Keeping up Your Fertility Organically - Adding Nutrients

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Just like animals (including us) plants need the right sort of nutrients in the right amounts to be happy healthy and productive and when we remove crops from the soil and consume them, the nutrients must be replaced. Originally this was done with naturally occurring materials such as manures, ash and compost but with the invention of inorganic fertilisers (originally called artificial manure) we went away from naturally occurring materials and, as usual, stuffed things up. The inorganic nutrients don’t take into account the importance of soil micro-life and as the yields reduce more fertiliser is needed to keep pace. They also tend to be very soluble being easily leached into our waterways and ground water causing pollution and some are oil based and come with all the problems that entails.

However, the wheel is turning and organic farming and gardening is making a very strong comeback and you can be part of that comeback in your own backyard veggie patch.

The theory at the start may be a bit heavy but it will give you a good basis on which to make decisions on how to use the materials available to you to keep your little patch of heaven producing the food you love.

A little Bit of Chemistry

While it does not tell the whole story, a measure of the usefulness and effects that a fertiliser will have, for both chemical and organic fertiliser is the NPK ratio. The NPK ratio gives an indication of how much of the three major nutrients a given fertility increasing material contains, but perhaps I am getting ahead of myself because we need to talk a little bit about the chemical elements that a plant needs and these are generally divided up into three major nutrients, three secondary nutrients and six minor or trace nutrients.  What follows is a summary of what each nutrient does, what the effects are when the plant is suffering from a deficiency of that particular nutrient what you can add to the soil to bring the nutrient level back to scratch.

The Major Nutrients

The major nutrients are nitrogen (chemical symbol “N”); phosphorous (chemical Symbol P) and potassium (chemical symbol K) hence the three together are referred to as NPK.

Nitrogen (N) – is important for leaf growth – deficiency results in pale or yellowing leaves - The best way of correcting a nitrogen deficiency in an existing crop is to add a well rotted high nitrogen manure such as chook or pigeon or to dilute human urine 1:10 with water and apply with a watering can.

Phosphorous (P) – is important for healthy plant growth, the formation of flowers and setting of fruit and seeds – deficiency results in poor root growth and stunted and sometimes purplish leaves – To correct this deficiency add bone meal if you can get it or blood and bone or apply human urine as above.

Potassium(K) - is important for strong support cells in plants and to ensure plants are healthy and resistant to disease – deficiency causes weak stems with limp yellowish leaves that may have scorched looking edges. Fruit set will also be reduced on fruiting plants – to correct potassium deficiency wood ash is the best additive or seaweed as mulch or made into a tea as set out under Trace Nutrients.

The Secondary Nutrients

These are the “tweens”, being required in relatively larger quantities than the trace nutrients  but not so much as the major nutrients.

Calcium (Ca) –is important for strong cell walls and growing tissue like root tips – deficiency results in new growth being stunted and distorted and growing tips curling/dying, can cause blossom end rot in tomatoes – Correcting calcium deficiency is usually done with agricultural lime although dolomite or gypsum (both made of ground rock) will not affect pH but still add calcium. Ground eggshells or sea shells can be used if you can get enough and blood and bone will also contribute calcium as will most manures.

Magnesium (Mg) – is important in photosynthesis for the plant – deficiency causes leaves to get yellow stripes, the older leaves being affected first – to correct a magnesium deficiency the classic thing is to dissolve 1 tablespoon of Epsom salts (magnesium sulphate) in 4 litres of water and apply with a watering can but  dolomite ( a mixture of calcium and magnesium carbonates) will also work.

Sulphur (S) – sulphur is a component of plant proteins and is associated with the formation of chlorophyll – Deficiency results in the older leaves going pale, followed by the whole plant. To correct a sulphur deficiency adding composted brassica leaves (cabbage, cauliflower, broccoli etc) or garlic to the soil will help. The classic fix was to apply a dusting of elemental sulphur or Epsom salts.

The Minor or Trace Nutrients – also referred to as “trace elements”.

While these nutrients are required in very small quantities, some can be toxic to plants when present in excess, they also make their presence felt when they are lacking, sometimes presenting strange symptoms as a clue to the deficiency disease you may be dealing with.

