• Maximising moisture conservation is the major reason why farmers would move towards no till. Each time we cultivate, moisture is lost. This is usually moisture that would have been otherwise used to convert to grain. Capacitance probes have proved that each cultivation (on our red soils) stimulates fluctuations in day/night soil moisture levels in the top 10-20cm, which in turn reduces shallow soil moisture levels. This shallow soil moisture is very useful for establishing crops (moisture seeking) in the absence of rainfall enabling your crop a quicker start to the season that it would have had in a cultivated scenario.

In addition, by not having a cultivated seedbed, access to paddocks following good rainfall is much easier, and causes less compaction.

How the no till system works.

Moisture accumulation after as little as 5mm of rain.

• The trial has shown that as long as fallow weeds are controlled (either by cultivation or herbicides) deeper soil moisture can be retained and will be used in the following crop. In some years, stored soil moisture can double the yield of crops sown with no stored moisture!

The obvious difference between controlling weeds by herbicides or cultivation is the time taken by each method, the costs associated, and the effect on following weed germinations during the fallow.

Eg for every 1000ha (average figures for normal gear around Hillston)

      * each weed control by cultivation costs you 62 tractor hours (av 16.2 ha/hr)

      * each weed control by spraying costs you 16 tractor hours (av 62ha/hr)

(as labour becomes harder to find, in a wet summer this adds up!)

We have also found that as a general rule you will have to cultivate 33% more often than spraying with herbicides. This is because cultivation stimulates weed germination, and buries weed seeds deeper in the profile, causing delayed and staggered establishment. If weed seeds are left on the surface, they tend to germinate more uniformly allowing a single control to be much more effective.

On the other hand, cultivation for weed control is a pretty simple operation, which is not the case when using herbicides in the summer months. Timing, chemistry, rates, application methods and weed growth stages are critical for success using herbicides in summer, and farmers must be switched on and attentive for acceptable results to occur. This is especially the case for long fallow situations (ie 1yr in crop, 1 yr in fallow) which accounts of approximately 30% of the western cropping area. Weed control in summer fallows using herbicides is probably now the biggest challenge for growers using no till.

• In most years, we have been able to save between 8-25% of the costs associated with growing the crop, whilst still maintaining or even increasing yield potential. The cost variation is mostly associated with the difference in controlling weeds by either herbicides or cultivation. This depends heavily on the rotation used. As most of these costs are before sowing, the risks associated with the crop are much less if the season doesn’t progress favourably.

• Long term trials undertaken by Malinda in Wagga Wagga over a 30 year period, showed that wheat yields were halved when soil loss of only 6.5mm (or 84 tonnes/ hectare) occurred. Based on this information, every 1mm of lost topsoil has the potential to reduce crop yields by 7%.

Trials in the Mallee area of northern Victoria, have estimated that it costs farmers over $2.00 per hectare for every minute of a 75km/hr wind event – depending on fallow management. These costs are associated with lost production and replacement costs of nutrients.

Reducing wind erosion for these reasons is essential for maintaining profitable and sustainable farming systems. We have found that so long as the previous season allowed a crop to produce sufficient stubble (usually >0.8t/ha grain yield) wind erosion was either eliminated or minimised.

Managing lighter stubbles following harvest is essential for the stubble to remain heavy enough to maintain protection. In other words following light crops (<0.8t/ha) = no stock!

Heavier stubbles can provide short periods of grazing, and can infact help reducing stubble blockages at sowing, however this grazing must not be too intense leaving adequate protection for the summer, and must not occur when conditions favour compaction (wet and boggy).

Equally as important, a good set of straw spreaders on the harvester allow sowing into heavy stubbles an easier task.

• Following the first three years of the trial, the weed numbers and spectrum changed significantly. The no till system showed a greater incidence of weeds that preferred germinating on the surface such as annual ryegrass, whilst the conventional system experienced a greater incidence of wild oats, mustard and other broadleaf weeds. The no till system overall experienced less weed pressure, especially when sown using a disc seeder.

To manage the weed spectrum, it has been essential to have a proper rotation. Two cereals in three years seems to be a happy medium in our environment, allowing weed pressure to be minimised during the rotation crop. Alternatively a good fallow is even better at minimising seed set. Where the system has more than two cereal crops in a row (particularly in the no till system), annual ryegrass becomes a huge issue and resistance to herbicides is likely to occur.

One positive for the no till system when using knife points is that incorporated by sowing (IBS) techniques and herbicides can be used, allowing higher herbicide rates and safer conditions for the crop to emerge in. This often allows a better herbicide management plan to be practiced with stronger ‘tools in the basket’ available to combat resistance.

A good target is to have two of the three year rotation completely weed free.

Wheat sown into pea stubble, showing very few weeds, even in the absence of a roundup or pre emergent before sowing.

After 11 years, it is still difficult to measure any changes in soil health. Soil nutrient levels whilst varying following different rotations, have remained consistent between tillage methods.

One significant change that has occurred however is the incidence of glomalin, a protein produced by Arbuscular mycorrhizal fungi. Glomalin has been shown to act as a ‘glue’ in the soil, giving it tilth and stability. The fungi it’s associated with have many small hyphae, which cover much more soil area than plant roots. These hyphae supply plant roots with nutrients (particularly phosphorous) and moisture. In return the fungi use carbon from the plant to grow and make glomalin.

Glomalin levels were measured in 2005, and were significantly higher in no till systems than conventional systems. This is probably because cultivation destroys fungial hyphae.

• The main reason for no till to fail in the initial years of conversion is plough pans, or compacted layers of soil that limit moisture infiltration and root penetration. These plough pans are usually minimised by cultivation, but when we just scratch the seed into a furrow as we do in no till, we are not allowing the plant the critical soil conditions it will need to yield an acceptable result.

Our trial had a significant plough pan, which took three years of no till to begin to alleviate. In that three year period no till yields were sometimes less than half of conventional.

Experience has shown that this drop in yield may have been minimised if we ripped the pan just below the compaction layer (50cm spacings is sufficient). It is important that after ripping, practices that accelerate compaction (eg cultivation, stock etc) be minimised. In an ideal world, following ripping the grower should be completely no till on tram tracks.

An example of a bad plough pan on red soil.

• Over the period of the trial, many plant and soil disease samples have been taken (eg Predicta B®). The only real plant diseases that have impacted on the following crop are yellow leaf spot in wheat, scald and net blotch in barley, and blackspot in peas. In every instance, these can be managed by using the appropriate rotation (ie max 2 cereals in 3 years).

Root diseases however are a little more difficult, in particular rhizoctonia and Pratylenchus neglectus nematodes. Nematodes have been able to be managed by break crops such as peas, however rhizoctonia has shown to be a little harder to manage. Whilst we have managed rhizoctonia reasonably well by break crops such as peas (peas reduce nematodes which seem to increase disease incidence), either fallowing or cultivation of soil hyphae seems to be the best form of control.

In high risk years however, rhizoctonia may have only reduced yield potential by 10% at worst.