• Removing subsoil compaction is critical and for some soil types can dramatically improve access to deep soil moisture.
• Correctly ground-truthing the depth of the compaction layer can drive the success or failure of ripping outcomes.
• Yield increases at the Goomalling site were largely driven by very deep ripping, with either the very deep ripper or delver, with yield increases of 0.55-0.74 t/ha, an increase of 74-93%. The only other treatment to increase yield was mouldboard ploughing on its own with a 0.44 t/ha, 55% yield increase.

• A high application of potassium (K), 25 kg/ha and standard nitrogen (N) rates, 70 kg/ha improved wheat yield and grain quality up to 0.47 t/ha on mould boarded deep sand.
• In the presence of adequate potassium (> 40-50 mg/kg), in favourable seasons, wheat can respond to the application of N) fertiliser, resulting in high yield and protein. Where K is limited, returns from N are likely to be poor.
• The results indicate that a higher rate of K than banding 11 kg/ha K can lead to a significant increase in yield and profitability.
   

• Cultivation will often see improved yields in the first two seasons, particularly on lighter soils.
• The 2018 season saw 409 mm of growing season rainfall (GSR) resulting in a significant response to nitrogen (N) and a response to a residual high potassium (K) applied in 2017.
• In soils deficient in K (below 40-50mg/kg) at 0-10 cm, application of higher rates of top dressed K to take advantage of the residual benefits across seasons could be considered.
   

1. Inversion ploughing of water repellent sands can significantly reduce repellence and increase critical components of grain yield.
2. Deep ripping in the presence of problem background ryegrass can stimulate ryegrass emergence and worsen weed competition with the crop.
3. The strength of the subsoil resource (i.e. clay component) appears important in sustaining the crop production potential and realisation of grain yield improvement.

A summary of the main results from the first season at the Moora trial are presented in Figures 1 and 2.  Due to technical issues, the trial was not seeded at the same time as the rest of the paddock, which was supposed to be used as an untreated control. For this reason, a comparison of the treatments to a control treatment without tillage and clay spreading is not available.  A statistically significant effect of tillage on early plant establishment was found when analysing the plant counts measured about four weeks after sowing (Figure 1, left). All the treatments with the off-set disc (in combination or not with clay spreading) had more plants per linear meter in comparison to the one-way plough treatments. This is likely due to uneven seeding depth following tillage with the one-way plough (deep tillage) compared to the shallower tillage with the off-set disc. Surprisingly, incorporation of subsoil clay at any given rate did not show any significant effect on early plant establishment although this result could be explained by the wetter than usual weather in April-May reducing the severity of soil water repellence.

Again, when looking at the tiller counts recorded 8 weeks after sowing (Figure 1, right) the addition of clay at different rates did not affect the number of tillers. However, the wheat growing in the one-way plough treatments overcame the initial delay in germination giving higher tiller number than those recorded in the treatments with the off-set disc (except for the treatment with 250 t/ha of clay). This trend continued at harvest, with the one-way plough treatments producing higher yields (4.5-4.6 t/ha on average) than the off-set disc treatments (4.1-4.3 t/ha on average) at any given rate of subsoil clay.

Due to the low rates of clay spreading and the low cost of the incorporation methods, all treatments provided a positive return of investments in the first year (ROI= ($/ha gain – $/ha total direct costs) / $/ha total direct costs), based on mean values in Table 1. Not surprisingly, the best ROI in the first year was obtained by the one-way plough treatment without clay spreading (1.42 $/ha), followed by the off-set disc without clay spreading (1.22 $/ha) and the treatments clay spread at 50 t/ha incorporated with one-way plough (1.17 $/ha). These estimates are indicative only, as indirect costs and interests on the initial capital investment are not included in the calculations. For more accurate estimates of ROI, yield results from multiple seasons and crops will be collected in the next 3 years.

 

A summary of the main results from the first season at the Moora trial are presented in Figures 1 and 2.  Due to technical issues, the trial was not seeded at the same time as the rest of the paddock, which was supposed to be used as an untreated control. For this reason, a comparison of the treatments to a control treatment without tillage and clay spreading is not available.  A statistically significant effect of tillage on early plant establishment was found when analysing the plant counts measured about four weeks after sowing (Figure 1, left). All the treatments with the off-set disc (in combination or not with clay spreading) had more plants per linear meter in comparison to the one-way plough treatments. This is likely due to uneven seeding depth following tillage with the one-way plough (deep tillage) compared to the shallower tillage with the off-set disc. Surprisingly, incorporation of subsoil clay at any given rate did not show any significant effect on early plant establishment although this result could be explained by the wetter than usual weather in April-May reducing the severity of soil water repellence.

