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Pea Inoculants

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Our first look at inoculation of peas left us asking more questions. We got a high level of inoculation on one paddock but very little in another.

Everything pretty much the same: Both were the same pea variety planted at the same rate on the same day with the same equipment using the same inoculator.

  • Why did we get different effects?
  • What encourages or discourages inoculation?
  • How many nodules is enough?

Some background

GRDC recently published an excellent guide to inoculating legumes. Their Back Pocket Guide is quick to review and very informative.

Legume inoculation involves encouraging specific strains of rhizobia bacteria to colonise plant roots. They form a symbiotic relationship, fixing atmospheric nitrogen and getting resources from the plant. Each type of legume is nodulated by a specific type of rhizobia, and different legume – rhizobia associations will tolerate different soil conditions.

The GRDC Pocket Guide notes pea rhizobia prefer a neutral to alkaine pH of 6.0 – 7.5. It suggests peas nodulate with Inolculant Group E, but also with Group F. The likelihood of crop response to inoculation is said to be high where peas or vetch have not previously been grown. Where there has been a recent well nodulated host crop, the likelihoood of crop response if said to be low.

The GRDC Pocket Guide that after 8 weeks, 100 pink nodules per plant on heavier textured soils and 20 nodules per plant on lighter soils are satisfactory.

What did we do?

We planted Ashton peas VA 1301 on 12  November at 200kg seed per hectare.

Soil testing in June had showed the two Paddocks had almost identical nutrient status including nitrogen. Both were very low in sulphur. Paddock 2 had slightly more organic matter.

Becker Underwood Nodulator supplied by BASF Crop Protection was applied at slightly different rates in the two paddocks.

The seed was drilled by Parick Nicolle using his modified Great Plains drill. The Nodulator was in a separate box to keep it away from fertiliser and avoid separating out. New tubing directed the inoculator into the disc coulter so it was applied with the seed in the seed furrow.

GreatPlains Nodulator tubes W Hazelwood  2 Nodulator Seed tube connection W Hazelwood  3 Inside disc coulter W Hazelwood

Drill Images: W. Hazelwood, BASF Crop Protection
1: Nodulator delivery tubes
2: Nodulator/seed tube junction above coulter
3: Inside view of double disc coulter showing final delivery spout with combined seed and Nodulator

What did we see?

Paddock 2 had the highest pea yield but least evidence of nodulation.


In Paddock 6 we saw significant development of nodules on the pea roots as shown in the photo above. We noted the nodules were much bigger than we are used to seeing, and appeared almost as a series of nodules fused together.

In Paddock 2 we found very little nodulation. Not even as much as we might usually see in crops in this region.

Why the differences?

The obvious background differences are irrigation and the paddocks’ histories.

Paddock 2 is our buried-drip irrigation block and the pea crop received significant irrigation which kept it above moisture stress point. Paddock 6 had no irrigation, and the crop did go into moisture stress. We suggest this is the primary cause of the yield difference.

Paddock 6 was planted out of long term pasture which had received little fertiliser in the last ten years. Paddock 2 was planted out of an over-winter cover crop of broad beans, a legume with potentially similar inoculant relationships to peas. The ground had been cultivated prior to bean planting, and the beans were chopped in to prepare the Paddock for pea planting.

So some possible mechanisms spring to mind:

  1. The rhizobium niches in Paddock 2 might have been occupied by “wild” strains. As the GRDC Pocket Guide indicates, where a recent bean crop has been grown, a crop response to inoculation is less likely. Even if the wild strains did not inoculate our peas, and we saw little evidence of nodules, they may have reduced the ability of Nodulator to do so.
  2. Possible higher soil nitrogen after the bean cover crop may have provided sufficient for the crop without a need for nodulation. In retrospect, some more soil nutrient testing at the end of the crop may have helped clarify the potential role of different nutrition.

Many thanks to:

Nicolle Contracting, True Earth Organics, Drumpeel Farms, BASF Crop Protection, McCain Foods, Ballance AgriNutrients, Fruitfed Supplies, Haydn Greville Groundspraying and Agronica, ThinkWater and Netafim and the Centre for Land and Water for supporting this preliminary investigation.


Mission identification using Wordle

It is an interesting process – getting common understanding and agreement of two dozen people at the start of a loosely defined project.

We have an interest group establishing itself around our Micro-Farm. We had a meeting about vision and purpose, and what everyone wanted to get out of their involvement.

At the end of the meeting, we agreed everyone would submit ten words that summarised their vision for the Micro-Farm, maybe as a vision statement.

We collated the responses and put them all into  This is what we got.


This seems a fair representation of our discussions to date.

It seems to me the big words have nailed the “what we want”.  We talked of maximising production, by increasing yield but while maintaining the soil. To achieve that we need management for sustainable cropping and controlled traffic (CTF) was frequently mentioned.

Many of the little words are “how we might get there”. They include possible practices and rules for engagement, as well as a wealth of ideas of things to try, to measure and to keep in mind.

I think this is something we need to repeat at intervals: wordles is a very interesting way to review messy information!

Sandpit to play in

It is great when you have a sandpit to play in. You can dream a bit, try out things you wouldn’t do normally, and push the boundaries with little fear of hurt or harm. That’s what we want to do at the Centre for Land and Water.

A small group of enthusiasats that met at the Green Shed has begun formulating plans to develop the whole field as a group “sandpit”. The idea is for stakeholders to discuss and implement ways of cropping that may be outside the ordinary. Our intention is for the site to be cropped using conventional “farmer and contractor” equipment.

While full size commercial equipment is bigger than needed for this small site, the point is to use “real gear” so we can be sure the effects are easily translated to any other farming situation. We also think using controlled traffic principles is a base-line for management. We don’t think we’ll always be able to do that, especially as we intend process peas to be a feature of the rotations. But why not get what benefits we can, and worry about the problems when or if they actually arrive?

This aerial view (click for larger image) of the Centre site shows the layout. The buried drip irrigation is in Block 2.

GoogleEarth_Image Blocks

We have six micro-paddocks, three either side of the central axis access way. We have determined to have a five year rotation plan as a starting point. This can be varied, but gives a clear direction to start the journey. Initial thinking is to chop-in the broadbeans in spring and plant a vining pea crop across the site. We have a few different  ideas to try out. We’ll follow the peas with  some summer crops.

Mark Redshaw from Ballance AgriNutrients has taken soil samples from each of the six micro-paddocks. They are to be analysed at Hills Labs to establish base line levels across the site. We are grateful for their support as we get underway.