Presentations & Papers:
    Phosphate Mining Confer.
    Importance of Soil Building
    FIPR CMA Research (pg. 13)

Field Photography:
    Eucalyptus Trees @ 2nd YR.
    Pictorial History of Site

Related Treepower Sites:
    Crop Tree Yields
    Harvesting Research

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Blog on Phosphate Mining!

The Nature of Heavy Clay Soils & Commercial Scale Tree Planting on Clay Settling Areas (CSAs).


As empirical "field results" from our tree farm continue to build, it is becoming increasingly clear that this project is as much about phosphate mining reclamation as it is about creating a renewable energy resource.

It can take ~15 years for an older Clay Settling Pond to De-water enough to work soils. Clays at our Site reach depths of 30 to 60 feet.

We believe an "industry reclamation model" is being defined on this ~60 year old phosphate mining clay settling area site (mined by American Cyanamid) with respect to at least four critical aspects:

  • Planting Procedures to maximize initial tree survival.
  • Stabilization of Sites from harmful invasive weeds.
  • Soils Remediation, or perhaps better stated, soil building.
  • Re-introduction & Establishment of Native Trees and Flora.
  • Our Opinion on CSA Soils: We very strongly believe in the following two statements, which may sound contradictory:

  • CSA soils are highly fertile.
  • CSA soils are not conducive to tree or native flora/plant
        establishment.
  • Fertility:   While many opponents of phosphate mining state that CSA Sites are "worthless" or of "little value" -- this just isn't correct. CSA soils are high in Potassium (K) and phosphorus (P) -- two key components of productive soils.

    While we can provide science based papers discussing the productivity of CSA soils (1) -- sometimes a picture is worth a thousand words:

    21/2 year old eucalyptus trees planted on a CSA Site,
    averaging +40 feet in height.

    By adding two points to the above picture, we believe our statement that CSA soils are fertile becomes even more credible:

  • This is not a small plot demonstration. The above picture is
        representative of tree growth achieved on a 135 acre Site.
  • The Commercial Scale Development Costs were very
        reasonable at ~$1,250 per acre:
  • Components of Establishment Costs Per Acre.

    The Problem with Heavy Clay Soils and Tree/Flora Establishment: After decades of Research on Phosphate Mining Clay Settling Areas, the following points are well established in scientific literature -- that CSA Soils are:

  • Heavily Compacted (Bulk Density).
  • Have a high pH (from ~7.5 to 8.0).
  • Are Nitrogen Deficient (Carbon to Nitrogen Ratio)
  • However, what prior research has failed to clearly identify is the inability of heavy clay surface soils to hold almost any level of moisture when planting/establishing trees or native flora especially in dry seasons.

    As anyone who has worked CSAs knows, these sites are highly unstable for commercial farm equipment -- dictating that tree establishment (site prep, bedding, planting) must occur in winter or early spring (Florida's Dry Season).

    Bedding Equipment Used: After first herbiciding our cogongrass infested CSA site (Roundup Pro appears to work best) and then disking soils (to target below ground cogongrass rhizomes which can produce 3 tons per acre),

    View of Cogongrass on Site after Herbiciding but before Disking.

    Tree Beds were established using:

  • A Savannah Bedding Plow, creating beds on 8' and 11'
        centers, allowing either 1 or 2 rows of trees to be planted
        on each bed.
  • A D-5 Bulldozer, creating 23' center macro beds/mounds,
        where 4 rows of trees were planted on each bed.
  • Picture of 23' Macro Beds/Mounds created with a D-5 Bulldozer.

    There are positives and negatives in using either approach. Clearly, the Savannah Bedder created the best non compacted soil bed. However, even at creation, these beds were only ~2 feet high (and settled quite a bit through time). When summer rains came, standing water accumulated over the apex of the beds (located in low areas), causing tree mortality.

    In creating Macro beds with a D-5 Bulldozer, material for the beds was created by deep trenching every 23 feet -- accumulating clay soils for the bed. Under this approach, the apex of beds were ~ 4 feet in height.

