Farming systems – Spring Ridge, northern NSW

Take home messages

• To date, differences between systems in total grain production for three crop years is small with values ranging from 11,084 kg/ha (high legume system) to 8,573 kg/ha (high crop intensity).
• Commodity prices between systems has driven gross margins, not yield, with the low crop intensity system (wheatxxcotton) $2,739 $GM/ha outperforming the high nutrition (wheatxchickpeaxwheat + 200 kgN/ha) system, $2,011 $GM/ha.
• WUE is a useful metric i.e. $ GM/mm water used (rain + change in soil water) to determine farming system benefits and derive profitable crop sequencing. To date, the low crop intensity system has returned $1.66 $GM/mm compared to the high nutrition system $1.30 GM/mm.
• Changes in pathogen loadings are small across all systems, to date. The Spring Ridge site has no Pratylenchus thornei and below threshold levels of Pratylenchus neglectus. Common root rot and crown rot levels were not detectable at the onset of the experiment and have only risen slightly due to non-host crops being grown in the systems.

Introduction

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 (Hochman et al. 2014). 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.

The Queensland Department of Agriculture and Fisheries (QDAF), CSIRO and the New South Wales Department of Primary Industries (NSW DPI) are collaborating to conduct an extensive field-based farming systems research program. This program is focused on developing farming systems to better use the available rainfall to increase productivity and profitability.

The generic systems

The northern farming systems projects are investigating how several modifications to farming systems will impact on the performance of the cropping system as a whole over several crops in the sequence. This involves assessing various aspects of these systems including water use efficiency, nutrient balance and nutrient use efficiency, changes in pathogen and weed populations and changes in soil health.

The key system modifications we are examining involve changes to:

• Crop intensity – ie. the proportion of time that crops are growing which impacts on the proportion of rainfall transpired by crops and unproductive water losses. This is being altered by changing soil water thresholds that trigger planting opportunities. High crop intensity systems have a lower soil water threshold (crop planted on 30% full profile); moderate intensity systems have a moderate soil water threshold of 50% full profile, and low intensity systems require a profile > 80% full before a crop is sown and higher value crops are used when possible.
• Increased legume frequency – crop choice aims to have every second crop as a legume across the crop sequence, with the aim of reducing fertiliser N inputs required.
• Increased crop diversity – crop choice aims to achieve 50% of crops resistant to root lesion nematodes (preferably 2 in a row) and crops with similar in-crop herbicide mode of action can’t follow each other. The aim is to test systems where the mix and sequence of crops are altered to manage soil-borne pathogens and weeds in the cropping system.
• Nutrient supply strategy – by increasing the fertiliser budget to achieve 90% of yield potential for that crop compared with a 50% of yield potential with the aim of boosting background soil fertility, increasing N cycling and maximising yields in favourable years.

This range of system modifications are being tested across 7 locations; Emerald, Billa Billa, Mungindi, Spring Ridge, Narrabri and Trangie (red & grey soils). The core experimental site, located near Pampas on the eastern Darling Downs, aims to explore the interactions amongst these various modifications to the cropping systems across a range of crop sequences that occur across the northern grains region. The core site is comparing 34 different system treatments.

The Spring Ridge Site - “Nowley”

The Spring Ridge farming area lies in the northern end of the southern region of the Liverpool Plains. Rainfall distribution and variability is shown in Table 1. This southern region has the highest summer rainfall, with relatively high winter rainfall, of any area in north eastern NSW. The Plains is one of the safest dryland cropping areas in the region with summer cropping typically a major component in the system. This is possible due to consistency of summer and winter rainfall, coupled with a large proportion of high water holding capacity vertosols.

Table 1. The, 90, 50 and 10 percentile rainfall and variability indexes (VI) for summer and winter rainfall (mm) and the summer/winter ratio for rainfall for northern and southern Liverpool Plains

Due to the low variability and high summer rainfall this area has a diverse cropping system with a range of summer and winter crops able to be grown, making this one of the most productive cropping areas in Australia. Zero tillage systems based on control traffic platforms dominate this region.

‘Nowley’ is owned by The University of Sydney and is located 21km north west of Spring Ridge on predominantly sloping black vertosol country with a plant available water capacity (PAWC) > 200 mm. The site has been cropped for over a hundred years and is representative of a large proportion of the Liverpool Plains. The site was in fallow out of a sorghum crop at the commencement of the trial and was planted to wheat across the entire site in 2015 to set a common starting point. The site is subject to major weed pressure but has no other biotic stresses of note.

