Australia
March 8, 2016

By GRDC northern region panellist Jack Williamson (pictured), Goondiwindi
 
The business of farming has had a seismic shift in recent decades. Not only has there been enormous changes in the way individual crops are grown, managed and marketed, the industry has also taken a far more systems-based approach to farming.

Through this systems-based approach, the way we utilise water has been transformed and as growers, one of our key performance indicators is how well we turn water into grain via a production system.

With longer dry spells and shorter, more intense wet periods we have been forced to learn how to capture, store and use that water more effectively.

The Grains Research and Development Corporation (GRDC) has invested heavily in water use efficiency research and figures suggests the investment is paying off - water use efficiency (Kg per mm rainfall) in dryland wheat production has doubled in 20 years.

In addition, wheat yields have increased 1.12% per annum over past 17 years (cf 0.62% since the turn of last century).

Industry certainly isn’t resting on its laurels though and water use efficiency research is continuing through a number of projects including the northern farming systems project led by CSIRO senior farming systems scientist Dr Lindsay Bell which aims to close the yield gap in northern Australia.

All indications are that there are still major gains to be made in water use efficiency, particularly in the north where maximising the amount of water in fallows is an important strategy in managing the region’s highly variable, summer dominant rainfall.

Fallow efficiency is also highly influenced by stubble cover and research is being carried out by the Northern Grower Alliance (NGA) to assess fallow efficiency under different stubble cover loads. As stubble management plays a critical role in fallow efficiency, it’s important that we undertake research to enable us to understand how the different crops in a rotation impact stubble loads, breakdown, management practices and the yield potential of subsequent crops.

When it comes to managing soil moisture, it’s worth keeping in mind the old adage that we can’t manage what we don’t measure and to do that effectively, there are a number of factors that need to be considered.

Firstly, it’s important to have a good understanding of how soils work in relation to water capture and storage and why some soils have the ability to hold more water for crop use than others.

Such baseline information collated in conjunction with the seasonal monitoring of soil water using tools that can range from something as simple as a push probe to simulation modelling, allows the setting of realistic decisions/goals on crop choice, inputs and yield potential.

Growers have used tools to measure soil water for years but technological advances are widening the spectrum of choice.

Growers wanting to gather and utilise more detailed information for specific productivity projections and management decisions can now easily calculate millimetres of water available according to soil type.

The level of sophistication at which growers invest in soil monitoring and management is entirely at their discretion.

While some growers will see benefits in using higher level technologies that provide easier and more accurate real-time access to soil water information and risk management tools such as simulation modelling, others may get sufficient value from using simple devices such as the push-probe more strategically.

In recent years, a range of soil water monitoring devices has been tested for practical application in dryland systems on both the cracking clay soils (Vertosols) and the southern rigid soils through a GRDC funded project.

The study concluded that no one device or field based technology was appropriate to all situations. It found in-situ capacitance or time-domain reflectometry (TDR) sensor probes were likely to provide a reasonable estimate of soil water in rigid soils whereas they faced difficulties in the shrink/swell clays due to soil cracking.

The surface based, EM38 (electromagnetic induction) mobile device was found to be a more practical and accurate option for these soils.

Soil water modelling (APSIM model) was also shown to adequately predict soil water levels when compared against the outputs of the in-situ technologies and was recommended as an alternative to field based monitoring.

More recently, the GRDC has funded the development of a new IOS SoilWater app by the University of Southern Queensland which gives growers access to locally specific soil water modelling to better estimate their yield potential at sowing, and make decisions accordingly.

So it’s a case-by-case basis when it comes to soil water measuring, monitoring and management but whatever the investment, it’s likely to pay dividends for crop planning and production.

• Jack Williamson is a private agricultural consultant and helps run a family broadacre farm near Goondiwindi, Queensland. Six years of retail agronomy and three years of chemical sales management have given Jack extensive farming systems knowledge, and diverse crop management and field work experience. He is a member of the Northern Grower Alliance local consultative committee and Crop Consultants Australia.

Website: http://www.grdc.com.au

Published: March 8, 2016