Growth of Pueraria phaseoloides (Roxb.) Benth. Inoculated with Bradyrhizobium Strain in Field Conditions.
abstract: This field experiment was established in Eastern Cameroon to examine the effect of selected rhizobial inoculation on N2-fixation and growth of Pueraria phaseoloides. Treatments consisted of noninoculated and Bradyrhizobium yuanmingense S3-4-inoculated Pueraria with three replications each. Ipomoea batatas as a non-N2-fixing reference was interspersed in each Pueraria plot. All the twelve plots received 2 gN/m(2) of (15)N ammonium sulfate 10% atom excess. At harvest, dry matter yields and the nitrogen derived from atmospheric N2-fixation (%Ndfa) of inoculated Pueraria were significantly (P < 0.05) higher (81% and 10.83%, resp.) than those of noninoculated Pueraria. The inoculation enhanced nodule dry weight 2.44-fold. Consequently, the harvested N significantly (P < 0.05) increased by 83% in inoculated Pueraria, resulting from the increase in N2-fixation and soil N uptake. A loss of 55 to 60% of the N fertilizer was reported, and 36 to 40% of it was immobilized in soil. Here, we demonstrated that both N2-fixing potential of P. phaseoloides and soil N uptake are improved through field inoculations using efficient bradyrhizobial species. In practice, the inoculation contributes to maximize N input in soils by the cover crop's biomass and represent a good strategy to improve soil fertility for subsequent cultivation.
authors.affiliation: Center for African Area Studies, Graduate School of Asian and African Area Studies, Kyoto University, 46 Shimoadachi-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Papa Saliou
authors.initials: PS
authors.lastname: Sarr
authors.affiliation: Department of Plant Biology, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon.
authors.forename: Judith Wase
authors.initials: JW
authors.lastname: Okon
authors.affiliation: Regional Biocontrol and Applied Microbiology Laboratory, Institute of Agricultural Research for Development (IRAD), P.O. Box 2067, Yaoundé, Cameroon.
authors.forename: Didier Aime Boyogueno
authors.initials: DA
authors.lastname: Begoude
authors.affiliation: Center for African Area Studies, Graduate School of Asian and African Area Studies, Kyoto University, 46 Shimoadachi-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Araki
authors.affiliation: Department of Plant Biology, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon.
authors.forename: Zachée
authors.initials: Z
authors.lastname: Ambang
authors.affiliation: Graduate School of Agriculture, Soil Science Laboratory, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shibata
authors.affiliation: Graduate School of Agriculture, Soil Science Laboratory, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Funakawa