Allotment Gardening Advice Help Chat
Growing => Grow Your Own => Topic started by: Hobnails on March 09, 2010, 10:54
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Can somebody please advise if an NPK 15;15:15 fertiliser is a suitable
substitute for Growmore if used at half the recommended Growmore quantities
TIA
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Yes.
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Growmore is 7-7-7 so it should be ok
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Many thanks for your advices.
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In principle 15:15:15 will only need half as much applied as 7:7:7 - but is otherwise the same balance/ratio of the main components. (Might be different trace elements - but I very much doubt that matters a jot)
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Can somebody please advise if an NPK 15;15:15 fertiliser is a suitable
substitute for Growmore if used at half the recommended Growmore quantities
TIA
yeah in principle it's the same,but like mentioned earlier you will only need half the amount.an easy way is to mix what your applying with an equal amount of sharp sand then scatter as normal.
saves you having to worry about too little or too much.just put it on as you would Growmore.bob
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Thanks again!
I'll keep the volumes the same by mixing half teh amount with sharp sand as you suggest.
There are no recommendations or instructions on the back of the sack.
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It is quite difficult to find recommendations for rates of fertilizer for different vegatable crops. Even in the advice area of this site advice is inconsistent and for some crops just not there in detail.
What we need is a table with grams per square metre of NPK required by each crop with notes on when to apply. - How about it John?
If you decide that you need 100g per square metre of fertilizer, weigh out 100g and spread it on a metre. That will tell you what 100g on a metre looks like and you can spread your fertilizer on the plot to look the same. Exact amounts are not critical.
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Get "Know and Grow Vegetables" from the library (out of print). I might try and type the table later but it is a bit tricky how it will come out.
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If you're typing direct from the book, you risk infringing copyright Ivah - please don't put the website at that risk.
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4 handfulls to the metre has always done me ok lol.not something that needs to be exact though,just dont over do it.
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"Know and Grow Vegetables" assumes the quantities of NPK in fertilizers are roughly equal and if you get the N correct the others will follow, you can usefully use a little extra P for root crops. Strangely the table doesn't give an application rate for Growmore 7-7-7 but you can use double the 15.
I'll try and reproduce the table - book long out of print Yorkie, published 1979.
Can't persuade a table to come out right so here is my calculation of ozs per square yard for Growmore 7-7-7, to convert to grams per square metre multiply by 34
Peas 0
Carrots, Radishes 1
Broad Beans, Parsnips, Swedes 3
Lettuce, Onions, Calabrese,
French Beans, Turnips 4
Leeks, Early Potatoes 6
Main Potatoes, Beet, Spinach,
Cauliflowers 8
Brussels Sprouts, Cabbage 10
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What we need is a table with grams per square metre of NPK required by each crop with notes on when to apply. - How about it John?
BUt then how do you know what the base EC of the substrate is in the first place? Without that information, and it will be different for every plot, such a table woudl at best be an approximation, and at worst miles out. Thats why growers spend large amounts of money on lab tests to find out nutrient levels in growing medium.
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Analysis is never going to be viable on the allotment or in the garden. Salmo asked "It is quite difficult to find recommendations for rates of fertilizer for different vegetable crops. Even in the advice area of this site advice is inconsistent and for some crops just not there in detail. What we need is a table with grams per square metre of NPK required by each crop" - this is what this table seeks to supply. I assume my good condition fertile ground with lots of organic matter needs a little less than this but that is for each grower to judge, at least it gives a starting point. If you want the full context I took it from :
"The amount of each nutrient required can be predicted accurately only if the amount in the soil has been measured by chemical analysis. As the gardener is unlikely to be able to get his soil analysed readily, a method of forecasting fertilizer needs without soil analysis can be used. Although it can only be approximate as it depends on a number of assumptions (in particular, that most plant waste is returned to the soil as compost) it is nevertheless a good guide".
For those who don't know, this book was written at The National Vegetable Research Station.
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Sounds like a useful book.
No need for it to be complicated. If you have the basic recommendations there are a few assumptions that can be made to allow you to fine tune what you apply.
e.g
- if you have put on lots of organic matter then you may need less nitrogen.
