Executive summary

Recently interest in the role of renovation cropping in the farming systems of the Western Australian wheatbelt has increased.  It has been proposed as a means of addressing the apparent decline in soil quality in some intensively cropped areas and the increased incidence of herbicide resistance. 

Renovation cropping involves either turning a crop into the soil at flowering or cutting the crop and leaving it on the soil surface.   This is done to maximise the amount of organic matter added to the soil and to control weeds most effectively.  In the Western Australian wheatbelt the focus has been on using pulses, although a range of crops can be used.  The pulse phase of a rotation is favoured as pulses improve the nitrogen status of the soil. In addition the returns to pulses are lower relative to cereals and canola, so the forgone profit in the year of renovation cropping is lowest.

Renovation cropping leads to changes in soil conditions that persist for at least the following season.  It reduces weed numbers in the following crop by reducing seed set, increases the availability of nutrients and may improve soil structure.  Lower weed numbers reduce the carry-over of root diseases thus providing a disease break for the following cereal crop.  Recent trials have shown likely yield increases of 20-30% above those after a pulse crop and increased grain protein levels in the following cereal.

The main cost of green manuring is the income lost by sacrificing grain production.  The loss in income plus any additional costs associated with soil renovation need to be recouped in the following season(s).  Therefore the income from the yield increase(s) in the subsequent year(s) needs to be equal to or greater than the total costs of renovation, including the income forgone.

Despite the increase in interest in renovation cropping, no comprehensive economic analysis has been undertaken to determine its role in Western Australian farming systems.  This study investigates circumstances under which renovation cropping is likely to be profitable and estimates the needed increase in farm profit, given the variability of yields that result from seasonal influences.

To investigate the consequence of risky yields historical rainfall data was used to generate yield distributions for different rainfall zones, soil types and crops.  The yield distributions were used as input to a simulation model to determine the distribution of income, resulting from renovation cropping, in a lupin:wheat:wheat rotation.  The mean yield boost resulting from renovation cropping was estimated to be 3% based on trial results (F. Hoyle, pers. comm.). 

The results of the analysis showed that there is a 30-40% chance of increasing profit if yield is increased by 30% on average.  However, the results were very sensitive to the average increase in yield.  The probability that profit will be increased was halved when yield boost was reduced to 20%. 

The yield increase required to make renovation cropping profitable can vary between 100% under the worst case and below 10% under the best case.  The variability depends on grain prices, grain yield in the renovation phase (if a commercial crop had been was harvested), and the cost of renovation and grain yields in the following crop phase.

The likelihood that profit will be increased depends largely on minimising income forgone relative to the increase in income in the following years.  Therefore green manuring will be most profitable when done in years when the grain yield of the pulse crop is low, and/or when the following cereal yield is very high. 

Weather forecasts are not yet sufficiently developed to predict potentially good years over 12 months ahead, so renovation needs to be undertaken in poor years to maximise the chances of increasing profit.

Identifying poor yielding years prior to renovation does present some difficulty although weather forecasts may improve the chances of undertaking renovation in the 'right' year.  .  Also yield potential is determined directly by biomass of the crop, so this may be used as an early indicator of yield.  Where waterlogging or disease has caused low vegetative growth, resistant weeds are widespread in a paddock, or where frost has damaged the crop green manuring is more likely to be a profitable option. 

This suggests a role for tactical use of renovation cropping so that it is undertaken in years where the forgone income is minimised (i.e. it is done in poor yielding years).  The results of the analysis show that only small yield increases in the following cereal crop are necessary to break even in these circumstances. 

The analysis highlighted gaps in the knowledge of the impact of renovation cropping that may be important for more comprehensive economic analysis, or information that may improve the grower’s ability to undertake the practice profitably.  Further research into green manuring could include:

• Determining whether the profitability of green manuring can be increased using long term weather forecasts.  Improving the estimates of the probability of achieving different yields may allow farmers to renovate soils in years that have lower risk.
• More information on the effects of green manuring on yield and protein for different crops under different conditions is required to better assess the economic advantages of green manuring
• The profitability of green manuring relative to other methods of improving sustainability of cropping also needs to be addressed.

 

This demonstration clearly showed that by adding a small amount of barley (16kg/ha) to serradella when re-seeding, early winter feed for livestock can be significantly increased.  However, as the photos from early September indicate, the serradella growth in spring can be held back due to competition from the barley. Increasing the frequency and intensity of grazing would help, as would the application of a grass selective herbicide to kill the barley in early spring when feed is becoming abundant. If the season was very poor, the barley might be left to increase total pasture production and groundcover for summer.  