    For macro beds/mounds, this combination of deep trenching (between beds) and 4 foot bed heights (at apex), addressed drainage and standing water issues very well . However, tree growth on the two outside rows has dramatically under-performed growth within the two interior rows.

    As the above graphic attempts to illustrate, macro beds/mounds gently slope from the apex to the trenched area. It is believed that the under-performance in tree growth on outside rows is largely the result of not enough un-compacted soil beneath the planted seedlings (compared to the two interior rows of trees).

    Generally, we are seeing the following tree growth (yields per acre):

  • Tree Growth on Interior Rows of Macro Beds/Mounds
        replicate the growth on double row planted trees on beds
        created with a Savannah Bedder -- i.e., high yields.
  • Tree Growth on Exterior Rows of Macro Beds/Mounds
        replicate the growth on flat planted trees (e.g., no beds)
        -- low yields.
  • Future Direction of Bedding Research: While we believe that the macro bed/mound approach is the "right concept" (especially for needed drainage), the issue of underperformance on outside rows needs to be addressed. Two potential directions of future research on bed establishment is:

  • Wider/Deeper Trenching, creating more un-compacted soil
        material beneath outside rows (i.e., creating a ~30' bed).
  • Using sub-soiling equipment on areas of the macro
        bed/mound's outside tree rows.

    Planting Equipment Used: Two types of commercial planting equipment has been used on both (1) Savannah Bedder Beds; (2) Macro Beds/Mounds:

  • A Whitfield Pine Tree Planter/Plow.
  • A New Holland Watermelon Planter.
  • Planting on Beds created by the Savannah Bedder:   We experienced two major problems in using the Whitfield Planter on these 8' to 11' center beds. First, as the Whitfield Planter ripped through the soil, it severely effected the structural integrity of the beds. In planting configurations of two rows of trees per bed, an accurate description is the Whitfield Planter destroyed the height of created beds. Second, the Whitfield was not able to sufficiently pack seedlings in the heavy clay soils. Average Tree Survival Rates using this approach was ~10% (or, ~90% tree mortality). It was also surprising just how quickly the seedlings began to die -- about 2 days.

    In an attempt to address the high mortality rate resulting from the Whitfield Planter, we moved to a New Holland Planter (used extensively for watermelon plantings). The design of the New Holland uses individual blades/scoops to penetrate the soils (with no ripping as in the Whitfield), creating a planting hole. The New Holland is also designed to inject water into the created hole (from a trailing water wagon source), mechanically inserting tree seedlings, and then pack with its packing wheels. A noticeable advantage of the New Holland was that it preserved the structural integrity of the tree beds (compared to the Whitfield Planter).

    The Critical Need for Packing:   At initial planting using the New Holland, we constantly "spot checked" the success of the Planter's soil packing efficiency around tree seedling. Gently tugging on the planted seedlings, they appeared to be securely and deeply planted into adequately moist soil.

    However, the day after planting, we noticed that seedlings started to exhibit severe stress/shock (wilting and drying of leaves, yellowing) -- similar to seedling characteristics previously experienced when using the Whitfield Plow Planter.

    In replicating our "tug test" of packing efficiency the day after planting, the seedlings easily slipped out of the hole. The clay soils surrounding the root ball was of a consistency of non-packed dry cement mix. Soil mesh sizes ranged from pulverized/granular clays to small pebbles. Thus, in less than 24 hours, the surface clay soils had entirely lost all soil moisture, creating massive air pockets around the root balls.

    Results of Water and Foot Packing:   In an effort to save failing seedlings, we went back over beds planted with the New Holland -- (1) applying water on each seedling from our water wagon; (2) aggressively (high psi) foot packing the wet clay soil around each seedling.

    In using this approach to planting, tree survival rates are consistently +90%. When this approach is not followed, tree mortality rates are +90%.

    One final point -- In the days following our water/foot packing, we checked on packing efficiency, again using our "tug test". While the surface clay soils had again become brick hard, the seedlings were tighly secured in the ground (as if encased in concrete). However, seedlings exhibited no stress characteristics and soon began to show new growth.

