Sustainability of a Short-Rotation Woody Biofuel System Compared to Grass Biofuel and Grain Cropping Systems

Sustainability of a Short-Rotation Woody Biofuel System Compared to Grass Biofuel and Grain Cropping Systems

Summary

Water quality equipment has been installed at the Centralia Research Farm and samples are taken regularly. Lab analyses for sediment, nutrient, and herbicide losses are ongoing. Analyses of runoff and water quality data have not been done at this time since the cropping systems are in their infancy.

The Switchgrass plots are now well established on the Centralia site. Yield in 2013 was typical for other studies on claypan soils sites ranged between 5 and 6 tons/acre, with very little difference seen between landscape positions. 

In 2013, miscanthus was planted on the plots previously planted in willows. Establishment was inhibited by a cover crop (cereal rye) allelopathy on the miscanthus. Attempts to replant in late-June with green rhizomes failed. The failure was attributed to insufficient energy reserves in the rhizomes to support vegetative growth. Some replanting will be required in 2014.

One positive result of incorporating miscanthus into this project has been the addition of two key studies; one on rhizome quality and the other on the effects of nitrogen on subsequent growth and development. 

Objectives/Performance Targets

Given project modifications, expected outputs for the second year were: (1) successful establishment of the miscanthus plots, (2) collection and analyses of runoff and water quality data from all plots, (3) provide project information through traditional media as well as eXtension, and (4) host a fall workshop on establishing energy crops where a minimum of 10 educators and 20 producers will attend.

Accomplishments/Milestones

Water quality equipment has been installed at the Centralia Research Farm and samples are taken regularly. Lab analyses for sediment, nutrient, and herbicide losses are ongoing. Analyses of runoff and water quality data have not been done at this time since the cropping systems are in their infancy.

The Switchgrass plots are now well established on the Centralia site. Yield in 2013 was typical for other studies on claypan soils sites ranged between 5 and 6 tons/acre, with very little difference seen between landscape positions. 

In 2013, miscanthus was planted on the plots previously planted in willows. Establishment was inhibited by a cover crop (cereal rye) allelopathy on the miscanthus. Attempts to replant in late-June with green rhizomes failed. The failure was attributed to insufficient energy reserves in the rhizomes to support vegetative growth. Some replanting will be required in 2014.

One positive result of incorporating miscanthus into this project has been the addition of two key studies; one on rhizome quality and the other on the effects of nitrogen on subsequent growth and development. 

The objective of the rhizome quality study is to quantify the impact of rhizome quality and depth to the claypan horizon on miscanthus emergence and early growth. The first year of this study is being conducted at the University of Missouri South Farm located near Columbia. Rhizome quality was characterized by measuring the mass, total length (found by summing the lengths of all protruding parts), diameter, and number of active buds. In order to insure accuracy of measurements each rhizome was rinsed in water to cleanse it of soil and debris. Rhizomes were selected at random from the population. Priority was given to healthier looking rhizomes for both characterized rhizomes and those that were not part of the study, which essentially act as controls.

The first week following planting, characterized rhizomes were visited every other day to record new shoot emergence. Visits to the site were lengthened to two weeks and then monthly intervals as new shoot emergence slowed. Yield data were obtained for each characterized plant at the end of the growing season. Basal circumference was also taken prior to harvest. Weekly soil temperature and seasonally soil moisture measurements were also taken during the initial months following planting. In the spring of 2014 mortality rates among the characterized plants will be evaluated. 

The first year of the rhizome quality study was a success in terms of establishment and meaningful data obtained. The following graphs provide some preliminary findings of how biomass production related with the quality of miscanthus rhizome (Figure 3). The bar chart below also shows the relation between average depths to claypan to biomass produced. In general, initial growth and establishment was impacted little by rhizome quality or depth to the claypan. 