• The combination of Triazine Tolerant (TT) and Roundup Ready (RR) herbicide provided superior control of ryegrass and wild radish over individual chemistry treatments.
• Canola is an important rotational winter crop however, with increasing herbicide resistance across multiple chemistries in WA, growers are experiencing increasingly limited options with the current herbicide tolerance technologies available.
• Hyola RT® Technology allows the combination of strong knockdown and residual broad-spectrum herbicides from different herbicide groups and modes of action, targeting a wide range of weed species.
•  Hyola RT® will provide an important role in addressing the increasing Clethodim resistance problem.
• RT® dual herbicide tolerant Hybrids have now demonstrated their value as a new competitive integrated weed management (IWM) tool, also providing increased convenience and flexibility of in-crop weed control.

Results from the initial establishment season have again confirmed the ability of hardseeded legumes to grow and set seed under adverse seasonal conditions.  The value of indeterminate pattern of growth in facilitating additional seed set was also shwon with biserrula where following late spring rain, an additional round of seed set resulted in a more than doubling of overall seed production.Bladder, with a slightly deeper root system, and gland clover which is early maturing also showed b etter capacity to produce seed in challenging condition s compared to subterranean clover.  With production of a seed bank critical for pasture performance  in subsequent years, the performance of hardsseded legumes was very encouraging.

• The 2000 season was not conducive to the spread of leaf rust with the hot dry summer preventing the carry over of rust spores on volunteer cereals.
• For further results please see the attached trial report.

• Wheat, barley, triticale, canary seed, sorghum, sunflowers, millet and panicum were grown in a copper deficient clay soil in pots in the glasshouse.
• For rates of copper from 0 to 6 mg per pot for winter crops, and the same plus 60 mg per pot applied to the summer crops.
• A rate of 6 mg per pot was not sufficient to maximise yield from the winter crops but some are crops produced maximum yields when 60 mg per pot was applied.
• Significant differences intolerance to copper deficiency were apparent between varieties within crops.
• Only the summer crops in triticale produce grain when nearly all the lowest rates of copper were applied.

• Tonic plantain and Grouse chicory are worth considering as summer forages, with the Tonic plantain likely to persist through the following winter and longer. Although not tried, Italian ryegrass (or perennial ryegrass) could be oversown for more winter feed. In this trial, winter feed production from Tonic plantain and sub clover was excellent, no doubt partially due to the high sub clover seed reserves and partially due to the high soil fertility on Tremaine’s.
• Banquet tetraploid hybrid perennial ryegrass could be considered for a medium term high quality pasture for finishing lambs/weaners in high fertility paddocks, with controlled rotational grazing over summer.

• Wheat yields were significantly reduced by competition from barley and brome grass.
• The use of knockdown post sowing but pre-emergent provided excellent control of the grass weeds, which translated into a yield benefit.
• The trends in control of grass weeds and yield benefits in barley were similar to the results seen in wheat.

• Winter habit canola has been successfully sown in spring, grazed over summer and harvested for grain in 2012, 2013 and 2014.
• Establishing canola in spring means larger, more resilient plants in autumn with less impact from slugs and waterlogging.
• Forage value comparable to commercially available dedicated forage rapes over summer and autumn with added benefit of oil seed production.
• Grazing management and timing of stock removal is proving to have an impact on grain yield.
• Vernalisation means winter wheats have the potential to be used in the same way.
   

• Winter habit canola has been successfully sown in spring, grazed over summer and harvested for grain in 2012, 2013 and 2014.
• Establishing canola in spring means larger, more resilient plants in autumn with less impact from slugs and waterlogging.
• Forage value comparable to commercially available dedicated forage rapes over summer and autumn with added benefit of oil seed production.
• Grazing management and timing of stock removal is proving to have an impact on grain yield.
• Vernalisation means winter wheats have the potential to be used in the same way.
   

• There was a significant step up in 2013 wheat yields from rotations which included a one year break previously compared to where there had been a two year break.
• The break crop benefit of a one year break may only last one season if grass weeds are a significant factor.
• Large break crop benefits of 0.5-1.25 t/ha were achieved following a two year non-cereal break phase compared to continuous wheat.
• The benefit of a two year break had little to do with the phases chosen for those two breaks.
• The eight most profitable crop sequences over a three year period in this trial had two year breaks in them.

Problems potentially identified by maps include:

• nutrient deficiencies,
• in crop weeds, and 
• root disease.