    Planting on Macro Beds/Mounds:   After initially creating our Macro Beds/Mounds we allowed 6 weeks for the beds to settle before planting. The basis of allowing sufficient time between bed creation and planting are two-fold: (1) allowing the beds to settle, reducing air pockets; (2) time for vegetation rolled into the bed at creation to decompose -- reducing the risk of fungus in bedded soils to develop disease affecting tree seedlings.

    As a result of the greater soil compaction of the Macro Beds/Mounds, significant operational problems occurred using the New Holland Planter. In penetrating the clay soils to create holes for the seedlings, the planting blades/scoops constantly bent -- creating downtime to straighten out or to order new blades/scoops.

    Because of these New Holland operational problems, we went back to the Whitfield Planter, which operated very well in the compacted soil. In using this Pine Planter approach to planting (which included hand watering and foot packing), tree survival rates have been +90%.

    The Nitrogen Deficiency in Clay Soils:   As previously mentioned, it is well established in science literature that CSA soils are deficient in available nitrogen to plants and trees. In the following discussion we wish to be clear that the context of our remarks are not directed at improving tree growth yields (this is a separate discussion) -- our comments are directed at initial tree survival rates.

    After tree seedlings have withstood the initial shock and stress of planting (~7 to 10 days -- checking for new growth), a light hand application of Ammonium Nitrate is applied around the base of each seedling (covering a narrow swath of the full width of the bed, left and right of the seedling). The application rate is one handful of Ammonium Nitrate per seedling. While this methodology deviates from traditional fertilization application, we have seen that mechanized broadcast over entire beds shortly after tree planting (1) greatly accelerates weed growth; and (2) is a waste of money.

    Weed Science and Field Results backs up this approach. Survival rates of trees are significantly enhanced when Ammonium Nitrate is applied to "jump start" a seedling's root system -- allowing the tree to quickly develop against the soon to come weed competition. If a young tree can not dominate over early weed competition, tree mortality or dwarfed growth for years may occur.

    One final note -- when Ammonium Nitrate is applied so closely to seedlings, its imperative that it be done under dry conditions. Under conditions where it immediately rained after fertilization, we have burned seedlings.

    Establishment of Native Plants/Flora on Forest Floor:   As discussed in our Bridge Crop Section, we believe that the stabilization of the forest floor with native plants is critical for:

  • Long-Term Productivity of the CSA Site as a commercial
        Tree Farm (e.g., coppice yields), or
  • Reforestation of the CSA Site into a native Upland (cypress,
        red maple, etc.).
  • As both agriculture-science literature and field research clearly conclude, it is virtually impossible to establish native flora/plants on undeveloped CSA Sites for the following reasons:

  • Dominance of Cogongrass and other Exotic Invasive Plants.
  • Soil Quality (lack of organics, soil compaction, high pH,
        nitrogen deficiency)
  • Extreme variability in soil moisture -- brick dry to swampy.
  • As we continue to state, no "paper studies" are really needed to validate that the concept of using "Bridge Tree Crops" is a solid approach to phosphate mining clay settling area reclamation -- The Site speaks for itself, as native plants are reappearing in mass.

    As our Trees canopy and densely shade, Nature is eliminating harmful Invasives (e.g., Cogongrass on the left) and replacing with Native Plants such as Creeping Dayflower (on the right).

    On every technical agriculture issue needed for successful native plant/flora restoration, the tree crops are doing their intended tasks (controlling cogongrass, building soil organics, reducing soil compaction and pH, increasing available nitrogen, stabilizing ground water levels).


    (1)Mislevy, P., W.G. Blue and C.E. Roessler. 1989. Productivity of clay tailings from phjosphate mining. I. biomass crops. Journal of Environmental Quality 18:95-100.

    Mislevy, P., W.G. Blue and C.E. Roessler. 1990. Productivity of clay tailings from phjosphate mining. II. forage crops. Journal of Environmental Quality 19:694-700.

    Mislevy, P., W.G. Blue, C.E. Roessler and F.G. Martin. 1991. Productivity of clay tailings from phjosphate mining. I. grain crops. Journal of Environmental Quality 20:788-794.