Again, when looking at the tiller counts recorded 8 weeks after sowing (Figure 1, right) the addition of clay at different rates did not affect the number of tillers. However, the wheat growing in the one-way plough treatments overcame the initial delay in germination giving higher tiller number than those recorded in the treatments with the off-set disc (except for the treatment with 250 t/ha of clay). This trend continued at harvest, with the one-way plough treatments producing higher yields (4.5-4.6 t/ha on average) than the off-set disc treatments (4.1-4.3 t/ha on average) at any given rate of subsoil clay.

Due to the low rates of clay spreading and the low cost of the incorporation methods, all treatments provided a positive return of investments in the first year (ROI= ($/ha gain – $/ha total direct costs) / $/ha total direct costs), based on mean values in Table 1. Not surprisingly, the best ROI in the first year was obtained by the one-way plough treatment without clay spreading (1.42 $/ha), followed by the off-set disc without clay spreading (1.22 $/ha) and the treatments clay spread at 50 t/ha incorporated with one-way plough (1.17 $/ha). These estimates are indicative only, as indirect costs and interests on the initial capital investment are not included in the calculations. For more accurate estimates of ROI, yield results from multiple seasons and crops will be collected in the next 3 years.

The topsoil sand at Yanda was severely repellent (Figure 1, left), as measured by the molarity of ethanol droplet test (MED). Clay spreading and tillage (either combined or separated) significantly reduced the severity of water repellency. When the subsoil clay was not incorporated by tillage or was incorporated using an off-set disc, the soil water repellency generally decreased with an increasing amount of subsoil clay. However, low-repellency (MED<1) was obtained only at rates over 150 t/ha of subsoil.

In contrast, spading (either at standard speed of the tractor or at half speed) was the most effective method for the alleviation of soil water repellency. In these treatments, the MED values were completely reduced to zero (non-repellent soil) and, most importantly, this was achieved independently from the presence, or not, of clay-rich subsoil. The significant reduction of the soil water repellency however did not convert to better plant establishment measured five weeks after sowing (Figure 1, Right).  This result could be explained by the wetter than usual weather recorded during April-May 2016 that reduced the impact of the soil water repellency on plant establishment. Nevertheless, tiller counts collected five weeks after plant counts showed a significant effect of tillage on the number of tillers. In particular, the spader treatments (standard and ½ speed) had the most tillers while the control had the fewest.

This trend was repeated with the barley grain yields at harvest time (Figure 2). Both tillage and rate of clay spreading, significantly improved grain yield in comparison to the control treatments (no clay and no tillage). The lowest yield were recorded in the control treatments and in the off-set tillage only (no clay) with an average of 1.41 t/ha and 1.36 t/ha respectively. The shallow tillage (or incorporation) using off-set discs did not yield significantly differently from the treatments with no incorporation at any given rate of subsoil clay. Clay spreading at 250 t/ha followed by spading at standard speed produced the highest yield on average (2.93 t/ha). Nonetheless, all treatments with spading (standard and ½ speed) were able to yield over 2.5 t/ha, even without the addition of subsoil clay (Figure 2). 

Field observations showed that the trial was also affected by frost, which explained the lower than expected yields. Head samples were collected in early November 2016 from all the treatments (except spading at ½ speed) for the assessment of frost induced sterility (FIS= number of sterile florets / total number of florets) and the results are shown in Figure 3.

The results on FIS showed that frost damage might be one of the main reasons of low yields and responsible of the large yield differences between treatments. The control treatments and the off-set treatment (no clay) had over 60% frost induced sterility. Even though increasing amounts of subsoil clay significantly reduced FIS (Figure 3c), the treatments with no incorporation or with incorporation by off-set discs still recorded FIS values above 50%. Spading was the most effective treatment to significantly reduce frost damage to below 40%, regardless of the presence or not of subsoil clay (Figure 3a and b).

Spading was the most successful treatment in this first year of the trial at Yanda. Most importantly, spading was able to produce the highest yields and significantly reduce the frost damage regardless of the addition subsoil clay. This was particularly evident when estimating the simple return of investments on the first year of the trial (ROI= ($/ha gain – $/ha total direct costs) / $/ha total direct costs), based on the mean values presented in Table 3. Because of the high crop-specific costs with barley at Yanda (500 $/ha) and the yield reduction due to frost, spading alone at standard speed was the only treatment that gave a positive ROI on the first year (+0.4 $/ha) followed by negative ROI with spading at ½ speed (-0.18 $/ha) and the control (-0.35 $/ha). These estimates are indicative only, as indirect costs and interests on the initial capital investment are not included in the calculations. For more accurate estimates of ROI, yield results from multiple seasons and crops will be collected in the next 3 years.

 

On deep sandy profiles subsoil compaction and acidity are major constraints. At this site the limited cropping history resulted in an expectation that the site would not be compacted but compaction was severe, indicating how susceptible these pale sands can be to compaction. For many deep sands, liming followed by deep ripping with topsoil slotting may be one of the most economical ways of effectively overcoming subsoil compaction and acidity to depths of 40-60cm.

