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Research & Development

A new method to take genetic material from wild plants to boost the disease resistance of food crops is the outcome of an international collaboration.

Harvesting Wild Genes Gives Crops Renewed Resistance to Disease

Author: Harbans Bariana, University of Sydney

Date: 5th February, 2019

 

A new method to take genetic material from wild plants to boost the disease resistance of food crops is the outcome of an international collaboration.
Professor Harbans Bariana from the Sydney Institute of Agriculture.

Professor Harbans Bariana from the Sydney Institute of Agriculture.

 

A global alliance of researchers has pioneered a new method to rapidly recruit disease-resistance genes from wild plants for transfer into domestic crops. The technique promises to revolutionise the development of disease-resistant varieties for the global food supply.

The technique called AgRenSeq was developed by scientists at the John Innes Centre in Britain working with colleagues in Australia and the US. It was published today in Nature Biotechnology.

The result speeds up the fight against pathogens that threaten global food crops, including wheat, soyabean, maize, rice and potato, which form the vast bulk of cereals in the human diet.

Professor Harbans Bariana from the Sydney Institute of Agriculture and the School of Life and Environmental Sciences is a global expert in cereal rust genetics and a co-author of the paper.

He said: "This technology will underpin fast-tracked discovery and characterization of new sources of disease resistance in plants."

The current research builds on previous collaborative work done by Professor Bariana with the CSIRO and John Innes Centre. It used two wheat genes cloned by this international team as controls and Professor Bariana conducted the phenotype assessments for the study.

AgRenSeq lets researchers search a library of resistance genes discovered in wild relatives of modern crops so they can rapidly identify sequences associated with disease fighting capability.

From there researchers can use laboratory techniques to clone the genes and introduce them into elite varieties of domestic crops to protect them against pathogens and pests such as rusts, powdery mildew and Hessian fly.

Dr Brande Wulff, a crop genetics project leader at the John Innes Centre and a lead author of the study, said: "We have found a way to scan the genome of a wild relative of a crop plant and pick out the resistance genes we need: and we can do it in record time. This used to be a process that took 10 or 15 years and was like searching for a needle in a haystack.

"We have perfected the method so that we can clone these genes in a matter of months and for just thousands of dollars instead of millions."

The research reveals that AgRenSeq has been successfully trialled in a wild relative of wheat - with researchers identifying and cloning four resistance genes for the devastating stem rust pathogen in the space of months. This process would easily take a decade using conventional means.

The work in wild wheat is being used as a proof of concept, preparing the way for the method to be utilised in protecting many crops which have wild relatives including, soyabean, pea, cotton, maize, potato, wheat, barley, rice, banana and cocoa.

Modern elite crops have, in the search for higher yields and other desirable agronomic traits, lost a lot of genetic diversity especially for disease resistance.

Reintroducing disease resistance genes from wild relatives is an economic and environmentally sustainable approach to breeding more resilient crops. However, introgression of these genes into crops is a laborious process using traditional breeding methods.

The new method combines high-throughput DNA sequencing with state-of-the-art bioinformatics.

"What we have now is a library of disease resistance genes and we have developed an algorithm that enables researchers to quickly scan that library and find functional resistance genes," said Dr Sanu Arora, the first author of the paper from the John Innes Centre.

Dr Wulff said: "This is the culmination of a dream, the result of many year’s work. Our results demonstrate that AgRenSeq is a robust protocol for rapidly discovering resistance genes from a genetically diverse panel of a wild crop relative," he said.

"If we have an epidemic, we can go to our library and inoculate that pathogen across our diversity panel and pick out the resistance genes. Using speed cloning and speed breeding we could deliver resistance genes into elite varieties within a couple of years, like a phoenix rising from the ashes."

Key grains events in Western Australia in February will hear how machine learning and artificial intelligence (AI) could help create the next generation of nitrogen (N) fertiliser decision aids for grain growers.

AI Could Help Create Next Generation Fertiliser Decision Aids

Author: Natalie Lee (GRDC)

Date: 7th Feb, 2019

Key grains events in Western Australia in February will hear how machine learning and artificial intelligence (AI) could help create the next generation of nitrogen (N) fertiliser decision aids for grain growers.

CSIRO researcher Roger Lawes will discuss with participants at the Grains Research and Development Corporation (GRDC) Grains Research Updates in Perth and Kendenup the potential for digital technologies to assist with N management.

Expenditure on N fertiliser is one of the largest annual costs for Australian grain growers and is challenging to get right in terms of achieving maximum profitability.

Dr Lawes says conventional crop N fertiliser decision aids require information about the supply of N from the soil and the N requirements of the crop.

“These tools are often complex to use, as growers need to measure the starting amount of N present in the soil, accounting for mineralisation and then estimate the requirements for N by the crop,” he said.

“These factors vary with the season and the soil type, complicating decision making.”

Dr Lawes said that, as part of a GRDC investment, CSIRO had developed a framework that could help modernise and simplify growers’ N decisions using machine learning, remote sensing, on-farm trialling and crop modelling.

“We found that modern analytical approaches, combined with on-farm experimentation and the sensing of multiple crops, may enhance N fertiliser recommendations for wheat crops,” he said.

Dr Lawes said previous research by CSIRO had found applying N according to the long-term mean yield of a paddock could provide an economically sensible approach to N fertiliser management.

“Since that study, artificial intelligence and machine learning techniques have evolved and it is now possible to process large volumes of information about crops, using satellite imagery or information generated from crop models like the Agricultural Production Systems sIMulator (APSIM),” he said.

“In essence, on-farm strip trials, combined with crop modelling and satellite imagery analysis, could help growers understand whether a crop in a particular paddock will respond to an application of N, regardless of crop type, soil or season.”

Dr Lawes said the study aimed to identify the variables that needed to be monitored to help growers make a profitable N fertiliser decision.

“The machine learning technique ‘Random Forest’ was used to determine which variables were the most important and useful for predicting the optimal N fertiliser rate for a paddock,” he said.

“As expected, this analysis found the most important variable was the long term historical mean site yield, as estimated from APSIM, the crop simulation model used in this study.

“Extractable soil water to a depth of 150cm and leaf N content determined by the ‘N minus strip’ were the two next most important variables.”

Dr Lawes said future studies would aim to integrate information from models, satellites and on-farm trials to develop a grower-ready package for making N decisions.

More information about the research will be presented at the GRDC Grains Research Update, Perth, to be held at Crown Perth on February 25 and 26, and at the GRDC Grains Research Update, Albany Zone, at Kendenup on February 28.

Early and effective control of summer weeds will be high on the to-do list for growers in Queensland and New South Wales with the start of the summer storm season.

