PASTURE PLANT IDENTIFICATION

Often we do not realise the significance of many plants that we take for granted. Grasses for example have an affect on the daily life of every person, sometimes we forget that sugar we use daily and basic foodstuffs such as bread all come from the grass family of plants. Even the lemon scent in some detergents comes not from the lemon as we are led to believe, but from lemon grass.

In pastures there are many plants of significance that we recognise, but often do not know how important they are. In contrast everyone realises the importance of finding a weed such as parthenium in our pastures. A good start to m ore informed management of your pastures is to do a Grasscheck workshop.

TYPES OF PLANTS

Annuals and weak perennials: plants that live for one or a limited number of growing seasons.

Perennials: plants with variable life spans, from a year to decades

In the grazing situation the main plants we are concerned with are:

Grasses: low growing vegetative plants that can tolerate grazing.

Forbs: non-woody broad leafed plants.

Legumes: plants with a varying ability to fix nitrogen with the help of bacteria in root nodules.

Sedges: grass like plants eg: nutgrass.

Woody weeds: plants with the ability to compete with pasture plants for sunlight, nutrients and mousture.

Other weeds: any undesirable plant in a pasture that affects carrying capacity of the pasture due to its un-palatability, competition with more favourable species or presence of poisonous principles.

FEATURES OF A HEALTHY PASTURE

A healthy pasture has

· High percentage of Palatable, Productive, Perennial grasses (3P grasses)
· Small numbers of annuals plants eh: small burr grass
· Small numbers of weeds eg: verbenas
· High frequency of desirable forbs eg: native legumes such as glycine
a variety of favourable species.

WHAT AFFECTS PASTURE CONDITION AND QUALITY?

· Climate
· Soil
· Pasture Plants
· Grazing

All these factors interact to determine the quality, quantity and sustainability of our pastures for stock.

Climate

· Rainfall and the climate are one of the main effects on our pastures. Given the wide variation in climate that we have it is un-reasonable to expect that we should have similar pasture bulk and quality every year.

· The nutritive value of a plant varies with the seasonal conditions and the soil fertility. Often in years of high rainfall, plant yeild m ay be high, by protein is low. The opposite can be the case in lower rainfall years. Frost, wind, humidity and heat can also impact on pasture quantity and quality.
 

The amount of effective rainfall is determined by a combination of the following factors:

· Pasture condition & type and species(table 1),

Table 1 : Pasture condition and type and the
Effect on erosion, run-off and infiltration.

· Soil condition and type - aggregate structure, pore size and amount of organic matter and minerals.
· Rainfall intensity
· Evaporation & slope
· Tree cover

Soil
· Generally the better the soil the better the pasture. While we often look at a particular grass as being very good for stock feed, the protein of that grass varies depending on the soil fertility. Phosphorus is generally the most common nutrient that is lacking in soils that restricts growth of pasture.
· Organic matter is an important soil component it provides plant nutrients, binds soil aggregates, improves infiltration, provides food for soil micro and macro organisms. Low organic matter leaves makes the soil a difficult environment for plant growth.
· Once pasture cover drops below 40% to 50% there is a serious risk of soil erosion occurring du to increased runoff. A healthy, growing speargrass pasture, 10cm tall, gives 30% ground cover.

· Much of the fertility in our soils is carried in the top 1 to 3 centimetres of the progile so it is imprtant to maintain this part of the resource. A pasture that is composed of annuals and large areas of bare earth soil looses significant quantities of fertile topsoil every year as shown below in Figure 1.

Pasture plants

· Native pastures (90% Qld pastures)
· Native pastures + legume
· Sown pastures

Native Pastures

Often under utilised & undervalued

Cheap resource-1 kg of liveweight gain inn cattle on grass costs 1 to 6 cents
1 kg of liveweight gain in cattle on grain costs app $1.60

Still contribute most of Queenslands primary production
Usually benefit from judicious burning
Careful management can be productive and profitable

Native pastures + legume

Oversowing of legumes into existing pastures tropical & sub-tropics - Stylos, Wynn Cassia clovers &medics-temperate areas - medics, clovers cost effective way of increasing production.
 

Sown pastures

Most productive - most expensive
Usually run down after 5-8 years due to loss of nitrogen
Will need up-keep with fertiliser, renovation and careful management

What is a Palatable and Productive grass?
Leafiness is the key to palatable and productive grasses and it varies between plant parts and the season.
 

· Leafiness varies with pasture species as seen in Table 3. Below:

Spelling pastures

Grasses need a spelling period if they are to set seed and produce to their maximum potential, especially after burning or heavy grazing.

Fire

Fire can be a useful tool for pastures if used correctly. In the speargrass region it is recommended that burning be carried out every 3-4 years. This however will depend on the season, stocking rates and your aims for the pasture.

Timber and woody weeds

The density of woody weeds affects pasture growth. Generally the less trees and woody weeds the more water that is available for pasture growth. However in the very long term a correct balance of trees and pastures is the best for maximum production and sustainability.

Grazing

· Stock select the highest quality diet possible
· Increasing the stocking rate reduces the animals ability to select and reduces the quality of the diet
· Forcing stock to eat more than leaf(eg:stem) will reduce weight gains per head
· Pasture grasses have about 25-45% leaf so aim to utilise this amount of pasture over twelve months

· 25-45% (approx 1/3) utilisation of grass plant affords stock the best quality diet and avoids overgrazing the pasture (see diagram below).
· Stock continually eating off the green shoots of grass as it emerges do not give the plant the ability to build up reserves of carbohydrate in the roots. This results in root loss and a resultant loss in the productivity of the plant (see diagram below).

· As the number of stock grazing on a pasture increases the potential liveweight gain decreases. Increased stocking pressure results in the loss of more palatable pastures species and eventual pasture decline (see figure 4: weight gain vs stocking rate).

Setting a Carrying Capacity

· determine the amount of feed available
· aim to utilise between 25-40% of feed grown, this will:

-give stock the best quality diet
-allow grasses the opportunity to grow to their best potential

· budget to leave a proportion of feed for:

- trampling by stock
- ground cover
- decompostition and use by other fauna

Compared to cattle, goats have:

· a larger mouth for the size of their heads - enables them to strip twigs, leaves, or flower heads from the fibrous stems often found in weeds.
· A longer mobile tongue, which provides greater dexterity for removing selected plant parts.
· A mobile upper lip which improves dexterity for removal of plant parts.
· A salivary gland tht has greater weight for their size - a possible counter adaptation to overcome the chemical defenses of some plants.

Grazing habits of goats:

· Are browsers as opposed to being grazers.
· Select a bite here and there from a variety of plants.
· Often consume up to 25 different plants, definite preference for a varied diet.
· Can distinguish between bitter, salt, sweet and sour tastes.
· Have higher tolerance for bitter tasting plants.
· Browsing propensity for bark, leaves, shoots, shrubs and branches.

Pastures for goats:

Due to a goats grazing preferences and ability they need:
A wide variety of plants, grasses, legumes, forbs and browse.