Field Report by: Susan Heffernan, Silja Kuerzinger,
Jim Cupitt & Colin McKay
INTRODUCTION
From Monday, 23 till Thursday 26 February 1998 the senior Soil Science class from Sydney University were at the Australian Cotton Research Institute, located 25 km west of Narribri on the Wee Waa road, NSW.
The soils at the site were identified as Brown Vertosols or Dermosols (Australian Soil Classification System), which are typical of the deep, loamy, alluvial profiles that have formed on the Namoi flood-plains.
The purpose of the study was to have an in-depth understanding of management options when considering such things as irrigation scheduling, tillage strategies, salinity threat and traffic management at this particular site. The way this was carried out was to test a variety of features such as hydraulic properties, soil strength, thermal and electrical conductivities. Many of the entities were tested with a variety of different methods and equipment, which were also evaluated for their precision, practicality and any other perameters which may be need to taken into consideration for management regimes.
Over a cross-section of 45 meters, ten reference pegs were placed with
five-meter intervals between them. Half of the survey site, that is five
of the ten sites, were in a field that has been cultivated in the past.
And at the time of the experiments was in a tilled state, while the other
half of the reference pegs were in an adjoining field which is believed
to have never been cultivated and was covered with pasture. A further consideration
when analysing the results was to see the long term effect of tillage on
soil physical properties, and to work out if cultivation makes a significant
difference to a soils physical properties. After carrying out all the required
tests, the results that were collected were entered into spread-sheet on
computers to be analysed.
BACKGROUND HISTORY OF THE SITE
The Australian Cotton Research Institute was established in 1958 to research the most suitable crops for the Narrabri area. The area is situated on an alluvial flood-plain, which is characterised by an extremely flat landscape with thick alluvial profiles. The soil at the Cotton Research Institute is a grey cracking clay typical of Australian cotton areas.
The climate of the area is semi-arid, with approximately 600 mm annual
rainfall, but on average another 700 mm of irrigation water is applied
per year. The sources of this water are the Namoi River, Keepit Dam as
well as sub-surface bore water.
The purpose of the survey was to advise the owner with regard to management options when considering such things as irrigation scheduling, tillage strategies, salinity thread and traffic management. The soil physical properties measured and the tools used to measure them include:
Hydraulic Properties of the soil
Soil StrengthAfter the description of each properties, an overall discussion will be presented.
