Posts Tagged: organic matter
If It's Brown, Leave It on the Ground
For quite some time, farmers and researchers have been focusing on how to bind carbon to soil. Doing so makes food crops more nutritious and increases yields.
However, because carbon is converted into CO2 when it enters the atmosphere, there is a significant climate benefit to capturing carbon in soil as well.
Too much carbon finds its way into the atmosphere. Should we fail to reverse this unfortunate trend, we will fail to achieve the Paris Agreement's goal of reducing greenhouse gas emissions by 40 percent by 2030, according to CONCITO, Denmark's Green Think Tank.
As such, it is important to find new ways of sequestering carbon in soil. This is where a team of researchers from the University of Copenhagen and the Technical University of Munich enter the picture.
In their new study, they argue for the potential of simply allowing agricultural crop residues to rot in fields.
"Fragments of dead plants in soil are often considered as fast food for microbes and fungi. But our study demonstrates that plant residues actually play a more significant role in forming and sequestering carbon in soil than what was once thought," explains Kristina Witzgall, a PhD Candidate at the Technical University of Munich and the study's lead author.
In the past, researchers mainly focused on carbon storage in the surfaces of minerals like clay. However, the new results demonstrate that plant residues themselves have the ability to store carbon, and perhaps for longer than once supposed.
This is because a number of important processes take place directly upon the surface of these plant remains.
"We demonstrate that agricultural crop residues are absolutely central to carbon storage and that we should use them in a much more calculated way in the future. Plant residues make it possible for carbon, in all likelihood, to be stored in soil for roughly four times longer than if they aren't added," states Carsten Müller, the study's co-author and an associate professor at the University of Copenhagen's Department of Geosciences and Natural Resource Management.
Fungi and soil clumps store carbon
To understand how plant residue sequesters carbon, it is important to know that plant tissue already contains carbon absorbed by plants from the atmosphere via photosynthesis. As plant matter rots, carbon can be transferred into the soil in a number of ways.
"Our analysis shows that plant residues, as they interact with fungi, play a surprisingly large role in carbon storage. As fungi fling their white strands around plant fragments, they 'glue' them together with the soil. The fungi then consume the carbon found in the plant matter. In doing so, they store carbon in the soil," explains Carsten Müller.
In addition to fungi, the researchers' analyses also show that the soil structure itself determines the amount of carbon that can be stored.
"When soil is glued together in large hard lumps by the stickiness of bacteria and fungi, plant residues are shielded from being consumed by bacteria and fungi, which would otherwise eat and then emit some of the carbon as CO2 into the atmosphere," says Kristina Witzgall.
She goes on to say that while carbon can be stored in soil from weeks to a thousand years, the usual duration is about 50 years.
Reducing CO2 in the future
The method of leaving crop residues like stalks, stubble and leaves to rot is not unheard of when it comes to enhancing agricultural land.
However, deploying rotten plants as a tool to store carbon should be taken more seriously and considered as a strategy to be expanded, according to the researchers behind the new study.
"The fertile and climate-friendly agricultural lands of the future should use crop residue as a way of sequestering carbon. We will also be conducting experiments where we add rotten plant matter deeper into the soil, which will allow carbon to be stored for even longer periods of time," says Carsten Müller.
If we work to create better conditions for carbon sequestration in soil, we could store between 0.8 and 1.5 gigatonnes of carbon annually. By comparison, the world's population has emitted 4.9 gigatonnes of carbon per year over the past 10 years.
All in all, the researchers' findings can be used to understand the important role and promise of crop residues for carbon storage in the future.
However, Kristina Witzgall goes on to say that a variety of initiatives are needed to increase carbon sequestration, such as crops that can absorb atmospheric carbon and the restoration of lost forests.
Read the whole story: https://www.nature.com/articles/s41467-021-24192-8
Images:
Scanning electron microscopy (SEM) images of the interface of plant litter (POM) and soil minerals, where soil minerals are (a) attached to the litter surface (scale bar = 100 µm) and (b) enmeshed with fungal hyphae and extracellular polymeric substances (EPS; scale bar = 10 µm). Similar images were obtained from at least 10 independent locations in each soil texture.
2021 Irrigation and Nutrient Management Virtual Meeting
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Healthy soils for healthy profits - How do we get to $2.50/lb cotton in the SJV? Webinar Introductory Video on You Tube - https://www.youtube.com/watch?v=NS20ZxJWx1g
August 16, 2020
Announcing the webinar, Healthy Soils for Healthy Profits - How do we get to $2.50/lb cotton in the SJV? slated for September 17, 2020 from 9:00 AM to Noon. Registration is now open at: https://ucanr.edu/sjvcottonwebinar
A short introductory video including interviews with presentingSJV farmers is available at
Sign up now!
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Capture You Tube SJV Soil Health Video 2020
Mulch. Read Some About It!