Spray Weeds Early To Save Moisture and Money

Author: Toni Somes, GDRC

Date: 20th December 2018

 

Early and effective control of summer weeds will be high on the to-do list for growers in Queensland and New South Wales with the start of the summer storm season.

Recent rains across much of the region have been ideal for a flush of summer weeds and the Grains Research and Development Corporation (GRDC) is encouraging growers to implement control tactics early to boost water use efficiency, preserve precious stored soil moisture and nutrients, improve herbicide efficacy and pest and disease control and protect the yield potential of future crops.

GRDC Crop Protection Officer North Vicki Green said most growers were aware that early summer weed control could deliver significant economic, agronomic and environmental benefits.

“In summer, the difference between effective and ineffective weed control is a matter of days, not weeks,” she said.

“Weeds can make or break efficient water storage. As a general rule, if summer weeds are allowed to establish, they will start extracting water from depth – more than 100mm depth – within about 12 days of establishment. That is water that could be used to grow a crop.

“Our research has shown that every dollar invested in summer weed control generates an average return of $5, with early control enhancing the potential benefits.”

This has been further backed up by the GRDC’s landmark National Water Use Efficiency (WUE) Initiative that found complete weed control, which involved spraying 10 days after a significant rain event, resulted in the greatest subsequent winter crop yield when compared with late summer weed control and no control at all.

Agricultural scientist James Hunt, who was one of the key researchers leading the WUE Initiative, encouraged growers to manage summer weeds at the three to five leaf stage using herbicides at registered label rates, as herbicide efficacy was generally highest when summer weeds were young and actively growing.

Dr Hunt, of La Trobe University (previously CSIRO), said summer weed control replicated experiments conducted during the WUE Initiative demonstrated average yield improvements in winter crop performance of 60 percent.

However, summer weed control will be important for growers in parts of the northern region where ground cover protecting topsoils is adequate. In areas where ground cover is scant following significant rainfall deficits and failed crops, growers will need to consider the risks of eliminating any existing vegetation too early, including weeds and volunteer crop plants, which can assist with erosion prevention.

So as part of their summer priorities’ list, Mrs Green said it was important growers had spray equipment ready and adhered to spray application recommendations on chemical and water rate, environmental conditions, droplet size and boom height.

“Weed control is generally more effective if plants are sprayed when they are small, leaving them too long can be a costly failure, requiring additional control measures and risking the development of herbicide resistance on farm. The most expensive spray is a failed spray,” she said.

“Efficacy is also impacted by temperature and humidity, travel and wind speed, droplet size and viscosity of spray so it’s important from a cost/benefit perspective to adhere to best management recommendations on spray equipment and conditions.”

She said an additional benefit of early summer weed control was it destroyed the green bridge (weeds and volunteer cereals) that could harbour pests and diseases between seasons, minimising the impact of these on the following crop.

More information on the importance of summer weed control, the latest research on problem weeds in the northern cropping region and advice on spraying – including tips for minimising spray drift – is included in the GRDC GroundCover™ Summer Weeds Supplement.

Growers are reminded to adhere to best practice when spraying summer weeds to reduce the risk of off-target spray drift and to be aware of new restrictions to the use of 2,4-D.

The Australian Pesticides and Veterinary Medicines Authority (APVMA) has suspended the labels of all products containing the active ingredient 2,4-D from October 4, replacing them with a permit.

Key changes for using 2,4-D under the permit include:

*           Applicators must now use at least a Very Coarse (VC) spray quality;

*           When using a boom sprayer, boom heights must be 0.5 metres (or lower) above the target canopy;

*           Downwind buffers now apply (typically less than 50 metres, subject to rate and product being applied) between application sites, downwind sensitive crops and environmentally sensitive aquatic areas.

The new permit also includes an advisory statement for 2,4-D use in cereals, fallow and pasture from October 1 to April 15. These statements advise operators to use an Extremely Coarse (XC) or Ultra Coarse (UC) spray quality and to take steps to mitigate the risk of spray drift such as adopting increased water rates and slower application speeds.

Grain growers and spray operators can access a practical guide explaining how to maintain efficacy when using coarser spray qualities in line with new restrictions to the use of 2,4-D. A ‘Maintaining efficacy with larger droplets’ fact sheet has been developed by the GRDC to assist industry understand the on-farm implications of the new restrictions.

Mrs Green said importantly, to achieve good spray coverage with VC, XC or UC spray quality, especially on small weeds in stubble, growers should consider using robust chemical rates, slowing down and increasing water volumes.

“Suggesting growers slow down and use in excess of 80L/ha of water (and preferably 100L/ha with contact herbicides) may cause angst, but compared to the costs associated with a failed job and potentially having to respray the paddock, it is worth making the changes,” she said.

Grain growers harvesting frosted crops this season are encouraged to take extra precautions to minimise machinery wear and tear and the risk of fire, and to be conscious of the quality of grain retained for seed.

Issues To Consider When Harvesting Frosted Crops

Author: Sharon Watt

Date: 23 Nov, 2018

Grain growers harvesting frosted crops this season are encouraged to take extra precautions to minimise machinery wear and tear and the risk of fire, and to be conscious of the quality of grain retained for seed.

Department of Primary Industries and Regional Development (DPIRD) research officer Ben Biddulph shares insights into harvesting frosted crops and other issues as a guest on the new Grains Research and Development Corporation (GRDC) podcast series.

Dr Biddulph said frosts in August and September impacted many Western Australian crops and included frosts in mid-September which affected a wide area of WA’s central, eastern and southern cropping areas, and involved temperatures below minus three degrees centigrade in some areas.

“The type and severity of crop damage varied according to the stage of crop development, but it appears barley crops are generally more likely to have been ‘grain frosted’, which may impact on seed quality,” he said.

“Within specific areas, frost damage has varied across the landscape in severity and scale.”

Dr Biddulph, who conducts frost research, development and extension at DPIRD with co-investment from the GRDC, said harvesting a frosted crop brought another layer of complexity to an already busy time of year.

“Some of the complications are limited to this season’s harvest, while others have ramifications for next season’s crop,” he said.

“If practical to do so, harvest frosted paddocks last so that grain from better paddocks is safely in storage first.”

Dr Biddulph said frosted crops were difficult to thresh due to higher residual sugars, lower grain volume and the green material in the case of a plant re-tillering.

 

“Despite lower tonnages, daily harvest maintenance and cleaning down equipment regularly still remain vital to minimise machinery fatigue and fire risk in these difficult harvesting conditions,” he said.

“Frosted crops generate more dust and the crop residue builds up on the machine when harvested, contributing to increased fire risk.

“This is due to the tough nature of frosted stems, shattering of frosted grains and increased saprophytic fungal and bacterial growth on the crop.”

