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EXPERIMENTAL ALTERATION OF SOIL MICROBIAL POPULATIONS FOR STUDYING EFFECTS ON HIGHER PLANT INTERACTIONS
Author(s) -
NEWMAN E. I.,
CAMPBELL R.,
ROVIRA A. D.
Publication year - 1977
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1977.tb02186.x
Subject(s) - lolium perenne , fumigation , trifolium repens , agronomy , monoculture , biology , soil water , lolium rigidum , lolium , ammonium , perennial plant , chemistry , poaceae , weed , ecology , organic chemistry , herbicide resistance
Summary In order to investigate how soil microorganisms can affect the balance between higher plants growing together, it would be desirable to have soils similar in chemical properties but differing microbially, and to be able to maintain differences for several months without special isolation techniques. Two methods for achieving this were tried. Firstly, soil was fumigated with two different chemicals, chloropicrin and methyl bromide. The second method was to sterilize the soil by γ‐irradiation and then add contrasting inocula, either seed‐washings, soil bacterial suspension or total soil inoculum. After treatment, the soils were placed in pots in a glasshouse. Lolium perenne, Rumex acetosa and Trifolium repens were grown on them, separately and in two‐species mixtures. The fumigation method proved unsatisfactory since the two treated soils differed significantly in ammonium content but only slightly in microbial abundance. The three inoculum treatments following irradiation resulted in large differences in abundance of various microbial groups, and some of the differences were still present after four months; ammonium contents of the three soils differed only slightly, though all three had much more ammonium than the untreated soil. Fumigation increased the growth of all three species in monoculture to about an equal extent but, in the two‐species mixtures, it altered the balance in favour of Lolium against Rumex and Trifolium , and in favour of Rumex against Trifolium. Irradiation increased the growth of Lolium but reduced the growth of Trifolium. Among the three inoculum treatments, all three species in monoculture showed faster growth with total soil inoculum than with seed inoculum in the early stages but the difference disappeared later. Following irradiation, the balance between species in mixtures was much as expected from monoculture growth; the one exception was Lolium v. Rumex , where bacterial inoculum gave a balance more in favour of Lolium than would be expected.