Thursday 21 September 2017

Are fertilisers a good thing?

My giant borders neither need or receive fertiliser. Were they to need extra nutrients I would have no hesitation to apply a top dressing of general fertiliser

I am tempted to say  fertilisers are ’the best thing since sliced bread’ but then I reflect that much bread today is not very nutritious. I might even say ‘junk food’. But then many gardeners think that fertiliser is junk food and sometimes it can be! Bonemeal anyone?

I have written about fertilisers many times before. I don’t like to repeat myself - although regular readers might not think so. I cannot completely avoid it when new readers have not yet heard  my ramblings. I have passed on most of what I know and worse, have used up my best ‘jokes’ and stories. Today I will limit my attempts to guide you to the more practical aspects of fertiliser use in the links below. (I don’t want to lose you by sending you into the ether too early) There are a lot of links today which I hope will serve as a reference. For example, I explain that when I talk about fertilisers I mean ‘concentrated sources of nutrient’ and not bulky manure. Bonemeal does not qualify as either.

Not only do my borders usually not receive fertiliser I do not import bulky manure  

Growmore is a far superior general fertiliser to bonemeal
The thrust of my item today is to question how much gardeners need to use fertiliser. Scientist Peter Williams has no doubt of their value and neither do I. If your plants have insufficient nutrients they will fail to achieve their genetic potential. This might include anything from size, speed of development, health and disease resistance, flower and fruit size, colour, absence of deficiencies and plenty of flavour. Neither of us have any inhibitions about using them when they will enhance the beauty of our gardens or the taste, health or yield of our crops.
That is not to say fertilisers are always necessary. Indeed in many cases there is no need to use them at all. Many garden soils are highly fertile; gardeners use manure and compost and good gardeners generally recycle soil organic matter and nutrients. Our soil can be a rich source of fertility. Why add more?

No need for fertiliser here
I have written before that my three naturalistic gardens have never had fertiliser. Neither does Cathi’s grass verge - indeed her complete garden -  nor my project in Lyndi’s field or in most of my own flower borders. Never-the-less in a year I almost get through a complete 25kg bag of yaramila fertiliser. Further on I will explain how.

No fertiliser for Cathi's new grass feature (although I am  pleased that her soil is naturally fertile)
Many gardeners seem to regard it as as a sacred duty to supply fertiliser in their planting hole (or less damaging adjacent to it). Sometimes this might be a good thing but usually there is a greater need to get the plant established and perhaps apply a top dressing of fertiliser later. Fortunately many amateur fertilisers - but by no means all - are mere toys and like bonemeal will do little harm (bonemeal will do no good either). 

Objections to fertilisers discussed
This is the real thrust of my article today

Do they damage soil structure?
In the round this is nonsense. However in the big wide world there are thousands of soils of different nature and hundreds of so called fertilisers. Many are of dubious nature and some growers excessively apply them. There are bound to be instances where there will be an adverse reaction between between chemical and soil. Ammunition for the anti fertiliser lobby!
More usually fertilisers are neutral in effects on a soil’s physical condition. A few such as lime and calcium sulphate are applied to directly improve it.
A secondary effect of using fertiliser is that increased growth means more biomass is available to the gardener and farmer. When decayed organic matter is recycled there is improvement to soil structure. I previously wrote about how use of fertiliser contributed to the greening of Yorkshire’s pit heaps and creating ‘new soil’.
I have also written how my former allotment which never received imported organics over the years, that with sparing use of inorganic fertiliser, recycling of organic matter generated on site and a no dig policy, that it became black with organic matter.

What gives credence to the myth that fertilisers are bad for the soil structure is the way some farmers abuse them to maintain high yields and neglect other aspects of good soil management. (‘Good soil management’ might be as simple as minimum cultivation).
Claims of bad soil management is often true. I hope it does not apply to you.

They pollute water courses, ground water, lakes and the sea
This is a problem when farmers use large quantities, apply near water courses and apply them when leaching conditions prevail - usually in late Winter.
The main problem is soluble nitrate which arises from ammonium and other soluble nitrogen-containing fertilisers.The problem is more or less restricted to misuse of these ‘nitrates’ and from agriculture the problem is significant. 
Phosphates pollute water too and significantly so. Fortunately virtually all phosphate applied by growers is strongly absorbed by the soil and other than being hugely significant in contributing to the health and nutritional value in crops never leaves the ground. Phosphate pollution by farmers and gardeners only occurs when the nutrient directly bypasses the soil. Hang your head in shame if your compost heap made on hard standing leaches out direct to a drain! (In limited but sometimes significant cases phosphate can directly enter the water by wind blown soil erosion)
The main source of phosphate pollution is when phosphate rich detergents from your washing machine empties to your drain.

