Am. Martensson et K. Carlgren, IMPACT OF PHOSPHORUS FERTILIZATION ON VAM DIASPORES IN 2 SWEDISH LONG-TERM FIELD EXPERIMENT, Agriculture, ecosystems & environment, 47(4), 1994, pp. 327-334
The presence of vesicular-arbuscular mycorrhizae diaspores in two long
-term Swedish field experiments at Ultuna and Offer was studied. The n
umber of diaspores decreased rapidly over time with increasing annual
additions of an easily soluble phosphorus fertilizer, 45 kg P ha-1 yea
r-1. Five years after the start of the experiment, at this level of fe
rtilization, the spore frequencies were reduced by 50% and 7% at Ultun
a and Offer, respectively. The spore frequencies later stabilized and
fluctuated between 0.08 and 0.56 diaspores g-1 of soil. Moderate addit
ions of easily soluble phosphorus fertilizers, 5 and 15 kg P ha-1 year
-1, did not affect spore frequencies, which fluctuated between 0.48 an
d 1.96 diaspores g-1 of soil. When excluding phosphorus fertilization,
spore frequencies doubled within 5-14 years. Twenty-eight years after
the start of the experiment, the spore frequencies of the zero-phosph
orus fertilized soils had doubled and trebled, respectively at the two
locations. The phosphorus additions increased the amounts of easily s
oluble phosphorus in the soils, which adversely affected the diaspores
. No relationships existed between the number of VAM diaspores and oth
er soil parameters such as the amount of difficultly soluble phosphoru
s, pH, organic matter, or total nitrogen content. A plant-production p
arameter, estimated as dry matter production, was independent of the p
resence of VAM diaspores but another plant production related paramete
r, uptake of phosphorus by the plants, was dependent on the presence o
f VAM diaspores.