Jane M. F. Johnson

Crop and Soil Productivity Response to Corn Residue Removal: A Literature Review

of greenhouse gases in the atmosphere (IPCC, 2001), and ability of our agricultural systems to sustain producSociety is facing three related issues: overreliance on imported fuel, tion at rates needed to feed a growing world population increasing levels of greenhouse gases in the atmosphere, and producing sufficient food for a growing world population. The U.S. De(Cassman, 1999). Many papers have been written on partment of Energy and private enterprise are developing technology these topics both individually and in the various combinecessary to use high-cellulose feedstock, such as crop residues, for nations (Doran, 2002; Follett, 2001; Janzen et al., 1998a, ethanol production. Corn (Zea mays L.) residue can provide about 1998b; Lal et al., 1999). However, few authors have ad1.7 times more C than barley (Hordeum vulgare L.), oat (Avena sativa dressed all three topics together. L.), sorghum [Sorghum bicolor (L.) Moench], soybean [Glycine max Recent developments in the energy industry and ac(L.) Merr.], sunflower (Helianthus annuus L.), and wheat (Triticum tivity by entrepreneurs have prompted new strategies aestivum L.) residues based on production levels. Removal of crop for addressing the first issue, overreliance on imported residue from the field must be balanced against impacting the environfuels (Hettenhaus et al., 2000). This strategy expands use ment (soil erosion), maintaining soil organic matter levels, and preof biomass for fuel production and is contingent on deserving or enhancing productivity. Our objective is to summarize published works for potential impacts of wide-scale, corn stover collection velopment of new organisms or enzymes to convert on corn production capacity in Corn Belt soils. We address the issue of cellulosic (a high concentration of cellulose) biomass crop yield (sustainability) and related soil processes directly. However, [opposed to grain (starchy) biomass] to ethanol for use scarcity of data requires us to deal with the issue of greenhouse gases as a motor vehicle fuel. The U.S. DOE, in concert with indirectly and by inference. All ramifications of new management pracprivate enterprise, is making great strides toward develtices and crop uses must be explored and evaluated fully before an oping enzymes and improving efficiency in fuel producindustry is established. Our conclusion is that within limits, corn stover tion from biomass (DiPardo, 2000; Hettenhaus et al., can be harvested for ethanol production to provide a renewable, do2000). mestic source of energy that reduces greenhouse gases. RecommendaSources of cellulosic biomass are numerous (woody biotion for removal rates will vary based on regional yield, climatic mass crops and lumber industry wastes, forage crops, inconditions, and cultural practices. Agronomists are challenged to develop a procedure (tool) for recommending maximum permissible dustrial and municipal wastes, animal manure, and crop removal rates that ensure sustained soil productivity. residues); however, currently few sources are perceived to be available in sufficient quantity and quality to support development of an economically sized processing facility of about 1800 Mg dry matter d 1 (Hettenhaus T of the most pressing issues facing our society, et al., 2000), except crop residues (DiPardo, 2000). Bain the midterm, are overreliance on imported fuels gasse [remaining after sap extraction from sugarcane [U.S. Department of Energy (DOE) Office of Energy Ef(Saccharum officinarum L.)] in Louisiana and rice (Orficiency and Renewable Energy, 2002], increasing levels yza sativa L.) straw in California are regional examples of crop residues collected in current culture and availW.W. Wilhelm, USDA-ARS, 120 Keim Hall, Univ. of Nebraska, Linable for production of ethanol (DiPardo, 2000). Creatcoln, NE 68583-0934; J.M.F. Johnson, USDA-ARS, 803 Iowa Ave., ing an acceptable use or disposal procedure for these Morris, MN 56267-1065; J.L. Hatfield, 108 Natl. Soil Tilth Lab., 2150 residues represents a huge problem in the regions where Pammel Drive, Ames, IA 50011-3120; W.B. Voorhees, USDA-ARS (retired), 803 Iowa Ave., Morris, MN 56267-1065; and D.R. Linden, they are produced although the total quantity is not USDA-ARS (retired), 1991 Upper Buford Circle, St. Paul, MN 55108sufficient to have a great impact on fuel needs for the 0000. This paper is a joint contribution of the USDA-ARS and the nation (DiPardo, 2000). On the other hand, the quantity Agricultural Research Division of the University of Nebraska. Pubof corn stover is large, but corn stover is generally not lished as Journal Ser. no. 13949. Received 12 Dec. 2002. *Corresponding author (wwilhelm1@unl.edu). Abbreviations: 13C, change in 13C atom percent; DOE, Department Published in Agron. J. 96:1–17 (2004).  American Society of Agronomy of Energy; HI, harvest index; SOC, soil organic carbon; SOM, soil organic matter. 677 S. Segoe Rd., Madison, WI 53711 USA

