All The Dirt On Soil

It goes without saying, but I said it anyway - crap soil is the vegie gardener's nemesis.

Take tomatoes. They're forgiving buggers, they'll grow in all sorts of conditions. They'll even try to grow in extreme - in terms of poor - conditions. The results will be less than optimum, but they'll give it a go.

This has been our third summer with the orto. For two years the tomatoes were less than what they should have been. Production was down on what I'm used to, the plants themselves never developed to sizes I was used to and nor did the fruit. I couldn't fathom it.

Until, this year, I decided to test the soil. Wherever I tested across the three terraces, the soil was utterly alkaline, up to and beyond 9 on the pH scale.

Quite a few vegies - for example, most brassicas - like alkaline soil. Except I don't grow them. I don't have the space. Tomatoes, on the other hand, don't mind neutral soil but they very much like slightly acid soil. Hence the orto's soil couldn't have been less to their liking.

Why should the soil be so utterly alkaline?

As I thought about it, a number of reasons emerged. First, Italian soil is chockers with limestone, particularly closer to the mountains. Limestone, of course, is the principal means of sweetening - which is to say, making more alkaline - acid soil. So our soil has no option other than to tend towards alkalinity.

Second, and unsurprisingly given the above, Italian water is also chockers with limestone. Anything with which Italian water comes into contact - washing machines, kettles, dishwashers, espresso machines, hot water services, water-heated radiators, taps, you name it - will gradually build up an internal crust of calcium. Water pressure only a trickle? The filter on the tap is blocked with calcium. I flush the inner workings of the espresso machine once a month to keep the pipes clean. The Italian word for calcium is calcare. The supermarket shelves are loaded with anti-calcare products. So every time I watered the orto, I was pumping up the alkalinity.

Third, and crucially, I have been at a disadvantage relative to other Italian market- and home-gardeners. Our orto was used for many years as a dumping ground for building rubble. One family owned our entire building:

Along with a lot of the building on the immediate left. There are four and a half apartments in our building, and, as the apartments were renovated over the years - along with the adjacent building - unwanted bricks, stone, concrete, timber, broken glass, metal, tin and goodness what else was dumped into our terraces and covered over with brought-in, very ordinary soil. All of which was left sitting untouched, uncared for, for 30 or more years, with the lime from the stone and cement undoubtedly leeching into the soil.

Sadly, there isn't a single earthworm on the property.

Enough history. The bottom line is that every time I watered the orto over the last two years, I was pouring hard alkaline water onto already rubbishy, alkaline soil.

What a dill. And no wonder the toms struggled.

Now, such alkaline soil, in such quantity as in the orto, is virtually impossible to amend sufficiently to turn it into neutral - or, better still - slightly acid soil. The amending products - sulphur, iron - would need to be in such quantities that they would create interactions likely to damage anything planted. Besides, given that the base soil will always be essentially limestone, the battle would be ongoing and mighty expensive.

Other options? Replace all the soil. Well, for starters, I can't afford it. For closers, the only access into the orto is through our apartment.

Solution? I suppose it's called micro-management.

For every tomato plant I put into the ground, I dug a decent-sized hole, sufficient to accommodate mature root systems in their entirety. I filled the hole with compost from the heap - essentially neutral in pH terms - mixed in with a couple of shovelfuls of potting mix designed for acid soil-loving plants like camelias and hydrangeas. The compost nicely balanced the acidity of the potting mix. Thus I created little oases of tomato-friendly soil in a desert of limestone.

Next, watering. How to avoid pouring hard alkaline water into the soil and undoing any good I'd already done with the soil? Rain water? Great idea. Except in an Italian summer when it doesn't rain for months on end.

So I improvised. I added a tablespoon of vinegar to every 8-litre watering can before watering. Someone told me it was storie della nonna - an old wives' tale - but, combined with the soil, it seemed to work:

A small portion of the best tomato crop in three years - a couple of Anna Russians with a pair of Pink Gaetanos, all between 450g and 600g. And delicious.

I'll have to do it all again next year.

But it will be worth it.