The Importance of Earthworms

[Graham]

The guts of biological farming appears to be commonsense: use soil conditioners particularly lime/dolomite (sometimes treated forms) to end up with a pH around 6.0 to 6.4, and add balanced minerals (usually from kelp etc to ensure all are present) and wait for the biological activity in the soil to increase, which will raise the grass/crop Brix. Worms are a particularly easy and important positive indicator for the technique. Again, commonsense. See

http://www.dpi.nsw.gov.au/agricultur...ogy/earthworms

Some practitioners hope to achieve 40 earthworms in every 20cm x 20cm x 20cm of topsoil, free workers and soil conditioners. Very few farms in NZ would be at that level.

Here is some info on our earthworms from the old DSIR..

“The Introduced Species form a small group of nine species belonging to four genera of the family Lumbricidae. The group is of European origin and must have entered the country in soil brought in on the roots of plants, and in the soil commonly used as ships’ ballast in the early days of New Zealand’s colonisation. Although the group is small it is of great importance, since the earthworm fauna of pasture and cultivated lands (in NZ) consists entirely of these few species.

The Endemic (native) Species make up a very large group, including more than 120 species, belonging to 23 genera of the family Megascolecidae. (The native worms have retreated to the bush areas, where they are still plentiful).

Suitable pH conditions: In some cases where the soil pH is very low, no earthworms are found, e.g. Otonga peaty loam (deep phase), a soil with a pH of 3.6. The common introduced species seem to be able to thrive in soils of pH ranging from 4 to 8 and have rarely to deal with soils of a pH outside that range in New Zealand.”

As pH is logarithmic (each 1pH is tenfold) worms can cope with hydrogen concentrations up to 1000 times more than is present in pure water. It’s possible our introduced worms prefer a pH closer to neutral, but pH6 is right smack in the middle of their range (above).

So what else is limiting most worm populations? -most farmers produce a lot of grass and effluent, which should be ideal. Are pugging events the main cause, affecting not just the grass, but the soil and biomass?

[Graham]

Dr Doug Edmeades wrote this reply on the defunct Ruralnetwork in 2008:

There should be no question about the importance of earthworms - being big beasties they are at the top of the soil microbial food chain. They work on the bigger bits of residues going into the soil breaking it down for the smaller cousins to work on. They are vital. The science says (for pastures) get the soil fertility correct so as to maximise pasture production, get the animal grazing to recycle the plant material and nutrients and in that way you will feed the worms.

There are several studies in NZ which show that earthworm numbers increase with increasing chemical fertiliser inputs (assuming you are starting with a nutrient deficient soil). Suggest you read some of my articles in The Fertiliser Review (the index is on my website). So food supply is the key to getting earthworms cranking but there are other factors too. Earthworms do not like dry conditions or coarse soils. For example there are some pumice soils which are too coarse and too dry for earthworms to establish. Raw peat also has few earthworms - it is too acid and too wet (no oxygen).

And to keep things in balance earthworms are not neccessarily all good news. Normally one would think that it is good that earthworms by their burrowing enhance soil drainage but this also enhances nitrate leaching.! Also by bringing nutrients to the soil surface in ‘casts’ they accelerate P runoff - so we must not get too romantic about these matters.
Doug Edmeades | May 24, 2008 |

Now from what I've read, the various introduced worm species have quite different burrowing and casting behaviours, and a mix of species is recommended. So I expect that in general, worms are largely very beneficial. It has been proven that the more biological activity there is in a soil, the higher the denitrification action becomes. Worms are usually a simple indicator of that activity.

A biochemistry student we know, expounded recently that earthworms by their actions also produce extra N2O (from gut bacteria), a powerful greenhouse gas.

However, in 2007, peer-reviewed science (Bertoli et al, 2007) has shown that the introduction of earthworms into soil has the opposite effect..

http://www.jgpress.com/archives/_free/001772.html

Worms are counted as part of the SOM. The Massey University studies that are underway, quote improvements in pasture production of up to 30% when missing earthworm species are introduced. I trust they removed any other factors. If that is the case, it's a great result, lining up with the DPI information above.

[Graham]

Chemical or Biological Farming?

Some testimonials from BioAg, a NZ biological farming company who use Brix meters as one way of measuring responses.

Sheep, Beef & Dairy Testimonials
Some more great testimonials to share...

