Sunday, September 27, 2009

Citrus fertiliser, wine and swimming

After Avocados, Citrus would be my next favourite fruit tree to grow. So trouble free and so bountiful. We were lucky in that we had 3 orange trees, 1 lemon, 1 tangelo, 1 mandarin and a huge grapefruit tree on the property when we brought it two years ago. We've added another lemon, a lime and a couple of mandarins since then. The trees were in reasonable condition, but were starting to suffer from a lack of attention.

This is pretty typical of many trees in back yards, as most people don't really give these the treatment they deserve. Trees that are showing yellowed leaves, crops of small acidic fruit with thick skins and weeds or long grass right up to the trunk are sure signs that the trees are not being looked after.

Our trees were very productive this year, except the grapefruit which I hacked back hard last winter. One Tangelo tree gave more than 60kg of fruit this season; juicy, sweet, gorgeous fruit. The secret? Clearing all the grass from around the base of the tree, out to the drip line. Citrus hate competition around the roots.

Trim the skirts off to about knee height so you can get underneath easily. Then fertilise with equal parts of dolomite, potash and blood & bone. This gives the trees an ideal nutrient ratio of nutrients, particularly for our soil which is very low in potassium. I throw about 3-4 handfuls of each fertiliser around each medium size tree. Then, cover with a 5cm+ layer of woody mulch.

Although commercial growers fertilise several times each year, in the home garden a good dose of fert and a mulch in early to mid spring will do the trick. The result, kilos and kilos of juicy sweet fruit that the kids can tuck into from late winter to late spring, just when they need that vitamin C. And seeing the kids were down at the point today for their first swim of the season they'll probably need it. What is it about getting older that results in adults hitting the water about two months after the kids have started swimming? Surely the extra padding should give us more insulation against the cold?

Anyway, the clearing. mulching and fertilising only took a couple of hours this afternoon, not much work for all the fruit these trees give. I would have done it in the morning, but was a bit seedy from the bottling of my new batch of feijoa dessert wine Saturday afternoon. This always involves a fair bit of tasting with friends and relatives, and usually includes breaking out some samples of previous wines for scientific comparison purposes. In this case a nice sweet red plum wine and a slightly drier yellow plum wine that my brother-out-law said should be called "CD cleaner 2009". Ingrate.

This is a damn good spring though. One out of the bag. About 6 weeks ago I planted my first spuds of the season, just after the full moon when its the best time for planting root crops. These have gone into tyre rings, and the stacks are already 3 high, with another one overdue to go on. That's about 10cm of growth a week!

Friday, September 25, 2009

Are Copper Sprays Really Organic?

Recently I have been doing some research on the use of copper sprays in horticulture, specifically Avocado production in this case, but this post applies to most crops.I have had some disquiet about the use of copper for some years, but as I've learnt more about it, I've come to the point where I will no longer use it in my garden.

Copper has been used for more than 100 years as a fungicide, most famously in the Bordeaux mixture developed in 1882 in France to combat grape diseases. Copper is usually applied as either Copper Oxychloride or Copper Hydroxide, but is sold under many different brand names. Copper sprays are used as protection against the fungi that cause Downy mildew, Late Blight, Early Blight, Black Spot, Brown Rot, and various bacterial diseases. As it is a protective spray, repeated applications are sometimes needed to prevent the diseases becoming established.

Copper is a heavy metal that is also an essential trace element for both plants and most animals. It is found throughout nature and most soils have natural copper levels of 10-30 ppm, with sandy soils sometimes being deficient and some soils having natural levels up to 100ppm.

It is commonly accepted that copper sprays are organic sprays, which leads people to believe that they are safe to use. In fact copper sprays are some of the most toxic and persistent pesticides used in gardens and orchards. In recognition of this, international organic standards list copper as a restricted product. In New Zealand, Bio-Gro allows a maximum copper application of 3kg/ha/year. Copper fungicides for organic horticulture have been banned completely in the Netherlands and Scandinavia, and use has been restricted to 6kg/ha/year elemental copper in other EU countries since 2006. In gardening terms that’s roughly the equivalent of one or two wet-to-runoff sprays per year.

However, in non-organic production and in home gardens there are no such restrictions and indeed many garden writers and horticultural experts continue to promote the regular use of copper, often calling it organic. In some crops such as Avocados, growers apply up to 12 sprays per year, while home gardeners are sometimes told to spray roses, potatoes or tomatoes every 2 weeks during the growing season!

Copper fungicides are actually synthetic pesticides that disrupt and kill the cells of a very wide range of organisms. In humans, copper can cause problems such as liver disease and anaemia, but fairly high exposure to copper is needed to produce these effects in humans, so only horticultural workers or gardeners that spray copper without good protection need to be worried.