Organic gardeners should not be complacent about water pollution. Their organic manures release copious nitrate too

The amounts of fertilisers used by gardeners are minute compared to those used by farmers. I would suggest that gardeners less commonly apply them to not-yet-sown soil than do farmers and rarely as early as February - a time when leaching is most likely. Gardeners certainly don’t use great machines that fling fertilisers a long way. (My own garden gets a boost when the farmer fertilises his field).
Leaching under most growing conditions barely exists in Spring and Summer. Heavy rain washes nitrogen just a little deeper and hungry roots find it.
In my view a responsible gardener should have no reservations about his fertilser causing pollution.

Fertilisers are very energy intensive and add greenhouse gases to the atmosphere
There is no doubt that agriculture is energy intensive and uses a lot of fertiliser and diesel. In addition to carbon dioxide production, the greenhouse gases such a nitrogen oxides  - and methane from cattle - are also an issue.

My hard yaramila prill stores very well and a 25kg bag satisfies most of my annual fertiliser needs. (Lots of little bags of 'specialist' fertilisers is wasteful folly)
I wondered about the energy used in my own annual usage of 25kg of yaramila. In a very much ‘back of the envelope’ estimation I calculate that the manufacture and distribution of my 25kg bag produces the same amount of carbon dioxide as when 15 litres of petrol burns in my car. Interestingly the monetary cost of each is almost exactly the same.

Fertiliser might scorch my crops and cause ‘soft’ disease-susceptible growth
Unskilled and heavy use of fertiliser can damage plants.This is perhaps why weak toy fertilisers are often sold and recommended to amateurs. Not that misdirected chicken droppings will do no harm or that inferior lawn fertiliser spreaders cannot lead to disaster.
Some gardeners excessively use single nutrient fertilisers which are not balanced. High nitrogen alone especially if delivered in poorly illuminated greenhouse conditions does create soft and disease prone plants,
Nurserymen tend to use high levels of nutrients to achieve more speedy production of their plants. My all time least popular post is about ‘soft growth’ (there seems to be a negative correlation between my effort and a post’s popularity). I still wonder why when I buy a new dicentra at the garden centre it almost inevitably dies….
Sensible use of fertiliser grows better plants. This does not always happen.

Excessive phosphate application
Superphosphate was the first major manufactured fertiliser nearly two centuries ago. It increased yield and transformed farming. Phosphate is an essential nutrient. 
It is not a bad thing that it accumulates in the soil but there are circumstances where there can be too much. Most gardeners and farmers needlessly apply more to their soils. Unfortunately most general fertilisers include more phosphate than is needed. It’s not usually a problem, more a waste of resources.
Gardeners sometime find excess phosphate a problem when they attempt to naturalise wild flowers in grass. It is not that wild flowers do not like it, it’s just that nettles and coarse grasses like it better.

Effects on soil micro - organisms
In the rich cycle of organic life in garden soil numbers and composition of bacterial populations vary by orders of magnitude within just a few days of changing conditions such as warm, wet or dry. As long as we manage our soil well such changes do not matter a jot to our gardening. Fertilisers might do all of stimulate bacterial action, have no effect what-so-ever or inconsequential inhibition.

Inhibition of mycorrhizal fungi is a more serious concern. Fertilisers seem to break the faustian mutualistic contract between soil fungus and plant. If the plants’ need for nutrients is easily satisfied by a fertile soil - however this is achieved - then there is no need for the plant to donate to the fungus its carbohydrate resources and ergo less mycorrhiza.
In the wild mycorrhizal associations abound. For some plants they are essential for survival. Fear not, there are more mycorrhizal associations in your garden than you think - even when you use fertilisers.

So how do I get through 25kg of YaraMila in a year?

Buy this analysis for general use. Your local supplier might sell suitable similar products. Not usually sold at garden centres.
Other than iron sulphate on my lawn, yaramila is the only  fertiliser I use.

My pot grown tomatoes need generous applications
1. In my vegetable garden I might lightly scatter perhaps 30gm per square metre over any area I plant or sow. This may be before or after plant establishment and if I remember. Overwintered brassicas might get a little extra in Spring

2. On my sandy soil I find that top dressing my soft fruits such as blackcurrants, blackberries and especially raspberries works very well. My asparagus too. In recent years I have found that very early application in late February is best!