At a basic level, simply overlaying in season aerial photography with yield data can provide some insight into
potential problems:

• If yield deficiencies correlate with high growth areas, then weeds could be the issue.
• Root diseases can show patterns of growth that are particular to that problem.
• With aerial photography or  a NDVI, it may be possible to see colour differences that may indicate areas of nutrient deficiency and ground truth work is crucial to confirm suspicions.

• Barley leaf rust (LR) was observed on barley regrowth in the lower Great Southern and South Coast of WA in the summer/autumn of 2016. This contributed to the first observations of infected barley crops in the region in July 2016. All barley varieties including those with Adult Plant Resistance (APR) were under severe disease pressure and responded to application of fungicide.
• The high levels of LR in 2016 and the possibility of barley regrowth in autumn 2017 means a significant LR risk for the 2017 season and fungicide programs for APR varieties should be considered.
• LR is a social disease and all growers should be proactive in eliminating the volunteer barley green bridge. To minimise early onset of LR, the regrowth barley should be eliminated at least 4 weeks before seeding.
• Star of Bethlehem (an alternate host) should be sprayed to eliminate the likelihood of new pathotype developing in the region.
• Selecting varieties with adult plant resistance genes will reduce grain yield loss. However, performance of these varieties against LR is influenced by seasonal weather, time of disease onset, crop agronomy, and is hard to predict season to season. Depending on the LR pressure in the crop they may need early foliar fungicide intervention to reduce development of disease on plants during the growing season.
• Oxford possess two partial resistance genes (Rph20 and Rph24), and under high LR pressure application of foliar fungicides increased yield up to 64 per cent.

• ‘Compass type’ varieties with good early vigour, combined with a prostrate growth habit are the best competitors (Compass, Fathom, Scope CL, RGT Planet).
• ‘Hindmarsh type’ and ‘Urambie type’ varieties with very slow early vigour are poor competitors (Hindmarsh, Spartacus CL, Urambie).
• In the presence of grass weeds there was an average of 0.9t/ha yield loss across all barley varieties.
• Three years of data has reinforced that certain varieties can be used as a non-herbicide option for grass weed control.

• High rates of seed and fertiliser could indeed be a useful tool for controlling weeds. Seed costs would be a little greater but the ability to control the weeds without using chemical - particularly in a situation where resistant weeds become a problem, could certainly make the cost acceptable.

•  Yields were significantly higher under narrow row spacing, but sowing direction had no influence on yield.
• Weeds had a significant effect on yield, but the scale of yield penalty (t/ha yield loss) did  not alter with row spacing or sowing direction in 2015.
• Weeds established faster where row spacings were wider, however by late tillering, all treatments had similar weed numbers and biomass levels.

• Yields were significantly higher under narrow row spacing, but sowing direction had no influence on yield.
• Weeds had a significant effect on yield, but the scale of yield penalty (t/ha yield loss) did not alter with row spacing or sowing direction in 2015.
• Weeds established faster where row spacings were wider, however by late tillering, all treatments had similar weed numbers and biomass levels.

• Velocity and Precept selective herbicides are based on a new active pyrasulfotole.
• This is a new mode of action on broadleaf weeds in cereals in Australia (Group H).
• Velocity and Precept showed excellent crop safety.
• Broad spectrum and reliable broadleaf weed control.

• At Warmur and Kalkee, Bannister was the highest yielding milling oat and Brusher the highest yielding hay oat variety in 2016 – an excellent season.
• Application of fungicides to oats did not create hay or yield benefits in the Wimmera in 2016.
• Choice of oat variety and management should be made according to the intended end-use traits – versatility if conditions change, disease resistance, ability to control problem weeds and likelihood of making premium markets.

• At Warmur and Kalkee, Bannister was the highest yielding milling oat and Brusher the highest yielding hay oat variety in 2016 – an excellent season.
• Application of fungicides to oats did not create hay or yield benefits in the Wimmera in 2016.
• Choice of oat variety and management should be made according to the intended end-use traits – versatility if conditions change, disease resistance, ability to control problem weeds and likelihood of making premium markets.

DBA Aurora and Mace showed similar ability to compete with weeds in 2014. Using higher seeding rates improved weed control. Increased crop seeding rate resulted in reduced crop screenings in 2014

DBA Aurora and Mace showed similar ability to compete with weeds in 2014. Using higher seeding rates improved weed control. Increased crop seeding rate resulted in reduced crop screenings in 2014

• Ryegrass and broadleaf weeds such as toadrush and capeweed are the main weeds to control in oat crops on the rising hill country in hte southern Wimmera.
• In this trial, the most cost effective option to control these weeds was Diuron and Glean applied at the 3-leaf stage of the oats.

