Madagascar Soil Composition

[joe_OC]

Since a lot of my palms are from Madagascar and similar islands, I researched what the soil make up was to see how much of it I could mimic.  I found these articles informative to provide some insights to how the soil works in Madagascar:

 

Madagascar Palm Tree Ecosystem

http://www.wildmadagascar.org/overview/rainforests2.html

 

I found this passage very insightful:

 

NUTRIENT CYCLING 

In the rainforest, most of the carbon and essential nutrients are locked up in living vegetation, dead wood, and decaying leaves. As organic material decays, it is recycled so quickly that few nutrients ever reach the soil, leaving it nearly sterile. 

Decaying matter (dead wood and leaf litter) is processed so efficiently because of the abundance of decomposers including bacteria, fungi, and termites. These organisms take up nutrients that are released as waste and when organisms die. Virtually all organic matter is rapidly processed, even fecal matter and perspiration. It is only a matter of minutes, in many rainforests, before dung is discovered and utilized by various insects. Excrement can be covered with brightly colored butterflies, beetles, and flies, while dung beetles feverishly roll portions of the waste into balls for use later as larval food. 

As vegetation dies, the nutrients are rapidly broken down and almost immediately returned to the system as they are taken up by living plants. Uptake of nutrients by plant roots is facilitated by a unique relationship between the roots and a fungi, mycorrhizae. The mycorrhizae attach to plant roots and are specialized to increase the efficiency of nutrient uptake nutrient from the soil. In return, plants provide the fungi with sugars and shelter among their roots. Studies have also shown that mycorrhizae can help a tree resist drought and disease. 

Tropical rainforest trees are well-adapted to the poor soils of their environment. Since the first 6-8" (15-20 cm) of soil is a compost of decaying leaves, wood, and other organic matter, it is richest pool of nutrients on the ground. Canopy trees are generally shallow rooted to better tap this resource. 

Being shallow rooted, compounded by the wet soils, has serious disadvantages for tall rainforest trees, especially with the strong winds of the upper canopy that can accompany periodic cyclones. To counter this inherent instability, some rainforest tree species have extensive root systems that run for over 325 feet (100 m). Other trees, especially tall emergent species, have buttress roots, which are large, thin extensions of the trunk that begin some twenty feet from the ground. These structures are thought to also aid in water uptake and storage, increase surface area for gas exchange, and collect leaf litter for additional nutrition. Some trees, especially palms have developed stilt roots for further support.

[sonoranfans]

Beccariophoenix Alfredii and Bismarckia do not come from the jungle, they are high plateau palms and grow in lateritic soil(low nutrient content).  Madagascar is a huge island and has highly variable weather and soil.  That high variability has, in part, led to the massive number of palm species found there.  

[joe_OC]

14 minutes ago, sonoranfans said:

Beccariophoenix Alfredii and Bismarckia do not come from the jungle, they are high plateau palms and grow in lateritic soil(low nutrient content).  Madagascar is a huge island and has highly variable weather and soil.  That high variability has, in part, led to the massive number of palm species found there.  

I agree 100%.  But those palm species are the minority, not the majority of the number of species of palms in Madagascar.  I don't grow either of those palms.  

[Tyrone]

So what those articles told me, was that you can grow most Malagasy palms on a base of poor soil as long as the top 15-20cm is organically rich and replenished in the home garden. That makes sense.

Also habitat loss is the main threat to palm and forest extinction in Madagascar. I doubt seed collection by unscrupulous seed collectors is the main threat. If the seed collectors are educated enough to understand that cutting down your small seed source of trees will mean that you can never harvest and sell that seed ever again, then you'll protect those trees and not kill them for one harvest of seed. Also it's all very well and good to say that the seed should remain to fall and grow in habitat. However when that habitat is disappearing quickly that would be a complete waste of a valuable resource.

[joe_OC]

1 hour ago, Tyrone said:

So what those articles told me, was that you can grow most Malagasy palms on a base of poor soil as long as the top 15-20cm is organically rich and replenished in the home garden. That makes sense.

Also habitat loss is the main threat to palm and forest extinction in Madagascar. I doubt seed collection by unscrupulous seed collectors is the main threat. If the seed collectors are educated enough to understand that cutting down your small seed source of trees will mean that you can never harvest and sell that seed ever again, then you'll protect those trees and not kill them for one harvest of seed. Also it's all very well and good to say that the seed should remain to fall and grow in habitat. However when that habitat is disappearing quickly that would be a complete waste of a valuable resource.

Tyrone,

Now read my other post on palm root systems.  

[LJG]

3 hours ago, Tyrone said:

So what those articles told me, was that you can grow most Malagasy palms on a base of poor soil as long as the top 15-20cm is organically rich and replenished in the home garden. That makes sense.

