Incitec Pivot Fertilisers, Media Release, 29 June 2022

As sugarcane growers prepare for this year’s harvest, many will not be equipped with a holistic knowledge of the health of their soil to inform management decisions.

Sugar Research Australia (SRA) Principal Agronomist Danielle Skocaj said there has been a focus on managing nitrogen (N) and phosphorus (P) nutrition in recent times, rather than gaining a full understanding of soil health.

“Growers often say you can’t put a value on improving soil health. However, the industry tends to focus on routine assessment of soil chemical properties rather than a holistic assessment of soil chemical, physical and biological properties,” Dr Skocaj said.

“Sugarcane soils are quite unique with high variation in soil properties often encountered between and within sugarcane fields even of the same soil type.

“There are large areas of soil prone to dispersion, but dispersion isn’t routinely assessed.

“Additionally, it’s important not to look at dispersion results in isolation and consider other soil chemical properties. Dispersion is often linked to high sodium levels, but other factors including high exchangeable magnesium, low exchangeable calcium and salinity, may also contribute. A comprehensive soil health assessment is needed to understand the reasons for the dispersion and identify the most appropriate remediation strategies.

“Reducing dispersion is important because it will improve soil structure, making the soil easier to manage and reduce the risk of erosion. It will also improve, water infiltration, lateral soakage in irrigated crops and plant rooting depth. This will improve nutrient and water uptake; ultimately leading to a healthier crop and increased productivity.”

Incitec Pivot Fertilisers (IPF) Nutrient Advantage Laboratory has recently reviewed data collected from hundreds of soil health tests completed across Australia and segmented this data by crop type.

IPF Tropical Systems Agronomist Rob Dwyer said the insights highlight considerations that are particularly pertinent for sugarcane growers.

“Comparing soil health in sugarcane growing districts to soil health in pasture, horticulture and cropping regions shows just how unique those sugarcane soil systems are,” Mr Dwyer said.

“Many cane growers may not have measured their soil health before but with commodity prices remaining strong in this regulated market, we’re seeing cane growers becoming increasingly interested in soil health.

“By knowing and understanding the unique and often varying soil health conditions in sugar growing regions, cane growers can be empowered to make decisions that boost their productivity today while safeguarding the sustainability of their businesses into the future.”

The Nutrient Advantage soil health test package provides a snapshot of three key characteristics of soil which are crucial to its overall health: Physical (Aggregate Slaking and Dispersion), Biological (Microbial Respiration), and Chemical (Active Labile Carbon; Total Carbon; Total Nitrogen and Carbon to Nitrogen Ratio). This provides growers with precise objective analysis and industry leading agronomic advice to help build healthier soils.

Dr Skocaj said understanding differences in soil chemical, physical and biological properties is valuable for cane growers.

“There’s increasing interest in soil biological assays, but routine soil testing doesn’t cover labile or total carbon (C), or soil physical properties such as slaking and dispersion. Many growers wouldn’t be aware of their soil’s slaking score,” Dr Skocaj said.

“Slaking provides an indication of soil aggregate stability, resistance to erosion and soil structure. High slaking scores are largely encountered on soils with low organic matter. Organic matter helps bind soil particles into larger, more stable aggregates. Increasing soil organic matter by retaining crop residues, adding organic inputs (such as cover crops, mill by-products, compost) and reducing aggressive tillage practices will reduce the likelihood of slaking.

Insights from Nutrient Advantage soil health tests show that organic matter in sugarcane regions is low, which is likely impacting slaking levels.

SRA has developed a Soil Health Extension Toolkit to assist growers and advisors assess and monitor some key soil health indicators in the field.

Dr Skocaj said combined with commercially available soil assays, the Toolkit could help growers identify opportunities to improve their soil health.

“Growers should develop a soil testing program before collecting soil samples to ensure useful and meaningful results. Samples need to be collected from the right location, which differs according to soil assay; and at the right time, not only in relation to the sugarcane cropping cycle but crop stage and recent environmental conditions are also important considerations,” Dr Skocaj said.

“The option to package dispersion and slaking assays into routine soil testing with the Nutrient Advantage soil health test package requires no additional effort to current soil collection practices.

“A holistic soil health assessment is valuable for identifying any undiagnosed problems or limitations affecting crop performance. The cost savings through better targeting inputs and addressing soil constraints that impact productivity, could very quickly outweigh the investment in soil health testing.”

The Nutrient Advantage soil health test package can be added to any existing Nutrient Advantage soil test and can be requested using the code ‘Health1’.

For nearly 60 years, Nutrient Advantage has been widely regarded as one of Australia’s leading nutrient testing laboratories, with the broadest range of National Association of Testing Authorities (NATA) accredited nutrient tests in Australia. To find out more, visit www.nutrientadvantage.com.au or call 1800 803 453.