Cropping systems

Six systems were identified as priorities through consultation with farmers and advisers in northern NSW;

1. Baseline - The baseline system was designed to represent a standard cropping system for the majority of the northern NSW cropping areas, which is desired to be kept relatively consistent across farming systems locations. Planting trigger will be 50% of full profile. The area has both winter and summer crop with a diverse range of cropping options. At present the baseline system consists of wheat/fallow/sorghum/double cropped chickpea/ wheat/chickpea/.
2. Higher nitrogen supply - This system is a duplicate of the crop sequence for the baseline system which is designed to examine the economics and system performance of high nitrogen fertiliser inputs. Fertilising will be targeting a higher yield (90% of seasonal yield potential for nitrogen).
3. High crop intensity – the trigger for planting will be soil moisture at 30% of full profile. This mirrors current cropping system sequencing on the Liverpool Plains and is based around a standard crop sequence of; wheat/fallow/sorghum/double cropped chickpea.
4. Higher crop diversity - This system is investigating alternative crop options to help manage and reduce nematode populations, disease and herbicide resistance. The profitability of these alternative systems will be critical. A wider range of ‘profitable’ crops may enable growers to maintain soil health and sustainability as the age of their cropping lands increase. Crop options considered for this system include: wheat, durum, barley, chickpeas, field pea, fababean, canola, mustard, sorghum, maize, sunflowers, mungbeans and cotton.
5. Higher legume - The high legume system is focused on soil fertility and reducing the amount of nitrogen input required through fertiliser. It is required that one in every two crops is a legume and the suite of crops available for this treatment is: wheat, durum, barley, chickpeas, faba beans, fieldpeas and mungbeans. Crops will be planted at an average moisture trigger (50% full soil moisture profile).
6. Lower crop intensity - This lower intensity system is designed to plant at a lower frequency when the profile is >80% full. High value crops are targeted and the crops included are, wheat, barley, chickpea, sorghum and cotton.

Crop sequencing at Spring Ridge

In 2015 wheat was planted across all systems after a 12 month fallow out of sorghum. All treatments had 50 kg/ha of Granulock® Zn and 100 kg/ha of nitrogen as urea applied at sowing. Yield data suggested that the site was uniform. Crop sequences for the various systems in the following 3 years are shown in Table 2.

In 2016, systems started to become more diverse with crop choice mainly consisting of a range of winter pulse crops (chickpea, faba bean and field peas). The high crop intensity system followed the Liverpool Plains commercial practice and was fallowed through to sorghum in 2016/17.

The 2017 season was one of the most demanding and difficult winter growing seasons on record with an unprecedented frost incidence.

Luckily, the 2016 crops were mainly composed of pulse residue and not large amounts of cereal straw as this would have exacerbated the radiant frost incidence. A reasonable summer fallow rainfall in 2016/17 ensured there was adequate soil moisture reserves coming in to a very dry winter 2017 crop period (see Table 3).

Table 2. Cropping sequence for the six farming systems at Spring Ridge, 2015-2017

Table 3. Summer and winter rainfall for Nowley, 2015-2017

In 2017 wheat was planted across most systems following a range of winter pulses in 2016, except the high intensity system which was double cropped to chickpea after a 2016/17 sorghum crop.

All treatments had 50 kg/ha of Granulock® Zn and 100 kg of nitrogen as urea applied at sowing while the high nutrient system had an additional 100 kg N/ha applied as urea at the late tillering stage.

Crop system yields at Spring Ridge

The cumulative grain (or grain + lint) yields (Figure 1) are quite similar for the five main systems with 2,500 kg/ha separating highest yield(high legume @ 11,084 kg/ha) from fifth highest (high crop intensity @ 8,573 kg/ha). The major yield differences in these systems emanated from the 2016 winter crop choices, with chickpea (baseline @ 3063 kg/ha and high nutrient @ 3329 kg/ha) yielding lower than field pea (3631 kg/ha) and faba beans (4256 kg/ha) in the crop diversity and high legume systems, respectively. The high intensity system was fallowed in 2016 into sorghum (2978 kg/ha) and then double cropped into a late chickpea crop (1981 kg/ha) in 2017. The low intensity system was cropped to cotton in the 2017/18 summer season and this yield value represents seed + lint (2078 kg/ha).

Figure 1. Cumulative grain (or grain + lint) yield of the Spring Ridge systems (kg/ha)

Crop systems economics at Spring Ridge

Gross margins ($/ha) have been calculated for each crop within the six systems. Table 4 contains the grain pricing used in these calculations based on median prices over the past ten years.

Table 4. Ten (10) year median port prices, less $40/t cartage costs, for selected crops

After the first three growing seasons of the farming systems experiment at Nowley, the low crop intensity system (2 crops in 3 years) has the greatest cumulative gross margin with $2739/ha (Figure 2). This is entirely due to the high value cotton crop that produced around 4 bales/ha in the 2017/18 summer crop season. The other five systems are comparable to one another with the high legume system (wheat/faba bean/wheat) returning $2252/ha and the high intensity (wheat/sorghum/double crop chickpea) returning $2198/ha. The next best is the baseline system ($2184/ha), followed by crop diversity ($2022/ha) and high nutrition systems ($2011/ha), which are comparable to each other.

