Myth soil amendments

Eric Frei · 13th December 2009, 11:03 AM

I also added this PDF to this thread.

Soil Aeration Experiments| Grade Changes| Compaction| Decompaction

But looking at greater detail into this specific area it's interesting to read.

Quote:

In some studies, plants in amended soil outperform those in unamended soils, but interactions with other factors make it difficult to determine what is actually providing the benefits. For example, Querejeta and others (1998) studied the combined effects of terracing, organic amendments, and mycorrhizal treatments. Organic amendments enhanced growth and nutrient uptake in Pinus halepensis, but at least some of the benefit likely came from the terracing. Significant differences in survival and growth were found between the two types of terracing, as well as the amendment status. Not surprisingly, plants in the mechanically terraced areas, which involved excavating and amending a large planting area (not just the planting hole), had better growth and survival rates. For many growth factors, as well as overall survival, significant differences existed between terracing types, but not between amended or unamended soils within a terracing type. The experimental design makes it difficult to say what factor had the biggest effect on plant health, but it appears that the amendments alone provided little real benefit.
Soil amendments not only influence plants, but can impact the mycorrhizae associated with plants. In a study with Trifolium pratense (red clover) and Cucumis sativa (cucumber), Sainz et al. (1998) found that mycorrhizae would not grow in soils amended with either composted or vermicomposted urban waste. Although the crops had some gain in yield, the amendments reduced root length and reduced mycorrhizal activity, which could seriously damage the agricultural systems. In a related study, Roldan and Albaladejo (1993) found that using urban refuse to amend a xeric loamy clay harmed vesicular-arbuscular mycorrhizae (VAM). Adding even small amounts of organic matter caused a decrease in mycorrhizal spore concentrations, root colonization percentages, and production of viable infective propagules. Three years after the amendment was added, VAM populations increased, but remained lower than or no different from those in native soils, suggesting the amendment inhibited VAM growth.
The vast majority of research on woody landscape plants shows that soil amendments are not an economically or ecologically sound investment. Amendments are not only unnecessary and inefficient, they can also be quite costly. Hummel and Johnson (1984) looked into the cost of adding soil amendments, and estimated that they increase the per tree installation cost by 27-30 percent. These costs are not offset by any benefits in plant growth or establishment, making them a wasteful venture. As Corley (1984) says, the real ‘five dollar hole’ is a wide, well drained, well mulched, amply fertile one, not one with amended soils.
Sometimes, even those who recommend soil amendments admit that they are generally of no real benefit (Watson et al. 1992; Hartman et al. 2000). Watson and others found that amendments neither hurt nor helped Fraxinus pennsylvanica (green ash). Instead, they noted that creating wide planting holes with loosened soil provides a greater benefit than amendments, particularly in compacted soils. Henderson-Cole and Hensley (1992) also studied F. pennsylvanica and found that soil amendments had little effect on plant growth and did not benefit root establishment.

Eric Frei · 13th December 2009, 11:26 AM

More reinforcement.

Quote:

No scientific studies to date show any measurable benefit of soil amendment except in containerized
plant production. Plants grown in native soil consistently showed better root establishment and more
vigorous growth. Only one study reported no negative effects of amending soil with organic matter - but
there were no benefits, either. When you consider the cost of materials and labor needed to incorporate
soil amendments, it's difficult to justify the practice.
This outdated practice is still required in the specifications of architects, landscapers, and other groups
associated with landscape installation. It is still recommended by garden centers and gardening articles.
And there is a multi-million dollar soil amendment industry that has little interest in debunking this myth.
As responsible green industry professionals, we need to recognize and avoid non-sustainable management
practices.
Bottom line:
• Select suitable plant species for site conditions
• Don't be an "enabler": use native soils for backfill without amendment
• In extreme cases, replace the entire planting site with topsoil
• Mulch landscapes well with wood chips or another water-holding material

jeffelder · 21st December 2009, 09:07 PM

So be it!
Jeffe

windthrown · 22nd December 2009, 10:36 AM

Yah, I have debated with the bamboo society over this one. I have always been a fan of mulch and top dressing, but not adding or turning amendments into the soil. But oh no! All the organic greenies are all over me about the benefits of adding soil amendments. And now thay are all ranting about adding expensive fungus spores to the soil too. What a waste of money that is.