- as a rule heavy soils are low in phosphate and have plenty of potash.
- as a rule light soils are high in phosphate and low in potash and magnesium
- some crops respond to higher phospate or potash. e.g. tomatoes like high potash.
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Analysis is never going to be viable on the allotment or in the garden. Salmo asked "It is quite difficult to find recommendations for rates of fertilizer for different vegetable crops. Even in the advice area of this site advice is inconsistent and for some crops just not there in detail. What we need is a table with grams per square metre of NPK required by each crop" - this is what this table seeks to supply. I assume my good condition fertile ground with lots of organic matter needs a little less than this but that is for each grower to judge, at least it gives a starting point. If you want the full context I took it from :
"The amount of each nutrient required can be predicted accurately only if the amount in the soil has been measured by chemical analysis. As the gardener is unlikely to be able to get his soil analysed readily, a method of forecasting fertilizer needs without soil analysis can be used. Although it can only be approximate as it depends on a number of assumptions (in particular, that most plant waste is returned to the soil as compost) it is nevertheless a good guide".
For those who don't know, this book was written at The National Vegetable Research Station.
hmm i remain unconvinced. To use an analogy, you will never predict the ETA of an air plane if you dont know the wind speed. Best bet is to go by the instructions on the bag.
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Best bet is to go by the instructions on the bag.
Ex b***y actly!
This is far too complicated for a normal veg growing allotment er. No-one will ever get it perfick, just get it as close as you can.
Leave this perfect ratio/conundrum to the supermarkets IMO
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I found the table very helpful -- in the sense that it tells me a ratio of hungry-ness between the plants - what to feed more heavily, and what to feed less so.
I know not to waste money putting Nitrogen on Peas and Beans, but I wouldn't have fed Broad Beans and French Beans at all ... nor Parsnips. And I would have fed Calabrese the same as Brussels Sprouts & Cabbage (all Brassicas ...)
My take from this is that I need to put some more thought into what I feed, and how much, rather than chucking a few handfuls around the plants as they grow (especially as I have recently read on this forum that P & K doesn't work its way into the soil very far without some cultivation - hence working it in a week or so before planting out.
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i wont be using any supplimentary fertilisers this year.be interesting to see how things compare to last year.
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Without accurate soil testing you can't state exactly how much fertiliser is required to start with. Different crops have different requirements as stated above.
The thing to remember is that home growing is not rocket science. Near enough is good enough.
More important is to have a good soil structure - plenty of compost and manure (if you have a safe source of manure) This also ensures the trace elements are available. We need carbohydrates and protein plus vitamins. Plants need NPK plus trace elements.
And don't forget the pH of the soil is important. Low pH retards the absorption of nutrients. For the average gardener lime regularly and rotate crops around the plot to make use of nutrients not used by the previous.
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I was thinking of using an excel spreadsheet for this, then realized some comments I had made in an earlier post. ::)
I am glad that all my science's I was taught are used between 9-5 and are left at work and never taken down 't' plot.
Ahh well, back to the simple ways for me.
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Well this has certainly opened a discussion thread and given me much to work on/Thanks guys - for all your input.
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I agree, near enough is good enough.
There are too many variables.
Soil type.
Organic matter content.
Subsoil type.
Depth of cultivation.
Accuracy of application.
Depth to which it is incorporated.
Crop (each variety of e.g. parsnip is different so has a different requirement)
Planting density
Rainfall
Temperature.
Residue from previous crops.
Timing of application.
Weeding regime.
The list goes on.
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Slightly off topic but still relevant to this thread, there has been some direct quotation from a book in sufficient quantity that this site would be put at risk of copyright infringement. One or two sentences is allowed by most writers and publishers, but anything more is direct copyright infringement. The author owns full rights to the whole of the text regardless of what format is used to convey it elsewhere. Period. Most authors renew their rights regularly so they still own it regardless of how old the book is. Rights can also be passed to heirs so nothing is ever too old to be considered 'free use'. We ask that members find other means to convey the thoughts of the book by perhaps paraphrasing, or a direct link to the book if it is online or available to purchase. Books are the author's living, so please respect their rights.
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Topic locked by Aunty - enough said I think :)