I top dress my contorted robinia three times a year
3. We have a large number of plants in display containers growing in soil. Nutrients do leach from containers and plants have a much smaller root zone than in the ground. Some of our tubs itinerate between indoors and outside. These might receive a top dressing as often as four times a year - as well as having been ‘made up’ with fertiliser content. This nutrient need would be greater if my plants were growing in regular potting compost.

Although I apply yaramila to my tubs of agapanthus I never need to fertilise those in the ground
4. I make up my own seed and potting composts from my own sandy soil. Most garden soils are unsuitable for this practice - but I think many gardeners do miss an opportunity. I sometimes add small amounts of yaramila. More sensible folk might use a slow release fertiliser.

5. I don’t liquid feed. I do not disprove of liquid fertilisers it is just that I am lazy (and mean) and top dress with fertiliser instead. All our pot plants have a scattering at some time or other. Even the orchid collection with a dozen granules or so per pot. They love it

6. A typical gardener might annually apply lawn fertiliser at say 20gm per square metre to their lawn. I have perhaps 600 square metres of lawn and grass paths embracing my borders.
I prefer to not box off my mowings and consequently return nutrients when I 'mulch mow'. Perhaps every other year an area of grass will receive a little fertiliser. Perhaps about 20gm yaramila per square metre. If a little goes on my borders when I fling it so much the better.
To apply this rate to the whole of my lawn would take 12kg of yaramila - half a bag!
In different circumstances Peter Williams applies 20gm/sq m of yaramila three times a year to his lawn - including midwinter!

This amount of homemade charcoal will be 'charged' with about 1kg of yaramila over the next year before I use it
7. Readers will know my penchant for making my own biochar when I douse the embers of all my garden fires with water. This wonderful medium initially is powerfully absorptive of nutrients and needs charging. If I have fertiliser handy when I pass my maturing pile it gets some.....

To buy yaramila you will need to find your local horticultural trade supplier or more easily order on the net

These links provide more detail

Why you do not need to buy lots of little bags of specialist fertiliser. 
My thing against bonemeal
All year round use of fertiliser
Why general fertiliser is suitable for your lawn
My penchant for using charcoal
Restoration of a slag heap 
Buying professional fertiliser
Crushed rock myth
Do fertilisers degrade soil? - whoops I have been repeating myself
My homemade soil potting compost
My post about hard and soft growth was a damp squib

This vigorous plant finds its own nutrient
So do these delicate ones
 Delphiniums need a little help on my very sandy soil
The annuals are rather lush on my former vegetable garden


  1. Love the annuals. Did you broadcast them? What are your views on foliar feeds?

    1. Thought I might draw you in Sue with the comment about my former veg garden but not quite. Yes they were broadcast
      Foliar feeds can be of value in certain 'trouble shooting' situations where a quick fix is needed. But in general I think they are an expensive and inferior substitute for good growing. Certain commercial ones are a con.

  2. I am halfway through my first bag of Yaramila and have used iron sulphate on the lawn for the first time this year, so that's at least one reader taking notice of your ramblings!

  3. I received this interesting comment that somehow got lost in the ether!

    BrendaR has left a new comment on your post "Are fertilisers a good thing?":

    Thank you very much for opening your garden to the public. I came with my husband and we both enjoyed seeing your vigorous and beautiful flowers and eating the delicious cakes. Also many thanks for giving your time to answering my questions.

    As I have a very stony flowerbed, where the plants don’t thrive as well as they do on the other borders I followed you advice and went to Newton upon Derwent to obtain some YaraMila. I was persuaded to buy Compo NovaTec Classic instead. I was advised to wait until the spring to use it.

    We have an apple tree that is about fifty years old. I have created a shrubbery underneath, with bulbs in spring. I never put any fertiliser on this bed, just returning the windfalls to it, feeding the tree with its offspring. I’m probably not doing the right thing and am wondering if a fertiliser would be better appreciated by the tree.

    1. Firms often change their top fertiliser manufacturer!
      The product you quote looks pretty good with a very sensible NPK analysis + magnesium + sulphur + three trace elements. I like its retarded release rate of nitrogen
      I have no idea if your apple needs any fertiliser but if you do feel it needs a boost apply your fertiliser in February rather than now.
      If you clicks the relevant links above I write about year round use of fertiliser and the value of products like yours for lawns.
      Interestingly your new product trails suitable rates of application between 30 gm and 90gm per square metre. (1 to 3 oz a sq yard in old money!)
      They say suitable for coarse grass- I think they are doing themselves an injustice! I would be happy to use it on my fine grass at about 25gm per square metre.


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