No Tillage and Stubble Retention

No tillage and stubble retention commenced in 1983. The system produces crops whilst maintaining surface soil cover at all times. Since 1983, all crop residues were retained and continuous cropping was commenced using no tillage/stubble retention (NT/SR).

With the forecast of the severe drought in July 1982, all livestock was sold whilst the pasture paddocks still had sufficient dry matter to prevent wind erosion. However, the severity of the drought resulted in dust storms from cultivated fallow paddocks in early 1983. Thus to eliminate any future loss of top soil, all fallow utilizing cultivation for weed control and water retention ceased. Cultivation was replaced with herbicides.

After the removal of livestock, pasture was replaced with grain legume crops to introduce another source of nitrogen. This improved soil fertility, provided a disease break and increased income. Legume crops included chickpea, fababean, and lupin. Barley, canola, safflower and linola were also introduced to the rotation to provide further disease breaks for cereal crops, as was linola in 1994. Canola, being a high value crop, also had the added advantage of providing another crop to reduce the financial risk of having only a few crops in rotation.

In a dryland farming situation where crop yields are totally dependant on rainfall for production, crop yields should be measured in terms of water use efficiency and measured in terms of crop yield per mm Growing Season Rainfall.

Wheat is the most consistent cereal crop in terms of production. Prior to 1982, with all crops grown following ten months of cultivated fallow, the trend in wheat yields rose. After 1982, without a fallow period, and with all crops sown directly into stubble using no tillage and stubble retention, wheat yields still continued to rise.

No tillage starts at harvest by harvesting the straw short enough to enable trouble free seeding. The chaff must also be evenly distributed across the swath widths. To assist with chaff spreading all harvesters need an upgrade in straw and chaff spreaders. This achieves an even distribution across the swath width of the harvester. Soil surface cover eliminated wind erosion and reduced the evaporation. It slowed down the movement of water on the soil surface and allowed more water to infiltrate eliminating water erosion.

All no tillage seeding is carried out with knife points for minimal soil disturbance. Wide row spacing (usually 14 inches) is used to reduce blockages at seeding time. Wide rows increase fertilizer concentration with the seed. Therefore fertilizer is deep banded below the seed. Deep banding of the fertilizer cultivates a band below the seed zone which reduces the incidence of a serious plant root disease namely Rhizoctonia. Rhizoctonia root disease is often a problem in the early years of no tillage. Press wheels are used to firm soil around the seed to improve germination. It is important to keep residues out of the drill row – particularly with canola residues due to the allelopathic effects on emerging crops.