veggielover2012
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Joined: Wed Apr 11, 2012 6:05 pm
Location: State College, PA

The difference between fertilizers

What is the difference between say one fertilizer that has N-8 P-4 K-8 ratio
and another like the tomato plant fertilizer I bought with an N-20 P-18 K-20
ratio?

Why the difference and why would I want to use the former rather than the latter?

Rabbits2
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Joined: Sun Apr 15, 2012 1:31 am
Location: Pa.

The easy way to explain is to take a 5-10-10 fertilizer and a 10-20-20 which is basically the same except for the double amount per ponund in the 10-20-20
which is usually used on corn. The first number is nitrogen and that is I would say the one to be most careful of or you will have lots of greens with maybe no fruit. Sometimes you have to know what makes up the fetilizer and how slow it is released. Its not a simple thing and takes time to learn! Organic fertilizer is best for house planting since it is not as strong and can be applied more carefully! I like sea week or kelp fertilizers depending on what you are planting. i probably confused you more!
Love my cats and rabbits!

Tonio
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Appears you have the N vs P vs K down?


Another way to look at is :

Organic fert- less than 10 per NPK e.g. 4-5-3

10-10-10 ( or more) is normally considered synthetic( chemicals).

However, all dry ferts need to be broken down to a chemical compound before plants can intake the nutrient. Does that confuse you more?

Synthetic ferts are immediate (especially liquid form), and organic ferts need to be broken down ( some faster than others). Organic ferts are milder - "doesn't burn the plants" like synthetic ferts' can - best to dilute 1st to 1/2 or more.

Feeder roots actually intake the nutrient in a vapor form- from what I have read. Thus the media and moisture level, plants are grown in are as much importance to nutrients.



T
San Diego / Z10
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veggielover2012
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Joined: Wed Apr 11, 2012 6:05 pm
Location: State College, PA

I've got a decent understanding of the fertilizer basics.

Ok I am growing at this moment some peppers, some sugar snap peas and some garden beans in containers. The one thing I am fuzzy on though is why I would want to use a veggie/plant fertilizer which is dry with a 4,8,4 ratio over the liquid fertilizer with an 20,18,20 ratio? I know both are synthetic, but the box for both says to feed the plants every two weeks.

So basically I have two fertilizers, one which seemingly supplies the plants with a much lower ratio of nutrients and minerals, while the other is much higher? Is there a reason to use one or the other? I have both but have been using the 20,18,20.

I guess I am just not understanding the reasoning of the different ratio's of fertilizers over other ones.

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rainbowgardener
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veggielover2012 wrote:I've got a decent understanding of the fertilizer basics.

Ok I am growing at this moment some peppers, some sugar snap peas and some garden beans in containers. The one thing I am fuzzy on though is why I would want to use a veggie/plant fertilizer which is dry with a 4,8,4 ratio over the liquid fertilizer with an 20,18,20 ratio? I know both are synthetic, but the box for both says to feed the plants every two weeks.

So basically I have two fertilizers, one which seemingly supplies the plants with a much lower ratio of nutrients and minerals, while the other is much higher? Is there a reason to use one or the other? I have both but have been using the 20,18,20.

I guess I am just not understanding the reasoning of the different ratio's of fertilizers over other ones.
You are feeding them 20-18-20 every two weeks? You will grow them to death! That is very concentrated. Especially being so high on the nitrogen, you are likely to get huge, leafy plants that don't make any fruit (i.e. peppers). The peas and beans are nitrogen fixers, they take their own nitrogen from the air and don't need any added. In fact they add N to the soil, which is helpful for other plants grown there later (especially if you cut the plants off at ground level and leave the roots).

Plants don't need anything like that much NPK and by adding it, you are distorting the growth patterns, killing the other life in the soil, which plants do depend on, and tying up other nutrients. That is besides the NPK plants need trace amounts of things like magnesium, calcium, sulfur, boron , copper, iron , chloride, manganese, molybdenum and zinc. Having such huge quantities of NPK in the soil ties up the micronutrients and makes it difficult for the plants to uptake them.

Fertilizer boxes used to say feed every 6 weeks and I thought that was too much. If the box is saying every two weeks, they are just trying to sell you more product at the expense of your soil and plants.

I never use any fertilizer in my garden except compost and mulch which breaks down to feed the soil and I have a good garden, with a lot fewer problems than a lot of the people who write in here. When you are forcing your plants to grow so much and so fast, you make them very tender and vulnerable to any pest/disease that is around. More is not better!
Twitter account I manage for local Sierra Club: https://twitter.com/CherokeeGroupSC Facebook page I manage for them: https://www.facebook.com/groups/65310596576/ Come and find me and lots of great information, inspiration

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