Robert: This will probably apply to people who have a little bit more land – the best thing you can ever do is get your soil tested – I’ve still got my original report – it’s about 12-13 years old and it tells you what you’ve got plenty of and what you haven’t got enough of because there are two ways of doing things – you can grow things organically or you can grow things with chemical fertiliser – I try to strike a happy balance between the two and you can do things with chemical fertilisers that you can get results with chemical fertilisers that you can’t get with organic fertilisers. If you want a quick response to something, you’re not going to get it with an organic fertiliser but on the whole I do use organic fertilizers. Occasionally if something needs a kick start or you want to put a certain element on that the tree needs, you are going to need chemicals. My particular soil type is a red-brown clay loam: what they call volcanic soil – it’s not like the type you get at Lismore where you just keep going downwards: with mine it varies between a foot and 3 feet and you then you get a nice friable soil underneath: a little bit of soil and a little bit of clay: it’s well drained, it holds good amounts of moisture: haven’t tried avocadoes in it because as far as I am concerned, they take up too much space and I haven’t got enough.
George: How big is your block?
Robert: It’s just under 2 acres but it’s not all useable: there’s steep patches, there’s a dam and basically down the bottom it’s too cold for some of the things I want to play with. If you don’t have enough water you can’t really play with much at all! In most of the red soils around SEQ, even in northern NSW there are a few things you are going to be short of and there’s a few things that are really important. A lot of people think NPK is the main thing but I tell you that if you have one of your major trace elements missing, you can put all the NPK on you want and your tree is not going to do anything. Basically, most red soils are deficient in zinc, first things that will show symptoms will be custard apples – you get tiny little leaves on the ends. Boron normally doesn’t become apparent until the tree is fruiting and you will get bumpy fruit. With custard apples you’ll get gritty bits in there – normally that’s a boron deficiency.
Sheryl: Robert, do you do your own soil testing?
Robert: No, I had it done but I won’t give the name of the people who did it because they mucked it up. They said I had plenty of zinc and being new to the area, I didn’t know that red soil was always 99% deficient in zinc The reason I didn’t twig to it until about 18 months after I put my trees in is that with all the trees I put in, I used about 10 grams of zinc sulphate/hydrate – mix it in a bucket and use that to water the plant in and it just helps the plant to take off. With that, the trees really took off but after about a year they just stopped and it doesn’t matter what I did, I couldn’t get them started again and luckily for me my cousin came around – he works for the CSIRO – and he said you’ve got little leaf which is a zinc deficiency and I said look at my soil test and he said I don’t care what your soil test says, just mix up a bit of zinc and spray it on one of your trees and see what happens so I did that and in six weeks it flushed twice so that might be an extreme case, but trace elements are important. If you use organics wholly and solely, you’ll get some in your organics but if you’ve got a chronic shortage, it pays to address it.
George: A lot of Australia is like that – you’ve got a lot of old soils – basically they are leached out.
Robert: In most rainforest habitats it’s all cycled again anyway – once you’ve stripped it down, you’ve lost it. Anyway, I supplement my zinc, boron and sulphur: most of the red soils need that sulphur. Also, the fertiliser companies are out to sell products. When I got my report back, I thought – I’m sitting on toxic soil. I had toxic levels of manganese: well, that’s only true if the soil pH goes below 5 – I’ve got plenty of manganese and magnesium but the thing is they didn’t say and it was only after the pH goes below 5 and my soil pH is 6.2 and it’s got a high buffer pH of 5.5 – what a buffer pH means is that it’s hard to raise it or lower it – it’s pretty stable. I called Nambour and spoke to someone – I went up there for a field day and showed the chap the report and he said you’re nearly running out of time for this season – just stick your trees in and don’t worry – there’s nothing wrong with your soil and he explained everything to me and I was a happy chappie then. So, what do you do if you’re deficient in any of your trace elements? Boron – if you want to grow pawpaws, you need Boron if you want to grow a good pawpaw but lots of things need Boron – 5 gms per m2. watered in well but don’t put anymore than 5gms on because the tree will go yellow. I nearly lost a rare Mangos teen doing that. (For Citrus & Custard Apples use 1.5 g per m2.) Where pawpaws come from, the average boron level is 3 times that of what you’d find in good boron holding soils in Australia so it’s very high. I just use Borax. You can get Solu-bor – it’s about twice the strength. You have to halve your dose but it’s 4 times the price so it’s better to go to the local supermarket and get Borax. Zinc: Zinc Sulphate hyptohydrate – the good thing about that is that Zinc of Boron is something you can put on your Custard Apples every year.
