Sunday, October 18, 2009

Rain, salt and sea

Well its' been a couple of weeks of water. First the tsunami warning emanating from Samoa - and my heart and thoughts go out to the lovely gentle people from those Islands that were affected by this tragedy - and then the rain, lots of it. The tsunami warning really hit home, reminding us of the downside of living on what is basically a peat bog about a metre above the high tide mark and a few hundred metres from the waters edge. It would not take much for us to be in the same predicament as those other poor people. Once we realised that the tsunami was probably not going to be more than a tidal surge, my thoughts went from our safety to my garden, naturally! All I could think was how to get the chooks above ground level, and what would happen to the soil if salt water went over it. As it happened, the arrival of the surge coincided exactly with low tide, and we barely noticed it.

This got me thinking though, about salty soils and tidal inundation in general. Many areas around the world suffer from this problem, for a variety of reasons. One of the best ways of overcoming this problem is to apply gypsum to the soil, in fairly large quantities. The way this works is the calcium in gypsum replaces the sodium in the soil. If there is sufficient rainfall, or a sufficient supply of quality irrigation water, then the sodium leaches out into the subsoil or the ground water. Of course this requires a good amount of water, and somewhere for the sodium to go to. If there is not enough clean water, or the soil is quite shallow with a hard pan beneath it, then this does not work as well.

I used this technique just last week, when I treated blocks of coir fibre that I use for potting up my bromeliads. Great stuff, which the broms just love, as it is very free draining. However some of it, like the fibre I use, is produced in regions where there is not enough fresh water to process the coconut husks to produce the coir fibre. Any fresh water they have is a precious resource. The salt water they use instead impregnates the fibre with sodium, which is toxic to the plants planted in it. So, before I use it, it gets a dusting of Gypsum which is mixed in and then left to soak overnight. The next day, fresh water is run through until the salt level drops enough to use, after which the fertilisers can be added. I check the level with a handheld salt meter (also known as a CF or EC meter). Apart from the transport from places like Sri Lanka to NZ, using this product ticks all the boxes for me. Aside from being great for the broms, it is a renewable and sustainable product, with very little detrimental impact on the environment, and also helps support families in some pretty low income areas.

All this reminds me just how lucky we are in New Zealand, particularly up North, where the rainfall is plentiful and the water quality is usually superb. A bit too plentiful this last two weeks, where we've had rain nearly every day. This makes it a bit hard to get out into the garden, but I have managed to set up two more raised beds. These are really simple to make. I just get 5 macrocarpa sleepers, 2.1m long. One I cut in half for the ends, and the others make the sides, all held together with nail plates. So easy. This makes a bed 20cm high, 4.0 m long and 1.0m wide. Some so-called garden experts recommend making the beds much higher than this, up to 1 metre high! This is fine if you've got medical issues so you can't bend over or kneel, but is otherwise quite useless. A high bed just uses up much larger quantities of good soil, dries out much quicker and provides no added benefit to the plants. The sleepers are great, as they are so heavy they don't need additional stakes or framing to keep them in place and they provide a place to kneel on when you're weeding or planting the garden. We now have 7 of these beds in our vege garden, filled with a mix of 50:50 compost and peat soil.

One downside of all this rain and humidity is an increase in fungal diseases. I noticed late blight on the potatoes, aagh I hate this disease. This year I am determined to not let it beat me, which is easier said than done in the humid North. Anyway, I thought I might try Potassium bicarbonate, which is like baking soda (sodium bicarbonate), but slightly more effective. Well it worked better than I thought it would. Stopped the disease in its' tracks as well as any commercial fungicide. I made sure I got good coverage with the spray, and followed it up with another 10 days later to make sure. While one success proves little, it certainly gave me a enough of a indication to use it again later in the season when the disease pressure is greater. Fingers crossed.

On a less gloomy note than natural disasters, rain and disease, we harvested our first decent pick of strawberries today. An icecream container full of them; big, firm, sweet and juicy. Aah the joy of the first berries of spring, with vanilla icecream and cream. It looks like we're in for a good crop.

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