Energy Crop Agriculture -- Notes from the Field.

Agriculture

Pigweed Control: An issue that continues to plague farmers here in Florida and the Southeast is glyphosate resistant weeds, specifically Palmer Amaranth. A technical service representative for Syngenta, suggest farmers apply a fall weed control treatment now in order to get a head start for next year’s crop. We've had decent control using Dual Magnum

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Dry Weather: With little rainfall in recent weeks, meteorologists from the South Florida Water Management District (SFWMD) reported that last month was the driest October in South Florida since record keeping began in 1932. The low monthly rainfall total, coupled with seasonal forecasts of exceptionally dry conditions, underscores the risks of farming, especially on non-irrigated lands where our sweet sorghum yields are all over the map -- ~40 green tons per acre per harvest, to ~20 green tons per acre per harvest.

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Ergot in Sweet Sorghum: A major misconception of Farmers and non-Farmers (especially here in the Southeast and Florida) is that growing sweet sorghum for ethanol feedstock will be a "piece of cake". This belief is based primarily on the success of growing forage sorghum for decades. But as more field experience develops, farmers will be shocked that forage and sweet sorghum are very different crops. One very serious problem is a plant disease called ergot, which attacks the unfertilized ovaries in the sorghum heads. In our field experience, we've seen Brix (sugar content) go from ~18 in healthy plants to 0 in just 5 days. Ergot can hit with either high humidity, cooler temperatures, or a combination of the two. We are working with seed producers, farming equipment companies (i.e., John Deere), and applying weed control to near-by Johnsongrass (and also Cogongrass) areas to address this devastating problem.

Soil Micro-Nutrients: This is a good lesson in never really trusting anybody for advice unless they have "dirt underneath their fingernails" -- which are typically the "Old Timers". In walking our fields with typically ~15 foot height sorghum, we always saw what we describe as "crop circles" -- circular or oblong shaped areas where the sorghum was dwarf of a couple of feet tall. After extensive soil testing, we added a micro-nutrient pack to our fertilizer (N) regiment, but the problem still remained. Talking to an "Old Timer" who had worked similar fields, we applied a foliar manganese application -- problem solved!

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Phosphate Mining and Climate Change

Land Use and Mining

While today's blog treads into the subject of phosphate mining in central Florida, the bigger picture involves all surface mining (e.g., mountain top removal for coal), and an even bigger picture of large land use development anywhere on our Planet. The following discussion is neither pro or anti mining or land development, but raises a question "Don't we need to talk about something?" -- where the "Something" is Climate Change.

In arguments (and legal fights) over mining or land development, the major environmental issues usually involve topics of water (pollution, use) and habitat loss, with wetlands being the focal point. Never (at least here in Florida) have we seen the subject of Climate Change even enter into the discussion of land use development (like mining).

According to the U.S. Army Corps of Engineers, phosphate mining has occurred on 1.32 million acres (~2,100 square miles) in central Florida. Additional mining is being requested for ~100,000 acres. And here is the problem -- in mining 1.42 million acres, has this resulted in a significant Climate Change event? Nobody really knows, because the question has never been asked.

In phosphate mining, has the greenhouse gas mass balance (i.e., the release of primarily CO2 through land clearing and soil disturbance and the carbon capture post-mining practices of land reclamation) been: (1) relatively carbon cycle neutral, or (2) resulted in large carbon deficits?

One science based scientific citation that can be used in an initial discussion is work performed by Kimble, Heath, Birdsey, and Lal (The Potential of U.S. Forests Soils to Sequester Carbon and Mitigate the Greenhouse Gas Effect). The below table presents an estimate for total carbon capture (above and below ground) associated with forests which would be representative of pre-mined phosphate lands.

Type of Forest (Pre-Mining):	C in Biomass (t/ha)	C in Dead Mass (t/ha)1	Soil Organic C (1-m depth)(t/ha)2	Total Forest C (t/ha)
Oak-Gum-Cypress	81.1	26.5	152.2	259.7

(1) Dead mass includes standing dead trees, down dread trees, and forest floor.
(2) Soil includes both mineral soil and organic soils (i.e., histosols).

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Estimating the carbon released from mining 1.42 million acres (from the above proxy estimates from Kimble, et al.) results in ~548 million tons of CO2 released. Putting 548 million tons of CO2 into perspective -- would be the approximate CO2 release equivalents of:

-- Operating a coal power plant like TECO's Polk Power Station for 515 years.

-- Operating all coal fired power plants in Florida for ~8 years.

-- Operating all power plants in Florida (coal, oil, gas) for ~4 years.

-- Approximately 3 years of total volcanic activity on the Earth.

Of course, the above illustrations only reflect one part of the total greenhouse gas mass balance -- the initial emissions from land clearing and soil disturbance. According to landmark research on phosphate mined soils performed by the U.S. Department of Energy's Oak Ridge National Lab, carbon capture/sequestration on heavily forested post-mined lands and/or wetlands can be dramatic. However for lands reclaimed to pasture, the majority of the sequestered carbon is soon converted back to CO2 through respiration (Murray, Economics of Forest Carbon Sequestration, 2003).

In conclusion, it is believed that the topic of Climate Change needs to be on the "Table" whenever large land use applications (such as mining) are being decided. Clearly it is impossible to develop any type of "Actions" if the magnitude of the Climate Change concern is simply not known -- where in our opinion, the best actions are always voluntary and market based solutions.

As Mike Myers used to say on Saturday Night Live!, "feel free to discuss amongst yourselves."

(A draft of the letter to the U.S. Army Corps of Engineers is available for comments).

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