This study has shown that substantial savings can be made with the use of this technology. It essntially allows the farmer to have a zero tolerance on summer weeds, without having to apply economical thresholds. The study also identified that the savings will not always result. If there is consistently, 60-70% ground cover, the economical returns may not be as great. This is due to the way the technology is designed. Often in relatively high densities, two sensors would come on to spray one weed, hence twice the amount of water. This is most likely the cause of more water being used in the areas with the High density. Overall, the Weed Seeker technology has the potential to reduce chemical costs and increase the efficiency of spray applications.

• Optical Spray Technology (OST) systems are used for broad spectrum weed control for summer weed and fallow weed control. This type of sprayer is widely accepted in broad-acre cropping situations.
• In-Crop weed detection is the sensing and identification of non-crop plants within the growing crop.
• This technology is not as advanced, nor as widely used as the optical sprayer technology.

• In the past four (dry) years on this demonstration farm the fallow/wheat/oats/lucerne (Phase farming) and wheat/fallow rotations have proved the most financially rewarding, probably due to the moisture storing benefits of fallow.
• Urea seems both less risky and more reliable than the pulse or ley in increasing wheat yield.
• The extreme dryness has caused problems with weed control (chemicals not effective) and with growth of pulse crops and subclover leys.

Sowing cereals in early April on a soil profile full of water is possible if:

• long season varieties are planted to ensure that the crop does not flower before the high-risk frost period has passed,
• the topsoil is moist at seeding to ensure that the crop germinates and allows for early root growth down into the stored water in the subsoil, and
• weeds can be controlled.

• Seeding rate had a bigger impact on wheat establishment than soil wetting agents
• High seeding rates on soils with low yield potential were sometimes a disadvantage; optimal seeding rates would need to account for yield potential as well as the degree of soil water repellence.
• Delaying sowing providing an opportunity to get a knockdown of weeds was important on water repellent soils where staggered weed germination, and reduced herbicide activity, reduces efficacy of in-crop and pre-emergent applications.
• In these trials soil wetting agents did not consistently improve wheat establishment and despite some evidence of benefits to vegetative growth this generally did not translate into a grain yield benefit.

• Commercial viability has been difficult to demonstrate.
• Field trials demonstrated that the H Senor was able to accurately classify annual ryegrass in several broadleaf crops, including canola, faba bean, lentil and field pea.
• Other grass weeds such as brome grass and wild oats were also correctly identified as grasses in these crops.
• Broad leaf weeds were accurately classified in cereal crops, however this was more difficult due to the overlapping nature of the cereal crops at the time when the broadleaf weeds had emerged.
• Classification accuracy was lower for detection of grass weeds in cereal crops and broadleaf weeds in broadleaf crops, and these scenarios were not pursued for that reason.  

Traditionally sowing wheat in Western Australia was not recommended until after Anzac Day.  A date based on the yield performance and maturities of commercially available wheat varieties in the 1990s. Since then growers have seen the release of Mace, a high yielding and very adaptable variety which at 67% dominates the area sown to wheat in WA in 2015 (Data courtesy of CBH group). Growers are now set up and keen to take advantage of any summer rainfall, but there is limited information on which wheat varieties to grow with a very early sowing opportunity.

Research carried out by James Hunt et al. (2014) suggested that the faster maturing winter wheat Whistler appeared well adapted to WA. When sown in mid-April Whistler was able to yield equivalent or better than Mace planted in late May (Crop Updates 2015). Results from Dandaragan and Katanning trials do support this suggestion but this research also suggests there are commercial varieties currently available in WA which can yield similar or higher and have a superior grain quality classification compared to Whistler. However these varieties can still be at the risk of frost and grain quality problems associated with very early sowings.

At all three sites in this trial series, barley out yielded wheat with both the mid-April and the early May planting (note we have included the predicted yield for barley with mid-April planting at Dandaragan of 7t/ha in this assessment). Barley was over 1.5t/ha better than wheat with both mid-April and early May planting. Whilst this research continues to highlight the need for a wheat variety which is more suitable for early sowing opportunities in Western Australia, growers looking for a cereal to sow in April could consider barley as being their new wheat variety until such wheats are released. Whilst this is only one year of observations there are many reasons to consider barley particularly with mid-April planting ahead of planting a wheat variety, including reduced (but still possible) frost risk.