Dr Biddulph said grain quality might be compromised depending on the timing of the frost.

“Frost-affected grains usually have a lower hectolitre weight and higher screenings. Adjusting header settings and/or grading can be beneficial but check the feasibility first,” he said.

“If keeping seed for next season, it’s important to source seed from least-affected areas to maximise establishment.

image of Frost-affected wheat
Frost-affected wheat. Photo by DPIRD.

“Even after grading, frosted grain can have 20 to 50 per cent lower crop establishment than unfrosted grain during the following season.

“As a result, growers need to retain more seed than normal, sow into an optimum seed bed and increase the seeding rate to compensate for lower crop germination and vigour of frosted grain.”

Seed quality can be tested closer to seeding by DPIRD’s Diagnostic Laboratory Services (DDLS) for a small charge. 

Dr Biddulph said frosted stubble could rot at ground level and be difficult to seed into, in the following season.

“To minimise trash flow problems in subsequent seasons, frosted stubbles may have to be cut low during harvest or in a separate operation later on,” he said.

An increasing trend by Western Australian growers to use grain bags after harvest has led to new research into the impacts of this type of on-site storage on cereal seed quality.

Bagging Grain No Impediment To Quality

Author: Natalie Lee

Date: 12th October, 2018

image of grain bag
Research with GRDC investment being carried out by SEPWA is finding grain can be stored in these types of grain bags at harvest with limited risks of quality damage or poor germination in retained seed for the following year. PHOTO: SEPWA

Key Points

  • Use of on-farm grain bags at harvest is gaining popularity in WA to help manage logistics
  • Research shows grain can maintain acceptable moisture levels during summer storage in grain bags
  • Seed germination rates of 99-100 per cent after summer grain bag storage were recorded in trials that have GRDC investment.

 

An increasing trend by Western Australian growers to use grain bags after harvest has led to new research into the impacts of this type of on-site storage on cereal seed quality.

Results to date from the South East Premium Wheat Growers Association’s (SEPWA) Bagging grain profits project are giving this tactic a tick of approval, with minimal evidence of adverse impacts on grain quality or seed germination rates after planting the following year.

The group conducted trials of grain bags across the Esperance region during the 2017-18 harvest, as part of a suite of Grains Research and Development Corporation (GRDC) investments into local issues that have been identified by grain growers as impacting on their profitability.

SEPWA’s research will be repeated during this year’s harvest period and include monitoring grain quality factors such as seed moisture, protein levels, temperature, colour and germination, and assessing any market liability risks.

SEPWA project officer Aidan Sinnott said results from last summer indicated daytime maximum temperatures, including quite big fluctuations from low-20⁰ Celsius levels up to the mid-40⁰C range, did not have a big effect on temperatures inside the grain bags.

He said across the trial sites, and after about 40 days of storage in the bags, barley and wheat grain moisture was maintained at industry acceptable levels of about 13-14 per cent and grain quality was not adversely impacted by this type of storage in the summer conditions.

Mr Sinnott said at one location, wheat did heat up more than barley when monitored in grain bags for 38 days at an average daytime temperature of about 20⁰C, but not to a level that impacted on its key quality parameters.

Part of the Bagging grain profits project was to assess the germination rates of cereal seed retained in grain bags after sowing in 2018.

Across all trial sites, germination rates were 99-100 per cent for this seed, some of which was stored in grain bags for up to 74 days.

“Overall, there was very little effect on seed germination percentages for wheat and barley stored in grain bags in the conditions experienced in the 2017-18 harvest and summer period,” Mr Sinnott said.

“During the coming harvest, we plan to extend the storage period of grain in bags and add other crop types to our evaluation.

“At the end of the two-year GRDC-SEPWA project, we hope to have developed comprehensive tips for using grain bags and best-practice guidelines for industry stakeholders down the supply-chain, including how to manage any potential grain quality risks.”

 

Mr Sinnott said the use of grain bags for on-site storage was now a recognised management tactic in WA, providing logistical advantages for growers in allowing them to fast-track harvest operations, manage grain moisture and quality and capture freight cost advantages.

“SEPWA advocates early harvest in the South Coast region to optimise grain quality and crop value,” he said.

“Grain bags enable management of moisture and quality parameters prior to grain leaving the farm, or can be used for storing retained seed for subsequent planting.

“Use of these bags also offers opportunities for growers to access grain quality upgrades and extend the truck freight period to further reduce peak harvest grain freight costs.”

GRDC grower relations manager – west, Lizzie von Perger, said the SEPWA-led Bagging grain profits project was the direct result of this issue being raised as a challenge by WA growers.

“It is vitally important that GRDC responds to emerging issues, such as optimising results from the use of innovative grain storage tactics, in a timely manner,” she said.

While advances in agronomy and the performance of individual crops have helped grain growers to maintain their profitability, current farming systems are underperforming; with only 30% of the crop sequences in the northern grains region achieving 75% of their water limited yield potential.

Can Systems Performance be Improved by Modifying Farming Systems? Farming Systems Research - Billa Billa, QLD

Author: Andrew Erbacher and David Lawrence (GRDC)

Date: 25th July, 2018

 

Take home messages

  • Different farming systems comparisons conducted over 3 years at Billa Billa QLD have shown that the baseline system (wheat-barley-wheat) has so far returned the highest gross margin ($2.77) per mm rainfall.
  • Increasing or decreasing cropping intensity has returned similar gross margins, but had low returns in 2016/17 summer.

Project background

While advances in agronomy and the performance of individual crops have helped grain growers to maintain their profitability, current farming systems are underperforming; with only 30% of the crop sequences in the northern grains region achieving 75% of their water limited yield potential.

Growers are facing challenges from declining soil fertility, increasing herbicide resistance, and increasing soil-borne pathogens in their farming systems. Changes will be needed to meet these challenges and to maintain the productivity and profitability of our farming systems. Consequently, the Queensland Department of Agriculture and Fisheries (QDAF), New South Wales Department of Primary Industries (NSW DPI) and Commonwealth Scientific and Industrial Research Organisation (CSIRO) are conducting an extensive field-based farming systems research program, focused on developing farming systems to better utilise the available rainfall to increase productivity and profitability, with the question;

Can systems performance be improved by modifying farming systems in the northern region?

This research question is being addressed at two levels by the northern farming systems initiative; to look at the systems performance across the whole grains region, and to provide rigorous data on the performance of local farming systems at key locations across the region.

Research began in 2014 with local growers and agronomists identifying the key limitations, consequences and economic drivers of farming systems in the northern region; assessing farming systems and crop sequences that can meet the emerging challenges; and developing the systems with the most potential for use across the northern region.

