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Miranda Hodgson

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Egg-like spheres on roots and signs of the sparrow hawk

Posted by Miranda Hodgson on 11 Nov 2010 at 03:31 PM

I was taking down the bean plants last week and stopped to admire some nodules on the roots. You could be forgiven for thinking that the plant had been infested with some horrible pest, but these are not pests and, indeed, they are highly desirable, for they are naturally forming nitrogen nodules. They are found on the roots of many plants of the pea family (including beans, peas, clover and alfalfa) as well as alder trees. It’s useful to know about them so that they aren’t confused with pest eggs and destroyed.

Briefly, these amazing things are formed by a bacterium called Rhizobium; these invade the plant roots, causing them to form nodules. The rhizobium then take in nitrogen from the air in the soil and fix it into ammonium ions, which is passed on to the plant’s cells. In return, the rhizobium are supplied with carbohydrates. Nitrogen fixing means that less nitrogen fertiliser is needed, because the plant can do that for itself. Isn’t that amazing.

When we arrive at the garden, I get out to open the gate and my partner drives the car through the field that leads to the garden gate. I like to walk across the field so I can look in the hedgerow and see if anything is happening. It wasn’t that day, but what was happening elsewhere in the field was a sparrowhawk (Accipiter nisus) making a meal of a pigeon. It flew off as soon as we approached, leaving the half-eaten pigeon behind, surrounded by the tell-tale scattering of feathers.




When we passed that way a few hours later, only the feathers remained. Did the sparrowhawk fly away with the carcase, or did an opportunistic fox pick it up? We shall never know.


asj said:

Nice blog, Miranda, but you shouldn't be opening gates in your condition!!

on 11 Nov 2010 at 04:13 PM

Miranda Hodgson said:

You are right, of course, asj. I was ever so careful, honest!

on 11 Nov 2010 at 05:11 PM

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on 11 Nov 2010 at 07:40 PM

EvaInNL said:

LOL - reminds me of when I pulled out all my bean plants and fed them to the sheep. My neighbour was watching me do this and only after the sheep were happily munching away on the plants did he mention it was better to leave them in... Oh well, at least I know better for next year now!

on 12 Nov 2010 at 10:55 AM

Miranda Hodgson said:

Typical, Eva, fancy leaving it till the sheep had eaten it all! Still, they probably enjoyed it and at least you know now. So, did you notice the little nodules on the roots?

on 12 Nov 2010 at 04:28 PM

EvaInNL said:

Indeed, typical of the man, very generous in other ways though! And I did notice the nodules, but they were very tiny at the time, I surrounded the bean plot with nasturtiums and they totally overcrowded the beans who didn't get a look in this year!

on 13 Nov 2010 at 12:07 PM