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Improving soil health and productivity on challenging sandy soils

biofumigant pic

This information was released in conjunction with Derwent Catchment NRM

A unique approach to soil management is being undertaken in the Derwent Valley and farmer Jim Alright is hoping it will reap some surprising returns for him and son Nick.

Jim Allwright and his family own and run Jones River farm in the Derwent Valley. The farm enterprise comprises sheep for wool, lambs and a cropping rotation of cash crop poppies, wheat / canola for grazing and grain, and forage and seed brassicas.

What led to the change?

Jim and his son Nick were concerned about soil health, the decline in crop yields and associated increase in weed infestations on farms in the region and were interested to see what options were available for their property.

The farm’s sandy duplex soils are typical of soils in the Derwent Valley and in other agricultural areas of Tasmania. They often have poor structure which can quickly lose soil carbon through cropping. Although the farm is under a central pivot irrigation system, the limiting factors at present are soil structure and in turn moisture holding capacity and fertility. The risk is that under current crop rotations soil health and crop yields will decline.

Jim, says: “These duplex soils are the ones that we have to learn how to crop.”

Jim and his family have been running trials and testing different approaches for managing soil health on their farm for many years and Jim has instilled this way of thinking in his sons since an early age. Nick knew they had to look for new ways to continue cropping but maintain, or possibly increase, soil health in the process.

Nick looked at a couple of trials in the north of the State using biofumigation crops. Biofumigation refers to crops that contain chemicals that have the abilities to inhibit soil borne pests and pathogens. They include special bred varieties of radishes, sorghum, and brassica’s. These cover crops typically form part of a crop rotation and are finely chopped or ploughed in prior to planting the main cash crops.

Biofumigant crops can not only improve soil conditions and productivity by suppressing soil borne pests and pathogens, they provide cover through winter and once incorporated add organic matter and scavenge soil nitrogen for the subsequent crops to use. Biofumigants have been used in Tasmania, mainly in the potato industry, with promising results.

The trial

As a result of concerns within the Derwent Catchment Farmers Discussion Group, facilitated by Derwent Catchment NRM (DCNRM) and run by Macquarie Franklin, it was decided to support a trial to see whether the apparent success of biofumigant crops in the potato industry could be shown to work in poppies in the Derwent Valley. Serve-Ag were engaged to design and run the trial, which involved pre and post soil health checks by looking at soil chemical, physical and biological qualities.

The trial has also been supported by NRM South through a public benefit grant.

A field day was held on 24 June 2014 in conjunction with the farmer discussion group workshop on soil health with Bill Cotching, with mulching and incorporation over the next two days. Timing is critical for maximum result with incorporation needing to occur within 30 minutes of mulching.

It is hoped that the poppies can be sown late July after which Serve-Ag and TPI Enterprises (poppy company) will monitor the weed burden, poppy growth, yield and alkaloid in all combinations as well as the control, with results hopeful available in late summer 2015 ready for that year’s program.

What we would hope to find

Currently the soils aren’t robust enough and Jim hopes the trial will demonstrate that there are sustainable long-term options to maintain good fodder and cash crop yields under his current system without compromising soil health.

Jim says: “We had also hoped to see some effect on the soil compaction that has evolved over several years of cropping as well as grazing over a very wet 2014 winter/spring. It didn’t appear at the field day that the brassica’s were robust enough to significantly penetrate the compaction layer, although this will be confirmed with further testing”.

 

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