ICC project learnings – a grower’s perspective

Take home messages

The ICC has delivered several projects thanks to GRDC investment, and the results have given practical insight into irrigated cropping. Variety trials, irrigated chickpeas and lentils and canola agronomy trials are currently being funded by the ICC making membership, sponsorship and alternative funding so important.

Background

The Irrigated Cropping Council (ICC) has been involved in irrigated trial work since its inception in 1999. The ICC increased its trial program in 2013 after securing GRDC and other investment. This enabled projects such as the Irrigated Cereals and Canola, Soils after Rice, Crop Sequencing in Double Cropping, Maintaining Profitable Farming Systems with Retained Stubble to address issues related to irrigated cropping. This paper and presentation are short summaries of this work.

Projects have delivered practical outcomes but as with any cropping system there are seasonal and long-term issues that need addressing. The relative plateau of canola yields, getting the best out of alternative pulse crops, achieving good drainage (highlighted in irrigated pulse and soil projects as a constraint), and protein contents are issues raised by the projects completed by the ICC.

Results and discussion

Irrigated Variety Evaluation

Take home messages

• It’s the only irrigated barley and canola variety evaluation conducted in the region.
• NVT trial results need to state if trials are irrigated or not.
• Increasing yields since 2002, however canola has not seen the same gains as wheat, barley and faba beans.

Background

Not all varieties respond equally to irrigation, so when making decisions it’s important to use irrigated variety trial results as part of the selection process. ICC’s long term irrigated barley, canola, faba bean and wheat variety trials generate agronomic information about how dryland varieties currently available perform on irrigation.

Since the ICC first started the Trial Block at Kerang in 2002, there has been a rise in the trial averages for all crop types except canola. The variety results from 2017 were the best attained in 16 years at the Trial Block, with barley averaging 9.33t/ha, faba bean averaging 7.4t/ha, wheat averaging 9.97t/ha and the canola equalling 2009 at 4.3t/ha (Figure 1).

Figure 1. Variety trial averages for barley, canola, faba bean and wheat (2000 – 2017).

Figure 1 indicates that there are some ups and downs but the overall trend is for increasing yields. Low yields from wheat in 2005 was as the result of stripe rust with the decision to rely on promoting resistance rather than fungicides; failure from faba bean in 2006 was as the result of bean leaf roll virus and to a lesser extent in 2009; and the two poor canola years were due to the decision to pre-irrigate and then rely on post sowing rainfall to get the trial established. This is not a strategy to be used going forward.

There are a few contributing factors:

1. Sound agronomic strategies – sowing timing, N management and irrigation which are refined every season
2. Use of soil moisture monitoring to ensure the trial does not suffer from moisture stress, particularly leading into flowering
3. Varieties are getting better, particularly with faba beans where several trials have seen the ‘breeding’ lines all out yield the available varieties
4. Seasonal variation does play a large part in the results – both negative (e.g. wet winters (2014), extreme spring temperatures (2015), rain, wind and disease pressure (2016)) and positive (e.g. cool springs and regular above average rain (2016) and increased sunshine pre-flowering (2017)).

What does stand out is the lack of progress in lifting canola yields.

There are some positives:

• There are regularly one or two varieties exceeding 5t/ha
• There has been a general improvement in the Roundup Ready variety performance
• Achievement of a better understanding of the phenology (crop development) of various varieties, in particular; matching sowing date and flowering.

But there are some negatives:

• Yield of the triazine tolerant (TT) varieties still lag behind the other herbicide tolerance groups
• Seed supply issues which has meant accepting poorer performing varieties or those not quite suited for maximising high yields
• The rapid turnover of varieties - just when we get a good understanding of a particular variety, it is withdrawn

Part of the reason the canola yield average was high in 2017 was due to the better, relative performance of the TTs. Over the years, the TTs yield approximately 89% of the trial average. This varies from the low in 2016 at 79% to the high in 2017 at 96%. According to the ICC’s Trial Manager, part of the answer is the lower radiation use efficiency of the TT trait which results in less biomass at maturity. When conditions are wet and cool in winter, the TTs that are already not as efficient at converting the solar radiation into growth, struggle further compared to their non-TT counterparts.