I also recommend big chunky mulch to avoid soil abscission layers. My neighbor spends tons of time and energy grinding up his own compost, then he overworks the soil to death with a tiller, several times a year. He winds up breaking up all the roots and all the compost is gone in a year or two to the worms and rot. I till at most once a year, and I do not add anything, except super phosphate. I get huge results. My corn was 9 feet tall this year. Eveyone asks me what I do. I say, next to nothing? No, that is not right. I do feed inorganic water soluble fertilizers, and I water. Oh no, you must be doing something else??? No... nothing else. Not even wood chips for that stuff. We live on flood plain riverbed soil, and that stuff is as good as it gets. My brother asked me if we sould buy more soil and bring it in. I looked at him and asked him if he was crazy. We should be SELLING the soil we have as top quality loam.

Eric Frei · 22nd December 2009, 06:52 PM

Crops and farming are a bit different to trees, they're sort of a one off event and you need to get the most out of it (productivity).

A lot of the soil over here is crap frankly, it would be extremely rare to be able to put a spade in the ground coz it's hard too.

Few hundred years ago when the Poms arrived they got a rude shock about farming this land.

windthrown · 22nd December 2009, 09:04 PM

I have found over the years that farming is not all that much different than growing trees. I learned about silviculture in school when I was living with the ex, and I managed the 85 acre tree stand there. See, here in Oregon trees are just grown as a 60 year crop. Bamboos are not that much different either. They are just big perenial grasses. The soils, roots, microbes, nutrients and growing processes are all the same. The only difference is the length of time between planting and harvesting.

21st December 2009, 09:07 PM	#3
jeffelder Sappling Join Date: Sep 2009 Location: UK Swindon Posts: 5	Re: Myth soil amendments So be it! Jeffe

22nd December 2009, 10:36 AM	#4
windthrown Former Member Join Date: Dec 2007 Location: In the Great Pacific Northwest Posts: 1,211	Re: Myth soil amendments Yah, I have debated with the bamboo society over this one. I have always been a fan of mulch and top dressing, but not adding or turning amendments into the soil. But oh no! All the organic greenies are all over me about the benefits of adding soil amendments. And now thay are all ranting about adding expensive fungus spores to the soil too. What a waste of money that is. I also recommend big chunky mulch to avoid soil abscission layers. My neighbor spends tons of time and energy grinding up his own compost, then he overworks the soil to death with a tiller, several times a year. He winds up breaking up all the roots and all the compost is gone in a year or two to the worms and rot. I till at most once a year, and I do not add anything, except super phosphate. I get huge results. My corn was 9 feet tall this year. Eveyone asks me what I do. I say, next to nothing? No, that is not right. I do feed inorganic water soluble fertilizers, and I water. Oh no, you must be doing something else??? No... nothing else. Not even wood chips for that stuff. We live on flood plain riverbed soil, and that stuff is as good as it gets. My brother asked me if we sould buy more soil and bring it in. I looked at him and asked him if he was crazy. We should be SELLING the soil we have as top quality loam.

22nd December 2009, 06:52 PM	#5
Eric Frei Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane Posts: 12,792	Re: Myth soil amendments Crops and farming are a bit different to trees, they're sort of a one off event and you need to get the most out of it (productivity). A lot of the soil over here is crap frankly, it would be extremely rare to be able to put a spade in the ground coz it's hard too. Few hundred years ago when the Poms arrived they got a rude shock about farming this land. __________________ Protect your rights to work - Join Australian Tree Association My businesses:- Qualified Brisbane Tree Lopping \| Stump Grinding Brisbane \| Brisbane - Gold Coast Consulting Arborist

22nd December 2009, 09:04 PM	#6
windthrown Former Member Join Date: Dec 2007 Location: In the Great Pacific Northwest Posts: 1,211	Re: Myth soil amendments I have found over the years that farming is not all that much different than growing trees. I learned about silviculture in school when I was living with the ex, and I managed the 85 acre tree stand there. See, here in Oregon trees are just grown as a 60 year crop. Bamboos are not that much different either. They are just big perenial grasses. The soils, roots, microbes, nutrients and growing processes are all the same. The only difference is the length of time between planting and harvesting.

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