Experiments were established at seven locations; a large factorial experiment managed by CSIRO at Pampas near Toowoomba, and locally relevant systems being studied at six regional centres by QDAF and NSW DPI (Table 1). Several of these systems are represented at every site to allow major insights across the northern region, while the site specific systems will provide insights for local conditions.

The following report details the systems being studied in Billa Billa (Goondiwindi), how they are implemented locally and the results after the first three years. Data and system performance indicators have been developed to compare performance across sites.

Table 1. Summary of the regional farming systems being studied at each location in the northern farming systems initiative.

 

   

Billa Billa - 2015 to now

The Billa Billa site is located 50 km north of Goondiwindi on the Leichhardt Highway. The soil is a grey vertosol. The original belah and brigalow trees were cleared and the paddock used as a long-term pasture before being developed for crops in the late 1990s. The previous paddock management has meant there was 360 kg N/ha available at the beginning of the trial.

The paddock grew chickpeas in 2014, so was quite bare prior to commencing the trial in autumn 2015. All of the systems were planted to wheat in the first season to provide stubble cover, yielding 4.7 t/ha. After harvesting this crop, the higher soil fertility system had 75 t/ha of compost broadcast across it to supply an additional 10 t/ha of carbon to this system, which increased the soil carbon by 27% in the top 30 cm of soil. Deep phosphorus was then applied to all of the cropping systems supplying 70 kg P/ha applied in the form of Granulock® Z. After 2015, rotations in the different systems have been quite diverse (Figure 1).

The baseline system was planted to barley in 2016, wheat in 2017 and is planted to chickpea in 2018 (Figure 1).

The summer of 2015-16 was dry with storm rain contributing to the majority of the profile moisture accumulation. The higher crop intensity system triggered an opportunity to be double cropped to mungbean on 15 January. The next effective rainfall this crop saw was after spraying out, so yielded 0.35 t/ha (Figure 2). This double-cropped mungbean crop was planted with the same starting water as the baseline system, which was held in fallow over summer and planted to barley in 2016. This gave the higher crop intensity system a fallow efficiency advantage of 71% versus 30% in the Baseline system(Figure 5). However, differences in the timeliness of in-crop rain had a major impact on the yield outcomes of the mungbean and barley crops (Figure 2).

Autumn 2016 was also dry, requiring faba bean and field pea to be deep sown in the higher legume and higher crop diversity systems respectively. Baseline, higher nutrient supply and higher soil fertility systems were planted to barley on 1 June (Figure 1), with the season remaining quite wet until November. The faba bean and field pea crops matured in early October, and had a wet harvest with a full profile of water, allowing a double crop opportunity in both of these systems. However, the barley in 2016 (baseline, higher nutrient supply and higher soil fertility systems) lodged and put out late tillers, so was harvested mid-November with weather damaged grain. Grain yields averaged 6.3 t/ha for barley and 3.45 t/ha for faba bean and field pea (Figure 2). The yield per mm of water used (water use efficiency) of the two pulse crops were similar to each other, but lower than the barley grown in the same season (Figure 5).

Differences in the economics of the systems to date have largely been driven by the high yields of the 2016 winter crops (Figure 3). The high starting available nitrogen levels at this site has allowed the baseline, higher nutrient supply and higher soil fertility systems to grow 11 t/ha of cereal grain over the first two years, without the expense of nitrogen fertiliser. As such, these three systems have been the most profitable, with the only difference being a higher starter P fertiliser rate in the two higher nutrient systems.

The higher legume and higher crop diversity systems were both planted to pulses in winter 2016 that yielded similarly to each other, but the value of faba bean vs field pea meant the faba bean income and $/mm was similar to the much higher yielding barley, whereas the field pea was quite a bit lower (Figure 3 & 4). The pulse crops in 2016 appear to have fixed nitrogen despite the high starting N. They have similar nitrogen removed in the grain to the barley crops but have an extra 50 kg N/ha left in the soil profile post-harvest. Add to this, the early maturity date of the pulses left an extra 150 mm plant available water, which provided an opportunity double crop. However the dry summer that followed provided poor returns on that double-crop.

The lower intensity and higher intensity systems were planted to sorghum on 15 October, with 200 mm and 120 mm plant available water (PAW) respectively. With only 80 mm in-crop rainfall, these crops were low yielding at 1.5 t/ha and 0.8 t/ha (Figure 2). These yields both lined up with the APSIM predicted yield for the driest 10% of years, for their starting plant available water.

Apart from the 2015 wheat crop that is common to all systems, this sorghum crop was the only crop grown in the low crop intensity system from November 2015 to May 2018, whereas the higher crop intensity system grew three crops to achieve similar cumulative gross margins, with a fourth (sorghum) crop putting the higher crop intensity system slightly ahead. The major commonality in these two systems, that is different to the other systems, is all the crops grown after the initial wheat crop have had received below average in-crop rainfall. Two of these crops were grown in the driest 5 % of seasons for Goondiwindi. As a result the higher crop intensity and lower crop intensity systems are providing the lowest economic returns to date.

After 2016 winter crop was harvested with a full profile of water, the higher legume and higher crop diversity systems were planted to mungbean and sorghum respectively at the next planting opportunity, which wasn’t until December (Figure 1). With no effective rainfall before flowering, the mungbean yielded 0.15 t/ha, whereas the sorghum held on to take advantage of autumn rain for a yield of 1.5 t/ha, harvested in July.

The three systems that grew barley in 2016 were all planted to wheat in May 2017. The higher crop intensity system was also double-cropped to wheat at the same time. This crop received 25 mm rainfall prior to maturity, but received a further 83 mm before it could be harvested. The fallowed systems (baseline, higher nutrient supply and higher soil fertility) yielded 1.7 t/ha on average and the double cropped wheat (higher crop intensity) yielded 1.4 t/ha. These systems had similar crop water use efficiencies (WUE) of 12.5 kg/mm on average (Figure 5). The difference in yield is reflecting differences in starting plant available water.

The mungbean grown in the higher legume system had only dried the top 30 cm of soil, so was one rainfall event off being planted to wheat. With the dry winter this did not eventuate, but 80 mm of rain in October allowed it to be planted to spring sorghum with a good profile of plant available water. This sorghum was looking good with 200 mm of in-crop rain, but a dry January capped the yield at 2.9 t/ha with 40% screenings.

The wet spring in 2017 allowed the higher intensity system to be double-cropped again to sorghum. This crop had a dry start, but 150 mm in February and March allowed it to tiller again for a yield of 2.4 t/ha, harvested in May.

Six systems have been planted to winter crops in 2018 (Figure 1). Higher crop diversity has been planted to canola and lower crop intensity to wheat, both after long fallows. Baseline, higher nutrient supply and higher soil fertility were planted to chickpeas after a short fallow and higher legume double-cropped to chickpeas. This leaves only higher crop intensity in fallow, having received no rain from sorghum harvest to the end of June 2018.