On severely repellent sands however, it may be that deep ripping alone is inadequate and options which overcome the repellence and assist with weed control while at the same time addressing subsoil compaction and acidity may be required to get sustained productivity benefits (Davies et. al. 2017). The impact of deep ripping on highly repellent soils is variable with anecdotal reports that ripping can sometimes worsen the expression of repellence and result in poorer crop establishment. Other reports indicate substantial productivity gains can also be achieved (Blackwell et. al. 2016). Deep ripping may help overcome soil water repellence by: 1) creating a rougher soil surface allowing water to pond and infiltrate over time; 2) loosening the dry topsoil making it a more effective mulch, reducing soil moisture loss from the subsurface soil; 3) delving some seams of subsoil to the surface which act as pathways for water entry, with some ripper tine designs and attachments facilitating this more than others. Conversely the negative effects of deep ripping can include: 1) enhanced drying of the repellent topsoil from the loosening action; 2) increased expression of the water repellence when the soil is ripped when it is quite dry. Repellence severity, or expression, is increased with these negative effects which was the case for this site. For other sites where repellence is more moderate any benefits of deep ripping may outweigh the negative impacts. The mixed effects of deep ripping on repellent soils needs further research to be better understood. It is likely that rippers with C-shaped or parabolic shaped tines with broader points and wider ‘face’ plates will achieve more subsoil delving into the topsoil. Some rippers can also be fitted with wings which can also increase the degree of soil mixing. A greater degree of subsoil delving could result in development of more effective infiltration paths and longer lasting reductions in topsoil water repellence.

In this study rotary spading and modified one-way ploughing were effective in improving water infiltration on severely repellent sand even if they did not remove the deeper compaction. Second-hand one-way disc ploughs have a relatively low capital and operating cost (Table 1) and are relatively cheap to modify into a simple but robust tool for partial soil inversion (Davies et. al. 2016), although good seed bed preparation is still essential.

Crop establishment and nutrient supply had a greater effect on crop growth than soil water repellence at this site. Interestingly, grain yield showed a weak, slightly positive relationship with our measurements of water repellence e.g. grain yield was highest at points that had higher levels of water repellence (data not shown here). The positive relationship between soil water repellence reflects the role of soil water repellent organic matter and soil nitrogen supply. Our results suggest nitrogen supply was a major limitation to growth therefore it is reasonable that higher grain yields occurred where soil organic carbon (soil nitrogen supply) was high. Water repellence may have had a minor effect because it was not severe at this site; the MED values ranged from 0.1 (Low water repellence, King 1981) to 2.1 (Moderate water repellence) and the average was 1.0 (Moderate water repellence). However, the samples for MED measurement were taken in winter when the expression of soil water repellence is lowest.

Gamma thorium provided a reasonable prediction of shoot K concentration and gravel content and provides a feasible method for delineating K management zones on sandy gravels in the Badgingarra area. Figure 2 shows that high shoot K concentration is associated with gravel content and vice versa. The critical shoot K concentration for wheat at anthesis is 1.5%; based on the data shown in Figure 2 the areas where gamma Thorium is less than 40 ppm would be responsive to potassium fertilizer application.

The gravel measurements separated into 2 clusters; non-gravelly soil where the fraction of gravel was less than 15% by weight and gravel soil where the fraction was greater than 15%. The mean Colwell K 0 to 10 cm was 17 mg kg which is well below the critical range of 51 to 57 for high yield potential on deep grey sands. Based on current prices and a wheat yield potential of 2t/ha, the DAFWA K calculator shows profit would be maximized with 40 kg K/ha applied. However, the efficacy of topdressed K on this sand may be low. The mean Colwell K for the gravel soil was 24 mg / kg which is also well below critical levels but shoot K concentration was adequate. This suggests that the crop is accessing K from the subsoil and that tissue testing may be an important component of assessing nutrient supply from different parts of the sandy gravel landscape.

These grower scale on-farm soil amelioration demonstrations have been managed by the growers according to standard practice. Both soil types are highly water repellent and in general the amelioration treatments have improved crop establishment, vigour and grain yield. Economic analysis indicates that the return on investment has been large as the benefits from the treatments have tended to last for at least 5-years or more at these sites. While it is possible to improve establishment, water and nutrient use efficiency and crop productivity using these techniques it is important to recognise that other constraints such as poor water and nutrient holding, soil acidity and compaction can still limit the yield potential of these soils and this needs to be considered when investing in amelioration. Liming to improve the soil pH and very deep ripping to remove compaction below 30-40 cm may well provide further yield gains beyond those achieved through amelioration of the top 10-30 cm only, and this may also help sustain the benefits of amelioration over a longer time.