Phosphorus Deficiency in Lupinus albus (Altered Lateral Root Development and Enhanced Expression of Phosphoenolpyruvate Carboxylase)

The development of clustered tertiary lateral roots (proteoid roots) and the expression of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) in roots were studied in white lupin (Lupinus albus L.) grown with either 1 mM P (+P-treated) or without P (-P-treated). The +P-treated plants initiated fewer clustered tertiary meristems and the emergence of these meristems was delayed compared with -P-treated plants. Proteoid root zones could be identified 9 d after emergence in both P treatments. Amounts of PEPC mRNA, PEPC specific activity, and enzyme protein were greater in proteoid roots than in normal roots beginning at 10, 12, and 14 d after emergence, respectively. The increases in PEPC mRNA, PEPC enzyme, and PEPC specific activity suggest that this enzyme is in part under transcriptional regulation. Recovery of organic acids from root exudates coincided with the increases in PEPC specific activity. The -P-treated plants exuded 40-, 20-, and 5-fold more citrate, malate, and succinate, respectively, than did +P-treated plants. Data presented support the hypothesis that white lupin has concerted regulation of proteoid root development, transcriptional regulation of PEPC, and biosynthesis of organic acids for exudation in response to P deficiency.

Phosphorus Stress-Induced Proteoid Roots Show Altered Metabolism in Lupinus albus

Proteoid roots develop in Lupinus albus L. in response to nutrient stress, especially P. Proteoid roots excrete citrate and thus increase the availability of P, Fe, and Mn in the rhizosphere. In an effort to understand citrate synthesis and organic acid metabolism in proteoid roots of lupin, we have evaluated in vitro enzyme activities of citrate synthase (CS), malate dehydrogenase (MDH), and phosphoenolpyruvate carboxylase (PEPC) in proteoid and normal roots of plants grown with or without P. Organic acid concentrations, respiration rates, and dark 14CO2-labeling patterns were also determined. The in vitro specific activities of CS, MDH, and PEPC and in vivo dark 14CO2 fixation were higher in proteoid roots compared to normal roots, particularly under P stress. Western blot analysis showed that PEPC enzyme protein was more highly expressed in -P proteoid roots compared to other tissues. The majority of the fixed 14C was found in organic acids, predominantly malate and citrate. A larger fraction of citrate was labeled in P- stressed proteoid roots compared to other root tissue. Respiration rates of proteoid roots were 31% less than those of normal roots. The data provide evidence for increased synthesis of citrate in proteoid roots compared to normal roots, particularly under P stress. A portion of the carbon for citrate synthesis is derived from nonautotrophic CO2 fixation via PEPC in proteoid roots.

Soil Microbial Community Response to Corn Stover Harvesting Under Rain-Fed, No-Till Conditions at Multiple US Locations

Harvesting of corn stover (plant residues) for cellulosic ethanol production must be balanced with the requirement for returning plant residues to agricultural fields to maintain soil structure, fertility, crop protection, and other ecosystem services. High rates of corn stover removal can be associated with decreased soil organic matter (SOM) quantity and quality and increased highly erodible soil aggregate fractions. Limited data are available on the impact of stover harvesting on soil microbial communities which are critical because of their fundamental relationships with C and N cycles, soil fertility, crop protection, and stresses that might be imposed by climate change. Using fatty acid and DNA analyses, we evaluated relative changes in soil fungal and bacterial densities and fungal-to-bacterial (F:B) ratios in response to corn stover removal under no-till, rain-fed management. These studies were performed at four different US locations with contrasting soil-climatic conditions. At one location, residue removal significantly decreased F:B ratios. At this location, cover cropping significantly increased F:B ratios at the highest level of residue removal and thus may be an important practice to minimize changes in soil microbial communities where corn stover is harvested. We also found that in these no-till systems, the 0- to 5-cm depth interval is most likely to experience changes, and detectable effects of stover removal on soil microbial community structure will depend on the duration of stover removal, sampling time, soil type, and annual weather patterns. No-till practices may have limited the rate of change in soil properties associated with stover removal compared to more extensive changes reported at a limited number of tilled sites. Documenting changes in soil microbial communities with stover removal under differing soil-climatic and management conditions will guide threshold levels of stover removal and identify practices (e.g., no-till, cover cropping) that may mitigate undesirable changes in soil properties.

Introducing the GRACEnet/REAP Data Contribution, Discovery, and Retrieval System.

