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Bradyrhizobium Inoculation and Nitrogen Fertilizer Effects on Seed Yield and Protein of White Lupin
Author(s) -
Ayisi K. K.,
Putnam D. H.,
Vance C. P.,
Graham P. H.
Publication year - 1992
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1992.00021962008400050018x
Subject(s) - lupinus , inoculation , agronomy , fertilizer , biology , loam , bradyrhizobium japonicum , yield (engineering) , point of delivery , bradyrhizobium , nitrogen fixation , zoology , horticulture , rhizobium , symbiosis , soil water , rhizobiaceae , bacteria , ecology , genetics , materials science , metallurgy
Variation in seed yield and protein levels of sweet white lupin ( Lupinus albus L. cv. Ultra) in the North Central USA has limited production of the crop in this region. Poor N nutrition from biological or exogenous sources may be one of the causes of this variation. Studies were conducted under irrigation in 1988, 1989, and 1990 at Becker, MN, on a Hubbard loamy sand (sandy mixed udorthentic haploborolls) to examine the impact of Bradyrhizobium inoculation and N fertilizer on lupin seed yield, protein concentration, and yield components. Bradyrhizobium sp. ( Lupinus ) strains (WU425 and 96B15) were compared separately with non‐inoculated lupin controls in 1988 and then in combination in a 1:1 cell ratio in 1989 and 1990 at four concentrations of N fertilizer (0, 56, 112, 168 kg N ha −1 ). There were no significant differences in seed yield or protein between the two strains in 1988 but there was a trend for higher yield with WU425. Seed yield of inoculated plots was increased by an average of 51% in 1988 and two to five fold in 1989 and 1990, respectively, compared with noninoculated controls. Yield increases were due to changes in pod number or seed weight, depending upon the year of evaluation. Inoculation resulted in seed protein increases 28 to 45% greater than non‐inoculated controls at zero N. Symbiotic N 2 ‐fixation by the difference method contributed 63 to 85% of seed N but these amounts decreased with addition of N fertilizer. Nitrogen fertilizer did not significantly increase seed yield, protein content, or protein yield of inoculated plants and seed yield of inoculated plants at zero N was always greater than that of well fertilized non‐inoculated plants. These results indicate the importance of Bradyrhizobium symbiosis in white lupin for both maximum seed yield and seed protein. Addition of N fertilizer to effectively nodulated lupin offered no advantage for either seed yield or protein.