This first year study has shown that the adoption of a strategic tillage practice (one-way plough) provided a significant improvement in terms of crop establishment and grain yields on a moderately repellent sandy gravel. The adoption of other agronomic options, such as paired-row sowing or wetters, in this instance did not provide any noticeable improvement in comparison to the control treatments. In fact, in one case (wetter 1), the cost of the treatment was not covered by the yield increase.

Without doubt, the tillage proved to be the most effective treatment for reducing SWR but at this stage it is not possible to evaluate the extent to which this improvement alone contributed to the significant increase in yields.

With this long term experiment, we expect the following seasons to give us more information to better understand what changes drive the yield increase and possibly the potential longevity of these improvements.

In the first growing season, the one-off tillage treatments showed to reduced significantly the water repellency of the soil. Significantly better plant establishment and grain yield were obtained in all the tillage treatments. In terms of grain yield, better results were achieved with the tillage treatments that mixed the soil more efficiently, such as the “Deep ripping + Spading” and the “Mouldboard plough” treatments. The “Deep ripping” treatment, which effectively targeted only subsoil compaction, provided the lowest improvements in terms SWR and the lowest grain yield.

The greatest profit in the first growing year was achieved using the “Modified one-way plough” thanks to its low capital cost which reduces its operating cost. Nonetheless, further growing season will be necessary to establish its long term profitability in comparison to the “Deep ripping + Spading” and the “Mouldboard plough” treatments.

Changes in the soil pH profile were also observed after the tillage treatments, with increased acidity in the topsoil. That was particularly the case with the “Mouldboard plough” treatment and the management of soil pH with addition of lime after the tillage needs to be considered.

We expect the next four growing seasons to give us more information to better understand the long term effects of these soil modifications on soil productivity.

 

All tillage treatments had a little effect on the management of SWR and plant establishment in the severe water repellent gravel sand at Moora. Nevertheless, yield improvements were recorded, in particular with the “Large offsets” and the “Modified one-way with standard discs” treatments.

At this stage, it is not possible to clearly state what changes drove the yield increase. Given the little effect that the cultivations had on the SWR it is possible that improved soil structure, increased nutrient availability and nitrogen mineralisation may have played a role on the increased productivity.

The yield potential of the canola crop in 2015 was low given it was sown relatively late, plant numbers were low and there was a dry finish, this may have compromised the response to the tillage treatments. Observation of the trial in the following growing seasons and the response of a cereal crop in 2016 will help us to better understand the long term effect of the treatments on crop growth.

• This large scale on-farm demonstration has shown how soil inversion with a mouldboard plough can provide wheat yield benefits on sandplain soil.
• The mouldboard ploughing reduced the soil water repellence by about a third, but moderate repellence was still present. In this trial frost affected the mouldboard plough treated area more than the untreated area which is opposite to what some growers have reported who felt that crops on mouldboard ploughed soil were less affected by frost.
• Soil type, soil moisture, crop biomass and timing of the frost event may have had an impact in 2014.
• Short-term grain yield responses to cultivation on sandplain soils are typical and the potential benefits need to be studied for several more seasons before the value of the practice can be properly assessed.
• Other deep soil cultivation practices, such as deep ripping, can also give wheat yield responses in the first year.

These grower scale on-farm soil amelioration demonstrations have been managed by the growers according to standard practice. Both soil types were highly water repellent and the amelioration treatments have generally improved establishment but have probably had an even bigger impact on crop vigour. While it is possible to improve establishment, water and nutrient use efficiency and crop productivity using these techniques it is important to recognise that other constraints such as poor water and nutrient holding, soil acidity and compaction can still limit the yield potential of these soils. Pale sands which overly a clayey gravel or clay base within the top 1 m often have greater potential than the very deep sands.

• 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 degress of soil water repellence.
• Delaying sowing providing an opprtunity to get a knockdown of weeds was important on water repellent soils where staggered weed germination and reduced herbicide activity, reduces the efficacy of in-crop and pre-emergent applications. 

(i) Several options exist to ameliorate subsoil acidity with incorporated lime. The method chosen will depend on pH profile, yield potential, budget, area affected, soil type and occurrence of other constraints that may be impacted. (ii) Modified deep ripping techniques can incorporate more topsoil and surface applied lime while at the same time effectively removing subsoil compaction. (iii) Applying adequate lime to ameliorate the soil pH profile to depth is of utmost importance and the rate of lime applied should not be compromised to pay for incorporation, although lime applications can be split with some applied before and some a year or two after incorporation.

One way ploughing slightly improved establishment, head numbers, biomass production and yield but is not a viable long term solution for the severe non wetting on this soil type.

Deep ripping and spading improved head numbers by over 60% and biomass production by 87% compared to the control.

