Have you been driving in rural eastern Iowa lately? You might have noticed those choppers and wagons a few weeks ago harvesting miscanthus fields, but what have you seen most recently? Planters! You might have noticed that they don’t look like the grain planters most of us are used to seeing. Miscanthus x giganteus is a perennial grass that does not produce a viable seed; therefore, planting methods are different compared to our conventional row crops. Today, we’ll focus on rhizomes, the most common planting material for miscanthus in Iowa.
Miscanthus rhizomes
Rhizomes (Figure 1) are underground stem segments that are used to generate new plants. They also store nutrients that are recycled between the shoot and roots each year, minimizing the need to apply fertilizer. The rhizomes used in the Iowa Biomass Fuel Project are grown in “mother fields” in North Carolina by a company called AGgrow Tech. These rhizomes are dug anytime between the first and the last frost, when nutrient contents are at their highest. Healthy rhizomes should be light colored and firm with at least 3 nodes, noted by the arrows in Figure 1.[1]
Field preparations
Field site preparations vary slightly if the field is in pasture/perennial vegetation or row crop production. We do not generally recommend converting pasture or set-aside land to miscanthus, but if it is to be done, a year in herbicide tolerant soybean is recommended to fully eliminate competing pasture/perennial vegetation. Few to no changes are needed if the field is already in crop production. We recommend fields be tilled to at least 5 inches to allow the planter to fully cover rhizomes.[2] Soil pH should be between 5.5 and 7.5, and nitrogen, phosphorus and potassium at planting should be at levels similar to those recommended for corn.
Planting
In Iowa, miscanthus planting can begin when soil temperatures are 50 ℉. Rhizomes are tolerant of frost before shoots emerge, which is typically about three weeks after planting, when soil temperatures are consistently in the upper 50s. Currently, rhizomes are being planted using specialized planters (AGgrow Tech’s ACCU DROP ® planter) for commercial fields (Figure 2). The recommended planting depth for rhizomes is at least 4 inches; this prevents the rhizomes from being exposed to the air and drying out. A planting density of 5000-12000 plants per acre, or about 1000 lbs of rhizomes per acre is recommended. Our work has shown that on average, 20-30 percent of the rhizomes will die or not grow within the first year.[3] The final and optimal stand density at maturity is 4000-6000 plants per acre. Planting miscanthus can seem pricey at first: typical costs are in the $1,000 per acre range, but considering that the crop can last 15-30 years and has few inputs, the annual operating costs are actually far below typical Iowa grain crops.
Iowa State CABBI and Potholes projects
Miscanthus planting at the CABBI and Potholes project sites, right here in Central Iowa, will hopefully be happening today and tomorrow in collaboration with AGgrow Tech!
[1] “Giant Miscanthus Establishment”. Iowa State University Extension and Outreach. Accessed December 17, 2018. https://store.extension.iastate.edu/Product/Giant-Miscanthus-Establishme...
[2] “Planting and Managing Giant Miscanthus (Miscanthus x giganteus) in Missouri for the Biomass Assistance Program (BCAP)”. United States Department of Agriculture Natural Resources Conservation Service. September 2011. Accessed December 17, 2018.
[3] Giant Miscanthus Establishment. Iowa State University Extension and Outreach. Accessed December 17, 2018. https://store.extension.iastate.edu/Product/Giant-Miscanthus-Establishme...