PERENNIAL FUEL, FEED, AND CEREAL: HIGH DIVERSITY PERENNIALS FOR BIOFUEL AND INTERMEDIATE WHEATGRASS FOR GRAIN AND FORAGE

Abstract

Perennial crops may counteract negative effects of annual agriculture, such as carbon emissions, water pollution, and erosion, and systems are being developed that supply fuel, feed, and cereal. One source of fuel is cellulosic ethanol from perennial sources, and one source of feed and cereal is intermediate wheatgrass. Regarding cellulosic ethanol, markets are not currently supported by policy, making adoption of these systems largely a matter of carbon storage benefit. Regarding intermediate wheatgrass, little is known about its nitrogen balance and reproductive morphology, complicating long-term management. In the perennial cellulosic ethanol system, I measured aboveground biomass, change in total soil C, soil microbial biomass, and extracellular enzyme activity with and without nitrogen in four species mixture treatments ranging from 1-24 native species at four sites across Minnesota. I found no overall trends, possibly due to variation across sites or due to minimal management over the 12 years since establishment. Over time, soil carbon increased in the shallower depths at one site and decreased in the deeper depths at two sites. I measured plant, tiller, and rhizome densities in plants from sown seed, vegetative propagation, or seed shatter at four sampling times in 1 year old and 2 year old intermediate wheatgrass stands. Tiller density was similar in both stands, but rhizome and propagule densities were greater in the 2 year old stand. Likely, tiller replacement and death rates are equal, but vegetative propagation increases between years, increasing plant population, possibly leading to competition and affecting long-term yield. Also in intermediate wheatgrass, I measured nitrogen in shoot, root, and grain tissue along with soil mineral and mineralized nitrogen in three nitrogen treatments (80 kg N ha-1 in spring, 40-40 kg N ha-1 in spring and summer, and unfertilized control) at four sampling times in 1 year old and 2 year old stands. The spring treatment had greater root nitrogen, but it also had greater lodging. The late fall sampling had the greatest soil nitrogen, and since soil mineral N was low at that time there was likely an influx of organic nitrogen, likely due to root turnover.