Trees and pastures - finding a balance

In this two-part excerpt from a longer presentation, Peter Simpson, Regional Director of Agriculture, NSW Agriculture, Goulburn, looks at the issues facing farmers as they contemplate the Landcare goal to plant more trees in the landscape. While Mr Simpson specifically addresses pastures versus trees on the higher-rainfall tablelands, the discussion is relevant across rural Australia and offers some strategies for developing appropriate farm plans. The second part, focusing on agroforestry vs pastures, will appear in the next issue of Ground Cover.

We have changed the vegetation pattern, be it pasture or trees, during the past 200 years and there is currently a great deal of soul-searching reflecting on causes and effects.

It is useful to have an overall vision, either for a catchment or for an individual farmer. My vision statement for my own farm near Collector is "to harmoniously develop and/or maintain the landscape in ways that protect or improve the natural resource base". One of my main objectives is "to maintain or increase ground cover with perennial species".

There is ample evidence to show that the need for trees in tablelands landscapes is indisputable. It is really a matter of determining what types of trees, where they best fit, and why.

The pluses for trees

Generally speaking, it seems that up to 10-15 per cent of most properties could be retired from active grazing and revegetated and the overall effect of stocking rates would be minimal. There is also the added bonus of:

  • reducing dryland salinity somewhere in the landscape
  • reducing pasture pest problems such as wingless grasshoppers which tend to have their major breeding sites on dry degraded ridges (it is known that wingless grasshoppers will not move through dense woodlots)
  • dealing with serrated tussock, one of the most-invasive, introduced noxious weeds which loves degraded pasture sites. Revegetation is an effective way of reducing and controlling this problem
  • attracting additional capital gains increases over time when resold (this has certainly been the case in Victoria and, according to local real estate agents, the same applies on the NSW Southern Tablelands)
  • reducing our import bill for timber (currently in excess of $3 billion/annum). There will be much more concerted action looking at trees as an enterprise in their own right, which fits very comfortably with the challenge that Australia must stabilise and progressively reduce greenhouse gas emissions with possible future carbon tax credit income
  • reclaiming degraded erodible sites, particularly non-arable acid soils.

The minuses

Like most things in life, not everything is 'beer and skittles' and there are some minuses for individual landholders. These include:

  • additional fencing and maintenance costs
  • many native and feral animals including kangaroos, wombats, foxes, rabbits, etc, quickly seize on the protection that windbreaks offer; controlling the feral plant and animal problem in these areas is difficult, time-consuming and costly
  • whilst there could well be off-farm benefits for a well-planned, integrated whole-farm plan involving revegetation, you still pay rates on your total land area irrespective of the cash flow it earns
  • though there is a need for revegetation and planting more trees, in some environments there could be selective harvesting of these trees and the right to harvest and current taxation and local government laws provide major hurdles.

On - farm action

How do you read your landscape and know how to arrive at a balance between trees and pastures? Here are some critical points.

  • Determine those areas that are arable (that is, trafficable with ground-driven machinery and able to be cultivated with minimal problems for crops or introduced pastures). Generally speaking, these areas are our most fertile soils even though they can become water-logged occasionally or discharge areas for dryland salinity, namely, mid to lower slopes and valley floors.
  • Non-arable areas provide major limitations for development options. Aerial pasture development is not suited to acid soil landscapes and is a high risk venture.
  • Slope, erodibility of soil type and aspect are all important features to consider. Shallow, low-fertility erodible soils with western aspects have major limitations for pasture growth, are generally the most exposed and therefore should be seriously looked at when considering the relative economics of trees and pastures as a collective mix.
  • Acid soils are widespread throughout the NSW Southern Tablelands - many of these are naturally acid though the problem has increased over the last 50 years with pasture improvement. In the arable areas where we can apply lime and incorporate this strategy with other pasture and development options, pasture still has a viable role to play in its own right.
  • Non-arable areas with acidity to depth (below 20 cm) result in major restraints on pasture productivity and development options. These areas should be non-destructively developed within the existing native pasture, depending on the species present, or should be seriously looked at for revegetation of trees.
  • Individual landholders need to identify and understand the major pasture and weed species present on their property, be they native, naturalised or introduced. There is no perfect grass or legume, each has its own combination of strengths and weaknesses. This diversity allows landholders choices when considering pasture development options that relate to the range of landscape features present on their properties.

It then becomes a matter of developing a whole farm plan and setting priorities for action that are compatible with the vision, resource base and enterprise requirements for each farm.

Features and broad options for land classes
Land class*Key featuresOptions
1-2
  • arable
  • high fertility
  • minimal erosion risk
  • non-acid (pH above 5)**
  • unlimited for both pasture and crop production in seasons when the amount and distribution of rainfall is adequate
  • high input-high output systems should work well
3
  • semi-arable
  • lower natural fertility
  • moderate acidity (pH 4.5-5.0)
  • moderate erosion risk
  • lower to middle slopes
  • irregular cropping
  • ground cover and pasture persistence important
  • maintain native pastures or non-destructively develop (e.g. direct-drill)
4
  • non-arable
  • low fertility shallow soils
  • acidic (pH below 4.5)
  • moderate to high erosion risk
  • middle to upper slopes
  • suitable only for permanent pasture
  • generally hostile
  • environment for most introduced perennial grasses
  • best suited to low-input system based on year-long green native grasses
  • manage to maintain pasture stability and ground cover
5
  • non-arable
  • low fertility shallow soils
  • acidic (pH below 4.5)
  • usually highly erodible
  • steep upper slopes
  • leave undisturbed to timber or revegetate
  • lightly graze to maintain existing native pasture/ ground cover
  • retire from agriculture for conservation

NOTES
* Land classes as per NSW Agriculture:

  • Class 1 — arable land suitable for intensive cultivation
  • Class 2 — arable land suitable for regular cultivation for crops but not suited to continuous cultivation
  • Class 3 — grazing land or land well suited to pasture improvement. It may be cultivated or cropped in rotation with pasture
  • Class 4 — land suitable for grazing but not for cultivation
  • Class 5 — land unsuitable for agriculture or at best suited to light grazing.
ul>** All pH measured by CaCI2 test