Difficulties in accessing high-quality data on trace gas fluxes and performance of bioenergy/bioproduct feedstocks limit the ability of researchers and others to address environmental impacts of agriculture and the potential to produce feedstocks. To address those needs, the GRACEnet (Greenhouse gas Reduction through Agricultural Carbon Enhancement network) and REAP (Renewable Energy Assessment Project) research programs were initiated by the USDA Agricultural Research Service (ARS). A major product of these programs is the creation of a database with greenhouse gas fluxes, soil carbon stocks, biomass yield, nutrient, and energy characteristics, and input data for modeling cropped and grazed systems. The data include site descriptors (e.g., weather, soil class, spatial attributes), experimental design (e.g., factors manipulated, measurements performed, plot layouts), management information (e.g., planting and harvesting schedules, fertilizer types and amounts, biomass harvested, grazing intensity), and measurements (e.g., soil C and N stocks, plant biomass amount and chemical composition). To promote standardization of data and ensure that experiments were fully described, sampling protocols and a spreadsheet-based data-entry template were developed. Data were first uploaded to a temporary database for checking and then were uploaded to the central database. A Web-accessible application allows for registered users to query and download data including measurement protocols. Separate portals have been provided for each project (GRACEnet and REAP) at nrrc.ars.usda.gov/slgracenet/#/Home and nrrc.ars.usda.gov/slreap/#/Home. The database architecture and data entry template have proven flexible and robust for describing a wide range of field experiments and thus appear suitable for other natural resource research projects.

Determinants and Prediction of Carbon/Nitrogen Ratio in Five Diverse Crop Plants

Multivariate relationships in and statistical moments of eight biochemical constituents and their impact on estimating carbon/nitrogen (C/N) ratio in alfalfa, corn, soybean, cuphea, and switchgrass residues indicate that (1) equal portions of variation in C/N were explained by differences among crops and among organs; however, the largest variations in N and C were explained by differences among crops and among organs within crops, respectively; (2) variation in N, but not in C or N + C, content explained the greatest variance in C/N ratios; (3) biochemically, stems were closer to roots than to leaves; hence the large portion of variation in C/N ratio in roots explained by variation in biochemical constituents in stems and leaves (R2 = 61.0%) and in stems only (R2 = 58.0%); and (4) statistical moments, other than mean values of biochemical constituents, significantly impacted C/N ratio estimates and the reliability of these estimates, both of which were positively correlated (r = 0.64, p < 0.001).

Spring camelina N rate: balancing agronomics and environmental risk in United States Corn Belt

ABSTRACT Camelina (Camelina sativa (L.) Crantz) seed oil has desirable properties for producing advanced biofuels and as a healthy cooking oil. It has been grown for centuries, but basic recommendations for nitrogen (N) fertilizer requirements are still needed to support widespread industrial cultivation across North America. A replicated N-response plot-scale study was conducted on a northern Mollisol soil for two growing seasons to 1) determine seed and oil yield, seed oil content, and vegetative response; 2) determine indices of N use efficiency; and 3) measure post-harvest residual inorganic soil N as an index of environmental risk. Seed and oil yield response to N fertilization was described with a quadratic function, which predicted maximum seed yield (1450 kg ha−1) and oil yield (580 kg ha−1) at about 130 kg N ha−1. However, seed and oil yield did not differ significantly among N-rates above 34 kg N ha−1. Seed oil content averaged 400 g kg−1 among all N rates. Agronomic efficiency declined above 34 kg N ha−1, which coincided with an increase of post-harvest soil nitrate-N plus ammonium-N (residual N). Considering N use efficiency, simple cost analysis, and risk associated with residual N, a rate of 34 kg N ha−1 is recommended.

Row-Crop Production Practices Effects on Greenhouse Gas Emissions

One of the grand challenges facing humankind is meeting projected demands for agricultural products in a world undergoing global climate change. As demands increase for the reliable and environmentally responsible supply of food and fiber, how management is adapted to meet these demands will determine the sustainability and climate change mitigation potential of row-crop production systems. This chapter addresses direct greenhouse gas (GHG) emissions from agricultural soils resulting from row-crop production practices. The chapter is focused on globally dominant grain cropping systems (maize, wheat, rice) and on identifying agronomic management practices that help reduce GHG emissions, increase SOC sequestration, and subsequently improve soil health.

The Next/Pemex Petrophysical Reservoir Characterization Programme – Effective Blending of Training, Projects, and Mentoring

A challenge faced in conventional E&P training is developing true applied skills and providing opportunities to practice those skills with real world data and problems.