Grain yields were improved by over a 1 t/ha and gross margin by about $200/ha when treatment costs were amortized over 5 years in the combined ripping and spading treatments.

It is critically important to sample soil pH to depth prior to investing large sums in lime application and incorporation. Typically it has been found that on sandplain soils the yield benefit of one-off deep cultivation or deep ripping is large enough to cover the cost of the tillage in the first year so the subsequent productivity benefits associated with more rapidly fixing the soil pH by incorporating lime can be realised sooner. Other factors such as water repellence, herbicide resistant weeds, subsoil compaction, wind erosion risk and soil type will impact on the choice of incorporation implement used.

• Soil inversion with a mouldboard plough, rotary spader and one way plough created equally patchy soil.
• The one-way plough created the most vertical redistribution of the surface 10 cm of soil.
• At least ten soil samples are required to gain a reliable mean for soil pH after inversion.

Funded by DAFWA and GRDC through DAW00204 ‘Delivering agronomic strategies for water repellent soils in WA’ and DAW00218 ‘Wheat agronomy systems profitability’. Thanks to LivingFarm for management of sites at Wickepin and Cranbrook. The provision of sites and support of growers Ray Falconer, Kyle Carson, David Stacey, and Kim Oliver is greatly appreciated. Thanks to Trevor Bell, Anne Smith, Stephanie Boyce, Paul Bartlett, Virginia Smee and Greg Brown for technical support. Thanks to West Midlands Group, Northern Agri Group, Facey Group, Gillami Centre and the soil wetter product manufacturers for ongoing support.

• 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.

• This trial clearly demonstrates the importance of matching clay application rate and incorporation method when clay spreading for water repellence. For subsoils with a clay content of about 30% using a rate of 100-150 t subsoil/ha incorporated with offsets to a depth of 120-150 mm was sufficient to overcome the repellence and given wheat yield increases of 11-18%.
• Alternatively subsoil application rates of 250-350 t/ha are probably required if the clay is to be incorporated to 250-300 mm with a rotary spader and this gave similar yield increases of 11-14% on what is a better soil type with higher inherent yield potential.
• The main benefit of higher clay application rates and deeper incorporation seemed to be in the canola year, although more seasons with canola need to be assessed to confirm the validity of this finding.

• Soil pH results after liming and tillage treatments were applied was found to be quite variable and more sampling needs to be done before pH results can be quoted. Soil loosening indicates that only the deep tillage techniques were likely to incorporate lime into the deeper 20-30 cm acidic layer.
• This trial highlights the importance of measuring subsoil pH levels and applying sufficient rates of lime to prevent and correct subsoil acidification. Where tillage treatments are used to incorporate lime it is important to understand to what depth lime will be incorporated and which subsoil layers need correction. It is intended to monitor this trial for the next few years to further assess the benefits of correcting subsoil acidification. Yield response to lime incorporation can increase over time as the untreated soil continues to acidify further and as lime has more opportunity to react and neutralize the acidity that is present.

Many wheat varieties grown in WA already have the major gene for acid soil tolerance. In this trial several other acid tolerance traits are being assessed under field conditions to determine if they confer growth and yield advantages in addition to the major gene. If the traits do prove useful they can then be back-crossed into current well-adapted WA wheat varieties and ultimately become available for growers to use. In addition to these field trials, the project aims to identify molecular markers to facilitate the breeding process. The traits are likely to be beneficial in situations where soils are being limed to correct soil acidity but are not likely to help in highly Al toxic soils in the absence of liming. This trial and others like it will help determine under what soil acidity levels the traits are likely to be beneficial.

Acid soil tolerance in wheat is not a stand-alone solution for managing acid soils, rather it complements a liming program to ameliorate subsoil acidity. Subsoil at the site is acidic to a depth of at least 40 cm as demonstrated by the indicative site soil pH (CaCl2): 0-10 cm = 5.4; 10-20 cm =  4.2; 20-30 cm = 4.3; 30-40 cm = 4.3. Prior to the site being seeded 1.5 t/ha limesand was spread and this has lifted the topsoil pH to ~5.4 on average. More lime will need to be applied to the site to lift the low subsoil pH values.

• The one-off 2010 mouldboard ploughing treatment has resulted in yield increases of 1.0 t/ha or more for the past 4 seasons.
• The measured yield increases were partly a result of overcoming the water repellence by soil inversion and improving crop establishment.
• For further details please see attached trial report.