Copper sprays are of much more concern for the effect on soil life, particularly beneficial soil bacteria, fungi and earthworms. Soil copper levels as little as twice natural levels can reduce earthworm populations, while soils with levels of more than about 250ppm may have no earthworms at all. Vital nitrogen fixing bacteria are also inhibited once the soil level gets above this level.

Spraying with copper also kills beneficial microorganisms on the leaves and some studies have shown that some diseases can actually increase after copper sprays, as the beneficial microbes have been killed off, allowing the disease to flourish once the copper has been washed off by rain.

A typical copper spray can raise the topsoil concentration by up to 2 ppm, so with frequent applications toxic levels can be reached fairly quickly. You might relax at this point, thinking that the amount of copper you’ve applied would no way reach toxic levels. But do you know the history of your soil? Was it once a market garden or an orchard? Many suburbs and lifestyle blocks are established on old horticultural land. You might be adding copper to a soil that already has high levels.

Where copper sulfate has been regularly used over many years, such as the vineyards of Europe, soil copper concentrations can be found up to 1500 ppm. If this were an industrial site, it would be labeled as a toxic waste dump and shut down! In soils with a shorter history of regular copper use, such as Apple, Avocado and Stone fruit orchards, levels in the top layer of soil can reach up to 400 ppm, still high enough to drastically affect soil microbes and worms.

Copper does not degrade in the soil and is not easily leached out, except in very sandy soils, as it is bound onto organic materials, clay particles and mineral surfaces. Like the gift that keeps on giving, once the copper is in the soil, you are pretty much stuck with it. As it kills one microbe, which then rots away, the copper molecule is then available for the next microbe and so on.

Think carefully before using Copper sprays. Although they might be called organic, they may be doing more harm than good.

Tuesday, September 15, 2009

Saving The Avocado Tree

I'm in a frenzy of clearing, planting and mulching. This week I got someone in to mulch the huge pile of tree branches that I'd cut down over winter. This made about 2 cubic metres of great mulch, which has gone on the new Bromeliad garden, the Avocado tree and the strawberry patch. I'm hoping that this will cut down my weeding this summer, which will pay off with more days floating in the harbour on my back, or fishing off the rocks at the beach. That's the theory anyway.

It's amazing how much vegetation can be chopped out in only a half acre section. Aside from the mulch, I've also cut nearly 3 cubic metres of wood for the fire next winter and filled all 4 compost bins, each another cubic metre. Mostly this is scrubby self sown natives, but also many noxious weeds and some prunings from overgrown fruit trees. I think this property had every noxious weed listed for the Auckland region.

The Avocado is a bit of a project. The tree was nearly dead when we arrived two years ago, with almost no crop and hardly any leaves. Everyone has been telling me that Avos don't survive at the Point, on account of the peat soil being loaded with the dreaded phytophthora root disease and the sandstone layer only about half a metre below the surface. Strictly speaking they are correct, as Avocado trees prefer a deep free draining soil with at least 1m of soil before you reach any hard pan or poor drainage.

Of course that is like a red rag to a bull, as nothing is impossible for a fanatic. Anyway, after two years of mulching, applying gypsum, clearing away the arum lilies and fertilising, I have a tree that still doesn't look great, but at least it has a crop of about 150 fruit and many more leaves than before.

Mulching is the absolute key to success with Avos. A good layer of woody mulch helps keep the weeds down, feeds the microorganisms that fight Phytophthora, evens out soil moisture and provides a nice slow release form of fertiliser. Most importantly though, the feeder roots of Avo trees are designed to creep about just below the leaf litter layer and a layer of mulch is the best way of ensuring these roots stay healthy and white, maximising their ability to take up nutrients and water.

Tuesday, September 1, 2009

1st Day Of Spring!

Yay! The first day of spring, and what a good one! A lovely mild day, plenty of sunshine, no wind and a bit of cloud in the afternoon to keep it from getting too hot. Just perfect for gardening, with the soil nice and moist from the recent rain and not quite full moon so still good for planting. Just to prove it really is spring, check out this flowering cherry tree at our next door neighbour. The two dark blobs at the top are a pair of Kaka who successfully staunched out all the local Tuis to feast on these flowers.

Managed to plant 1 Goldfinger banana and 1 super dwarf cavendish, both of which are meant to be good fruiters here. Around them went 3 Hibiscus and 20 or so Broms, including some Neoregelia Exotica Velvet and some Tillandsia species which I attached to a Manuka with liquid nails. To get everything growing well, a decent dressing of blood and bone and a sprinkling of Potash went on the soil. Then I finished weeding the Strawberry patch, fertilised that with the same mix and did the Blueberries at the same time. Picked up all the dog poos (not my favourite job!) and mowed the lawn. To finish, collected some Grapefruit for a fresh juice to welcome the kids home from school and biked down to the water with them for a look. Great day!