Donald M. Vietor

Compartmentation of sucrose during radial transfer in mature sorghum culm

BackgroundThe sucrose that accumulates in the culm of sorghum (Sorghum bicolor (L.) Moench) and other large tropical andropogonoid grasses can be of commercial value, and can buffer assimilate supply during development. Previous study conducted with intact plants showed that sucrose can be radially transferred to the intracellular compartment of mature ripening sorghum internode without being hydrolysed. In this study, culm-infused radiolabelled sucrose was traced between cellular compartments and among related metabolites to determine if the compartmental path of sucrose during radial transfer in culm tissue was symplasmic or included an apoplasmic step. This transfer path was evaluated for elongating and ripening culm tissue of intact plants of two semidwarf grain sorghums. The metabolic path in elongating internode tissue was also evaluated.ResultsOn the day after culm infusion of the tracer sucrose, the specific radioactivity of sucrose recovered from the intracellular compartment of growing axillary-branch tissue was greater (nearly twice) than that in the free space, indicating that sucrose was preferentially transferred through symplasmic routes. In contrast, the sucrose specific radioactivity in the intracellular compartment of the mature (ripening) culm tissue was probably less (about 3/4s) than that in free space indicating that sucrose was preferentially transferred through routes that included an apoplasmic step. In growing internodes of the axillary branch of sorghum, the tritium label initially provided in the fructose moiety of sucrose molecules was largely (81%) recovered in the fructose moiety, indicating that a large portion of sucrose molecules is not hydrolysed and resynthesized during radial transfer.ConclusionDuring radial transfer of sucrose in ripening internodes of intact sorghum plants, much of the sucrose is transferred intact (without hydrolysis and resynthesis) and primarily through a path that includes an apoplasmic step. In contrast, much of the sucrose is transferred through a symplasmic path in growing internode (axillary branch) tissue. These results contrast with the probable symplasmic path in mature culm of the closely related species, sugarcane. Phylogenetic variability exists in the compartmental path of radial transfer of sucrose in culms of the andropogonoid grasses.

Capacity of biochar application to maintain energy crop productivity: soil chemistry, sorghum growth, and runoff water quality effects.

Pyrolysis of crop biomass generates a by-product, biochar, which can be recycled to sustain nutrient and organic C concentrations in biomass production fields. We evaluated effects of biochar rate and application method on soil properties, nutrient balance, biomass production, and water quality. Three replications of eight sorghum [ (L.) Moench] treatments were installed in box lysimeters under greenhouse conditions. Treatments comprised increasing rates (0, 1.5, and 3.0 Mg ha) of topdressed or incorporated biochar supplemented with N fertilizer or N, P, and K fertilizer. Simulated rain was applied at 21 and 34 d after planting, and mass runoff loss of N, P, and K was measured. A mass balance of total N, P, and K was performed after 45 d. Returning 3.0 Mg ha of biochar did not affect sorghum biomass, soil total, or Mehlich-3-extractable nutrients compared to control soil. Yet, biochar contributed to increased concentration of dissolved reactive phosphorus (DRP) and mass loss of total phosphorus (TP) in simulated runoff, especially if topdressed. It was estimated that up to 20% of TP in topdressed biochar was lost in surface runoff after two rain events. Poor recovery of nutrients during pyrolysis and excessive runoff loss of nutrients for topdressed biochar, especially K, resulted in negative nutrient balances. Efforts to conserve nutrients during pyrolysis and incorporation of biochar at rates derived from annual biomass yields will be necessary for biochar use in sustainable energy crop production.

CGA-43089 effects on metolachlor uptake and membrane permeability in grain sorghum (Sorghum bicolor)

Phytotoxicity of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] toward grain sorghum [Sorghum bicolor (L.) Moench] increased as soil moisture increased. This was found with both unprotected sorghum and sorghum protected with 1.25 g CGA-43089 [α([cyanomethoxy]imino)benzeneacetonitrile] per kg of seed. However, under all conditions, metolachlor was less phytotoxic to protected sorghum than to unprotected sorghum. Metolachlor in sorghum coleoptiles increased as soil water increased. The rate of absorption of metolachlor and the total amount accumulated by excised sorghum coleoptiles was decreased by CGA-43089. Initial uptake of leucine by excised sorghum coleoptiles was decreased by metolachlor or metolachlor plus CGA-43089 but, after 24 h, uptake of leucine was increased by these treatments. Leucine incorporation into protein by coleoptiles was increased after 24 h treatment with CGA-43089. The apparent competitive effect of CGA-43089 on the absorption of metolachlor was most evident in the roots. Leakage of photosynthate from roots was highest following treatment with both CGA-43089 and metolachlor. Metolachlor did not increase leakage of labeled carbon from roots as compared with the control. These data indicate that the decreased rate of uptake of metolachlor in the presence of CGA-43089 was not a direct effect on cell permeability.

