No abstract

Increasing demand for renewable fuel sources has stimulated the need for alternative biomass crops. A study was conducted to determine grain, stover, total biomass, and estimated ethanol yields of annual and perennial crops at two locations in Kansas in 2007 and 2008. Th is study included corn (Zea mays L.) grown continuously and rotated with soybean [Glycine max (L.) Merr.]; fi ve sorghum cultivars, brown midrib (bmr), photoperiod sensitive, sweet, and two dual-purpose forage varieties; and three perennial warm-season grasses, switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and Miscanthus (Miscanthus × giganteus). Corn and sorghum plants were harvested for grain and biomass and sweet sorghum stalks were pressed to extract juices. Perennial grasses were harvested for biomass. Highest grain yields were achieved with corn across both years and locations with yields averaging 10.1 Mg ha -1 . Total biomass yields were greatest for sweet sorghum (32.6 and 28.2 Mg ha -1 in 2007 and 2008, respectively) and photoperiod-sensitive sorghum (26.8 Mg ha -1 in 2007). Sweet sorghum extracted fermentable carbohydrate yields averaged 4.8 Mg ha -1 . Perennial grass biomass yields ranged from 7.7 to 12.8 Mg ha -1 in 2008, the second year aft er establishment. Highest average estimated ethanol yields were achieved with sweet sorghum (9920 L ha -1 ). Th ese results indicate that the highest total biomass and estimated ethanol yields for renewable fuel production can be achieved from sweet sorghum and that perennial grasses were as productive as annual crops at producing biomass in the fi rst 2 yr aft er planting.

Nutrient removal is an important factor that must be considered in lignocellulosic fuel production. Th is study was conducted to determine the macronutrient (N, P, and K) composition of grain and stover, as well as the nutrient removal in grain, stover, and total biomass of annual and perennial C4 crops in northeast Kansas in 2007 and 2008. Crops studied were corn (Zea mays L.) grown continuously or rotated with soybean [Glycine max (L.) Merr.]; fi ve sorghum [Sorghum bicolor (L.) Moench] cultivars, brown midrib (bmr), photoperiod sensitive, sweet, and two dual-purpose forage cultivars; and three perennial warm-season grasses, switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and Miscanthus (Miscanthus × giganteus). Perennial grass yields were from the fi rst two harvests aft er establishment. Yields and total nutrient removal rates were greater for annual crops than for perennial grasses. Perennial grass nutrient concentrations were greatest in the establishment year (2007). Perennial grass yields increased from 2007 to 2008, but nutrient removal was not aff ected by the yield increase. Grain nutrient removal rates were greatest for corn even though nutrient concentrations were less than or equal to those for sorghum grain. Total nutrient removal rates were most aff ected by biomass yield and soil test P levels. Total K removal was greatest for the photoperiod-sensitive, sweet, and dual-purpose forage sorghum cultivars. Th ese results indicate that higher annual crop yields will remove more nutrients than perennial grasses during the grass establishment period.

Although energy crops could eventually supply a growing portion of cellulosic biofuel feedstocks, long-term comparisons of annual and perennial crops are rare. An experiment was established in 2007 near Manhattan, KS, to compare biomass productivity and ethanol yield of perennial and annual crops. Perennial crops included three C4 grasses: switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and miscanthus (Miscanthus sacchariflorus). Annual C4 crops were corn (Zea mays L.) in two rotations: continuous and rotated with soybean [Glycine max (L.) Merr.]; and five types of sorghum [Sorghum bicolor (L.) Moench]: photoperiod sensitive, sweet, dual purpose (grain and biomass), brown mid-rib, and grain; all rotated with soybean. Annual crops produced 7 Mg ha-1 yr-1 more biomass than perennial crops throughout 11 yr, with sweet sorghum exceeding 22 Mg ha-1 yr-1 , and 12 m 3 ha-1 yr-1 of ethanol. Biomass yield of miscanthus approached 14 Mg ha-1 yr-1 , essentially the same as for several annual crops but with half as much fertilizer nitrogen. Annual ethanol production from miscanthus and switchgrass was 3.6 m 3 ha-1 yr-1 , half as much as that of several annual crops that produced similar biomass yields. Big bluestem consistently produced the least biomass and ethanol, less than 7 Mg ha-1 yr-1 and 1.7 m 3 ha-1 yr-1 , respectively. Rotated corn averaged 7.1 m 3 ha-1 yr-1 of ethanol. Eleven years of results indicate that annual corn and sorghum crops as well as perennial grasses such as miscanthus and switchgrass could play a role as potential bioenergy feedstocks in diversified production systems.

Increasing bioenergy production will result in increased by‐products which will need proper disposal methods to prevent economic and/or ecological problems. Land application has potential for disposal and/or nutrient cycling if these by‐products have crop nutritive value. Our objective was to compare the fertilizer effects of two by‐products of bioenergy production, dry distillers grains with solubles (DDGs) and charcoal with urea in corn (Zea mays L.) and evaluate nutrient uptake. Treatments were DDGs under no‐till and tilled at four location‐years and charcoal under no‐till and tilled at three location‐years. No‐till urea was used as a baseline at all location‐years. Nitrogen rates ranged from 0 to 180 kg N ha−1. All materials were spring applied before tillage and planting. Corn yields for DDGs and urea were similar across tillage treatments and locations. Corn yields over all charcoal rates and tillage treatments were the same as 0 kg N ha−1. The charcoal, because of immobilization or lack of decomposition, did not contribute to the corn N nutrition. Neither material showed any negative effects on the corn yields. Stalk N, P, K, and grain N followed expected trends and had few effects compared with those from urea. Land application of DDGs and charcoal has merit for disposal/N cycling with DDGs being preferred for its N contribution.