AgResearch farms below the soil

7 October 2009

AgResearch scientists are looking to add soil bioengineering to the list of technologies that are used by pastoral farmers.

AgResearch Senior Scientist Dr Alec Mackay whose team have been looking at creatures, such as earthworms, mites, springtails and nematodes in our soil, and soil services management says this focus is long overdue.

“Our farming sector has spent a lot of time and effort on the above-ground aspects of our pastoral systems, these are now highly engineered, with attention paid to livestock breeds, crop and grass choice, fertiliser and irrigation. In comparison the size and composition of life below the ground is often given little consideration,” said Dr Alec Mackay.

“People would be surprised to find that on an average sheep paddock the life under the ground weighs more than the livestock. For example, in fields we have investigated, earthworms alone weigh nearly four times that of the live weight of the ewes grazing on top,” said Dr Alec Mackay.

Earthworms consume dead plants and manure and mix organic material with the soil. This increases fertility and plant growth and prevents plant nutrients accumulating on the soil surface and then washing away. Worms also create burrows that assist with air and water movement in the soil.

AgResearch’s Ross Gray, one of New Zealand’s few experts in this field, says “A key issue is that New Zealand only has a small number of useful pasture earthworms, and these are spread unevenly through the country. This is because most pasture earthworms were introduced accidentally by European settlers who brought over potted plants.”

“Northland, Auckland and Hamilton are lucky to have a large number of introduced species, including a number of very useful deep burrowing earthworms, which likely arrived in ships ballast. Other regions including much of the South Island have few such earthworms,” said Ross Gray.

In Europe earthworm species diversity under pasture is much higher. Ross Gray sees a need for research into better distributing the useful species that have established in New Zealand.

Alec Mackay says tests have shown improvements in pasture production of 10-30% from earthworm introductions to soils with little or no activity.

Soil communities also include mites, springtails nematodes, and various insect larvae. These invertebrates are also important for decomposition, incorporation of litter and nutrient cycling AgResearch, in partnership with Massey University, is developing a soil invertebrate index that describes and quantifies invertebrates living below ground with an aim to link these invertebrates to the services that our soils provide. This work is being undertaken by AGMARDT PhD student Nicole Schon under the supervision of Dr Maria Minor, Dr Alec Mackay, Dr Gregor Yeates and Dr Mike Hedley. The index will provide, for the first time, a basis for farmers to quantify their soils biology, including their earthworms, nematodes, springtails, mites, and assess the extent to which the soils biology is contributing to farm performance.

“What we hope to achieve is to add soil bioengineering to the list of technologies that are used by pastoral farmers to deliver greater agricultural output and enhancing farm profitability,” said Alec Mackay.

ENDS

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