Metabolism of Sucrose During Storage in Intact Sorghum Stalk

Grasses of the Andropogoneae, such as sorghum (Sorghum bicolor [L.] Moench) and sugarcane (Saccharum spp.), accumulate large amounts of harvestable sucrose in the stalk. Sucrose is translocated from the leaves, yet the metabolic fate of sucrose up to and during storage in the stalk is uncertain. This study determined whether sucrose is necessarily routed through inversion and hexose-phosphate isomerization for storage in cells of the intact stalk. Sorghum stalks were dual-infused with [U-14C]sucrose and [fructose-1-3H(N)]sucrose during stages of sucrose accumulation. Unperturbed tissue was used for subsequent sugar analyses. Solutes in cell extracts were separated sequentially through enzymatic conversion and ion-exchange removal of the reaction products. The hexose moieties of sucrose were analyzed separately. A mean of 95% of recovered 14C was in sucrose. In sucrose, 46% of 14C and 77% of 3H were recovered in the fructose moiety. The significant retention of asymmetry in tritium labeling of sucrose indicates that a cycle of cleavage and resynthesis did not dominate sucrose accumulation in cells of the sorghum stalk.

Effect of Turfgrass Establishment Practices and Composted Biosolids on Water Quality

Land application of composted municipal biosolids (CMB) enhances soil physical properties and turf establishment. Yet large, volume-based rates of CMB can increase nonpoint source losses of sediment and nutrients from urban soils to surface waters. The objectives were (i) to compare runoff losses of sediment, N, P, and organic C among contrasting establishment treatments for bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy, var. Tifway] and (ii) to evaluate relationships between runoff and soil measurements of N, P, and organic C. Three replications of seven establishment treatments were installed on an excavated slope (8.5%) under field conditions. Five treatments comprised sod transplanted from Tifway bermudagrass grown with and without CMB on soil with and without incorporation of CMB. Two other treatments were composed of Tifway sprigged in soil with and without CMB. Runoff from seven natural rain events was channeled into collection tanks for sampling and analysis. Runoff concentrations and mass loss of dissolved P and organic C forms were greater for CMB-amended sod than for sprigs planted in soil with or without CMB or treatments comprising sod established without CMB. In addition, a linear relationship (R(2) = 0.87) was observed between water extractable soil P of sodded and sprigged treatments and concentrations and mass losses of dissolved P in runoff. Transplanted sod reduced sediment loss compared with sprigged treatments and incorporation of CMB reduced sediment loss from sprigged treatments. Incorporation of CMB within soil on which sod grown without CMB was transplanted proved the best option for achieving benefits of CMB while reducing nutrient runoff loss compared to sod transplanted from Tifway grown with CMB.

Biosolid and Alum effects on runoff losses during turfgrass establishment

Large, volume-based rates of composted biosolids (CB) enhance turfgrass establishment and soil properties, but nonpoint-source runoff losses could occur during production and after transplanting of sod. The objective was to evaluate runoff losses of N, P, sediment, and organic C during establishment of sprigs or transplanted sod of Tifway bermudagrass (Cynodon dactylon L. Pers. X C. transvaalensis Burtt-Davey) with and without CB and aluminum sulfate (Alum). Four treatments comprised Tifway sprigged in a sandy loam soil with and without incorporation of 0.25 m(3) CB m(-3) soil and Alum. In four additional treatments, sod transplanted from Tifway grown with and without CB was established with and without a surface spray of Alum. During early establishment, CB incorporated in soil before sprigging reduced runoff loss of sediment and total N to amounts comparable to transplanted sod. In contrast, mean runoff losses of total dissolved P and soluble-reactive P (SRP) were more than 50% greater for CB-amended sod than for fertilizer-grown sod or Tifway sprigged in soil with or without CB. Yet, the surface spray of Alum reduced runoff loss from sod more than 88% for SRP and 41% for dissolved organic C. Both surface sprays and incorporation of Alum effectively reduced SRP runoff loss from CB, soil, and turfgrass sources during turfgrass establishment.

