Thursday, July 25, 2013

Mineral needs and interactions in plants (on soil)

I am reminded by recent learning that I need to look carefully at mineral interactions in the soil and the needs of plants.

I have been adding dolomite (a limestone with high proportion of magnesium) rather than normal agricultural lime (limestone essentially calcium carbonate) to my soil.

I have focused on magnesium because the use of lime not dolomite in broad acre farming almost certainly contributes to a magnesium deficiency in much commercial food, there being a need for calcium and magnesium to balance each other in nature. In humans many problems arise from calcium coming away from where it should be, causing deterioration in bone and muscle and contributing to nervous and cognitive disorders and poor metabolism.And while pharmacies and supermarkets are littered with calcium supplements, you really need the magnesium to get the calcium back where it belongs and staying there. You can get lots of information from the web on this, it's a good exercise in wading through 'marketing science' for facts.

A recent email from someone in the US (curiously in a discussion about a lemon tree in a pot in the UK) drew my attention to the fact that calcium is more soluble compared to magnesium and in high rainfall environments calcium deficiencies can rapidly arise, as also is the case with other minerals which are highly soluble.

We've had a lot of rain, some parts of my garden good, some not so good... 

So... I need add calcium but also to check my soil pH, must get a pH test kit, lent mine to someone...

pH is critical (see this introduction): an industrial way to achieve it is to add stuff to try to get the balance right. On the other hand, achievement of a high humus healthy soil, crowded with life, should itself nudge the soil towards the right pH.

Source here, same link as above

But it is also important to have an awareness of mineral availability. There is a thing called Mulder's Chart which can be found in many places on the web. In fact two charts, for animals and plants. This is the chart for plants, which I have borrowed from this site. This is a particularly helpful presentation, with its text, explaining the nature of interactions. I wanted to report here who exactly Mr/Dr/Prof Mulder might be, but mainly I got links to The X-Files.

Click on image to enlarge chart. Go below the chart for a bit more...
borrowed from this site

This becomes relevant when you find problems which may be identified in plant leaves. Here is a citrus leaf from my partner Helen's garden.

 It is growing in red sandy-clayey soil on a slope, recent heavy rains, rapidly drying soil. The task ahead is to work out what may be ailing the tree, and how to ffix it. Ideally we just help the soil fix it. There are pictorial guides to deficiencies evident in the coloration of citrus leaves. Try this, or this, or this... see if you can find better on the web, if so use the comment box.

My opening perspective is this:
  1. The tree is young, young citrus tend to struggle at times and much self correction is possible;
  2. The rains and wind have stripped compost, manures and protective mulch, first leaching away soluble nutrients, perhaps drowning a lot of microorganisms, and then drying the soil severely;
  3. When roots go deeper, the problems may reduce, as the tree gets bigger and feeds from more damage resistant levels of the soil... but under the tree the soil is pretty shallow because of the slope;
  4. So start simple: 
  • Use a broadfork and use carefully at and beyond the drip line, lifting soil, enabling water and nutrient entry to lower levels of soil;
  • Check the pH, as appropriate then add lime and Epsom Salts (giving the tree magnesium and highly soluble sulphur) and a bit of dilute urine (see earlier blog entry on urine in garden) for nitrogen and much more;
  • Throw in some rusty nails for possible iron deficiency (citrus love iron);
  • Add compost and well rotted manures;
  • Re-mulch (the protective layer, high in carbon, slow to rot, resistant to weeds coming up. Plant  bushy legumes (peas, beans) into the mulch and
  • Water well, deeply and not daily, allowing water to go deep and roots to follow, not spread near the surface.
May sound complex but not really that hard, and a good support like this should help for some time, as the tree finds its feet.

All this arising from discussion about a neglected lemon tree in a pot in England... Stimulus from small issues drives on to wider thought!

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