These observations raise questions, are there ways we can lift yields by encouraging vigour in the vegetative phase of the crop, and if conditions are good then maybe the inherent inefficiency of TTs doesn’t make as much difference? The ICC field trials this season seek to answer these questions.

Maintaining Profitable Farming Systems with Retained Stubble

Take home messages

• There are positives and negatives to retaining stubble.
• Wheat stubble may not have a large N content, so nutrient losses if burning may be less than anticipated.
• Retaining stubble doesn’t necessarily mean retaining organic carbon (OC). Fertiliser, moisture and incorporation are needed to ensure rapid breakdown.
• Stubbles can retain moisture to allow a longer sowing windrow after pre-irrigation, however variable cover can result in wet and dry areas.

Background

The project set out to determine how to maintain the profitability of retained stubble farming systems as growers’ experience has shown that stubble can create problems – from requiring new equipment to handle trash to creating conditions that may foster pest and disease if incorrectly managed.

The positives from stubble include soil protection, nutrient retention or addition in the case of pulses, soil biological activity and grazing opportunities. The negatives include issues with pre-emergent herbicides, capacity of equipment able to handle stubble, nitrogen tie-up, a harbor for pests and disease and increasing frost risk.

Retaining stubble is promoted as the ‘right thing to do’ for several reasons and this project allowed many of these to be tested. A couple that the ICC examined were the loss of nutrients from burning and increasing soil organic carbon by stubble incorporation.

Nutrient losses

The wheat stubble at the Trial Block demonstration had an N content varying from 5.4 –to 7.7kg N/ha, despite topdressing with 400kg urea/ha. This is a lot less than some studies have cited, which then goes on to affect the estimated $ value of nutrient losses when burning stubble.

Increasing soil organic carbon

An increase in soil organic carbon only happens if the stubble is incorporated with fertiliser and moisture to ensure rapid breakdown. It is then hard to measure unless specialist OC testing is used. Retaining stubble on the soil surface means most of the carbon ends up in the atmosphere.

There are numerous information sheets produced by the project, with many having specific reference to stubble management on irrigation. They can be found on the GRDC website.

Moisture retention

Stubbles can retain moisture to allow a longer sowing windrow after pre-irrigation, however variable cover can result in wet and dry areas.

Correct Crop Sequencing under Irrigated Double Cropping

Take home messages

• Large number of factors contribute to successful double cropping.

Background

The Best Management Practice guidebook produced with the trial results from this project is available on the ICC website. The results of this project highlighted layouts, delivery and drainage, weeds, disease and pests, cost of water, sowing times, soil moisture at sowing, nutrition, irrigation scheduling and timeliness of operations were critical when double cropping.

Even if you are not a double cropper, the Correct Crop Sequencing decision support tool is recommended to determine your gross margins and water requirements and can be used to look at just a single season rather than a planned sequence. The tool is available from the NSW DPI website.

Soils under an irrigated environment

Take home messages

• Large variation in what yields are being gained from irrigated wheat.
• Need to set realistic yield targets, match inputs and address constraints.

Background

There are several key messages coming from the project – when you should be irrigating to maximise yield potential, setting realistic yield targets, managing wheat after rice plus areas for future research. Much of the information generated was based on data collected from irrigators across all districts in the Murray Valley. It demonstrated large variation in what yields can be gained from irrigated wheat – some variation based on the environment (solar radiation variability between seasons), some variation from having the right plant population (head numbers, grains/head, row spacing and variety interactions) and some variation from varietal tolerance of waterlogging at crucial growth stages such as flowering.