• Average grain yield for the untreated control plots was 2.34 t/ha. Clay spreading and rotary spading gave the largest machine harvest grain yield responses of 400 kg/ha or more, mouldboard ploughing 270 kg/ha and one-way ploughing 180 kg/ha (Figure 1) compared to their nearest comparative control plots. Offset discs gave no yield response in 2013 but did have positive yield responses in previous seasons (Table 1).
• Grain protein levels averaged 11.4% for the untreated controls, clay spreading had 0.5% more protein and mouldboard ploughing 0.2% than their neighbouring controls (data not shown).
• Screenings for the majority of treatments averaged about 2.1%. Mouldboard ploughing was the only treatment to have significantly lower screenings of just 1.2% (data not shown).
• Total above-ground shoot biomass and head number was assessed using plant cuts (Table 1). Shoot biomass on average was increased by 95% (+4.3 t/ha) by rotary spading, 57% (+2.7 t/ha) by clay spreading and 47% (+2.3 t/ha) by mouldboard ploughing compared to the untreated controls. Head numbers on average were increased by 32% (78 heads) by spading, 22% (58 heads) by mouldboard ploughing and 17% (43 heads) by claying compared to the untreated controls.
• Observations made earlier in the season indicated that emergence of many plants in the untreated control areas was delayed and had fewer tillers than the earlier emerging plants in the many of the treated areas.
• The whole plant cut transects were taken across different soil types, rotary spading gave the best results on the poor pale deep sand at this site while mouldboard ploughing performed best on the better yellow sand (Transect 3).
• The net 3-year benefit and return on investment (ROI) has been determined for the first 3-years of the trial (Table 2). Estimated costs for the amelioration treatments are based on owner-operated and contract rates. Benefits associated with some of the treatments such as weed control for the mouldboard plough and reduced wind erosion for the claying treatment have not been included.
• The one-way ploughing treatment was the most affected by wind erosion in 2011, resulting in a loss in grain yield and income which has substantially reduced the net benefit and the return on investment for this treatment although the subsequent years have been profitable (Table 2). Of the other treatments rotary spading and mouldboard ploughing had the highest net benefit, driven largely by the large lupin yield increases measured in 2012. Claying also had impressive yield gains and substantial increases in income (Table 2) but the high cost of this treatment reduced the 3-year net benefit and return on investment relative to the deep cultivation treatments. Given that claying can show benefits for decades net benefit and ROI for this treatment should continue to improve over time and it still only took 2 years to cover the cost of the treatment. Offset discs had grain yield benefits for the first 2 years but showed no response in 2013 suggesting that the benefits of the shallow cultivation may have dissipated.

• Pale deep sand has inherently poor yield potential and given the high cost of the water repellence amelioration treatments it can be difficult to determine whether the investment is worthwhile.
• At this site the productivity gains have been sufficient to offset the costs and be profitable for each of the options tested.
• Claying despite being expensive does have the advantage of being long-lasting and reduces wind erosion risk. Shallower cultivation with offset discs or one-way ploughing can give profitable improvements but the example of the one-way plough demonstrated that the benefits can be reduced or even negated by wind erosion damage.
• It should be noted that other research indicates that improving the effectiveness of the seeding operation can give yield gains of similar magnitude or even greater than those measured for the offset discs without the erosion risk. Exploring this possibility is probably a first step for growers looking to manage repellence on these soils.

• This and other research demonstrates that it is possible to improve crop establishment and productivity on water repellent soils using modified furrow sowing techniques.
• Banded wetting agents are helpful with early dry or partially dry sowing before opening rains but show less benefit later in the sowing program when there has already been rain and the soil has started to wet up more (see Banded wetting agent paper WMG 2012 research annual). In very erodible conditions with high wind erosion risk the use of this strategy may be safer than the options with winged points or boots due to less soil disturbance and release of root anchorage for existing plant cover. Optimal wetting agents for WMG areas still need identification.
• Winged points and winged-paired row systems perform better than knife points under certain soil conditions but the benefits are variable and in some sowing conditions may provide little benefit. Further research is required. Winged points look most attractive when shallow moist soil can be ‘delved’ to the seed zone to provide early establishment (as in the winged knife point on the gravelly sand with shallow moisture).
• Simple approaches like sowing next to or at a shallow angle across the previous year’s crop row and broadcast spreading a portion of the seed in front of the seeding tynes are relatively simple approaches that can provide establishment benefits.
•  

Removal of subsoil compaction by deep ripping resulted in a 370 kg/ha (45%) yield benefit with spading giving an additional benefit of 12% (100 kg/ha) and mouldboard ploughing 39% (320 kg/ha) compared with the deep ripping treatment. Higher biomass and increased head density in the cultivation treatments are indicative of improved nutrient access and effcient use of available water through the season. Water use efficiency was 4.9 kg/ha/mm of growing season rainfall for the control treatment compared with 7.1 kg/ha/mm for ripped, 7.6 kg/ha/mm for spaded and 8.9 kg/ha/mm for mouldboard ploughing. Recent research is showing that nutrient availability is improved when top soil is buried by spading or mouldboard 
ploughing because nutrients become concentrated in the rootzone and less suscpetible to soil drying from evaporation, which can be the case when majority of the nutrients are on the soil surface, (Davies et al, 2012).

