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Legumes help fortify crop health as part of risk management strategy

Western districts farmer Tim Rethus grows pulses on up to 45 percent of his family's 5000-hectare farm to promote more robust, resilient cereals able to achieve better yield potential
Photo: Clarisa Collis

For Wimmera grower Tim Rethus, pulses are an important ingredient in his recipe for a balanced, diversified grains program that aims to optimise plant health and, ultimately, crop performance in Victoria's western districts.

Tim says that growing pulses on 35 to 45 per cent of his family's 5000-hectare grains operation spread across three properties near Horsham at Vectis, Noradjuha and Jung is part of a multi-faceted "risk management strategy".

The third-generation grower says the strategy drawing on their pulse portfolio - lentils, faba beans and vetch - was developed to help fortify plant health.

The theory is that pulse cropping promotes improved soil and plant health, leading to more robust, resilient crops able to achieve better yield potential and minimise losses from seasonal and climatic risks such as drought and frost.

Supporting this objective and complementing their pulse program, the family's risk management strategy also draws on early sowing, controlled-traffic farming (CTF) principles and zero-till practices.

It's a suite of tactics that saw the Rethus family achieve "six or seven-decile crops on two or three-decile rainfall" in the 2019-20 growing season, Tim says.

In other words, the Rethuses - Tim, Luke and Geoff - can secure yields commensurate with average rainfall conditions in dry seasons when rainfall is below average.

Twin benefits

The Rethus family hosted the Southern Pulse Agronomy field day on their Vectis property as part of the Australian Pulse Conference in Victoria's Wimmera region. PHOTO Clarisa Collis

The Rethus family hosted the Southern Pulse Agronomy field day on their Vectis property as part of the Australian Pulse Conference in Victoria's Wimmera region. Photo: Clarisa Collis

Tim says the main benefit of pulse cropping in their farming system is the supply of soil water and fixed nitrogen it provides for mainstay cereals: wheat and barley.

He estimates that a legume's ability to fix nitrogen and conserve moisture in the soil can lift the yield potential of the subsequent cereal crop by up to half a tonne per hectare.

While the respective contribution of soil nitrogen and moisture to improved yield potential is difficult to isolate, their nutrition regime shows growing a pulse crop saves on nitrogen fertiliser inputs.

For example, they often apply an extra 25 to 50 kilograms of nitrogen fertiliser per hectare where cereals are grown in cereal, instead of lentil, stubble.

However, the supply of fixed soil nitrogen depends on the seasonal conditions in which the pulse was grown, he says.

"A legume crop tends to use the soil nitrogen it fixes early in the season for itself," Tim says. "So it's only in situations where a legume crop does not achieve its yield potential later in the season, due to water stress, heat stress or frost, that significant fixed nitrogen is available to the following crop."

Deep nitrogen and moisture

Based on the farm's history of soil testing, much of the organic nitrogen that pulses fix for the following cereal crop tends to be concentrated deep in the soil profile where other sources of the nutrient can be difficult to apply, Tim says.

"With a drying soil profile in spring, pulses have fixed nitrogen in the subsoil where the roots of the following cereal crop are active (and can access it) later in the growing season."

He says the bank of soil moisture that legumes reserve for the following cereal crop also tends to be restricted to the soil's deep layers.

"Lentils have a relatively shallow root system that only forages for moisture less than a metre beneath the soil surface, which helps conserve moisture deeper in the soil profile for the following cereal crop."

The ability to vary their on-farm chemistry is another major benefit of pulse break cropping that has enabled the Rethuses to better control weeds and diseases, while reducing herbicide resistance risk.

With an important stake in the past, present and future of the family's farm business, Tim says they now plan to experiment with a "more creative" approach to legume sequencing.

This blueprint for "further diversification" is likely to see alternative pulses, either vetch (for hay and brown manure), field peas, chickpeas or faba beans, supplant some of the lentil country across nearly one-third of the total farm area.

On-farm pulse trials

Tim Rethus is looking to implement a more creative approach to legume sequencing.
          PHOTO Clarisa Collis

Tim Rethus is looking to implement a more creative approach to legume sequencing. Photo: Clarisa Collis

Informing these management decisions is a series of pulse trials the Rethuses are hosting on their Vectis property, about 15 kilometres west of Horsham, as part of Southern Pulse Agronomy (SPA) research.

The on-farm trial site at Vectis was the focus of the annual SPA field day, which marked the first day of the three-day Australian Pulse Conference program.

"The trials show there are so many different options and we're always looking for new ideas," Tim says. "Hosting the trials and field day has been eye-opening and gets me challenging my agronomist."

In particular, he hopes the findings of the pulse trials will help identify new herbicide and agronomy options, as well as new vetch, field pea, lentil and faba bean cultivars, including new variety releases, suited to the farm's cropping country.

More information: Tim Rethus, 0425 791 651,

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