Walk through the decades…

Controlled Traffic Drainage Project

Researchers: Peter Kealy (SFS), Bruce Wightman (DNRE- Geelong)

1999 SFS Trials Results Book

Background

Poor soil structure combined with high winter rainfall throughout much of south western Victoria produces conditions almost every year which results in waterlogged crops.

Farmers cropping well drained soils are obtaining cereal yields over 5 t/ha and canola yields over 3 t/ha. For example, the introductions of the premium malting barley Franklin has given many farmers a new target in expected yield-some farmers are consistently producing yields over 7 t/ha.

The new canola varieties including Dunkeld and Triazine resistant types have taken the risk out of this excellent break crop.

The release of the red wheat varieties with their early sowing capability has given farmers the means to take advantage of an early break and fully utilised the long growing seasons. Crop nutrition has also gone ahead in leaps and bounds in recent years soil testing, tissue testing, sap testing and nitrogen test strips have all led to a much improved management of crop nutrition.

Although these breeding and agronomic advantages have produced wonderful benefits, they have predominantly been on well drained soils. Waterlogging remains the biggest constraint to have crop expansion and improved yields over a large part of the southwest. There is a limited number of well drained paddocks in southwest Victoria. With the average cost of producing a cereal crop over $185/ha and canola over $250/ha, farmers have naturally been reluctant to expand their cropping programs except on good country programs or expanding their current program.

The key to further crop expansion and improved yields with reduced risk is the development of cheap and effective drainage techniques suitable for southwest Victoria. In 1996 our drainage project consisted of four treatments these included wide (20m) raised beds, an underground system including plastic pipes and moles, a control and narrow 1.5 metre raised beds.

Results

The wide raised beds, underground and control, were sown with a Napier Trask cult drill while the narrow beds were sewn with a cone seeder. The narrow beds have not been maintained since installation in early 1996. The shoulders of the beds were quite rounded and the cone seeder could not sow at an even depth across the bed. Poor establishment was obtained on the narrow beds while the remainder of the site established reasonably well. Due to this discrepancy in establishment final yield data was not collected. For the SFS November field day soil pits were dug across the site to ascertain the subsoil condition under each treatment and the plants’ rooting depth.

The main observation was that the field pea roots did not penetrate very far into the subsoil which remains dense and quite hostile under each treatment, even though extremely good moisture prevailed. The topsoil on the narrow raised beds was very friable and more friable than all of the other treatments. The challenge is to determine how we can enhance the subsoil conditions to allow easy root penetration and survival. At the moment the subsoil is usually cracked open in the autumn and early winter and this would probably be quite attractive to plant roots. However by the time the plants establish a root system excess rainfall has fallen and the subsoil swells and becomes anaerobic.

	20m Beds	Underground Drainage	Control	1.5m Beds
1996 Canola	3.52 t/ha	3.52 t/ha	2.2 t/ha	3.45 /ha
1997 Barley	6.55 t/ha	6.90 t/ha	5.7 t/ha	6.30 t/ha
1998 Wheat	4.85 t/ha	5.70 t/ha	4.80 t/ha	4.30 t/ha