Archive | November 2015

Gum tree Blight

Dear Xavier,

Evaporation 15 to 21 November 5, 6, 10-1, 6, 5-10, 1-21, 3

While on the weather, The Guardian reports that NOAA (the US weather people) report that this El Nino has broken all records on two out of three El Nino criteria – they won’t know if it has broken the 3rd until later in the year, because they cannot measure the third until later. Certainly our rains got off to a late kick-off.

I am not sure how many other farmers have got this blight in their gum trees. Blight is probably the wrong word, but it is a disease/pest affecting the leaves of gum trees, leaving them looking decidedly short of leaves. I first saw it on James Chance’s farm, but Patrick’s are also affected and James tells me many other people have it too. On my farm (and Patrick’s) it seems that grandus is much less affected than terretricornis (not sure of spelling of either of them) and I wonder if other people have a similar experience? I don’t know of any camaldulensis in the area, but it would be worth checking any. I also have a few p? p? p? (I cannot remember their name, but black stringy bark) and I will check them out. It is a reminder that we should plant as many different species of tree as possible – in case one is vulnerable to a disease or pest. I doubt that a dry El Nino year is going to help.

Talking of pests, any sign/news of the yellow cane aphid? Best4now,Bruce


My the rain fall soft upon your fields

Dear William,

Evaporation 8th to 14th November, 10,11,11,10,10,15,12 which I think is the highest weekly total I have ever recorded.

I have switched my pivot to a 13mm a day nozzle pack. Even with this, I should not (in theory) be able to keep up with this evaporation, given the frequency of power cuts, but I think two things have happened, that is making the tobacco ‘perform’ differently from the theoretical model. Firstly, it has been growing more slowly than ideal (because of a shortage of water) and secondly, it has shut down somewhat, so that the Et/Eo is again lower than it should be. This is a ‘safe’ position to be in, because the tobacco is not too soft and so not too prone to scorching. How long I can keep it like this before it rains is anybody’s guess.

I have learned a few other things too. Firstly, my nozzles on the pivot (which are now 10 years old) do not appear to have worn out very much. I have been meaning to do it for sometime, but, I finally got around to measuring the flow-rate into a bucket at three places along the length of the pivot. All three were bang on their spec – which is a relief. The second thing is that I am definitely losing 20% of the water through evaporation. What I measure in my rain-gauge is constantly 20% less than the measured output of the nozzles. That is no surprise, but one has to make sure one budgets for it. What is surprising is there doesn’t seem to be much difference between day and night time evaporation. (Sometimes the pivot passes over the gauge at night, but the loss is the same as during the day.)

Doug Watt (from Kabwe) attended the ZESCO/ZNFU meeting. Although Zambia has used up our allocation of water (and so must pay a penalty on any further use) there is still some water left in Kariba for generation. His other news was that some people had installed PF correcting equipment in Lusaka area – which didn’t work. I have heard of at least three different suppliers in Choma, so make sure your system works before you pay.




Dear Vance,

Evaporation 1st to 7th November 8,9,8,4,5,7,5

I was told about a book called “The Checklist Manifesto” in a blog called “The Art of Troubleshooting” (which I recommend) and had ordered it sometime ago. When it came there were other books in the queue, so it had to wait it’s turn. Then, a friend recommended the latest book by the same author (“Being Mortal”) and so I decided that Checklist could jump the queue. It is a very inspiring read. He discusses how the medical profession could benefit from adopting check-lists. He tried to learn from both the building/construction industry and from the airline industry. He decided that the airline industry was more appropriate to surgery – because they both have so very little time. Their checklists have to be VERY short and brief. Farming is more like the construction industry, we (mostly) have far more time to plan and to check, and I do believe checklists are going to help us significantly. (Especially as we get older, and our memories fail us more often). I have been feeling my way towards a check-list anyway and have several. All written in Excel, they are a little like a diary, for seedbeds; for the whole growing of tobacco from planting through to topping; for the whole year so that we don’t forget to do some of the maintenance jobs that we ought to do every winter. But, I am now adding proper checklists to this to make sure we have all the equipment for planting or all the chemical that we need in stock. Being Excel it is easy to update the dates from one year to the next (Sundays are coloured differently) and again, being Excel, it is easy to show (by different coloured text, or different coloured cells) what has been done and what hasn’t. The checklist can also specify who is responsible for each item.

I would be interested in sharing any checklists that anyone else may have developed as I am sure other people will have ideas worth incorporating into mine.



solar hot water

Dear Ursula,

Evaporation for 25th to 31st October 7,7,8,8,8,7,8

Very few of us recorded any rain in October and this is true of only 25% of my records – going back to 1950. However, my records also indicate that, in years with no October rain, the total is actually higher than the average of wet October years – so the verdict is still wide open.

I hope those of you who attended the Greenleaf presentation on Saturday at the Sports Club were inspired to think more and more in terms of solar power. David Falkenberg told me of a company, Freedom Won, who are converting vehicles to electric battery power. Their website is quite fun, even if their prices are beyond me. (However I am asking them to quote for a suitable battery).

David, Steve Hodge and I also discussed the challenge of fitting a solar hot water system to a thatched house. One doesn’t want to fit it to the roof (as one would normally do) because the thatch would quickly rot, and it is quite awkward to plumb a solar water heater if it is situated some distance from the house, where it will get proper exposure to the sun. I had hoped that Steve and David would work this one out, but my mind wouldn’t leave it alone and I think I have a solution that is worth trying. Put a single 300W panel wherever it suits you (i.e. in full sunlight). Fit two geysers in series. The second one, just before your bath/shower, is connected to ZESCO. The first one receives the cold water and is heated by an element, powered by the solar panel. A single panel in 6 hours of sunshine could easily heat 200 liters of water a day from 20C to 90C. Because the water is already hot when it moves into the second geyser, the ZESCO element has to do nothing more than maintain the temperature. This would cost a fraction of the cost of an evacuated tube glycol solar heater and has no moving parts The only tricky part is finding a suitable element……watch this space.

I also hope to meet with ZESCO when I go to Lusaka on Wednesday/Thursday this week. I hope to get all my load shedding (and therefore the load shedding of the Sibanyati line, all the way down to Kala) moved to daylight hours. Not only would this allow me to get maximum benefit from my solar panels (with minimal use of batteries) but would also mean I run my generator during daylight hours (when it is easier to monitor). I will be negotiating for a price of my surplus solar power at least 60% of what I pay ZESCO for their Kariba power. I am prepared to give them this 40% margin as they provide the service of storing my surplus energy for when I need it – much cheaper than batteries! However, I have yet to receive confirmation of an appointment, so I suspect that ZESCO will be a more difficult solution to crack than finding the correct technology.