Picture shows timing of crops grown at the Billa Billa farming systems trial, presented on a time scale.Figure 1. Crops grown at the Billa Billa farming systems trial, presented on a time scale. The coloured sections are planting to harvest of each crop, and the grey bars are fallow periods.

Picture is a column graph shows cumulative grain yields of the seven grain systems at the Billa Billa farming systems trial.

Figure 2. Cumulative grain yields of the seven grain systems at the Billa Billa farming systems trial

Graph shows cumulative cash-flow from the seven grain systems at the Billa Billa farming systems trial. This shows the actual production costs and incomes, based on 10 year average commodity prices, over time for each of the systems.Figure 3. Cumulative cash-flow from the seven grain systems at the Billa Billa farming systems trial. This shows the actual production costs and incomes (based on 10 year average commodity prices), over time for each of the systems.

Picture shows gross margin per mm of rainfall for each crop grown, including the preceding fallow period, and total for each system, up to the harvest of the last crop. Figure 4. Gross margin per mm of rainfall for each crop grown, including the preceding fallow period, and total for each system (up to the harvest of the last crop). The coloured bars represent the crops depicted in Figure 2.

Picture shows crop water use efficiency and fallow efficiency, overlaid onto the crop durations represented in Figure 2.

Figure 5. Crop water use efficiency and fallow efficiency, overlaid onto the crop durations represented in Figure 2. The value in the coloured bars is the kg of grain produced per mm of plant available water used + in-crop rainfall. The value in the grey bars is the proportion of rainfall available at planting of the next crop.

Table 2. Grain pricing used in calculations based on median prices over the past ten years, less $40/t cartage costs, 
for selected crops

 

Acknowledgement

This trial is part of a collaboration between the Grains Research Development Corporation (GRDC) Queensland Department of Agriculture and Fisheries (DAF), New South Wales Department of Primary Industries (NSW DPI) and Commonwealth Science and Innovation Research Organisation (CSIRO). DAQ00192.

Grain growers in Queensland and New South Wales are being encouraged to consider the potential impact of residual herbicides as they weigh up what to plant this summer.

Consider Herbicide Status Ahead of Summer Crop Planting

Author: Toni Somes (GRDC)

Date 10th August, 2018

 

Grain growers in Queensland and New South Wales are being encouraged to consider the potential impact of residual herbicides as they weigh up what to plant this summer.

Experts warn dry conditions across much of eastern Australia’s grain belt through winter may have prolonged the efficacy of residual herbicides applied in paddocks earlier in the season.

image of sprayer herbicide

Dry conditions during winter may mean herbicides are present in the soil in greater concentrations then growers would usually expect going into summer planting.

 

Grains Research and Development Corporation Crop Protection Officer – North Vicki Green said the simple fact was herbicides generally needed moisture to breakdown.

“The ongoing dry conditions during winter may mean herbicides are present in the soil in greater concentrations then growers would usually expect going into summer planting,” she said.

“This is not a dire situation, rather it just means growers and their advisers may have to look more closely at crop choice and variety selection ahead of planting.

“Most growers will be aware of the potential risks of residual herbicides in a season like this, but GRDC do have up-to-date information available if people want guidelines to soil behaviour with regard to pre-emergent herbicides.”

Mrs Green said when it did rain growers could also use the emergence of specific weeds as an indicator to what herbicides were still active in the soil.

“Unfortunately, when it rains weeds are usually the first things to respond, the upside is growers can use what weed types emerge as an indicator of what residual herbicides are still in the soil,” Mrs Green said.

The GRDC is committed to building grower and advisor knowledge about weed management and more specifically herbicides and their performance in different soil types under different seasonal conditions.

In recent years the GRDC have run a series of workshops, aimed at enhancing industry knowledge of herbicides. The workshops were co-ordinated by Independent Consultants Australia Network’s (ICAN) Mark Congreve, who has also developed technical manuals to complement the workshops, explaining the science that underpins how herbicides work.

“Greater knowledge of how herbicides work enables grain advisors to better optimise their advice to growers on herbicide use,” he said.

“Manuals and training covered both the soil behaviour of pre-emergent herbicides and the modes of action of post-emergent grass herbicides.

“In the pre-emergent workshop this included volatility, photodegradation, influence of organic matter, soil binding coefficients and cation exchange capacity of the soil. Also, water solubility, breakdown pathways and DT50 values and how these product features coalesce to inform how different herbicides behave in the soil.

“For the post-emergent herbicides, we covered how different modes of action work, herbicide entry through the leaf, translocation and metabolism. The complexities of herbicide resistance and the implications these factors have in optimising performance of particular modes of action.”

Mr Congreve said more than 1000 advisors and growers attended the 57 workshops held across Queensland and NSW.

“The feedback post the workshops was very positive and supports the GRDC’s decision to invest in industry training,” he said.

“The broadacre agronomists who attended the workshops reported that the material presented was informative, easy to understand, had practical application and was complemented by the comprehensive technical materials that were part of the package.

“Importantly the material presented proved to be beneficial to both highly experienced and graduate agronomists.”

Mrs Green said the take home message message from the series of workshops was both growers and agronomists appreciate opportunities to learn new information and build on their knowledge in areas that have practical application in their day-to-day work.

“We were impressed by the feedback from workshop attendees and it has been the catalyst for ongoing GRDC investment in this area,” she said.

“The GRDC is committed to building industry capacity and that means investing in agronomists and growers so they have the skills and knowledge needed to guide on-farm management decisions that influence profitability.”

Mrs Green said the value advisors put on the technical manuals, developed as part of the workshop series, has also prompted the GRDC to make online versions available to all interested stakeholders.

“When advisors and agronomists tell us something is valuable and worth having we listen, hence our decision to make technical copies of the manual available beyond workshop attendees.”

Image of flaxleaf fleabane

Controlling the weed, flaxleaf fleabane, continues to be a challenge for grain growers in Queensland and New South Wales, but research has proved targeting smaller plants during the winter fallow or winter crop phase is key to an effective management strategy.

Paddock Practices: Why is Winter the Best Time to Control Fleabane

Author: Toni Somes, GRDC

Date: 14th Jun 2018

Controlling the weed, flaxleaf fleabane, continues to be a challenge for grain growers in Queensland and New South Wales, but research has proved targeting smaller plants during the winter fallow or winter crop phase is key to an effective management strategy.

