Cardboard or woodchip are both excellent additions to manure, or compost feedstocks in combination with N-rich material, but I would not normally add them directly to soil. They would add C but at the expense of N, especially the woodchip. I would expect the main benefit of these materials to vertisols would not be improved water-holding, but improved drainage and workability. However, composted material is almost always preferable and easier to apply.

No, but adding C to soil is of paramount importance for C sequestration and humus synthesis. Soil C depletion is a massive global issue. Furthermore, including paper & card in compost feedstock can help to create a C:N ratio favourable to rapid decomposition.

It can be tried in small area both as shredded form with nitrogen and also as compost.It may benefit any soil and need not be clay soil alone.

Probably good for soil structure in the medium to long term (i.e. yes, improved water holding capacity). You will have a problem with nitrogen though in the short term as in order to eat the cardboard/wood the bacteria will need nitrogen. To get this they will pull it from the soil, so this nitrogen will not be available to plants. Is your problem improving the soil over the long term or growing something on it ?  

I HAVE LEARN A LOT WITH THE ANSWERS. THANKS.

Some related research in Australia that may provide some useful contacts:

http://www.iuss.org/19th%20WCSS/Symposium/pdf/2021.pdf

As others have correctly noted above, when cellulose additions raise the soil C:N ratio sufficiently, the soil microbes will win the tug-of-war with plants for any available N.

Card board may have chemicals in the form of glue etc.hence first it has to be removed.I have tried shredded waste paper mixed with wood shavings that has given better moisture retention and improvement in organic matter.

Very interesting question Turlough . Addition of  shredded cardboard having 100% cellulose to the soil  will expand the C:N ratio , since the cardboard doesn't contain any other nutrient . And in the process,  soil will expand its sink capacity to sequester more nitrogen in order to maintain that revised C:N ratio ( As a constant , any increase in C will trigger concurrent increase in N )  after cardboard addition . In addition to this ,   soil will surely experience an increase in water transmission properties through possible changes in soil aggregate size.

Why mix two materials with high/very high C/N ratio?

Some soil physical aspects of using paper products for soil improvement are investigated by the group of Christophe Schwartz in Nancy, France. It is not only about water holding capacity but also about compaction, settling, shrinking swelling, water repellency and so on

Literature: try e.g. this one: Sere, Geoffroy; Schwartz, Christophe; Ouvrard, Stephanie; et al.(2010) Early pedogenic evolution of constructed Technosols, JOURNAL OF SOILS AND SEDIMENTS 10(7): 1246-1254

Good success!

we have been ploughing in wheat and rice straw which has always increased the water holding capacity and invited microbes. Thus this practice is beneficial. It will help the soil but this C:N ratio is very important.

Continuous addition of organic matter as cellulose or other form to soil can not increase the organic matter content of soil indefinitely .There will be a level of saturation(Concept of carbon saturation in soil, Six and others, 2002).Added carbon may  be protected and stabilized physically in aggregates(small and micro),in silt and clay associated and biochemical stabilization in recalcitrant C compounds.Added organic matter  may be sequestered to a certain maximum level and beyond that limit the organic matter may remain in unprotected form as active or labile forms which may be subjected to oxidation and loss of carbon as CO2.Even continuous organic farming with addition of large amounts of organic matter every year/season may attain a level of saturation in soil and beyond that limit soils may lose organic  carbon (labile pools) as CO2.

Thank you all for the answers and comments.

Note that I have added further photos of the 50:50 mixture that has been added to the soil.

It appears that :

• the added C will not be a problem but will tend to use avail N and sequester more N into the soil to achieve equilibrium C:N (for that soil), and
• the soil physical properties will be improved

I have attempted to answer some of the questions that you have posed.

1. Note that the mixture has been prepared as our intention is to use the material on site and the primary purpose was initially as a mulch to help in the establishment of landscape plants. It may be that we need to incorporate the mix into the soil to reduce the potential for it to become wind blown, reduce the groundcover fire hazard and to enhance its biodegradation (given that we won't need a mulch after 6-12 months when landscape plants are established.