Boron(B) – is important for growing tissue in young plants – deficiency results in stunting of growth with yellowing stripes on the leaves and pale green tips of leaves, it can also result in breakdown of internal tissues in vegetables such as celery stems and broccoli flower buds.

Copper(Cu) – Is an enzyme activator and important in photosynthesis – deficiency results in “burning” of the leaf margins and yellowing with resetting or multiple bud formation in flowering plants. It may cause dieback in citrus and some other fruit trees.

Iron(Fe) – is also important for formation of chlorophyll in plants and is an enzyme co-factor – deficiency results in yellowing between the veins of young leaves but no initial stunting of growth, later older leaves become affected and growth becomes stunted.

Manganese(Mn) – is similar to iron – deficiency results in yellowing similar to iron leading to a striped or spotted appearance of the leaves.

Molybdenum(Mo) – is important to allow the plant to convert nitrogen into plant proteins – deficiency shows similar symptoms to nitrogen deficiency leaves turning pale green then stunting of the whole plant and leaves bleaching and withering.

Zinc(Zn) – is an enzyme activator similar to copper – deficiency results in growth stunting and the formation of “little leaf”.

The easiest way to provide trace elements for the veggie patch is to add wood ash, compost, well rotted sawdust, horse manure or seaweed tea made by washing the salt of seaweed in fresh water then steeping in fresh water for three to four weeks and dilute to the colour of weak tea and add with watering can or spray onto affected plants.

What about pH?

The soil acidity or alkalinity, generally referred to as soil pH and covered in detail in other articles, also has an impact on the nutrition of you backyard veggies because if the pH is wrong, some nutrients may be bound up and unavailable to your plant while others may be available to the point of toxicity. The graph below has been around forever and is reproduced by everyone and it gives an excellent representation of the availability of nutrients as the pH varies. The wider the line the more available the nutrient, of course the message to take away from all this is if you pH is between 6.5 and 7 you have nothing to worry about, but as you move away from this ideal range the availability reduces in most nutrients to a greater or lesser degree.

pH Versus Availability of Soil Nutrients (after Truog)

NPK of Materials available in or close to urban/suburban areas

So now you hopefully understand a bit more about what nutrients plants need to be healthy and productive, here is a list of commonly available organic materials that can be added to the soil to increase fertility and what the NPK levels are for each.
These figures are rough and will vary from batch to batch

Material

N

P

K

Beans, Garden (seed & hull)

0.25

0.08

0.3

Blood & Bone

3.6

8

10-20

Cattle manure (fresh)

0.29

0.25

0.1

Chicken Manure (fresh)

1.6

1.0-1.5

0.6-1.0

Clover

2.0

0

0

Coffee Grounds

2.0

0.36

0.67

Corn cobs

0

0

2.0

Cornstalks

0.75

0

0.8

Compost

0.5

0.27

0.81

Couch Grass (green)

0.66

0.19

0.71

Cucumber skins (ash)

0

11.28

27.2

Eggs

2.25

0.4

0.15

Eggshells

1.19

0.38

0.14

Feathers

15.3

0

0

Grapefruit Skins (ash)

0

3.6

30.6

Grass clippings

1-2

0-0.5

1-2

Hair

14-15

0

0

Horse Manure (fresh)

0.44

0.35

0.3

Human Urine

15-19

3-5.4

1-2.5

Lemon Skins (ash)

0

6.33

1.0

Lucerne hay

2.45

0.05

2.1

Milk

0.5

0.3

0.18

Mud (fresh water)

1.37

0.26

0.22

Oat straw

0

0

1.5

Orange Skins

0

3.0

27.0

Peanut shells

3.6

0.15

0.5

Pea Pods (ash)

0

3.0

9.0

Pea (vines)

0.25

0

0.7

Pigeon manure (fresh)

4.19

2.24

1.41

Pine Needles

0.5

0.12

0.03

Potato Skins (ash)

0

5.18

27.5

Potato haulms (dried)

0.6

0.16

1.6

Rabbit manure

2.4

1.4

0.6

Seaweed (dried)

1.1-1.5

0.75

4.9

Sheep & Goat Manure (fresh)

0.55

0.6

0.3

Sorghum Straw

0

0

1.0

String Beans (strings & stems, ash)

0

4.99

18

Tea leaves (used)

4.15

0.62

0.4

Tomato leaves & stems

0.35

0.1

0.4

Wheat bran

2.4

2.9

1.6

Wheat Straw

0.5

0.15

0.8

White clover (green)

0.5

0.2

0.3

Wood ash

0

1.0-2.0

6.0-10.0

Worm castings

1.0

1.0

1.0


Home Produced Soil Additives

Compost – is a good all purpose fertility improver and by composting leftover food waste some of the nutrients removed in harvesting can be returned to the soil. More details on composting and making a bokashi bucket are covered in articles elsewhere on this site.