Six tips for effective fleabane control:

  • Management in winter (crop or fallow) can be more effective than summer
  • Increase crop competition with narrow row spacing and or higher planting rates
  • Consider strategic cultivation for seed burial or for salvage management
  • Utilise residual chemistry where possible and control ‘escapes’
  • Including 2,4 D or picloram/2,4-D in the first application is a critical for consistent double-knock control
  • Control escapes and prevent weed seed set.

 

Image of flaxleaf fleabane
Research has shown flaxleaf fleabane management is often more effective during winter, both in crop or fallow.

An investment by the Grains Research and Development Corporation (GRDC) into trials conducted by the Northern Grower Alliance (NGA) found fleabane management improved dramatically when grower focus shifted from controlling the weeds in summer fallow to using fleabane control tactics during winter cropping at pre-plant, in-crop and post-harvest stages or in winter fallows.

NGA’s Richard Daniel said flaxleaf fleabane (Conyza bonariensis) control had become an increasingly complex and expensive weed for northern grain growers, as a result of the industry’s heavy reliance on glyphosate and due to the wide spread implementation of no-till or reduced tillage farming systems.

“For nearly two decades, fleabane has been a major weed management issue in the northern cropping region,” Mr Daniel said.

“Factors that make fleabane a major weed includes the fact it is a prolific seed producer, with each plant producing up to 110 000 seeds; it is windborne and occurs in fallows, summer and winter crops and pastures; is difficult to control with herbicides with some populations glyphosate resistant; and the weed can emerge throughout the year.”

Mr Daniel said one of the key issues leading to fleabane being such as problem was that knock-down control of large plants in the summer fallow was expensive and delivered variable results.

“Glyphosate resistance has been confirmed in fleabane, but resistance status is variable with many samples from non-cropping areas still well controlled by glyphosate, whilst increased levels of resistance are found in fleabane in reduced tillage cropping situations.”

So what are the control and management options for growers?

Monitoring

Image of fleabane
Germination of fleabane can occur all year round when wet conditions and temperatures of 10-25°C occur, with fleabane often emerging with winter crops or during the winter fallow in the northern regions.

Monitoring is a key part of weed management but it is particularly important for fleabane.

Germination of fleabane can occur all year round when wet conditions and temperatures of 10-25°C (optimal 20°C) occur. These conditions are more prevalent in autumn and spring, with fleabane often emerging with winter crops or during the winter fallow in the northern regions.

Knowing when new germinations of fleabane occur in an attempt to target control of small plants is critical as it is more effective than on larger plants. As fleabane grows its stem becomes harder and it develops a strong root system. The harder stems and large root system of larger plants enable the plants to regrow more effectively following herbicide applications.

Actively managing fleabane during winter in fallows or in-crop is more effective then summer as emerging seedlings are slower to grow. This slower growth allows more time to apply effective herbicide control options. It is also very important to manage winter germinating fleabane prior to spring as fleabane grows rapidly as the season warms and rainfall increases in northern regions leading into to summer.

While paddock control is critical so is monitoring fencelines and channels as fleabane is wind dispersed, continual replenishment of the seedbank can occur if these areas are ignored.

Crop Competition

Managing fleabane in-crop is a useful tool as fleabane does not establish well in low light conditions. Light conditions can be manipulated by planting crops at higher density and on narrower row spacing. Narrow rows and higher plant populations are primarily used when planting winter crops compared with the wider summer row spacing configurations in the northern region.

Image of fleabane
Due to its small seed size, fleabane will only emerge from the top 1cm of soil.

It is important to monitor crops as fleabane can survive at small growth stages under a competitive crop and be easily overlooked. However, once the crop is removed the fleabane which is present can develop quickly and the opportunity for effective control can be missed without regular monitoring.

Cultivation

Fleabane is a weed that proliferates in no-till farming systems. This is partly because many populations of fleabane present under this system now have a level of resistance to glyphosate but also due to the weed’s ecology. Due to its small seed size, fleabane will only emerge from the top 1cm of soil.

Cultivation to bury seed to a depth deeper than 1cm can be an effective tool to manage fleabane populations. Although this approach can dramatically reduce the number of fleabane which emerge, it also increases the longevity of the seed i.e. seed that is buried will not germinate but it will remain viable for a longer period. Occasional cultivation can be a useful tool for seed bank management but this is not a technique to utilise frequently as it will simply return viable seeds to the soil surface.

Cultivation may also be a viable option for salvage management. Where ‘blow outs’ occur this may be the only economic option to effectively control large flowering plants.

Herbicide strategies

Fleabane management improved dramatically when growers switched from trying to control large plants in summer fallow to targeting small weeds still in the rosette stage during the winter crop phase. There are three key stages where herbicides can be useful to manage fleabane populations; pre-plant, in-crop and post-harvest.

Image of fleabane
There are three key stages where herbicides can be useful to manage fleabane populations; pre-plant, in-crop and post-harvest.

Residual herbicides (fallow and in-crop)

One of the most effective strategies to manage fleabane is the use of residual herbicides in fallow or in-crop. Trials have consistently shown good levels of efficacy from a range of residual herbicides commonly used in sorghum, cotton, chickpeas and winter cereals.

Residual (and knock-down) in fallow:

In Fallow, at least 3 months prior to planting sorghum:FallowBoss® Tordon® (300 g/L 2,4 D + 75 g/L picloram + 7.5 g/L aminopyralid) at 700 mL/ha + atrazine (600 g ai/L) at 3-5 L/ha

Trial work to date has indicated that increasing water volumes from 50-100 L/ha may help the consistency of residual control with application timing to ensure good herbicide/ soil contact also important.

Knock-down herbicides in fallow:

Group I herbicides have been the key products for fallow management of fleabane with 2,4 D amine and picloram/2,4-D products the most consistent herbicides evaluated. Despite glyphosate alone generally giving poor control of fleabane, trial work has consistently shown a benefit from tank mixing glyphosate with 2,4-D and picloram/2,4-D products in the first application.

  • Amicide® Advance (700 g/L 2,4-D) at 0.65-1.1 L/ha + Weedmaster DST (470 g/L glyphosate) at a min of 1.4 L/ha. Follow with a double-knock of Nuquat® (250 g/L paraquat) at 1.6 -2.0 L/ha when weeds are from stem elongation to flowering.
  • FallowBoss Tordon at 700 mL/ha + glyphosate (450 g/L) at 1.6-2.4L/ha (can also be followed 5-7 days later with Spray.Seed® at 1.6 L/ha as a double-knock) - prior to winter cereals or sorghum.
  • Tordon® 75 D (2,4 D + picloram) at 0.7 L/ha + glyphosate
  • Sharpen® (700 g/kg saflufenacil) at 17-34 g/ha + 1% Hasten® spray oil.