The feed barley varieties Lockyer, Oxford, Rosalind and Urambie did not provide any yield advantage over those with a ‘malt’ classification at Dandaragan in 2015. The ‘malt’ varieties would therefore have been more profitable than the feed varieties as they were received with a premium over the feed barley varieties (either Malt 1 or Malt 2) at a similar grain yield.

With any early planting opportunity growers need to factor in increased fungicide costs. At Dandaragan powdery mildew and barley leaf rust in the barley plots and yellow spot in the wheat plots had to be controlled, particularly in the mid-April planting.

 

• Commercial viability has been difficult to demonstrate.
• Field trials demonstrated that the H Senor was able to accurately classify annual ryegrass in several broadleaf crops, including canola, faba bean, lentil and field pea.
• Other grass weeds such as brome grass and wild oats were also correctly identified as grasses in these crops.
• Broad leaf weeds were accurately classified in cereal crops, however this was more difficult due to the overlapping nature of the cereal crops at the time when the broadleaf weeds had emerged.
• Classification accuracy was lower for detection of grass weeds in cereal crops and broadleaf weeds in broadleaf crops, and these scenarios were not pursued for that reason.  

• Commercial viability has been difficult to demonstrate.
• Field trials demonstrated that the H Senor was able to accurately classify annual ryegrass in several broadleaf crops, including canola, faba bean, lentil and field pea.
• Other grass weeds such as brome grass and wild oats were also correctly identified as grasses in these crops.
• Broad leaf weeds were accurately classified in cereal crops, however this was more difficult due to the overlapping nature of the cereal crops at the time when the broadleaf weeds had emerged.
• Classification accuracy was lower for detection of grass weeds in cereal crops and broadleaf weeds in broadleaf crops, and these scenarios were not pursued for that reason.  

Nitrogen use has resulted in great improvements in crop yield in favourable seasons.
In dry seasons too much applied nitrogen can result in haying-off and lower yields.
Good guidelines are now available for nitrogen use to reduce the risk of crop failure resulting from applying too much fertiliser nitrogen.
The critical factors are:
• Stored soil water (control summer weeds)
• Measure how much nitrogen is in the soil prior to sowing
• Calculate nitrogen requirement from the target yield
• Do not pre-drill more than 60 kg/ha of urea in the 350mm rainfall zone (100kg/ha in the 450mm zone)
• Split applications are safer
• Topdress with urea if the soil test indicates a need, the crop is healthy, and the outlook is for an average to wet season

In 2014, an estimated 61 per cent of the seed bank germinated throughout the season, enabling a rapid reduction of the wild radish population and having a positive effect on grain yield. However, due to the long dormancy of the seed (six to eight years), 100 per cent control would be needed to eradicate the entire seed bank.

Approximately 30 per cent of the seed bank germinated as a result of summer rainfall; best practice is to make the most of seasons that deliver a summer break to get a good knockdown.

Aim to control 100 per cent of seed set by using multiple cultural, chemical and mechanical practices to eradicate the seed bank and stop resistance development.

Windrow burning can reduce small pointed snail populations by over 90%. If there are weeds or fallen stubble that are not burnt then snails can still be present in the paddock.

Windrow burning can reduce small pointed snail populations by over 90%. If there are weeds or fallen stubble that are not burnt then snails can still be present in the paddock.

To effectively establish windrows requires forward planning and potentially slows harvest tand increases harvest costs. Burn as early as conditions allow. Make it a priority job. Small rainfall events may germinate weeds in burnt areas that require attention before the whole paddock area.

• While there is little difference between the results it would appear that the best sowing rate for winter wheat in the Hamilton District is between 100 - 120 kg/ha.
• Interestingly the higher rates were not significantly different from the standard rate in a dry year.
• What was evident was the increased number of weeds in the plots with the lower rates despite the plots all being sprayed at the same time. 

• Pasture cropping systems can provide grain (and out of season fodder) on deep sandy soils and reduce the likelihood of groundwater recharge.
• Potential yield penalties associated with pasture cropping across perennials on deep sandy soils in the west midlands appear to be less than 20%.
• Pastures started competing with the crop for soil water during grain filling, but impacts on soil water and grain yield were generally small given average rainfall in spring.
• During the crop growing season, there was little difference in soil water under annual crop, perennial pasture, and pasture-cropped plots.
• Soil water contents were much lower under pasture and pasture-cropped plots during summer and autumn.