Acidity

Since the beginning of September, I’ve been attending one of the RBGE’s short courses – specifically ‘An Introduction to Horticulture’.  It’s been a really enjoyable course –  especially the last lesson, which was centred on soil properties and composition.  We were asked to bring in small soil samples from our gardens to do a pH test on so I brought three samples – one from the ‘oldest’ bed, one from this years newly cultivated bed and one from the newly dug back bed.  To say the results were surprising would be a gross understatement.  I’d suspected the soil at the back wasn’t great quality, and knew it would need a decent injection of organic material to get it off to a good start but I did not suspect quite how bad it was.

The tutor borrowed one of my samples to show us how to use the chemicals and it was whilst I was working on adding the bits and pieces to my second test tube that I heard an amused “what in the world do you grow in this soil?” .  I looked to the front of the classroom to see a red container.  Not just a wee bit red but BRIGHT RED.  The colour wasn’t even on the chart which the tutor passed around – she estimated the pH of my soil to be around 4.5!    pH 5 is considered ‘very acid soil’ and for those who’ve not done chemistry for a while, pH runs on a scale of 0-14 with 0 being the most acid and 14 most alkali (though it can go outwith those values, but for simplicity’s sake…).  It’s a logarithmic scale, meaning that a soil with a pH of four is ten times as acid as one at five – so it’s not even just a ‘wee bit more acid’.

What this means in real terms is that there are very few nutrients available to the plant – many of the nutrients plants use react with other things at lower or higher acidities – which most being available for the use of plants around the neutral range.  It completely explains why my hydrangea was having trouble, even as a plant which can usually handle both fairly acidic or alkaline soils.  I’m not sure, to be honest, how the daffodils planted there have managed to cope, but I can perhaps understand why they didn’t always flower – they probably just couldn’t get the required mineral nutrients for that kind of growth.

Action, then, was needed.  There are several ways to deal with acidic soil – as our tutor went over in class.  The first, and most basic, was to put in acid-loving plants – but this is rather limiting and with my soil even acid loving plants might have issues.  The second is to add organic material – preferably not too much leaf mould as that is fairly acidic, too.  This is slow-acting and I had already begun to do this as it’s my preferred method overall for improving my soil.  The third is to add lime – which will help increase the pH more quickly but need to be reapplied to keep the pH up.  I’ve also decided to go down this route – even if just to ‘sweeten’ the soil a little more, so that it’s not deadly-death to most plants.  I’m hoping that liming it now will help with the spring bulbs and give me a decent soil to plant into come early summer, and, thenceforth, I can plant a wider range of plants and continue to improve the soil to allow it to be a better growing environment.

The other big surprise, for me, was that my ‘good’ veg bed showed as fairly acidic too.  Not nearly on the scale of the back bed, but definitely acid rather than neutral.  This surprises me as I’ve grown a fair bit of veg in there – including some good sized brassicas which I’ve read prefer alkaline soil.  The last ‘surprise’ was at least a good one – the side bed, which I dug at the beginning of this year, has fairly neutral soil which bodes well for next year!  I may try adding a little extra lime to whichever area I decide to grow my brassicas in (which I’ll need to decide soon, to give it enough time to break down) to see if that gives them a boost of some sort.

In other news, this year is mild – I still have sunflowers (above) blooming in November!  My poor broad beans have come up and are growing away like monsters – unless we have a super-mild winter they’re doomed so I’ve planted some more, hoping that this lot will only just peek their heads above ground before harsher weather comes along.

 

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