Íslenskar landbúnaðarrannsóknir - 01.09.1982, Side 57

ÍSL. LANDBÚN.
J. AGR. RES. ICEL.
1982 14, 1-2: 55-68
Spring Grazing on Icelandic Rangelands:
a Review of Factors to Consider
Steve Archer
Range Science Department and. Natural Resource Ecology Laboratoiy, Colorado State Vniversity. Fort Collins, Colorado
USA 80523
and
Andres Arnalds
State Soil Conservation Sevice of Iceland, Reykjavík, Iceland
ABSTRACT
Cropping ofvegetation by animals upsets and alters normal plant growth and development. Preliminary
results from Icelandic grazing trials in Solvaholt and Kelduhverfi indicate that heavy grazing early in the
growing season can dramatically decrease plant vigor and production. Gaps in our knowledge of range
plant physiology are currently limiting the accuracy and precision with which we can predict
productivity of grazed rangelands. These gaps also represent “unknowns” with regard to predicting and
assessing the degree to which key range plants can tolerate biotic and abiotic stresses while maintaining
their productivity on a sustained-yield basis. This article will discuss (1) why proper turnout dates are
inportant to plant productivity; (2) why proper tournout dates might optimize financial returns in
pasture and rangeland systems; and (3) research needs and priorities in these areas.
INTRODUCTION
The timing of the initiation of spring
grazing of hayfields, pastures, and range-
lands in Iceland is ofvital importance with
regard to subsequent plant and animal
productivity. Classical grazing system
management schemes, such as rest rota-
tion, do not generally apply to Icelandic
grazing lands. In Iceland, livestock are
typically transferred from winter housing
units to hayfields and lowland pastures
which are grazed until highland ranges
become accessible. These highland ranges
are then continuously grazed by livestock,
primarily sheep, for the remainder of the
growing season. The time or plant develop-
mental (phenological) stage at which
grazing can be safely initiated in the spring
is a controversial topic among farmers and
range managers. Due to lack of quantita-
tive information, there are, at present, no
firm guidelines to dictate when to begin
spring grazing in Iceland. As a result,
grazing is commonly initiated too early in
the plant’s growing season. The practice of
turning sheep and horses onto rangelands
before the plants are physiologically suited
for grazing can accelerate range deteriora-
tion and lead to decreased short- and long-
term profits as stocking rates and animal
gains will be subsequently reduced.