Two questions and comments came up last week about the use of mulch in orchards. The first is that mulch is two edged. It serves to combat erosion and root rot, but it can also burn. Mulch and wood piled up against tree trunks and near trunks can cause damage to those trunks. A Fillmore grower actually goes through the orchard with a blower to move mulch away from trunks when alerted to fire. On the other hand, irrigated orchards have been shown to be effective at suppressing fire encroaching on homes.
So where to read more about fire? About mulch? Check out some of the blogs from the past.
Phire, Phlood, Phreeze and Fytophthora
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22760
Mulch and green waste applied to avocado orchards and More
Green Waste, Yard Waste, Whatever You Call It- It has Simple Rules for Use
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=13093
A Safer Source of Inexpensive Orchard Mulch
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12867
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6458
Cellulase Production by Various Sources of Mulch
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6809
A Caution on Free "Compost/Mulch"
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11712
A Safer Source of Inexpensive Orchard Mulch
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12867
Mulch, Avocados and the Home Garden
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14906
Mature Compost Does NOT Kill Phytophthora
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19856
Use of Mulch in Organic Orchards Called into Question
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=21394
mulch
Green Side Up. Brown Side Down. Planting a Tree
A recent letter which followed a farm visit to another grower and finally a phone call about planting an avocado tree from another grower. The basics of planting are often overlooked and we should revisit them to make sure we know how to do the basics.
The letter:
I am going to plant some avocado trees on a slope. I will be drilling a hole with an 18 inch auger about three feet deep.
I have lots of wood chips from avocado trimmings. Should I mix some avocado wood chips with the soil to insure good drainage when I plant the new trees?
Or should I mix in some compost to help good drainage? Some areas here have poor drainage because of clay soil.
The response:
DO NOT put anything in the planting hole. It makes drainage worse. And if its not fresh the decomposing gases will kill the roots. And gradually over time, the organic matter decomposes and the tree sinks deeper into the ground, covering the graft union and the tree dies. I[m glad you asked. Someone is spreading the word that this is how to plant. It's a disaster if you do this. DON'T. You think you are doing everything right, but it is wrong. There's physics and biology involved and a good horticulturist knows better because of experience. Mulch applied to the soil surface is not the same as organic matter – planting mix put in the hole.
And watch out for the auger. Especially in heavy soils, the auger can seal the sides of the hole, making an impenetrable surface to the roots. The sides need to be scrapped or scratched to make sure the seal hasn't been created. And don't go 3 feet deep. Go to the depth of the planting sleeve. When you go deeper, the refill soil will compact and the root ball sinks, burying the crown.
From the UCR Avocado website:
http://ucavo.ucr.edu/general/answers.html#anchor1423493
Planting
The avocado is a shallow rooted tree (most of the feeder roots are in the top 6" of soil) which needs good aeration. They do well if mulched with a coarse yard mulch. Current recommendation is to put approx 1/3 cu yd per tree when planting. When applying the mulch, be sure to stay about 6-8 inches away from the trunk of the tree. They like the soil pH around 6 - 6.5. If you can, plant your tree in a spot protected from wind and frost. Also, avocado trees typically do not do well planted in lawns so try to plant your tree in a non-lawn area.
- When should I plant my avocado tree? Avocado trees like warm ground. Ideally, they should go into the ground from March through June. If they go in during the summer there is always the risk of sun damage because the trees can't take up water very well when young.
- How big a hole should I dig? As deep as the current root ball and just as wide as the width plus a little extra so you can get your hands into the hole to plant it. Don't drop the tree into the hole, the roots don't like that, ease it into the hole. The avocado root system is very sensitive and great care should be taken not to disturb the root system when transplanting. If the tree is root bound, however, loosen up the soil around the edges and clip the roots that are going in circles.
- Should I put some gravel, crushed rock or planting mix at the bottom of the hole? No. Do not put gravel or anything else like planting media in the hole. The sooner the roots get out into the bulk soil, the better the tree will do. Planting mix creates a textural difference between the root ball and the bulk soil and causes water movement problems. Remember, there are 5 million acres of tree crops in California planted without planting mix.
- I have a heavy clay soil. Should I elevate the tree in a mound for better drainage? Yes, good idea. Make the mound 1 to 2 feet high and 3 to 5 feet around. Put down 20 pounds of gypsum spread around the base of the tree and mulch the area with 6 inches of woody mulch keeping the material about 6-8 inches away from the tree trunk.
- What do you mean by a "coarse yard mulch" and where can I get some? Redwood bark will work and maybe cocoa bean husks and shredded tree bark. Need something that is woody and about 2 inches in diameter. Coarse yard mulch is available at some garden supply centers. Be sure it is COARSE, not fine, yard mulch - and disease-free to prevent introducing diseases to your tree (like root rot). Another source of coarse mulch would be a tree trimming operation, like Asplundh or Davy. They usually have material that has been pruned from the tops of trees and doesn't contain any diseased roots. Just go through the yellow pages looking for tree services.
These directions hold true of all trees, citrus, avocado, mango..............And for a nice discussion of avocado planting and root rot, go to:
http://www.avocadosource.com/journals/avoresearch/avoresearch_02_01_2002.pdf
upside down tree