Post emergent herbicides in winter cereals:

  • Amicide Advance at 1.5 L/ha
  • FallowBoss Tordon at 300 mL/ha
  • Hotshot® (10 g/L aminopyralid + 140 g/L fluroxypyr) at 750 mL/ha + either metsulfuron (600 g ai/kg) at 5 g/ha or MCPA LVE (600 g ai/L) at 580 mL/ha (refer to label for appropriate growth stages)
  • Lontrel® Advanced (600 g/l clopyralid) at 150 mL/ha
  • Paradigm® (200 g/kg halauxifen Group I + 200 g/kg florasulam Group B) at 25 g/ha + MCPA LVE (600 g ai/L) at 300-600 mL/ha.

Double-knock control

The use of a double-knock strategy is recommended for the control of fleabane in fallow systems as weed size increases and herbicide efficacy generally reduces. The most consistent and effective double-knock control of fleabane has involved including 2,4 D or picloram/2,4-D products + glyphosate in the first application followed by paraquat or Sharpen as the second. Glyphosate alone followed by paraquat will result in high levels of leaf desiccation but plants will generally recover. Trial work conducted by the NGA in the north has shown regrowth observed following the application of Sharpen as the second knock to be more consistent than other group G herbicides or paraquat when applied at the same timing.

Timing of the second application in fleabane is approximately 7-14 days after the first application. However, the interval to the second knock appears quite flexible. Increased efficacy is obtained when fleabane is actively growing or if rosette stages can be targeted. Although complete control can be obtained in some situations, control levels frequently only reached approximately 70-80%, particularly when targeting large flowering fleabane under moisture stressed conditions. The high cost of fallow double-knock approaches, and inconsistency in the control level of large mature plants, is a key reason that proactive fleabane management should be focused at earlier growth stages.

Nitrogen rates, crop rotation and root health are proving to be the biggest factors affecting yield for southern region farmers according to interim results from the GRDC’s National Paddock Survey.

With The Grain: National Survey Providing Widespread Yield-gap Information

Author: Rachael Oxborrow, GRDC 

Date: 7th June, 2018

Nitrogen rates, crop rotation and root health are proving to be the biggest factors affecting yield for southern region farmers according to interim results from the GRDC’s National Paddock Survey.

CSIRO group leader and farming systems scientist Dr Roger Lawes revealed these key yield gap variables at GRDC Research Updates earlier this year. He outlined preliminary results which showed for a given amount of rainfall the most dominant factors affecting yield were nitrogen nutrition and crop health, with weeds proving a lesser factor.

Consultants and researchers from farming systems groups across the country are now preparing for their fourth and final year of data collection for this GRDC investment led by Birchip Cropping Group (BCG) and CSIRO.

Their work will give farmers a region-by-region understanding of what variables they should be most concerned with in bridging the gap between their actual yield and water limited yield. This is defined as the maximum possible yield based on optimal sowing date, current cultivars and nutrients, pests, disease and weeds not limiting yield.

National Paddock Survey project lead and BCG consultant Harm van Rees says final results from the investment will equip farmers with a clear idea of the manageable factors limiting yield in their region based on results from their location.

“This research is trying to take previous yield gap analysis a step further and take it to individual paddocks rather than a soil type,” he says.

“We monitor two zones in each paddock and work out the size of the yield gap for each zone and then analyse the data for factors limiting production over a four year rotation.

“This analysis is only for factors that farmers can manage. For example, if a grower has subsoil limitations on their property with high salt levels then that can’t be changed as it is a physical limitation, but if they’ve got a disease level, then that can be managed.”

In the western, northern and southern GRDC regions across the Australian grain belt, 250 paddocks are being monitored, with 90 locations being monitored in the south. These farms were selected by local consultants and farm groups and represent the range of prevailing rainfall and soil conditions across the grain belt.

Consultants and farming systems groups monitor two zones within each NPS paddock which includes: deep soil cores prior to sowing which is analysed for soil N, soil water content and subsoil limitations. They also record tillage, stubble retention, crop type, cultivar, sowing date and monitor the crop for weeds, insects, diseases and take plant root samples which are analysed for root health. At the end of each season, crop yields are measured using a harvester’s yield monitor. The data collected for each season is reviewed at annual project meetings, to allow consultants and researchers to discuss insights and information regarding individual paddock performance.

Dr Lawes says results so far show the yield gap cannot be attributed to one factor but rather a number of factors as shown in table 1. The level of impact of each factor varies by region and in some cases the factors were driven by the first limiting constraint.

Dr Lawes says the survey has identified the yield gap, or the difference between actual and potential yield in wheat, was 1.1 tonnes per hectare in the northern region, 1.2t/ha in the southern region, and 1.3t/ha in the western region.

Frost and heat shock are yield limitations many farmers would identify as major concerns in the southern region.  Mr van Rees says this is particularly the case as the timing of frost and heat shock events appears to be changing.

“Frost and heat shock are manageable in some ways through cultivar and sowing dates, but they can never be completely avoided,” he says.

“Most farmers are already managing many limiting factors and information from the National Paddock Survey will help them further with recognising their exposure to the most limiting factors and options for management.”

GRDC research code: BWD00025

WA growers who hope to take advantage of early-season moisture now have a new variety option following the release of Australian Grain Technologies’ (AGT) winter wheat Longsword.
Derived from Mace, Longsword is best suited to low and medium rainfall areas.
The new variety can be sown from early April

New early-season wheat variety released

WA growers who hope to take advantage of early-season moisture now have a new variety option following the release of Australian Grain Technologies’ (AGT) winter wheat Longsword.

Derived from Mace, Longsword is best suited to low and medium rainfall areas.

The new variety can be sown from early April, fitting into the planting window between the longer season, traditional winter wheats and the more commonly-sown spring varieties.

AGT wheat breeder Dr James Edwards said the new variety had unique maturing characteristics that made it suitable for planting within a wide and flexible sowing window, while remaining less susceptible to frost and heat damage.

“In environments with a distinct dry finish, if flowering occurs outside of the optimum time or grain fill occurs too slowly, drastic yield reductions can occur,” Dr Edwards said.

“With its three vernalisation genes, Longsword will remain vegetative across a broad planting window and should deliver an optimal flowering time, but not linger through grain fill.

“There is nothing else like it on the market as winter wheat breeding and selection has traditionally been undertaken in areas where there is a softer finish to the season.”

AGT national marketing manager Dan Vater said AGT had been working on Longsword for the past eight years.

He said the winter wheat variety was ideal for WA growers wanting to capitalise on opportunistic earlier sowing.

“Growers are constantly expressing a desire to get into paddocks earlier but we are already pushing the limits on how early we can sow our current spring varieties, Mr Vater said.

“We finally have a variety that you can plant through most of April before you swap over to a spring wheat like Scepter in May.

