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Ongoing project

Impact of groundwater quality on the management of centre-pivot-grown potato crops (PT16001)

Key research provider: Serve-Ag (E.E. Muir & Sons)

What’s it all about?

This project for and funded by both the fresh and processing potato industries is looking at groundwater quality in areas of potato production in South Australia (where groundwater quality is most variable) and investigating how regional and seasonal water-quality variability impacts on potato production and quality. It will ultimately deliver effective management strategies and tools for sustainable and profitable potato production under varying soil and water conditions.

The project team reports progress across the following trials since its last update.

Infiltration trials

Where the presence of non-wetting soils was common, the application of Transformer, a soil conditioner that improves soil wetting uniformity, has proven to lift yields across all treatments, particularly through the reduction in blemishes associated with inefficient watering that occurs with hydrophobic soils.

Both trial sites measured improved yields and reduced blemishes (compared to the control) when Transformer was applied, either in-furrow, as a blanket application or both. Cost benefit analyses are yet to be completed, but early results are showing positive returns on investment for all treatments.

Some growers were uncertain about using this treatment, however feedback has been very positive, with ease of use and it being a more natural composition (orange oil base) accepted well.

Agronomy trials

These trials encompassed revised nutrition programs and the application of specialty fertilisers, soil conditioners and bio-stimulants to assist with flushing harmful salts from soil mounds and improve nutrient balance and uptake for optimal potato production.

The application of various products was trailed with positive outcomes. The timely application of Thiocal, a liquid fertiliser (calcium thiosulphate), measured up to 28 per cent reductions in plant sap chloride levels. Reduced plant chloride levels are highly important for balanced nutrient and water uptake, and to minimise toxicity exposure to potato plants.

Most of the irrigation water supplies assessed through this project had very high chloride levels, which throughout any one season accumulate within soils. High chloride irrigation water also causes leaf scorching, particularly when irrigation occurs on hot windy days. Scorching may be difficult to minimise, however the application of Thiocal was effective at flushing some of these harmful salts from the root zone of the plants.

Future awareness campaigns for South Australian potato growers, aimed at improved understanding of the impact that irrigation water quality, variability and different salts may have on potato production will help them make management changes and longer-term improvements in both the fresh and processing potato industries.

The analysis of data obtained from the Northern Adelaide Plains will hopefully provide further insight to the potential benefits of bio stimulants for enhanced potato production in saline environments.

During the past six months, field assessments and data collection have occurred throughout the potato growing seasons for the Lower South East and the Mallee regions, with encouraging early findings.

Both infiltration trial sites in the South East and Mallee have been harvested, with data analysis now underway to evaluate the use of a soil conditioner formulated to improve water penetration and retention on hydrophobic soils, for fresh and processing potatoes.

Field inspections showed that the soil conditioner helped in holding mound shape, with less slumping and drift occurring during periods of high wind. Improved infiltration and uniform wetting of the mound profile was also noticeable, with fewer dry soil pockets compared to untreated controls. During the tuber initiation period, plants in treated areas generally had much larger and more fibrous root systems that are expected to enhance uptake of nutrients and moisture.

Early results from the trial harvests are indicating improved yields with soil conditioner use, with noticeable decreases in blemishes such as greens, misshapen tubers, insect and browsing damage, and disease presence.

The general agronomy trial site in the South East has also been harvested, with data analysis underway. This trial, also replicated in the Mallee, focused on three main areas:

  • Re-addressing crop nutrition through regular monitoring
  • Reducing salt accumulation within the upper soil profile
  • Improved stress relief through the application of specialty products and amendments.

Results from this trial showed that a liquid fertiliser markedly reduced the chloride and sodium levels in potato plants, when applied early to the crop. The fertiliser that was used provides calcium and sulphur to plants, and acts as a soil amendment helping to flush harmful salts from the root zone, as well as improving water penetration. Later applications were not effective, so earlier and repeat applications in highly saline situations should help to mitigate salinity issues faced by many fresh and processing potato growers in South Australia.

The project has expanded considerably with trial sites now established across the South East and Mallee regions. Two infiltration trials have been established, one in the Mallee and one in the South East, and a general agronomy trial has been set up in the South East. 

The team is undertaking a comprehensive assessment of sites including soil types and textures, soil pathogens and beneficial biology, soil chemistry pre-plant and post-harvest, along with irrigation water quality and local groundwater conditions.

Where possible, EM38 mapping is being done for sites to match imaging with the data collected on the ground. EM38 maps provide an understanding of spatial variability in apparent salinity, soil textures, elevation, slope and landscape change zones.

In addition, the team is making regular assessments of crop performance using satellite NDVI imagery which will be compared with the measurements taken from the sites to find out which factors are associated with crop vigour.

Sap testing of potato plants throughout the season also provided an insight to plant health and the uptake of nutrients during their growth. This combined with dry ash analysis of tubers and tuber peel, has helped to identify areas of each grower’s nutrition program that could be manipulated in future to optimize plant health and potato yield.

The researchers are using all the data that they are collecting to determine which tools can ultimately help to increase potato production under their specific site conditions.

They also hope to identify nutritional management options, or appropriate products that may assist with plant stress or microbial soil health, that will contribute towards ongoing production gains.

ACT NOW

The project continues to collect data for nine major potato varieties across three South Australian growing regions: the South East, the Mallee and the Northern Adelaide Plains. Due to differing potato growing seasons across the three regions being assessed, the establishment of sites and data collection has been staged over the last 12 months. As such, the project’s first six months were primarily focused in the Mallee, where crops were sown in the December/January window. Following this, the Northern Adelaide Plains region was the next to begin planting, which generally occurred during June and July 2017. More recently, October 2017 saw the South East region begin planting, where data collection and analysis is now underway.

The researchers are looking at site groundwater, soil characteristics and plant health conditions to see how specific conditions impact on the growth and health of plants, and associated quality and yields. Satellite imagery is also being assessed as a potential management tool, where regularly captured ‘normalised difference vegetation index’ or NDVI data (which provides a remote measure of vegetation density and condition) may provide early spatial variation information to assist with crop management activities.

Information collected through the project will ultimately be used to develop nutrition programs to maximise plant nutrient uptake and water use under a range of conditions.

In its first year the project is focused on collecting data for nine major potato varieties across three South Australian growing regions: the South East, the Mallee and the southern Murraylands. The researchers will be looking at site groundwater and plant conditions to see how specific conditions impact on the growth and health of plants, and associated quality and yields.

With its first six months now completed, the project’s team has collection data from specific sites within the Mallee region, including information on irrigation water quality, soil condition and plant nutrition information, along with trial harvest data. Selection of sites and data collection has also begun in the project’s other focus regions.

Information collected through the project will ultimately be used to develop nutrition programs to maximise plant nutrient uptake and water use under a range of conditions.

Details

This project is a strategic levy investment in both the Hort Innovation Potato – Fresh and Potato – Processing Funds