Populations of vesicular-arbuscular mycorrhizal (VAM) fungi and mycorr
hiza formation were examined in a field experiment studying the agricu
ltural application of composted animal manures, The replicate experime
nt allowed each crop of a Zea mays > vegetable > small grain rotation
to be sampled each of 3 years, Chicken litter/leaf compost and dairy c
ow manure/leaf compost enhanced spore populations of two VAM fungus sp
ecies type groups (Glomus etunicatum type and the general Glomus spp.
group, including G. mosseae) relative to those found in plots treated
with raw dairy cow manure and conventional fertilizer, Populations of
other groups were not affected by amendment, due likely to the large a
mount of P added in composts and manure relative to the conventional f
ertilizer applied, Crop rotation point had consistent, significant eff
ects, with both lower populations of spores and less mycorrhizal infec
tivity of soil in plots after the vegetable crop (Spinacea oleraceae a
nd/or Capsicum annuum) relative to maize and small grain (Avena sativa
or Triticum aestivum). This was due to the non-mycorrhizal status and
very low mycorrhization (approximately 1% root length colonized) of S
. oleraceae and C. annuum, respectively, Future agricultural applicati
ons of compost and manure to provide N for crops need to consider the
effects upon VAM fungi of other nutrients in these amendments. (C) 199
7 Elsevier Science B.V.