Sheryl: What time of the year do you put it on?
Robert: About September (spring) before the major growth flush. Peter might like to jump in if I’m saying anything that’s not right.
Peter: Spray it on the new growth
Robert: I don’t mind putting it on around the tree – it takes a bit of hassle because when you’re putting zinc in the ground you calculate roughly the square metreage of the root zone which is just slightly bigger than your canopy area and you give them 25-30gms if you’ve got a severe zinc deficiency but zinc is held up by organics so what you have to do – the way they recommend it – is that from your dripline to a foot in from the dripline, scrape away all your mulch and organic and put it just around that strip and water it in well.
George I think zinc is also locked up by alkaline soils as well
Robert: I don’t think we have a lot of alkaline soils. I think Florida has alkaline soils but I haven’t really researched this.
Member: Can you discuss rock minerals?
Robert: I’ve had some for a while I’m going to try.
George: The problem with rock minerals is that they are very slow release unless they’re ground up super fine.
Robert: The same if you want a quick pH change. You have to get the ultra fine – you can get lime in different grades. I had a pretty good calcium level in my soil test so I thought I wouldn’t put any more calcium on my trees – optimum was 10 and I had just under 8 but you always learn and one of the best field trips I went on was to Birdwood Nursery and calcium really makes a difference. You really can’t have too much of it. So in raising your calcium level a simple rule is that if your pH is low and you want to go up, then lime does both. If you want your pH up and you want calcium plus you want a bit of magnesium, then you use dolomite. If you don’t want to change your pH but you just want calcium, then use Gypsum so that’s basically how it goes. That’s about the 3 major sources of calcium you can get easily – so Gypsum gives you Calcium, Dolomite gives you Calcium to boost your pH and it gives you Magnesium, Lime ups your pH and gives you Calcium. Calcium: use 200g per m2 every 2 years. That’s what Birdwood uses and it works well for me.
Sheryl: What time of year?
Robert: I normally give it with my Spring fertilising although I don’t fertilise everything in Spring – some of the more tropical things, you don’t want to push them because it’s too early. I give 200g m2 (average man’s hand holds 70g) and it’s the type of thing you can’t overdose – same thing with zinc – you can’t overdose but you can overdose with Boron and Copper. With Copper if you have a bit of a deficiency it does show up in some soils – they just get Copper oxychloride – just make it up to maximum strength as a fungicide and spray the tree. A good thing is that you can put a little bit of Urea with Boron. The thing about Urea is that if you get a thunderstorm you have nitrogen coming out of the sky – it’s 46% Nitrogen – the trees can’t pick the difference so with your adding if you want to add trace elements, a little bit of Urea helps the tree take it in – normally 3g/litre. Boron is acid and if you put builder’s lime in with it to the same amount so you don’t burn your tree – you have to up the pH. Use 1g of Boron plus 3g of Urea plus 1 litre of water. I don’t just use that, when I address the Boron problem I do it in the ground on my soil type, I only have to do it once every 4 years. With custard apples because they like it, they get it every Springtime before the main flush. One thing you can use Boron for is 1g Boron 3g of Zinc and a litre of water is to spray it on your Mangoes and your Lychees – just as the flower pinnacles come up but before they open – give them a spray then halfway through flowering, give them another spray. When your fruit tree sets fruit, first comes pollination, then comes fertilisation, doesn’t happen in an instant. The pollen goes on but it has to grow down the tube to get to the ovaries to fertilise it to get the fruit to set. Now what they’ve found is that sometimes with the vagaries of climate, like not enough water, too much, a bit cold, not enough sunshine etc.
