Effects of nitrate and ammonium nitrogen on vesicular-arbuscular mycorrhizal infection in lettuce (Lactuca sativa) grown in sand with nutrient solutions.
1991
Owusu-Bennpah, E., Department of Soil Science, Faculty of Agriculture, University of Ghana, Legan, Ghana.
The amount of vesicular-arbuscular mycorrhizal infection in plants fed with nutrient solution was studied in sand culture. Complete nutrient solutions containing 0, 5, 10.20 and 40 ppm N as NaNO" NH4NO, or (NH4),S04 were added twice weekly to lettuce (Lactuca sativa vaT. Tom Thumb) plants grown in sand and inoculated with Glomus fasciculatus similar to the spore type E, endophyte of VA mycorrhizae. Plants given up to 20 'ppm N as (NH4),S04 had up to about 50 per cent of their roots infected but this fell to 7 per cent with 40 ppm N. The pH's of the nutrient solutions in the pots fell from 6.0 to about 5.0 and 5.6 for those containing (NH4),S04 and NH,NO, respectively. whereas there was little or no change with NaNO,. However, all the pH's were within acceptable range for E, endophyte. They support the view that levels of VA infection in the field may be controlled as much by nitrogen fertilizer as by phosphate le'fels in the soil.
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