2. No N-rich materials were added as we primarily wanted to produce a mulch

3. Why bother even to make clean cardboard? Good question. Chemical tests show it is clean apart from

Kenneth (belatedly), I think you are conflating two separate points that I made. Firstly, any addition of C to the soil contributes to sequestration, whether or not rapid decomposition is involved in part of the process. Secondly, I suggested (along with others) that composting the card before applying it would avoid N robbery from the soil. Adding the card directly would liberate just as much CO2, if not more; Compost, after all, is mostly C and has a degree of recalcitrance. There are other options, of course, if sequestration were the primary goal, like pyrolysing the card and woodchips into biochar; but that's a whole other debate!

I'm a little late to the discussion, but from a microbial perspective the addition of composted organic matter (OM) as a soil surface mulch can enhance soil microbial numbers and their functionality to a greater degree after several months than the incorporation of standard fertilizer+gypsum+lime additions in some soils. The enhanced soil microbial communities will, in turn, benefit nutrient cycling, the plant establishment and growth that you desire for landscaping and will also lead to better soil structure. However, non-composted wood chips and cardboard mulch will have much slower effects as the mulch will take longer to be microbially degraded (the cardboard would be broken down first). You might also try incorporating some composted OM to your wood chips and cardboard to help rev up its breakdown. There seems to be a lot of spare composted OM in NSW (assuming you are based in Sydney).

Kenneth, ideally more CO2 could be removed from the atmosphere if we didn't compost or decompose carbonaceous materials but also created more of them – we could keep planting more trees and harvest the sequestered C in more wooden things, like more wooden buildings and perhaps wooden-cased iPhones (the latter should take care of a lot of wood). Given that this is unlikely to happen, and as Lewis Ross Peake has noted previously, the addition of C to soil through decomposition and composting will result in some C sequestration through increased microbial biomass and the production of humic substances (together with some CO2 release via respiration). Remember that it is a C-cycle, so if we can't fix the C in a material through continual re-use of that material, then putting a significant proportion of that material's C back into the ground via decomposition is preferable to burning it and putting most of it straight back into the atmosphere. Soils are the foundation of all terrestrial ecosystems, yet the quality and quantity of healthy soil is in almost constant decline due to human activities. Putting more C back into soils via microbial decomposition of carbonaceous materials will both sequester some of the C and improve soil health.

I agree with the reasoning of Dr .Wildman.For better utilization of the shredded cellulosic material in soil,  decomposition and synthesis as humic material is required.For facilitating decomposition and formation of humus during composting,spraying of water periodically ,spraying of cellulose decomposing microbes or cow dung or compost slurries on the material  spread in the field may help. Aeration by turning the material frequently  may also help.This will be like some sort of on farm composting of shredded material.

Apologies to Turlough for getting off the track of your original question..... Kenneth, I think you are missing the point about composting and biodegradation – they are and always have been a part of the C cycle and thus their contribution to atmospheric CO2 levels remains constant over time. Plus they put organic matter (and C) back into soils. As you know, it's the rapid growth in fossil fuel CO2 emissions plus the decline in CO2 sinks on land and ocean which is the responsible for the rise in atmospheric CO2 levels. The composting and biodegradation by microorganisms of carbonaceous materials such as Turlough's wood chips and cardboard are a part of a rapid C cycle that has always occurred and which benefits soil health and its ability to act as a C sink.

As a post script to this question, I note that after 18 months of application of this material to the soil in question, there are a few observations worth noting: soil moisture is consistently higher cf adjacent soil; Self seeding of grasses is occurring on the mulch surface; the soil mulch boundary in May areas has merged such that it is difficult to determine where the mulch stops and soil begins; materials have remained in place and not redistributed by wind, water, etc.

Turlough,

thank you for keeping us up to date. Could you also say what kind of soil this is and what the climate is like ?

all the best

Hi Patrick - it is a low carbon, high clay content soil. It is known as a local steppe climate and there is little rainfall throughout the year, reasonably evenly distributed in summer and winter. . The temperature averages 18.5 °C and up into the 40s in summer. The rainfall here averages 479 mm.

The attached image shows how the material is now degraded and being incorporated into the soil, and the other how it is being re-vegetated.