Some lychees are a little bit slow and the pollen starts growing down, there’s a bit of thick tissue and it can’t get through and sometimes it might take 5 days to get down there to initiate fertilization. They say that using the Boron – 1 gm\ Boron + 3g Urea – the only reason to use Urea is to get a good uptake of Boron – I’ve had pollen grow down in 18 hours. The DPI have found that after Boron treatment, pollen growth has been as quick as 18 hours. So I tried it – I heard it from Birdwood, tried it that year – most of my Lychees set doubles so it works, but if you’re a little short on Boron, it’s not going to hurt anyway.
George: You can use it on just about everything.
Robert: If you’ve got something that’s a little bit stubborn or seedlings – a lot of seedlings when they flower they might not flower for a year before they actually set anything. Another thing it’s good for is that with some of the Persimmons that can set parthenocarpically (without fertilisation) the boron helps them to retain their fruit.
Slides: Mangoes – From a field day at the DPI Nambour I bought their book and they only recommended 2 varieties – Irwin and Florigon book 21st Oct 88 has the DPI list of varieties that grow in our area. Now the thing with Mangoes, if it rains in Springtime when they’re flowering, then the shows over. I’ve known years when we didn’t get much rain in Spring but it was cooler then average – daytime temperatures were average and the night-time temperatures were low. What affects mangoes roughly south of Bundaberg from setting that well is pollen tube damage caused by late night temperatures when they’re flowering – not just the rain – there’s 2 things – it is the rain at the wrong time but I feel that Mangoes down here can take a little bit more rain when they’re flowering than Mangoes further up north simply because it’s hotter up there and a little bit more humid around flowering time and there is more chance of getting Anthracnose and Black Spot and Powdery Mildew that some varieties get – a classic is Nam Doc Mai – it doesn’t get the other two but it gets Powdery Mildew. Nam Doc Mai almost made the ratings – they trialed them over 4 years, the first 3 years they performed very well but the fourth year they totally missed – there was one flower spike on the tree when the field day was on so that got struck off. Another thing I would fail it on is they split but I grow one because I think they are a beautiful Mango. The Irwin that was recommended has a Fruit Fly problem – I have two in – It’s a nice fruit but you can’t pick it too green – there’s not enough sugar level to play with – tastes a bit pineapply – some people like that but I like my Mangoes sweet. I don’t like a lot of the Asian types I don’t like the flavour. I’ll top work one and keep the other for old time’s sake. Florigon is a nice fruit
Sheryl: How do you tell when a Mango is ready to pick – I’ve heard that the end loses its point and rounds off.
Robert: I’ve never noticed – Nam Doc Mai is very pointy and they never lose it. People say, how do you tell when a Jackfruit is ripe – well, it depends on the variety – there’s too much variation – when you think of the amount of varieties of Mangoes and it’s only one species and it’s split up into races – your Indian race are more rounder and your Chinese race – basically your long skinny ones but it’s not a hard and fast rule. The good thing about grafted trees is they don’t get too big. Glenn is another good mango but it can’t take cool night-time temperatures – my block faces 3-NE so we don’t get frosts except down the dam. Put your mangoes up high. The warmer it is, the better they’ll set. Glenn and Nam Doc Mai are my favourite Mangoes. A friend imported a seed from Sulawasi which he grew on and fruited in Sydney and he then gave me some budwood – one was grafted onto Bowen rootstock and the other was grafted onto New Guinea Long rootstock – we don’t know whether it’s a variety of Mango. It’s has a very long leaf with wavy edges is a very upright grower. I tried them on different rootstock and they took on both but fruited earlier on the Bowen rootstock. It looks like a cashew when its very small then straightens up. I also have a Kasturi. Kuinis has less spotting in winter than the common mango (they tolerate wetter conditions). Lychees – needs a lot of water. My excess water bill for the last 6 months was just under $500.00. and that’s just to keep them alive. DPI recommended Whai Chi, Salathiel and Bosworth No. 3. Whai Chi and Salathial are low vigour varieties, which means that even if you get a good wet in late autumn or early winter they won’t go into a vegetative flush. B3 are upright growers – Salathiel are a very good variety – very tiny seed. Grumichamas – mine has one seed.