Growth responses of several plant species to mycorrhizae in a soil of moderate P-fertility

Abstract

The growth of twenty plant species was compared under field conditions in a methyl bromide fumigated and non-fumigated soil. The non-fumigated soil had a wild endomycorrhizal flora and contained 100 μg/g of available phosphorus. No phosphorus was added to the soil but both fumigated and non-fumigated plots received a basal fertilization of 100 kg/ha N−NH4NO3 and 100 kg/ha K−KCl. Based on plant growth responses, three groups of plants were distinguishable. Plants from group I were mycorrhizal and had better growth in non-fumigated than in the fumigated soil. This group was the most important, including sixteen plant species. Stunting of plants from group I following soil fumigation was mainly attribuable to the destruction of mycorrhizae. Plants from group II (oat and wheat) grew equally well in non-fumigated and fumigated soils. For these plants which were mycorrhizal in the non-fumigated plots, the P-content of the soil was sufficient for growth and therefore no stunting was observed in the absence of mycorrhizae. Plants from group III (cabbage and garden beet) grew better in fumigated than in non-fumigated soil. Their better growth in fumigated soil was tentatively attributed to the destruction of soil-borne pathogens. They did not form mycorrhizae in non-fumigated soil.