Evaluation of root effects on soil organisms under different fertilization regimes by comparing rhizosphere and interrow soil in a wheat field
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The aim of this study is to evaluate the effects of plant root on soil organisms. The response of soil organisms (microbes, nematodes, and microarthropods) to root and fertilization (four inorganic fertilization regimes and organic fertilization) was studied in a wheat field in Japan. Microbial substrate-induced respiration (SIR) and the population densities of nematodes and microarthropods in the rhizosphere and interrow soil were measured from April to June in 2004 and 2005. Application of inorganic NPK fertilizer had positive effects on the population densities of all three types of soil organism. Microbial SIR and the population density of bacterivorous nematodes were high in plots to which high levels of inorganic NPK fertilizer and/or ammonium nitrate for top dressing were applied. Application of ammonium nitrate increased the population density of microarthropods in 2005. Whereas organic fertilization regime had lower population density of nematodes and microarthropods than other inorganic fertilization regime having similar root biomass. Soil organisms in the rhizosphere and the interrow soil responded similarly to fertilization and, consequently, the rhizosphere/interrow ratio, defined by the ratio of the number of organisms per gram in rhizosphere soil to the number in interrow soil, was hardly affected by the fertilization regimes studied. The ratio indicated how much soil organisms were influenced by root. It was high for microarthropods population density and low for nematodes population density. Root biomass was strongly correlated with microbial SIR but it was not correlated with nematodes population density. With the results from the rhizosphere/interrow ratio and the correlations between soil organisms and root biomass, we suggested that fertilization affected microbial SIR and microarthropods population density through root. But the effect of root was not obvious to nematodes population density.
- Plant Root
Plant Root (1), 3-9, 2007
Japanese Society for Root Research