Manuring our allotments

Manuring Our Allotments

This is a complex subject and doubtless large portions of degrees on agriculture and horticulture are set around this subject.  If you can get hold of a copy of a book, now out of print – Know and Grow Vegetables –P.J.Salter;J.K.A. Bleasdale; and others – from The National Vegetable Research Station, it is a unique, interesting and  comprehensive study of many aspects of vegetable growing.

However, most plot holders just want to know which of the manures available will give the best results on their plots.

It must be remembered that adding any organic manure will contribute to the acidity of the soil due to the breakdown process of the compost. But, for most plotholders on our heavy clay ground, adding organic matter, no matter how poor in essential nutrients, helps to break down the heavy structure of the soil and allows for freer drainage and greater nutrient uptake – of course, it is more complicated than that.

As a simplification of the needs of plants – Nitrogen[N] is used for leaf growth, Phosphorus[P] is for seed germination and root growth and Potassium [K]  for flowers and fruit.

Not all of our members are dedicated organic growers and their choices must be respected though, continued addition of non-organic fertilisers brings its own problems and there is an argument to suggest it is not sustainable.

I have gained the following information from:

 http://www.allotment.org.uk/grow-your-own/fertiliser/npk-values-of-manures

NPK Values of Animal Manures
	N Nitrogen %	P Phosphorus %	K Potassium (Potash) %
Cow Manure	0.6	0.4	0.5
Horse Manure	0.7	0.3	0.6
Pig Manure	0.8	0.7	0.5
Chicken Manure	1.1	0.8	0.5
Sheep Manure	0.7	0.3	0.9
Rabbit Manure	2.4	1.4	0.6
Growers usually have a preference for either cow of horse manure but, for the most part it does depend on what is available and how much straw [or even hay] is mixed in. Of course, the addition of the straw is very useful for improving the quality of your soil, particularly in heavy clay. Resist the temptation to add fresh manure to your ground – it too strong. At least pile it up, cover it with a plastic sheet, a tarpaulin or an old carpet and leave it for a couple of months – longer is preferable. With all poultry manure it is generally too strong to use directly on the garden but it does make an excellent activator for a compost heap. There is little bulk in poultry manure so using it as an activator makes most sense. The only plant that you can apply it to directly is comfrey. NPK Value of Home Made Compost
	N Nitrogen %	P Phosphorus %	K Potassium (Potash) %
Average Home Made Compost	0.5	0.27	0.81

NPK of Natural Fertilisers

                                                                  N Nitrogen %               P Phosporus %                K Potassium %

Bloodmeal                                                     12                                        0                                       0

Bonemeal                                                        3.5                                      18                                    0

Hoof & Horn                                                  12                                      0                                        0

Fish, Blood & Bone                                            6                                          6                                       6       

ChickenManurePellets                                    4                                          2.5                                   2.3

NPK - Liquid Comfrey – although low, it is immediately available to plants

Having covered manures and compost, the next thing to look at is a fertiliser you make yourself, comfrey tea. Following the recipe of 6 Kg (14lbs) of wilted comfrey in 90 litres (20 gallons) of water in a barrel, produces a liquid feed with these values

                                                N Nitrogen %                                    P Phosporus %                      K Potassium %

Comfrey                                    0.014                                               0.0059                                    0.03440

http://www.allotment.org.uk

That said, none of these tables shows the availability of or the importance of the trace elements. And, how do we ensure our plants have enough of these to assure excellent growth and crops.

 I will put up more information on adding lime and trace elements on my next blog.

The importance of using lime

The Importance of Lime   

The importance of adding lime to our plots cannot be over emphasised. Apart from its ability to break up heavy clay soil – a serious consideration on my ground, its influence on the pH (acidity/alkalinity) of our soil is crucial. It must be said, heavy clay soils are more likely to be acid rather than alkaline. I’ve talked about the addition of lime with many of my allotment neighbours over the last year – it seems very few people now apply this essential ingredient. We keep adding cow manure, horse manure, green manure, etc., but fail to take into account the affect these have on the pH of our ground. We look at our crops – some doing well, some doing okay and some failing, although we keep adding manure – what can we be doing wrong? Do have a look at the tables below:-

The most important nutrients for our plants are :- N – Nitrogen – for leaf growth P – Phosphorus (phosphates) – for root growth K – Potassium ( potash) – for fruit and flowers The essential trace elements are probably already present in our soil and are:- S – Sulphur Ca – Calcium Mg – Magnesium Fe - Iron Mn - Manganese B - Boron Cu & Zn – Copper and Zinc Mo – Molybdenum

Check out – www.hydroponics.co.nz/images/large/pH_chart.gif

I hope the chart above makes sense – the thickness of the shaded lines indicates the optimum uptake of each the essential plant nutrients. For my soil it should be around 6.3 – 6.5. Where the pH is below 5 the plants’ uptake of nutrients tails off significantly and the ground can become toxic. Although the nutrients may be present the plants are unable to use them. The word ‘toxic’ seemed to me to be a somewhat dramatic statement. When I asked why ‘toxic’? I was told that in very acidic conditions, minerals such as aluminium can increase in the soil to toxic levels. Even acid loving plants like heathers are not so happy when it is very acid. I do know that pH of 7 is neutral. Someone was very quick to point out to me that 7 is neutral and not 6.3 - 6.5. However, neutral is not necessarily the best pH for your plants

A pH meter is inexpensive and easy to use. ( if you want to be really sure, it's probably worth investing in a proper kit). It will tell you almost instantly where lime should be added but, don’t add it to the ground before planting, for example - potatoes ( check out the soil conditions needed for individual vegetables), and don’t apply at the same time as manure. It is not a good idea to apply a lot of lime in one dressing. If the pH of your ground is very low, ( in some patches on my plot it has been as low as 3! ! - really!),  it is best to apply a light dressing over several years to bring the pH up to a reasonable level. It must be said that a high alkaline soil will have a similar effect as acidic, although it is likely to take some time to build it up to toxic levels.