Miscanthus has for the temperate American Midwest likely the largest yield potential for biomass of the contending crops.  The plant does pose the lignin and cellulose problems, but confidence is high those plant products will get solutions for fuel production.

Miscanthus Growth by the University of Illinois. Click image for the largest view.

Its in the field, where the production happens getting sunlight and soil nutrients into biomass where the research needs done, and the University of Illinois is busy doing just what’s needed for farmers to seriously look at and learn the optimal production practices with careful observation of the plants behavior in the field.

A recent study over 4 years analyzed water quantity and quality in plots of miscanthus, switchgrass, corn, and soybeans and found that miscanthus used substantially more water, but reduced the potential for nitrogen pollution to water bodies.

Greg McIsaac, environmental scientist in the College of Agricultural, Consumer and Environmental Sciences at UI said in the University press release, “We found that miscanthus tends to dry out the soil much more than corn, soybeans, or switchgrass later in the growing season. This would likely reduce runoff, stream flow and surface water supplies later in the summer and in early fall, when streams are typically at their lowest. It could reduce the amount of water available to those who are downstream in late summer and early fall.”  The authors paper reports the evapotranspiration (the loss of water drawn from the soil exiting from the plants leaves) of miscanthus was about 4 more inches of rain compared to corn and soybean crops.

Switchgrass on the other hand behaves like miscanthus early in the growing season, drying out the soil. Then it goes into a reproductive mode and uses very little water in the late summer and fall. McIsaac said that miscanthus’s impact on water supply might be small if it is planted on only a few acres in a watershed. “The severity of the impacts will likely vary depending on the nature of the soils and climatic conditions. In areas where water is in short supply, switchgrass may be preferable, understanding that switchgrass creates much less biomass than miscanthus,” he said.

With the water flow in mind McIsaac said, “It will likely be in the farmer’s economic interest to plant the most productive crop, which may also use more water than their current crops. When and where this occurs over significant areas, downstream water users should consider how it is going to influence their water supply. They may need to develop plans to address more frequent water shortages, or perhaps attempt to influence the planting decisions through incentives or policy. It is something to be aware of and plan for if miscanthus or a similar water-demanding crop becomes economically attractive to farmers.”  There is a basis for a fight, but just how much more water is going to be consumed?

McIsaac also offers the flip side, the fact that both miscanthus and switchgrass use more water early in the growing season than corn and soybeans could be seen as a benefit because flooding is often a problem that time of year. Drying out the soil earlier in the spring would reduce runoff from spring rains, he said, and thus reduce flood flows.  The realization that the balance is worthy of attention is a welcome perspective.

The study also looked at how nitrogen moves or “leaches” into the ground water beneath the four crops. With corn and soybeans where the field has tile drainage, the fertilizer and soil organic nitrogen gets converted to nitrate, which is highly soluble and moves with the water to the tile drains. From there it moves out to the ditches and streams, causing problems for drinking water supplies and contributing to the hypoxia in the Gulf of Mexico.

In this area both the miscanthus and switchgrass plots in the study received no added fertilizer and grew vigorously without it.  Not adding nitrogen can save a noteworthy amount of money for the inputs cost of production. Thus it wasn’t surprising that the unfertilized miscanthus and switchgrass had much lower leaching than soybeans or fertilized corn.

McIsaac explains that there are several factors at work, not just the absence of applied fertilizers. “The roots in perennial grasses go deeper into the soil. They’re more extensive and they are active earlier in the growing season – so if we had a perennial corn, it might behave more like these grasses. But even with soybeans, where we also didn’t apply fertilizer, the amount of leaching was almost as high as with corn. So it’s not just the absence of fertilizer, it’s also the perennial roots that retain more soil nitrogen.”

“We did not apply fertilizer to miscanthus or switchgrass because the study was designed to look at a low-input biofuel,” McIsaac said. “The results showed that you can get high productivity without fertilizing miscanthus, at least for the first three to four years. It is likely that if you apply fertilizer to miscanthus and switchgrass, there would be more leaching than what we saw in our study, with no application. But because of the root activity, I would expect fertilized miscanthus and switchgrass to leach less than fertilized corn. To be certain, this needs further study.”

These answers offer more questions.  Miscanthus isn’t expected at this time to be planted and harvested every year for eternity.  Some form of crop rotation is going to be needed.  Just what the other major fertility elements, potassium and phosphorus are used isn’t addressed.  These two elements can be quite expensive.

Yet the deep perennial roots offer a way to introduce carbon deeper into the soils, a major benefit for the next crop in the rotation sequence as well as answer some environmental concerns about carbon in the air.  The tall swaying plant will bring airborne soil building material to ground as well as reduce the soils getting born into the air or washed away with water flow.  Both miscanthus and switchgrass offer impressive benefits with the attributes of perennial growth.

The questions are still out there.  We now know more – both miscanthus and switchgrass are going to need substantial amounts of rain to make biomass.  Just how much is optimal, when over the course of the growing season the rain is ideal and the consequences of errant rain delivery are yet to be answered.  One would hope the UI team would connect out west where it’s dryer and learn more as rain is an input of irregular delivery in both the timing and the quantity.  Industry is going to need much more information before either miscanthus or switchgrass can command land area and industrial investment commitments.

The paper’s authors in addition to McIsaac are Mark B. David, and Corey A. Mitchell, which is published in the September-October edition of the Journal of Environmental Quality titled Miscanthus and Switchgrass Production in Central Illinois: Impacts on Hydrology and Inorganic Nitrogen Leaching.

Good work gentlemen – keep it going.


2 Comments so far

  1. RMida on September 16, 2010 9:30 AM

    Find out more information on Biomass Energy
    or download our Biomass Fact Sheet.

    Also see our relevant page on Biofuels.

  2. small business grants on November 8, 2010 6:39 AM

    Superb blog post, I have book marked this internet site so ideally I’ll see much more on this subject in the foreseeable future!

Name (required)

Email (required)


Speak your mind