“It gives them (growers) much more flexibility on when they can start sowing and if there’s some early rains then they might be able to take advantage of them.”

Mr Vater said while Longsword was not expected to replace more popular WA wheat varieties, it could be a useful cropping program option.

 

29 Nov, 2017

STRATEGIC deep tillage was chosen as a tool to ameliorate soil water repellence and subsoil constraints at a trial established by the Mingenew Irwin Group (MIG). MIG research and development manager Debbie Gillam said severe water repellent soils in the region were typically low in water holding capacity and fertility and as a result had limited productivity......

Delving into water repellence

05 Apr, 2017 02:00 AM

Farm Weekly

 

STRATEGIC deep tillage was chosen as a tool to ameliorate soil water repellence and subsoil constraints at a trial established by the Mingenew Irwin Group (MIG).

MIG research and development manager Debbie Gillam said severe water repellent soils in the region were typically low in water holding capacity and fertility and as a result had limited productivity.

"Low productivity means that the amelioration approach needs to be as cost effective as possible," Ms Gillam said.

The trial, which was funded through GRDC's water repellence project, looked at the use of the cost effective one-way disc ploughing.

The plough is a robust tool that is simple to modify for partial soil inversion.

Ms Gillam said the research site compared a one-way disc plough to rotary spading (a proven amelioration option) and to other deep ripping approaches, including some of the newer very deep rippers.

"One of the two key messages to come from the research includes the difficulty of achieving productivity benefits if other constraints such as weeds and compaction remain unaddressed," she said.

"The other is that rotary spading and modified one-way ploughing improved water infiltration, the evenness of soil wetting, weed control and crop yield."

Compaction was identified as an issue at the Mingenew trial site.

Subsoil compaction was severe (2.5MPa) from 22 centimetres and extreme (3.5MPa) from 30cm.

Of the rippers used, the Tilco deep ripper effectively loosened the soil to 54cm, the Terraland ripper to 48cm, the Ausplow ripper to 38cm, the one-way plough to 36cm and the spader to 30cm.

In the untreated control moisture infiltration followed the typical pattern for repellent soils with preferential flow paths and large areas of "dry patch" indicating bypass flow.

Water infiltration was significantly improved by rotary spading and one-way ploughing.

Deep ripping treatments did not improve soil water infiltration and soil water content.

DAFWA research officer Steve Davies helped with the trial and said for many deep sands, deep ripping with topsoil slotting could be one of the most economical ways of overcoming subsoil compaction and acidity (to depths of 40-60cm).

"However, on severely repellent sands it could be that deep ripping is inadequate and may require options that overcome repellence and assist with weed control while at the same time addressing subsoil compaction and acidity," he said.

"Addressing water repellence without also addressing the other subsoil constraints will limit the likely productivity benefits and must be addressed."

Trial work is on-going and MIG will release further findings in 2017.

Mixed farmer David Wolfenden says on-farm trials and his own observations have consistently shown that profitable returns are closely tied to the wellbeing of his land. David, who farms at Rand in southern NSW, became interested in soil health in 1978 when he hosted a New South Wales Department of Primary Industries (DPI) trial investigating minimum tillage........

Soil health checks keep profit potential alive

Date: 16.03.2017

Author: Nicole Baxter

Grain Research & Development Corporation 

Southern NSW grower David Wolfenden shares some of the lessons learned on his decades-long journey to tie improved soil health to income health.

 

 

Mixed farmer David Wolfenden says on-farm trials and his own observations have consistently shown that profitable returns are closely tied to the wellbeing of his land.

David, who farms at Rand in southern NSW, became interested in soil health in 1978 when he hosted a New South Wales Department of Primary Industries (DPI) trial investigating minimum tillage.

He could see the potential for improved soil health so he bought a one-pass seeder and became a founding member of the Southern Farm Management Group, a group of growers interested in trying new farm practices.

Soon after the group was formed the members looked into a system that had benefited irrigated growers.

The system, called Crop Check, encouraged soil and crop-health monitoring to improve returns.

Developed by former NSW DPI agronomist John Lacy, it suggested more than 10 checks were necessary to grow high-yielding wheat.

It was not long before David had implemented a dryland version of the system and was well on the way to improving yields.

“A key lesson was that good yields are a result of getting many factors right, with soil health a major contributor to most of these factors,” David says.

He points out that adopting minimum tillage followed by stubble retention started as an “act of faith” and took a decade to produce measurable benefits – the key indicator being improved profit.

As a consequence, David sees exploiting the benefits of improved soil biology as a long-term pursuit.

“We are only now starting to understand soil biology, and science is offering us the opportunity to open Pandora’s box,” he says.

“This research needs to continue if we want to fully harness the benefits of soil biology and increase our wheat yields to 10 tonnes per hectare.”

 

Water-holding capacity

David’s next step was examining if in-paddock variation of water-holding capacity (WHC) was limiting yield. Electromagnetic surveys were completed and zones mapped.

In 2011, a trial investigated whether targeting nutrients to soil WHC could improve crop returns.

At sowing, monoammonium phosphate was applied across three zones at 5, 10 and 20 kilograms/ha of phosphorus.

Nitrogen was applied at 40kg/ha as urea during early August. The crop’s response was judged visually and at harvest by yield map, and compared with a nil-phosphorus plot.

The results showed a yield response up to 10kg/ha of phosphorus, even though soil tests indicated there was a high level of Colwell phosphorus (38 to 61 milligrams/kg) across the zones.

A gross margin analysis showed the added net income from applying 10kg/ha of phosphorus was $37/ha, resulting in a $2.63 return for every $1 spent.

There was no response to added nitrogen, possibly due to the dry spring and the time of application.

 

Feeding the bugs

Recently, David attended a workshop where CSIRO’s Dr Clive Kirkby discussed the importance of ‘feeding the bugs’ in the soil as a way of increasing crop growth.

His work suggests some freely available sulfur, phosphorus and nitrogen are required for the soil biology to maximise activity and break down stubble into plant-available nutrients.

Over the years, David says soil tests have shown an improvement in most nutrients including phosphorus, sulfur, calcium and magnesium.

Adding lime has lifted soil pH and reduced aluminium toxicity, allowing crops to thrive.
Going forward, he sees the challenges as refining practices across the zones and fully using soil biology activity.

With organic carbon (OC) at 1.8 per cent, he wonders if his farm management will need to change as it moves beyond two per cent.

“On top of minimum tillage and stubble retention, Dr Kirkby’s work may point to ways we can increase the biological activity and further increase OC levels,” David says.

“Studies indicate that yields might plateau when my OC levels reach two per cent, but

I believe research needs to look at whether we need to change our practices to utilise higher levels and maximise the potential of soil biology.”