• Spading has mixed the non-wetting layer of soil in this paddock through the soil profile, resulting in an increase in crop yield in two out of past three years.
• Using the spader to mix lime and dolomite into the subsoil has improved the pH of the soil and increased yield. 
• Wind erosion is a big risk with spading and caused a yield decrease in 2010, the year the spading occurred. 
• Spading also reduces compaction at a similar level to deep ripping by physically breaking down any compacted layers in the top 30cm.
• Soil type is a large factor in the success of a spading operation; careful consideration must be given to this prior to commencing any spading program. 

 

Grower adoption of rotary spading and mouldboard ploughing in the West Midlands has been steadily increasing.

• This trial demonstrates the productivity and financial benefits that can arise from implementing rotary spading and indicates that the practice of deep ripping prior to spading appears to be worthwhile as not only does it remove obstacles and make spading easier it also appears to be a benefit to crop growth and productivity particularly in times of drought.
• Soil compaction was a significant constraint on this site and deep ripping alone has shown an advantage. Ideally controlled traffic system should be implemented after deep tillage to prevent re-compaction and loss of these benefits.

• The negative effect of water repellence management at this site is at odds with other work in this project. In both years we have observed a lower grain yield in the banded wetter, mouldboard ploughing and spading treatments than in the control at this site.
• However, the average yield response to mouldboard ploughing and spading was 550 to 600 kg/ha over 28 sites.
• For further details please see the attached trial report.

• This set of trials indicates that SACOA ‘Irrigator’ banded wetting agent can improve crop establishment and grain yield but that responses can be highly variable. The 27-32% yield increase seen in 3 of the trials is very encouraging. Based on these and other trials it can be suggested that banded wetting agents are most likely to be effective when:
• Soils are moderate to strongly repellent and there are few residual roots form the previous year’s crop; and points and tines are used for seeding.
• Banded wetter is applied in a consistent stream to the base of relatively stable furrows. Collapsing furrows, furrow infill and a disrupted band of wetting agent can reduce efficacy. Presswheels with a more rectangular cross section tend to rip up furrow walls and the disturbed soil buries and mixes banded wetting agent. ‘V’ section or round section presswheels with no deep flange reduce such problems.
• The banded wetting agent kit needs to be robust and reliable and needs to accurately apply the wetting agent in a continuous stream into the base of the furrow
• Crops sown early into dry or partially dry soil before opening rains derive more benefit from banded wetter. Banded wetting agents are typically less beneficial when used later in the sowing program when there has already been rain and the soil has started to wet up.
• Growers already using wetting agents are tending to modify their usage of banded wetter to better match the likelihood of significant benefits. Some growers only use banded wetter for the dry seeding or early part of the program and don’t use it later in the program after there has been more rain.  Other growers are planning to use higher rates of banded wetter early in the program but then aim to reduce the rates when sowing later in the season. Both of these strategies will reduce cost while maximising the opportunity for benefits to crop establishment and yield. Current research in the state is showing that different banded wetting agent products can have a wide range of effects of crop establishment and especially on yield. DAFWA is continuing to research a range of products to help growers evaluate which types of banded wetting agent are more suitable for their farming system.

• This trial was an un-replicated farmer demonstration, results should be interpreted with caution.  
• Observations: 13/7/12: Crusting of the surface reduced germination in mouldboard ploughed strips.
• For further comments please see the attached trial report.

Andrew’s management of water repellence demonstrates that a strategy of affordable progressive amelioration and better sowing methods for the rest of the crop can be a successful and profitable approach for managing soil water repellence. On-farm testing of water repellence management options can help confirm which strategies are likely to be successful and profitable on particular soils and landscapes. The use of winged paired-row systems, winged points, banded-wetting agents, on-row seeding or broadcast spreading a proportion of the seed ahead of the bar can all potentially improve the effectiveness of sowing on water repellent soils and this is the subject of ongoing research.

• More moderate clay rich subsoil application rates of 100-150 t/ha are less costly to apply, can be easily incorporated, can still improve crop establishment and productivity and importantly can reduce some of the risks associated with crops haying off due to water shortage during grain filling in dry seasons.
• Clay spreading is likely to be more beneficial in higher rainfall, longer season environments and in wetter seasons where the risk of water shortage at grain fill and haying off is reduced.

• In the first two seasons, 2009 and 2010, there was a strong and consistent yield increase in response to mouldboard ploughing. 
• In 2011 the mouldboard plough plots on average yielded 300 kg/ha (13%) less than the unploughed plots.
• This trial is an unreplicated demonstration so it’s hard to tell if the negative response is real or not. 
• For further results please see attached trial report.

