At the commencement of the study and at bimonthly intervals
for 2 years, plant height, number of leaves per plant and number
of leaves with herbivore damage were monitored. At the end of
the 2-year experimental period, pots were removed with the soil
and plants intact and transported to the laboratory. The pots
were removed and subsamples of roots were taken for ion
analyses. These roots were rinsed for 3 20 s in iso-osmotic
mannitol containing 2.5 mol m3 CaSO4 to remove soil and ions
from the root free space. Soil was removed from the remainder of
the roots by rinsing with tap water, plants separated into roots
and shoots, and fresh mass determined. Shoots were rinsed for
10 s in distilled water to remove surface salt. Roots and shoots
were oven-dried at 70 8C to constant mass, and reweighed. The
material was then ground in a Wiley Mill to pass a 40-mesh
screen and stored in plastic bottles. The number of leaves that
had holes, marginal bites and scrapes caused by leaf-mass
consumers (i.e. folivores) was counted at bimonthly intervals to
provide information on the effects on nutrient enrichment on
herbivory.