| dc.description.abstract | This study aimed at determining the presence of
mycorrhizal fungi in Kenyan soils. Using onion as a
test crop, the interaction between mycorrhizal fungi
and phosphorus was investigated in five different -
phosphorus de f i.c i.ent; Kenyan soils. Spore density of
mycorrhizal fungi determined by the Wet-sieving method
was used as an indicator of infection. There was a
significant variation in the spore population and
this ranged from 5 spores/g dry soil in Ferralsol to
11 spores/g dry soil in Luvisol.
Onions were planted in pots in a glass house
using the above soils. Some plants were raised in steam
sterilised soils while others were grown in unsterilised
s011s. Roots of plants grmm in unsterilised soils we re
heavily infected while the roots of plants in the
sterilised soils remained unjnfected. Plant growth
parameters namely fresh weight, dry weight, height, bulb
diameter and bulb fresh weight were larger for infected
plants than non-infected plants. These growth differences
were significant after eight wee ks of qrow+h , Increase
in shoot dry weight expressed as a percentage of the
non-mycorrhizal plants ranged from 990 - 6983% after
21 weeks of growth, wh i.Le the increase in percentage
phosphorus varied from 214% to 410%. The root:shoot
ratio was higher for non-mycorrhizal plants. It was
concludeo that mycorrhizal fungi enhances ~hosphorus
uptake and consequently promotes growth.
In another experiment, onions were grown in both
sterilised and unsterilised soils in which either
no phosphorus was added or phosphorus was added at
varying rates. It was observed that at 10,",' to moderate
levels of soil phosphorus, the mycorrhizal onions
performed better than non-mycorrhizal ,.ones
Infected plants also contained higher percentage
phosphorus in their tissue. However, at very high
phosphorus levels (100 ppm) both mycorrhizal and nonmycorrhizal
onions had comparable growth and tissue
phosphorus content. Hycorrhizal plants at 50 ppm of
phosphorus grew as well as non-mycorrhizal plants at
100 ppm of phosphorus. Thus mycorrhizal fungi contributed
approximately 510 ppm of phosphorus. These results
demonstrated that mycorrhizal infection may have practical
significance in low phosphate soils but not at high
soil phosphorus concentration.
It was concluded that onions are dependent on
vescular arbuscular mycorrhizal fungi for normal growth
and development. It was recommended that similar
experiments be, extended to other Kenyan soils and other
crops to ascertain the presence and importance of
mycorrhizal fungi.
Therefore, it was concluded that onions are
dependent on vescular arbuscular mycorrhizal
fungi for normal growth and development. It was
recommended that similar experiments be extended
to other Kenyan soils and other crops to ascertain
the presence and importance of mycorrhizal fungi | en |
