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• What labour and inancial resources are available for forage development and management?
• How many livestock require feeding? • What type and class of livestock require feeding?
• What level of production is expected? • What other sources of feed are available?
• What is the feeding value of all these feeds? • How will livestock be fed during winter?
• Is the forage permanent or a short-term forage? i.e. will the forage be part of a crop rotation?
• How will the forage be utilised - grazed or conserved?
• What forage species are adapted in the area? • Which forage species are best suited to the farming
system? These questions help to deine the role of the forage in
a particular farming system.
9.2.1. Plant Adaptation
Plants have evolved to grow and reproduce under a particular range of environmental conditions, and in
general, the further they are removed from their native environment, the less thrifty they become. For example,
some plants grow in deserts, others in swamps; some grow in fertile soils, others in infertile soils; some grow
in cold climates, others in hot climates. There is also considerable variation between and within plant species
in their adaptation to various soil conditions.
Plants that are eaten by animals also have developed speciic adaptation to frequency and intensity of
defoliation. Plants that are rarely grazed or browsed in their native environment tend to be taller and more
upright than those that are frequently heavily grazed, the latter often being more prostrate, with stems that root
down on the soil surface stolons or even creep below the soil surface rhizomes.
It is important, therefore, to know the characteristics of plants, their tolerances and susceptibilities to ensure that
they are compatible with the system into which they will be introduced. Use of plants that are poorly adapted
to the local environment will result in an unsustainable system.
9.2.2. Forage Species
Most sown forages come from the two large groups of lowering plants; the grasses and the legumes. About
10,000 grass species and 18,000 legume species have been identiied around the world. Apart from this
large number of species, there are many genotypes within each species, giving enormous variation overall.
However, not all grasses and legumes are eaten by grazing animals and not all legumes ix nitrogen.
Over the years, researchers around the world have identiied species in the various agro-ecological zones
with characteristics that might be valuable in sown pasture systems good palatability and feeding value,
wide adaptation, persistence under grazing etc.. Large collections of genotypes within these species have
been made by trained plant collectors, and saved in seed banks called Genetic Resource Centres in many
of the key countries. New varieties are produced from research programs selecting the best types from the wild
collections, or breeding programs designed to combine useful traits identiied in the various wild species.
Forages are classiied in various ways; on the basis of plant relationships, plant types, or adaptation Table 9.2.
Hence, a producer might need a late lowering, perennial grass, adapted to a poorly drained, infertile clay soil to
satisfy the forage needs in their particular system.
9.2.3. Legumes
Legumes are a group of lowering plants that produce their seeds in pods. What makes legumes diferent
from most other plants is the ability of many of them to extract nitrogen from the atmosphere by using a
symbiotic relationship with bacteria rhizobia in root appendages called nodules.
Why is this important? Since nitrogen is the basis of all proteins, the productivity of agricultural systems is
therefore strongly related to the amount of available
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Cold Winter Climates
nitrogen in that system. Unfortunately, atmospheric nitrogen cannot be used directly by plants, but can be
used by certain microorganisms, including rhizobia. The rhizobia form a mutually beneicial relationship with the
legume, the bacteria obtaining nutrient from the plant and the plant obtaining “ixed nitrogen” in the form of
ammonia NH
3
from the bacteria. As a result, legumes generally have a high level of protein
and non-protein nitrogen in their tissues without the addition of nitrogen fertilisers. This characteristic can be
used to provide high quality feed for livestock and to improve soil fertility. A very vigorous legume can ix over
500kgha of nitrogen equivalent to over one tonne of urea, although in most cases, the amount of nitrogen
ixed is considerably less, averaging about 100kgha. Legumes ix most nitrogen when growing conditions
are best; with adequate moisture and temperature, and soil fertility, particularly phosphorus, sulphur and
molybdenum. The amount of nitrogen ixed is closely related to the amount of legume leaf per unit area. A
sparse stand of heavily grazed legume may ix as little as 10kgha of N.
In countries with cold climates, legumes that are sown for use in pastures for grazing animals are
typically perennial species that persist for a number of years under ideal growth and grazing conditions
Table 9.3. Annual legumes are not widely sown in these areas. However, the potential exists to
utilise annual legumes such as subterranean clover Trifolium subterraneum, balansa clover Trifolium
Table 9.2. Forage classiication systems.
Characteristic Categories
Plant family • grass Poaceae, formerly Gramineae
• legume Fabaceae, Mimosaceae, Caesalpinaceae, formerly all grouped in Leguminosae
• other - includes brassicas Brassicaceae, formerly Cruciferae, daisy group Asteraceae
Preferred environment • temperate
• Mediterranean • subtropicalupland tropical
• tropical wet tropics, seasonally dry tropics
Growth cycle • annual
• perennial • biennial
Growth habit • herbaceous stoloniferous, rhizomatous, upright, prostrate etc.
• sub-shrub small woody-stemmed plant • shrub large, multi-stemmed woody plant
• tree
Flowering time • early
• mid-season • late
Soil adaptation • texture sand, loam, clay etc.
• fertility low, medium, high • drainage
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michelianum, and annual medics Medicago spp. in improved pastures, and local evaluation is required to
assess their potential.
9.2.4. Grasses
