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Effect of Phosphorus on the Effectiveness of Strains of Rhizobium japonicum
Author(s) -
Singleton P. W.,
AbdelMagid H. M.,
Tavares J. W.
Publication year - 1985
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1985.03615995004900030016x
Subject(s) - shoot , bradyrhizobium japonicum , nitrogenase , phosphorus , dry weight , nitrogen fixation , biology , zoology , rhizobium , symbiosis , horticulture , chemistry , agronomy , rhizobiaceae , inoculation , bacteria , genetics , organic chemistry
We examined the relationship between P nutrition of soybean [ Glycine max (L.) Merr. cv. ‘Davis’] and N 2 fixation by five strains of Rhizobium japonicum ranging from an ineffective (SM‐5) to a highly effective (USDA 110) symbiosis with soybean. Phosphorus at 0, 50, 125, and 400 mg P kg −1 soil (P 0 , P 50 , P 125 , P 400 ) as Ca(H 2 PO 4 ) 2 · H 2 O was applied to pots containing 2.7 kg of a P‐fixing humoxic tropohumult free of R. japonicum . Treatments consisting of + N and five strains of R. japonicum and the four P treatments were arranged in a complete factorial replicated three times. With 400 mg P kg −1 soil treatments ranked + N > USDA 110 > USDA 31> USDA 123> USDA 33>SM‐5 for shoot dry weight and accumulation of N in the shoot. There were no significant strain effects for shoot dry weight, shoot N or nodule activity at P o . Strain rankings were the same at the intermediate levels of P but differences were smaller. Although nodule number was somewhat enhanced by P, it bore no relationship to strain effectiveness and was not a factor limiting N 2 fixation at low P. Nodule dry weight and nitrogenase activities significantly increased with P additions. The concentrations of N and P in the shoot also increased with P additions. The concentrations of shoot P and N were higher in plants provided mineral N at the low and intermediate P levels than in the inoculated plants. The results show that P nutrition is important in interpreting the N 2 fixation capability of strains of Rhizobium . Synergism between P and Rhizobium inputs requires that to obtain maximal response to the application of one input necessitates employing the other at maximum levels.