Also habitat loss is the main threat to palm and forest extinction in Madagascar. I doubt seed collection by unscrupulous seed collectors is the main threat. If the seed collectors are educated enough to understand that cutting down your small seed source of trees will mean that you can never harvest and sell that seed ever again, then you'll protect those trees and not kill them for one harvest of seed. Also it's all very well and good to say that the seed should remain to fall and grow in habitat. However when that habitat is disappearing quickly that would be a complete waste of a valuable resource.

Good points. 1) my soils is almost all dg with maybe 4-6 inches of rich soil (took years to make) on top. Dypsis do great. 2) if seed isn’t taken out, there is a great possibility the plants will be extinct very soon. Earlier collectors like Mardy Darian brought plants to cultivation that are now extinct there - or at least haven’t been found again and the habitat was torched.

[Matt in OC]

So, is richer soil at a depth past 6” or so detrimental to some of these Dypsis? Perhaps this soil retains more water as well. What about other genus such as beccariophoenix?

[joe_OC]

11 hours ago, Matt in OC said:

So, is richer soil at a depth past 6” or so detrimental to some of these Dypsis? Perhaps this soil retains more water as well. What about other genus such as beccariophoenix?

I don't think so, unless the soil retains so much water that it rots the roots.  Palm tree roots behave very differently.  Here is an interesting read from the University of Florida:

Palm Tree Anatomy

I've copied the section on palm roots:

Roots

Palm roots differ greatly from those of broadleaf and coniferous trees in that they are all adventitious, emerging from a region of the trunk called the root initiation zone. Palm roots originate from the outer region of the central cylinder where they connect with vascular bundles in the stem. As they grow, the sheer volume of new roots may force the cortex and pseudobark to split and flare out from the base of the stem (Figure 5). If new roots develop aboveground and come into contact with dry air, their development will be arrested until more favorable conditions are encountered. If soil or mulch is mounded around aerial root initials, they will resume their growth down into the soil. Palm roots emerge at their maximum diameter, and no additional increase in diameter will occur. Some primary roots may grow downward, but the majority grow laterally, extending out 50 ft. or more from the trunk in large specimens. If primary roots are cut, they may branch from behind the cut, but the resulting roots will be primary in their size and morphology. Secondary, tertiary, and even fourth-order roots are proportionately smaller in diameter and length, are short lived, and often grow upward toward the soil surface. These are the roots that absorb water and nutrients. Specialized roots called pneumatophores may literally grow upward and out of the ground in some species (e.g., Phoenix spp.). Palm roots do not have root hairs like dicot roots. Because they lack a cambium, roots of adjacent palms cannot graft, as they can in dicot trees.

 

This is really interesting for me.  It seems I have been applying fertilizer in the wrong place!  It needs to be done FURTHER away from the tree where the root are.  

Edited November 3, 2018 by joe_OC

[mwardlow]

Excellent information Joe! Thanks

[Tyrone]

So it's all about mulch mulch mulch with our palm gardens and tropical rainforest trees. We kind of knew that but it's great to verify why.

[joe_OC]

The question I have now is how much water?  Knowing that the greatest concentration of roots is only a meter down, AND away from the trunk, should my drip emitters be placed further away from the trunk too?  

Edited November 3, 2018 by joe_OC

[Tyrone]

10 hours ago, joe_OC said:

The question I have now is how much water?  Knowing that the greatest concentration of roots is only a meter down, AND away from the trunk, should my drip emitters be placed further away from the trunk too?  

Just make a grid of your entire landscape and put an emitter where the grid lines intersect.

[BS Man about Palms]

I've been doing pretty good with my clay soil and mulching on a semi-regular basis..

[sonoranfans]

As each tree grows a larger and larger root zone they will need more emitters or a micro sprinkler spaced away from the trunk in an ever increasing ~ circle.  Bunching trees helps but if we look at one tree  the number/flow rates de needed to wet the entire root system will depend strongly on soil drainage and also on relative humidity(evaporative losses).  When I lived in arizona micro sprinklers made no sense, as a few 2 gallon/hr drippers watering for 4-5 hrs made huge wet zones in that heavy clay soil with a fraction of the evaporative losses that would occur with micro sprinklers.  Fast drainage soil means more drippers/sprinklers, at some point the drippers don't work as well as micro-sprinklers.   The solution for your soil may not be the same as some one else.  My soil is fast drainage, sandy soil that I top mulch, so drippers are inefficient at watering a larger root zone.  Also our relative humidity is mostly 50-75% so no so much evaporative losses as out west.  I look at drippers this way:  as drainage increases the surface wet spot size for each dripper shrinks and the water in soil depth increases.  In other words the water goes too deep too fast with drippers in sandy soil.  But in heavier soil with lower drainage, those drippers grow big wet spots with low depth penetration, they are their most efficient.