• Our results from the first year of the study show that the method used to manage soil water repellence had little impact on soil nutrient supply with the exception of phosphorus. The lack of grain yield response to applied P in the mouldboard and spading treatments suggest that soil phosphorus is more available in these soils, though is not clear whether this is due to the removal of the non-wetting constraint or mineralisation following tillage.
• The lower grain yield and harvest index in the spading treatment suggests that there was less soil water available late in the growing season. Further research is required to determine how these management practices, in particular inversion and rotary spading, changes fertiliser advice. The results of this work will be used to develop guidelines on if or how nutrition should be managed for crops sown on soils treated for water repellence.

• In general for the bulk of the paddock in the wetter 2011 season there was little obvious difference in establishment between the knife point and winged point with paired rows seeder. However there were a several water repellent patches where establishment was poor for the knife point seeder but was much improved for the winged point-paired row seeder.
• Plant counts in these areas revealed that establishment was more than doubled from <100 plants/m2 to >200 plants/m2 through use of the winged point-paired row system in both the sandy gravel and pale deep sand soil types
• The advantage of improved furrow sowing as a tool to manage water repellent soils is it can be applied over all the repellent cropping areas, potentially for relatively low cost if only points and press wheels need changing on an existing seeder.
• For further results please see the attached trial report.

• One of the greatest risks of the deep cultivation techniques is wind erosion as a result of the burial and removal of all surface cover. In 2011 strong post-seeding wind events in mid-June resulted in significant wind erosion and sand blasting of young crop seedlings. 
• The wind erosion and sand blasting of the seedlings was a significant setback for the crop and would be partly responsible for the relatively low yields at the site. 
• Grain yields at the site ranged from 1.3 to 1.8 t/ha.
• For further results please see the attached trial report.

• Good soil moisture conditions at sowing reduced the impact of repellence on establishment; all treatments established a healthy number of plants.
• Claying improved crop establishment, growth and grain yield in 2011; this appears to be driven by better seedbed moisture retention and reduced nutrient leaching, espeically nitrogen.
• Good soil moisture conditions during grain fill minimised any water shortage (haying off) effects from claying.
• Cultivation treatment had no impact on grain yield, possibly because seasonal conditions were not conductive to showing differences or because the cultivation impacts are reducing over time, ongoing assessment should clarify this.
• Drier conditions at seeding and harder finishes would be expected to result in greater impact from the repellence management treatments.

• Soil inversion with a mouldboard plough results in a layer of repellent topsoil being buried at depth with a layer of wettable subsoil brought to the surface. Water can readily enter subsoil brought to the surface but it can take some time for the buried water repellent topsoil to wet up.
• Soil moisture measurements made just after seeding and prior to emergence indicated that at both sites the top 10cm of soil in both the furrow and the ridge was wetter in the mouldboard plough treatment compared with the control treatment.
• For further results please see the attached trial report.

• The trial did re-iterate that early sowing provides more opportunity to ‘play the season’ and alter N management to significantly impact on crop yield outcomes compared with the late sown crops which, in the truncated 2010 season, provided little opportunity for changing N management.  This suggests that focusing on getting the N management of the earlier sown crops sown right for a given season is a good investment of time. Further testing will give a clearer picture as to whether Yield Prophet adds significant value to helping make these decisions. 
• Although the Farmer group were original concerned about the Yield Prophet N budget, tt appears that the model has utilized deep soil test data to reasonably assess the supply of soil N to plants and the movement of soil and applied N through the profile. From this point of view, with the addition of an accurately characterized soil profile, the model may allow growers to better account for and manage nitrogen supply and losses from below the 0-10cm zone.
• Although yields from the Farmer strategy tended to be higher than the Yield Prophet strategy (although not significant), returns per hectare (net of Nitrogen and application costs) were very similar due to the increased costs associated with the Farmer strategy. With further soil characterization and ‘ground proofing’ a tool such as Yield Prophet may be a useful way to reduce the risks and more accurately quantify the benefits associated with applying in-crop nitrogen.
• This trial will be repeated in 2011, and with a more accurate soil characterization it is expected that Yield Prophet will be more accurately assessed.

• Addition of clay-rich subsoil improved crop establishment at this site in 2010.
• There was a very dry finish to the growing season with <15 mm in total for September and October so those cultivation and claying treatments with increased biomass and higher yield potential would have been more prone to haying off.
• Poor incorporation of surface applied clay-rich subsoil can also hold more moisture near the surface which is then subject to evaporation and competes with the roots for water with small rainfall events.
• Despite these factors cultivation with or without the addition of clay-rich subsoil did increase grain yields from <700 kg/ha in the uncultivated situation to an average yield of 1.3 t/ha for the rotary hoe and rotary spaded treatments combined.
• Ongoing monitoring of this trial will be required to see the longer-term benefits of these cultivation and clay incorporation treatments on establishment and yield in seasons with a better finish.