Results highlighted the importance of setting achievable yield targets and matching inputs to achieve these returns. The project monitored 64 wheat crops over three years and found that 40% came close to their water limited yield but only one crop in the three years yielded over 8t/ha. This was backed up by modelling that suggested maximum yields vary between 6.2 and 12.2t/ha and yields over 8t/ha where only achievable once every four years. There are a range of yield limiting factors depending on the season, soil and layout. Record keeping is key to identifying the constraints that are consistently impacting on yields.

Fact sheets have been produced to summarise some of the project findings including what are the critical growth stages for high yields. These are available on the ICC website.

Irrigation Max

Take home messages

• Putting the majority of N upfront as opposed to splitting it throughout the season generally produced better results over the life of the project.
• Shorter irrigation intervals were of more benefit in hotter seasons and longer internal irrigation lead to reduced soil moisture below 45cm.

Background

The 2017/18 season completed the project, which looked at two N strategies (majority upfront versus split) and irrigation trigger points based on soil moisture content (25-40kPa versus 50-70kPa).

The ‘Upfront’ strategy has seen yield increases of just over 1.0t/ha greater than the ‘Split’ strategy (13.4 versus 12.2t/ha). While not significant in the 2017/18 season, the results from the previous years do suggest the ‘Upfront’ strategy has performed better over the life of the project. The shorter irrigation interval had been looking promising as a way of improving yield but it made no difference in the 2017/18 season. The shorter strategy may be of more benefit in hotter seasons. One aspect of the project was to monitor soil moisture down the profile. Soil moisture at 45cm under the longer irrigation interval was gradually drying out as the season progressed as the ‘fast flows’ were too fast and not allowing the profile to be fully recharged.

Irrigated Pulses

Take home messages

• One year’s data gave yields of 3t/ha for chickpea and lentil.
• Drainage appears to be a key driver but more data required.

Background

The results from 2017 were promising where good drainage was present. The Trial Block; border-check, grey clay with a slope of about 1:800, but relatively slow delivery of 6 ML/day, averaged just over 3t/ha chickpea and lentil yields from pre-irrigation only. Spring irrigation (either one just at the start of flowering or fully irrigated in the spring) saw no yield or grain quality benefit. Two other sites had trials sown –subsurface drip and overhead irrigation – but suffered from soil drainage issues as they were on flat sites.

Irrigated Durum Wheat

Take home messages

• Achieving 13% protein economically continues to be an issue.

Background

These trials started in 2014 and have had mixed results, with the biggest issue being to economically achieve 13% protein. This project is aiming to develop an agronomic package to ensure irrigated durum wheat achieves DR1 quality. The N inputs required to meet this standard are quite significant in a high yielding irrigated durum crop – around 500kg urea/ha. Some of the N input can be obtained by following a legume crop, but this does add a degree of uncertainty on determining how much N the legume crop will deliver to subsequent crops. Combined with variable yields achieved from the durum crop (2016 yielded 7.7t/ha, 2017 yielded 10t/ha despite later sowing but all other agronomic inputs were similar), calculating a N budget to accurately meet the N requirements is difficult.

Conclusion

Projects funded by the GRDC and ICC have delivered practical insights into irrigated cropping. It’s important to ensure we continue to receive local, independent research and extension in our region as irrigated cropping is a valuable industry. Research results from dryland NVT field trials are not directly transferable to irrigated systems as not all varieties and soils respond equally to irrigation, so clear distinction is required when research is delivered on-farm.

The ICC would like to continue to work with the GRDC and other partners to ensure irrigated research continues in northern Victoria and southern NSW. GRDC and government investment make up a considerable portion of our income but equally important is membership, sponsors, philanthropic investors and commercial companies.

Your ongoing support of the ICC will help to ensure a long-term future for irrigated cropping and pasture systems in the Southern Murray Darling Basin.

Useful resources

ICC membership
ICC annual Trial Summary
ICC website
ICC Newsletters

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the author would like to thank them for their support.

Contact details

Stuart Hodge
Numurkah
0417 378 869
stuart@hodgefarms.com.au