Reader questions answered: solar hot water and fixing nitrogen in soil

While I don't get much time to write these days with a young child and a growing business, but I do write to people who send questions that I have not yet blogged about, and I'm sharing my answers for my other readers too.

Here are a couple of questions from Andrew in Blackheath:

I am planning to install a solar hot water service at my house in Blackheath. Do you know if I am likely to have any problems with pipes or other components cracking or leaking if the water in the system freezes? Can you recommend a good plumber or similar tradesman that can do the whole job? Would Brendon McClement be able to do the whole job? I like the idea of using the same evacuated tube system that you used.

As a separate issue but related to your business, I have been advised that I need to increase the nitrogen levels in the soil on my 1,760m2 suburban block to successfully grow the fruit, vegetables and native plants that I would like to grow. I therefore need to find a source of a large amount nitrogen-rich mulch or similar source of nitrogen & mulch. Can you suggest an inexpensive but good value source of high-nitrogen mulch for that purpose? I have heard that tree chippings can be good if they have a large amount of green matter in them. Do you know if this is correct? Are there other sources of nitrogen suitable for gardens in my area?

Hi Andrew,

With regards to the solar hot water system:

There are many types of evacuated tube systems about and some can handle frost, others can't. You will need to check before purchasing. Generally suppliers are pretty clear in their descriptions about frost resistant or frost free models.

I would like to provide a little bit of feedback regarding my solar hot water system after running it for a year.

I still would certainly get the same one (or similar) again but it does require regular maintenance. I check the tank is full about once a fortnight which means me climbing on to the roof. I will eventually have a tap installed somewhere lower. I have not yet attached the system to the combustion stove to provide hot water on cloudy days (but will very soon).

If you are not planning to connect the system to a combustion stove, I would perhaps consider a split system where the water tank is at ground level and the evacuated tubes are on the roof. The downside to this system is that the hot water on the roof needs to get back down to the water storage. That will not happen unless it is pumped using an electric pump (hot water rises, cold water sinks). If you have a blackout, you don't have hot water. You could overcome this by running the circulating pump (often 12v) through an off grid system so it would work even if the power went down. It would add a fair amount of extra cost to the split system cost. At a rough guess I would say another $1000 but someone like will be able to help you out with that.

In conclusion, if you have the cash, don't want to connect a fire and want the convenience of hi-tech solar hot water, go with the Apricus split system and yes Brendan will do the lot for you. He also supplies Apricus systems from a distributor based in the mountains. Naturally if there are any problems they will be easily resolved and parts are locally available. That's going to cost you around $6000.

If you have the time to do a bit of DIY and 30 seconds a fortnight to top up the tank, the system similar to mine may be the go. That's going to cost you around $4000 if you get it up on the roof yourself. Brendan will plumb it and possibly even put it on the roof for you but you would have to source the unit. I would go through rather than then reseller I went through or alternatively there is a supplier in Hartley that sell similar systems. I can't vouch for them but I know a few people who have used them and have been happy. The plus side is there is support locally if needed.

With regards to nitrogen levels in your soils:

Without seeing your land I can't determine if your soil requires extra nitrogen. I generally would not advise anyone to try and fix their soil by providing a single element at a time (that is something that chemical agriculture advises) but rather I would try to address all the elements at once.

Wood chips will not provide you with nitrogen and will actually take nitrogen out of the soil in the short term. With that said, I would still use wood chips and by the truck load to build organic matter which, in time, will give you more than enough nitrogen, phosphorus, potassium etc. Cheap wood chips are often available from arborists. You will need to phone around.

I would use wood chips everywhere other than the areas that you want to grow veggies. Veggies don't like wood chips very much so use straw or lucerne. Lucerne is very high in nitrogen. You can address the lack of nitrogen by adding it around new plants while the wood chips are breaking down. You could add a bit of manure UNDER the mulch but ABOVE the soil around new plantings. You can also use urine (diluted 1-10) as a fantastic free high nitrogen fertiliser.

When adding wood chips, try and put down a layer about 15-20cm deep. Do that every year for about 3 years and the weeds will disappearAfter that your plants should be providing you with all the mulch you need to feed the soil and keep the weeds away. Just prune every thing regularly and chop it up as mulch and scatter it around the plants.

Good luck and happy harvests!


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