June 2009
Richard Hunter, Hunter Down Farms Ltd, Balclutha
“I have only been using BioAg for 8 months so I need to be cautious in what I say. I have certainly measured higher soil temperatures – up to 2 degrees – and better brix where I have used BioAg on young grass paddocks. I put this down to a higher level of biological activity and look forward to seeing how things progress”.


June 2009
Jonty Wall, Riverside Trust, Martinborough, Wairarapa
In response to questions regarding what he has seen change Jonty responds “It’s a whole lot of little things in combination - as though we are restoring a balance. The pastures are denser with greater diversity and variety of species. And the colour is rich – not the ‘fake’ green you often see with salt-based acid fertilisers. The clover and plantains have rebounded and bare patches have covered over. And the proof is in the stock – the cattle are happier and have a great sheen to their coats – I’m certain the palatability of the pasture is being reflected in better conversion and weight gain. I am also impressed how clean lambs have stayed after drenching with RumiMate, BioAg’s nutritional supplement which stimulates microbial activity in the digestive tract of animals. In fact everything is just smoking!’

“I now notice following heavy rain we don’t have the ponding issues we had. The soil permeability and water holding capacity have certainly improved, the worm castings are unbelievable and cow pats are breaking down much faster. Yes, it’s a whole lot of subtle good things happening in harmony. Mary and I are much happier with a more natural biological cycle which results in healthier food for people to eat. To us that is the bottom line!”

March 2009
Bill Hunt, Ratanui Farm, Otaki,
Bill has always been a ‘low chemical input’ farmer preferring to follow nature rather than read labels on bottles and bags to find answers to profitable dairying. BioAg Agent Tony Robinson worked with Bill using compost tea on his property prior to joining BioAg. “I think we had laid a pretty good biological foundation already” observes Tony. Both Tony and Bill have, however been delighted with progress since adopting a full BioAg programme in 2008. They have both observed more density in the pastures, grass as ‘thick as’ and no bare patches. Pastures have higher clover content and the pasture has a greater diversity of species. Bill’s hay contractor commented “There’s a hell of a lot more grass in the paddocks”. This response is repeated frequently by BioAg clients who say that visually they don’t see much difference but bulk is evidenced by higher yields when cut for hay or baleage or longer grazing cycles and cows grazing for shorter intervals and lying down in apparent content. Other observations include a ‘healthy’ green colour in the pasture, excellent worm numbers and activity and plenty of pink nodules on the clover roots – a sure sign that nitrogen fixing bacteria are hard at work supplying free nitrogen in a form that plants utilize fully.

Yesterday I was inspecting the paddock next door to us at work, which had been dosed with urea recently (under instruction from AgKnowledge). As expected, plenty of grass and weed growth, but Brix levels were lower than we had seen previously. Drystock pats that had been left weeks ago appeared to not have broken up at all, and were an indication that worm activity was minimal, and we have been told that the paddock is badly compacted. When we have looked for worms in this paddock, we have found little evidence of any at all.

Can any farmers tell me whether this is typical of Waikato farmland now? Is it anything to be worried about?

[Graham]

Novel Ways are going to establish a forage test plot of 5m x 5m near the workshop (with permission of course). We will ensure we establish some of the three main worm species in that area, if they are not already there.

http://www.agresearch.co.nz/our-scie...arthworms.aspx

Brochure with ID photos: http://www.agresearch.co.nz/our-scie...arthworms.aspx

Background on breeding worms in NZ: http://www.wormsrus.co.nz/aboutearthworms.html

1950s research: 30% to 110% improvement in grass growth with worms.

http://www.teara.govt.nz/en/earthworms/page-5

[Graham]

The area won't be sprayed with Roundup or derivatives.

http://www.ncbi.nlm.nih.gov/pubmed/20658223

http://www.foe.co.uk/resource/report...glyphosate.pdf

[Graham]

A recent article mentions worms, and shows the use of penetrometers.

http://www.stuff.co.nz/business/farm...to-soil-health

[Graham]

Now near the end of January 2014, and the test plot has had its protective fence removed, waiting for drystock to come through on their rotation. The plot is in the south-west corner of a paddock, and the most southern half (adjacent to the other paddock through the fence) has had an extra treatment of hay and garden compost under the overturned top layer of sods and topsoil.

This half of the plot has noticeably more ryegrass, and seeded better. Some lower profile weeds are present in the other half, along with the meadow mix of chicory, ryegrass, clover etc. After detailed lab testing of soil and plant material, all of the plot has had a standard fertiliser regime applied first. Every six months we'll top that up, until two years has passed.