How to Adjust the Carbon to Nitrogen Ratio in Composting Raw Materials

In previous articles, we have mentioned the importance of “carbon to nitrogen ratio” in compost production many times, but there are still many readers who are still full of doubts about the concept of “carbon to nitrogen ratio” and how to operate it. Now we will come. Discuss this issue with you.

 

First, the “carbon to nitrogen ratio” is the ratio of carbon to nitrogen. There are a variety of elements in compost material, and carbon and nitrogen are two of the most important:

Carbon is a substance that can provide energy for microorganisms, generally, carbohydrates, such as brown sugar, molasses, starch (corn flour), etc., are all “carbon sources”, and straw, wheat straw, and other straws can also be understood as “carbon sources”.

Nitrogen can increase nitrogen for the growth of microorganisms. What is rich in nitrogen? Urea, amino acids, chicken manure (food is high-protein feed), etc. Generally speaking, the materials we ferment are mainly nitrogen sources, and then we appropriately add “carbon sources” as needed to adjust the carbon to nitrogen ratio.

The effect of carbon to nitrogen ratio on composting

The difficulty of composting lies in how to control the carbon-nitrogen ratio within a reasonable range. Therefore, when adding compost materials, whether using weight or other units of measurement, various compost materials should be converted into equivalent units of measurement.

In the composting process, the moisture content of about 60% is most conducive to microbial decomposition, although the carbon-nitrogen ratio of food waste is close to 20:1, but their water content may be between 85-95%. so. It is usually necessary to add brown materials to the kitchen waste, the brown material can suck up excess moisture.The compost windrow pile must be turned over by thecompost turnerfor a period of time to encourage airflow, otherwise, the compost might stink. If the compost material is very wet, move towards a carbon to nitrogen ratio of 40:1. If the compost material is already close to 60% moisture, it will soon be able to rely on the perfect ratio of 30:1.

 

Now, we will introduce you to the most comprehensive carbon-nitrogen ratios of composting materials. You can adjust the number of famous materials according to the composting materials you can use and combine the above-mentioned measurement methods to make the carbon-nitrogen ratios to the perfect range.

These ratios are based on averages and actual C: N, there may be some variation in the actual process, however, these are still a very good way to control the carbon and nitrogen in your compost when you are composting.

 

Carbon to nitrogen ratio of commonly used brown materials

Material

C/N ratio

Carbon content

Nitrogen content

Shredded cardboard

350

350

1

Hardwoodbark

223

223

1

Hardwoodchips

560

560

1

Dried leaves

60

60

1

Green leaves

45

45

1

Newspaper

450

450

1

Pineneedles

80

80

1

Sawdust

325

325

1

Cork bark

496

496

1

Cork chips

641

641

1

Oat straw

60

60

1

Rice straw

120

120

1

Fine wood chips

400

400

1

 

Covered plants

Material

C/N ratio

Carbon content

Nitrogen content

Alfalfa

12

12

1

Ryegrass

26

26

1

Buckwheat

34

34

1

Clover

23

23

1

Cowpeas

21

21

1

Millet

44

44

1

Chinese milk vetch

11

11

1

Leaf mustard

26

26

1

Pennisetum

50

50

1

Soybeans

20

20

1

Sudangrass

44

44

1

Winter wheat

14

14

1

 

Kitchen waste

Material

C/N ratio

Carbon content

Nitrogen content

Plant ash

25

25

1

Coffeegrounds

20

20

1

Gardening waste(dead branches)

30

30

1

Mowed grass

20

20

1

Kitchen rubbish

20

20

1

Fresh vegetable leaves

37

37

1

Tissue

110

110

1

Pruned shrubs

53

53

1

Toilet paper

70

70

1

Abandoned canned tomato

11

11

1

Pruned tree branches

16

16

1

Dry weeds

20

20

1

Fresh weeds

10

10

1

 

Other plant-based composting materials

Material

C/N ratio

Carbon content

Nitrogen content

Apple pomace

13

13

1

Banana/Banana leaf

25

25

1

Coconut shell

180

180

1

Corn cob

80

80

1

Corn stalks

75

75

1

Fruit scraps

35

35

1

Grape pomace

65

65

1

Grapevine

80

80

1

Dry grass

40

40

1

Dry legumes plants

20

20

1

Pods

30

30

1

Olive shell

30

30

1

Rice husk

121

121

1

Peanut shells

35

35

1

Leafy vegetable waste

10

10

1

Starchy vegetable waste

15

15

1

 

Animal manure

Material

C/N ratio

Carbon content

Nitrogen content

Chicken manure

6

6

1

Cowmanure

15

15

1

Goat manure

11

11

1

Horse manure

30

30

1

Human manure

7

7

1

Pig manure

14

14

1

Rabbit manure

12

12

1

Sheep manure

15

15

1

Urine

0.8

0.8

1

 

Other materials

Material

C/N ratio

Carbon content

Nitrogen content

Crab/lobster droppings

5

5

1

Fish droppings

5

5

1

Lumber mill waste

170

170

1

Seaweed

10

10

1

Grain residue(big brewery)

12

12

1

Grain residue(microbrewery)

15

15

1

Water hyacinth

25

25

1

 

Composting catalyst

Material

C/N ratio

Carbon content

Nitrogen content

Blood powder

14

14

1

Bone powder

7

7

1

Cotton/soybean meal

7

7

1

 

Blood powder is a powder formed from the drying of animal blood. Blood powder is mainly used to increase the content of nitrogen cables in the soil, making plants grow denser and green vegetables more “green”. Contrary to bone powder, blood powder can reduce the pH of the soil and make the soil acidic. The soil is very beneficial for plants.

The role of blood powder and bone powder They have a good effect on soil improvement, and wrong fertilization will not burn your plants. If the soil is acidic, use bone meal to increase the content of phosphorus and calcium, making the soil alkaline, It is suitable for flowering and fruit plants. If the soil is alkaline, use blood powder to increase the nitrogen content and make the soil acidic. It is suitable for leafy plants. In short, adding the above two to the compost is good for composting.

 

How to calculate

According to the carbon-nitrogen ratio of various materials given in the above list, combined with the materials used in composting, count the total number of various composting materials, calculate the total carbon content, and then divide by the total number of parts to make This number should be between 20 and 40.

 

An example to illustrate how the carbon to nitrogen ratio is calculated:

Assuming that there are 8 tons of cow dung and wheat straw as an auxiliary material, how much wheat straw do we need to add to make the carbon-nitrogen ratio of the total material reach 30:1?

We looked up the table and found that the carbon-nitrogen ratio of cow dung is 15:1, the carbon-nitrogen ratio of wheat straw is 60:1, and the carbon-nitrogen ratio of the two is 4:1, so we only need to put the amount of wheat straw into 1/4 of the cow dung amount. Yes, that is, 2 tons of wheat straw.

 

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Post time: Jul-07-2022