We will be unable to repeat this study in 2014 at the Columbia location, thus the second-year experiment will be conducted at the Centralia Research Farm on the plots previously occupied by the willow plants. This study will be incorporated into the 2014 replanting mentioned above. Three plots (one from each block) will be used for this experiment. Rhizomes will be characterized as before, planted, and have measurements taken on them as described for SPARC previously. Three randomly spaced subplots for each landscape position (27 total subplots) within a plot will have four characterized rhizomes (108 rhizomes total). The rhizomes will be spaced at 76 cm in a quadrat, planted to a depth of 10 cm and flagged. Measurements will be the same as those made at the Columbia location.

The nitrogen study is to assess miscanthus N needs on claypan soils, and was conducted as two separate experiments. The first experiment evaluates varying levels of applied N on a mature miscanthus stand grown at the Columbia site. For this study, a block of miscanthus was planted in 2007 with plots overlaid for N rate treatments in 2012. A randomized complete block design was used to further divide the area into three main blocks (i.e., reps), each block was then divided into four separate main plots of 3.7 m x 13.7 m dimensions. Treatments of 0, 40, 80 and 120 lbs N/ac. were hand applied once in 2012 shortly after green-up (around May). This year no additional N fertilizer was applied because N build-up in the soil and miscanthus rhizome was thought sufficient to sustain this year’s growth while still providing treatment difference from N fertilizer but down in 2012. SPAD chlorophyll readings were taken at four-week intervals throughout the growing season (June, July, August, and September). In mid-December, each plot was harvested individually to determine yield. Subsamples were taken to determine moisture and nutrient content.

The second experiment is also an N rate experiment being conducted over the 2012-2015 growing seasons at Columbia site, as well as two producer fields; one in Cooper County (Weller silt loam) and one in Moniteau County (Menfro silt loam). Each of these sites were selected because they represent the unique characteristics of claypan soils, which exhibit a pronounced enriched-clay soil horizon, which is restrictive to root growth and grain production and in turn impacts grain yield negatively when topsoil overtop this claypan is eroded. Each of these sites had existing one-year-old miscanthus stands and were organized using a randomized complete block design with four main blocks divided into six separate plots. Plot dimensions varied between locations and were as follows: South Farm, 3.8 m x 9.1 m; Cooper and Moniteau County, 3 m x 4 m. Treatments of 0, 30, 60 and 120 lbs N/ac. were applied shortly after green-up in early May. Similar to the first experiment, SPAD chlorophyll readings were taken at four-week intervals throughout the growing season (June, July, August, and September). Again, in mid-December plots were harvested to determine yield, and subsamples were taken to determine moisture and nutrient content.

Miscanthus yield results are still being verified and cannot be provided at this time. However from general observation of the data, there appears to very little yield response of miscanthus to N fertilization. This could be due in part to the perennial nutrients that were recycled from last year’s growth, which supplied adequate nutrients even for those treatments with no N. A second year of data will be necessary to further strengthen this hypothesis. Early season measurements of chlorophyll content using SPAD readings were found to be impacted by N rates (Figure 4). However, as the season progressed, N rate treatments diminished.

• Figure 2. 2013 switchgrass yields, by landscape position, at the Centralia Research Farm.
• Figure 3. Biomass production in relation to rhizome quality as a function of mass, total length of all protruding parts, diameter, and number of active buds.
• Figure 4. SPAD readings to measure chlorophyll content, by location and N treatment taken four times throughout the growing season.
• Figure 1. Foreground shows surface water sampling equipment installed at the Centralia Research Farm. In the background miscanthus is being planted on the larg, 0.85-acre plot.

Impacts and Contributions/Outcomes

Farmers and educators will increase their knowledge of the soil-enhancing benefits of producing dedicated energy crops on marginal claypan soils, and they will learn how to produce these crops. Early-adopter farmers will use the information to successfully establish sustainable supplies of biomass that will support established bioenergy markets in mid-Missouri, such as the University of Missouri’s combined heat and power (CHP) plant in Columbia, or Show-Me Energy in Centerview, Missouri. The less intensive management in producing these energy crops compared to conventional grain cropping systems will reduce soil erosion and improve soil quality.

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