Simplifying methods to determine plant available water capacity of variable soils in Australian dryland grain production

Take home messages

• Australian grain growers lead the world in their ability to produce crops in climatically restrictive environments.
• An efficient method to quantify plant available water will add value to current precision agriculture (PA) techniques by allowing growers to match production inputs and expectations with reality.
• The Internet Of Things (IOT) in agriculture has the potential to revolutionise a grower’s ability to manage within their environment at an efficient cost.

Background

I manage a dryland grain growing property for the Warakirri Cropping business around the Lockhart Shire in the New South Wales (NSW) Riverina region. Warakirri Cropping operates a portfolio of 10 properties, owned by the Australian REST Superannuation business, throughout the Australian wheatbelt from Dalby in Queensland (QLD) to Merredin in Western Australia (WA).

The 8700 hectare ’Orange Park’ aggregation is 93% arable and the crops grown include canola, wheat, barley, pulses and oaten hay. Soils range from iron rich, quartz red loams through to sodic red clays to heavy black self-mulching Vertosols. There are three full time staff on property and a mixture of owned equipment and contract support is used to ensure timeliness of operations. We are progressively adapting our systems to a controlled traffic farming (CTF) platform which will be on a 12/18/36m system for harvest/seeding/spraying and spreading using 3m wheel centres.

Nuffield Scholarship

Personally, and also as a business, we had a desire to better understand the plant available water capacity (PAWC) of our variable soils. Existing methods for soil characterisation were slow, expensive and site and crop specific. I wanted to find a better way.

The opportunity arose to apply for a Nuffield Farming Scholarship in 2015 and with the support of the GRDC Northern Region, Nuffield Australia and Warakirri Cropping, I started a scholarship in 2016. My topic was to investigate ways to close the gap between potential grain yield and soil PAWC, with a focus on boosting productivity from sustainable dryland cropping systems.

The first leg of my overseas journey was to embark on a Global Focus Program, where a group of scholars travel the world for six weeks to provide a snap shot of world agriculture. The trip saw our group travel to Singapore, Philippines, Hong Kong, China, Canada, USA and the UK. The highlight of the trip was China and the incredible pace of development over such a huge area. Food quality and food safety were also major focuses for Chinese agriculture with consumer access to food processing now the key to rebuilding public trust.

On my personal study tours, I travelled to Israel, Brazil, Texas, UK and New Zealand. The world of agriculture is incredibly diverse and following sixteen weeks of overseas travel through annual rainfall zones from 100mm to 3000mm, I cannot recommend strongly enough the benefit of exposure to the challenges faced by growers in differing environments.

Australian growers lead the world, by necessity, in their understanding of the value of stored soil moisture. I was shocked to find in many high rainfall environments, such as Brazil, Southern Texas and Northern England, that a minor interruption in rainfall occurrence of perhaps 14 days was a yield reducing drought event even though water was still flowing from deep field drains. It demonstrated subsoil constraints and with ever increasing land values, the benefit: cost of amelioration seemed clear to me. Israel, on the other hand, was highly efficient at its use of very scarce water resources. In the 38 years from 1975 to 2013, Israel has reduced its irrigated water requirement (ML/ha) by one third, whilst incredibly achieving a 12-fold increase in production from the same volume of water. The technology now in use in Israel has exciting potential for Australian farms in the near future as costs reduce. Whole of farm wireless connectivity and plant growth tracking were important systems now helping Israeli growers to maximise production.

Another exciting prospective technique was the use of an in-field penetrometer to measure near infra-red (NIR) reflectance/adsorption developed by Texas A&M University in collaboration with Sydney University. This process allowed growers a 3-dimensional view of their soil without the disruption of excavation. A NIR penetrometer has now been commercialised by Veris as the P4000.

EM38 mapping was well regarded although not widely adopted around the globe as a means of differentiating soil zones based on their electrical conductivity (EC). EM38 systems are evolving and products such as the Austrian ’Soil Mapper’ are able to be installed to machinery as it passes over a field. This opens up the possibility of building relative soil water maps (as water is a strong driver of EC) in real time by measuring soil water at intervals throughout the season. This data could potentially apply nitrogenous fertilisers at variable rates in real time to match soil water to productive capacity.

Microwaves are also being used in experimental work to measure deep soil moisture and prototype sensors are now available to install on overhead irrigation systems (centre pivot/lateral) which can allow variable rate irrigation based on real time data.

Observation and recording of rainfall were found to be areas for improvement regardless of the annual rainfall. Recording systems were often remote from fields with questionable accuracy for the crops. New technologies allowing long range Wi-Fi with very low power demands are set to revolutionise such monitoring at a very reasonable expense.

Conclusion

The yield gap between crop production and available soil moisture exists globally, with Australian dryland growers very efficient compared to our overseas counterparts.

We need to do more to visualise our soils in 3-dimensions to allow us to address limitations in the root zone of crops and optimise inputs to match our soil’s productive capacity. The NIR penetrometer was the most exciting potential new technology observed for this purpose.

EM38 developments to allow low cost multiple field passes seemed the most likely of the observed technologies to allow ’on the go’ measurement of soil moisture.

Long Range Wireless Area Networks (LoRaWAN) are an exciting development which will allow remote monitoring of thousands of in-field sensors at very low cost.

Acknowledgements

My Nuffield Farming Scholarship was made possible by the generosity of Nuffield Australia proudly supported by my investor GRDC Northern Region.

Contact details

John Stevenson
’Orange Park’
Lockhart, NSW 2656
0429206238
orangepark@watag.com.au
@cropmad