Runoff and Nutrient Losses from Constructed Soils Amended with Compost

Composted organic materials used to stabilize roadside embankments in Texas promote rapid revegetation of soils disturbed by construction activities. Yet, adding compost to soil may increase total and soluble plant nutrients available for loss in runoff water. Composted municipal biosolids and dairy manure products were applied to soils in Texas according to prescribed Texas Department of Transportation specifications for stabilizing roadside soils. The specifications included a method for incorporating compost into soils prior to seeding or applying a compost and woodchip mix over a disturbed soil and then seeding. Applying compost and woodchips over the soil surface limited sediment losses (14 to 32 fold decrease) compared to incorporating compost into the soil. Yet, the greatest total phosphorus and nitrogen losses in runoff water occurred from soils where the compost and woodchip mix was applied. The greatest losses of soluble phosphorus also occurred when the compost and woodchip mix was applied. In contrast, nitrate-nitrogen losses in runoff were similar when compost was incorporated in the soil or applied in the woodchip mix. Compost source affected the nutrient losses in runoff. While the composted municipal biosolids added greater nutrient loads to the soil, less nutrient loss in runoff occurred.

Optimizing the Logistics of a Mobile Fast Pyrolysis System for Sustainable Bio-crude Oil Production

The GIS methods used to identify optimum locations for mobile pyrolysis units in the North Central (NC) region of the U.S. are presented in this paper. Optimum locations were based on feedstock availability. The feedstocks used in the study were corn stover and bioenergy sorghum. For corn stover, 10 year (1999-2008) average corn grain production values were determined for each county in the NC region. Feedstock harvest rates were limited to 25% of the available corn stover leaving 75% for erosion control and soil improvement. LaSalle County, Illinois, was used as a pilot study for the corn stover analysis. For bioenergy sorghum, it was assumed that the production rate was 15 Mg/ha and that bioenergy sorghum would be planted in place of grain sorghum. It was assumed that 100% of the bioenergy sorghum would be harvested for pyrolysis feedstock. ArcGIS and ModelBuilder were used for this feedstock assessment study. A square grid was placed over a map of fields planted with corn and sorghum in 2008. The size of the harvest grid was 6,200 x 6,200 m for the corn stover and 20,000 x 20,000 m for the bioenergy sorghum. The sizes of the harvest grids were based on, 1) the mobile pyrolysis unit requires feedstock at a rate of 80,000 lbs/day, and 2) the mobile pyrolysis unit would remain in place for 6 months. It was also assumed that the mobile pyrolysis unit would be located in the center of the grid and that the average feedstock hauling distance from the field to the mobile unit would be one half the grid size. Therefore hauling distances were 3,100 m for corn stover and 10,000 m for bioenergy sorghum. These short feedstock hauling distances demonstrate a primary advantage of mobile pyrolysis units over a central bioenergy plant. The top 100 locations for corn stover feedstock availability were determined with 57 sites in Illinois, 29 in Nebraska, and 14 in Iowa. The top 50 locations for bioenergy sorghum feedstock availability were also determined with 35 sites in Nebraska and 15 in South Dakota.

Cycling of Biosolids through Turfgrass Sod Prevents Sediment and Nutrient Loss

Land application of large, volume-based rates of municipal biosolids (MB) enhances soil physical properties and provides an alternative to disposal in landfills. Yet, topdressing or incorporation of the volume-based rates can increase non-point source losses of sediment and nutrients from excavated soils to surface waters. Cycling of MB through turfgrass sod produced on agricultural fields and transplanted back to urban landscapes could reduce non-point source losses of sediment compared to excavated soils amended with MB. Three research objectives were developed to evaluate the options for minimizing sediment and nutrient loss during cycling of MB through turfgrass sod. The first objective was to compare Tifway bermudagrass sod production between fields grown with and without MB under increasing rates of supplemental fertilizer N. The percent turfgrass cover of the MB-amended soil remained consistently greater (P=0.05) than the un-amended treatment throughout establishment and resulted in lighter sod weights with greater water content. The second objective was to compare runoff losses between excavated soils planted to sprigs or transplanted sod, with and without MB amendments. Runoff concentrations and mass loss of total dissolved P (TDP) were significantly greater (P=0.001) for MB-amended compared to un-amended sod. In addition, TDP concentration in runoff from MB-amended sod was greater (P=0.05) than excavated soil mixed with MB and bermudagrass sprigs. The third objective was to relate runoff loss of TDP to extractable soil P concentrations. A linear relationship was observed between water extractable P of soil and concentrations and mass loss of TDP in runoff.