Wood ash – if you have a wood burning stove or have friends with one, rather than throwing out the ash, add a light dusting next time you are preparing a veggie bed for planting. It is alkaline and so may raise the pH of your soil but a small amount added to healthy organic soil is unlikely to have a huge effect. Wood ash is great for adding potassium to your soil.

Seaweed/kelp – seaweed is a great addition to the veggie patch if you can get hold of it, gather it and bring home a bag full next time you take the kids to the beach. As well as contributing major nutrients it is a good source of the trace nutrients as well, but make sure you wash the salt off before you use it. You can dry it out, crumble it up and add it to the bed before planting, add it to an existing bed as a mulch or steep it in a bucket of water for three to four weeks and apply with a watering can as a general tonic. 

Worm castings – In an urban/suburban area you are most likely going to be producing this in smaller amounts, but it is very rich in beneficial soil bacteria as well as chemical nutrients. You can use it to make seed raising mixture, spread it around growing plants under the mulch or add it into the hole before planting your veggies to give the plant a boost when the roots find it.

Poultry manure – Even in the city most people can find room for a few chooks and while their manure is a bit rich to add fresh to growing plants it will give the soil a boost if added when preparing the bed or composted first. Rather than haul the stuff around, we use a chook tractor which means that the chooks apply it direct to the bed, and then when the bed is watered and mulched before planting, it attracts worms into the bed. If you have to buy it in, check that it has not been sprayed with insecticide to keep the flies down.

Urine- There is talk about “peak phosphorus” because we currently get our phosphate fertiliser supplies from deposits of ancient guano which are then mined, and is starting to run out. The answer is to recycle nutrients by diluting our pee ten to one with water and applying to the veggie bed. Contrary to popular belief urine is not sterile so if you are not well, particularly due to bladder infection, don’t use it. I wouldn’t broadcast about this fertilising practice too much either, the neighbours might not understand your good intentions.

Liquid manure – In general terms liquid manure is made by steeping a nutrient rich material in water for a time to extract the nutrients and then diluting the resultant “tea” until it looks like weak tea and then applying directly to the plants. The nutrient rich material can be seaweed as mentioned above, manure or better yet a mix of manures, comfrey or nettle leaves or even just a mixture of weeds steeped in water.

Bought In Soil additives

Blood and bone – This is a great way to add phosphorous and potassium to your veggie patch although if you are vegetarian or vegan you may have some ethical problems using it. You should keep it in a sealed container away from pets; years ago my father’s dog broke into his garden shed and ate his entire blood and bone supply. It didn’t hurt the dog but sure crapped off my father.

Rock dust – Rock dust adds trace nutrients to the soil in an insoluble form that is only accessible slowly as the dusts is broken down by the enzymes released by soil microorganisms. Rock dust also is good for and attracts worms to your soil. You might not see it in your local nursery or hardware store but it is available from supplies on the net such as remin.com.au who are on the south coast of NSW.

Horse/Cow manures – If you don’t know what the worming history of the horse is it is better to compost horse manure before applying it to the veggie bed but well rotted or composted horse or cow manure is a great way to add organic matter to your soil.

Dolomite & gypsum – These materials are ground rock containing calcium and, in the case of dolomite, magnesium as well. If you struggle with clay soils as we do around here adding a calcium containing material will improve soil structure. The clay is sodium clay and has very fine pores, adding the calcium material allowing it to react with the clay replaces the sodium with calcium and calcium clays have a much more open structure, so the soil becomes much more free draining. Gypsum is often sold as “clay breaker”.

Maintaining soil fertility is basic to producing our own veggies, and keeping our plants happy and healthy so that they have the same effect on us when we eat them. By returning nutrients to the soil using organic production principles you will make sure that your veggie production is maintained in a sustainable manner.

 


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