Figure 2. Cumulative grain gross margin ($/ha) of the Spring Ridge systems excluding fallow costs

In terms of wheat following pulses; wheat following chickpea had the lowest returns ($602/ha and $548/ha) compared to wheat following faba bean ($675/ha) and field pea ($724/ha).

Crop system water-use-efficiency at Spring Ridge

While crop water use efficiency (kg grain/mm crop water use) is a useful metric to compare performance of individual crops, it fails to account for the efficiency of soil water accumulation in the previous fallow, or legacy effects after a particular crop either in the form of residual soil water at harvest, or impact on subsequent fallow efficiency. Hence, to account for the efficiency of the farming system over time, we have calculated system water-use efficiency for the various systems over the first 3 years of this experiment. We define system water use efficiency as the $ gross margin return per mm of water used (i.e. rainfall + change in soil water). Gross margin over the whole crop sequence was calculated from the sum of yield multiplied by the 10-year average price for each crop, minus variable costs (fertiliser, seed, herbicides, and operations) accumulated over the whole crop sequence (Figure 3).

Figure 3. System water use efficiency ($ gross margin/mm water used) for the period from March 2015 to Dec 2017/March 2018 for different crop sequences modified to increase or decrease crop intensity, increase legume frequency and/or crop diversity. Note the low intensity system has been calculated thru to March 2018 at the conclusion of the cotton crop while the other systems are thru to the end of the 2017 winter season.

Only small differences have been observed between the systems, with WUE of between $1.30 and $1.66/mm The high nutrient supply (WheatxChickpeaxWheat), high crop intensity (WheatxxSorghum/double crop chickpea) and crop diversity (WheatxField peaxWheat) systems have all shown lower WUE returns of around $1.30/mm. Adding extra nitrogen, as a split application, into the high nutrition system in a low rainfall season (2017) resulted in a -$0.20 decline in the return on water compared to the baseline system (WheatxChickpeaxWheat).

Inserting faba beans into the system (high legume) has yielded equivalent WUE values to the baseline cropping system while growing a high value dryland cotton crop (low crop intensity) on a full profile of soil moisture has resulted in the best WUE ($1.66/mm) return to date.

Pathogens of the cropping systems at Spring Ridge

The entire site was sampled in early 2015 to examine the background pathogen status via soil DNA probing. When sampled, the site had been fallowed out of a sorghum crop and was to be planted to wheat.

Two DNA probes are taken each year; March and then in November-December. Table 5 compares the pre-sow DNA values in 2015 to the values at the end of the 2017 winter season for selected pathogens. The data presented in table 5 is for soil samples taken in the crop row, so represent primary points of infection.

Table 5. DNA soil sample values for selected pathogens before first wheat crop (2015) and at harvest 2017

#/g = number per gram of soil, pg/g = picograms/g soil

The difference in values in 2015, for individual pathogens across the systems, represents site variability as none of these different cropping systems had been invoked at the time of background sampling. There were virtually no nematodes at this site except for trace levels of Pratylenchus neglectus and no Pratylenchus thornei. P. thornei levels have not really changed in 3 seasons while P. neglectus have risen slightly in systems where chickpeas have been grown, but these values are extremely low. Nematode levels would need to reach > 2 nematodes per gram of soil to be considered damaging. These values need to be compared to the low crop intensity system which has been under long fallow, prior to cotton in 2017/18 summer period, where P. neglectus is at undetectable levels.

Sorghum, cotton and field peas present a low risk to nematode build up while chickpea, faba bean and bread wheat can present a medium to high risk. The biggest variations occur within chickpea and wheat varieties regarding nematode increases. PBA HatTrick is one of the least susceptible chickpea varieties (used at this site) while the wheat varieties Spitfire and EGA Gregory are both susceptible in terms of resistance to the nematodes as well as being moderately tolerant.

Yellow leaf spot (YLS) has come back into the zero tillage site and spiked sharply in the high nutrient system where 200 kg/N/ha was applied to EGA Gregory wheat as a split application in 2017. Both Bipolaris and Fusarium levels have risen over the three seasons but are again quite low with minor variance between systems. Spitfire and EGA Gregory are the only two wheat varieties to be sown across the site and both are susceptible to YLS, Bipolaris and Fusarium infection.

References

Hochman Z, Prestwidge D, Carberry PS (2014) Crop sequences in Australia’s northern grain zone are less agronomically efficient than the sum of their parts. Agricultural Systems 129, 124-132.

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 continued support.

We would also like to thank, specifically, our co-operator and host at ‘Nowley’, The University of Sydney who have assisted us in implementing this experiment. We must also thank Michael Nowland for his management of the experimental site along with Mat Grinter and Peter Sanson for technical assistance in the field and laboratory.

Contact details

Andrew Verrell
NSW DPI Tamworth
Mb: 0429 422 150
Email: andrew.verrell@dpi.nsw.gov.au

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