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Lab Report for C:N Experiment Note: every student must hand in a report. It is not done in lab groups! Due date: Thurs. 11/19, Fri. 11/20, Mon. 11/23 or Tues. 11/24, according to your lab section. Report will be uploaded to Canvas- assignment labeled “C:N report”. Length: ~4 -5 pages of text (excluding data tables or figures)– just an estimate. Format: typed, 1.5- or double-spaced. Objectives of Experiment: Examine how the C:N ratio of organic material added to soil influences: 1) plant-available N levels in soil. 2) microbial activity in soil 3) soil tilth (soil aggregate stability) Sections of Report 1. Title: 2. Introduction: Refer to background information handed out in Lab 1 and the introductory pages for Lab 9 entitled “Microbial Decomposition of Organic Materials in Soil” and Lab 12 (Soil Tilth) Why do we add organic amendments? What are the supposed benefits? What is C:N ratio, immobilization of N, and how might the C:N ratio of organic amendments affect levels of plant-available N in soil? How might we manage for immobilization if adding organic soil amendments? When might you use a low and high C:N amendments, respectively? Other pertinent background info. ==> List objectives of the experiment at the end of the Introduction. 3. Materials & Methods (M&M) Explain what was done in the experiment without giving minute details. • Experimental set-up (treatments, replication, experimental unit and conditions, etc.) • How soil nitrate was measured (extraction with dilute CaCl2, nitrate specific strips and visual reading with color chart for quantification). • Soil respiration: overall procedure (without details), what was determined (respiration rate: ug CO2/ g.O.D. soil/ day) • Tilth: measurement of soil aggregate stability 4. Results Describe results for each of our three datasets. Minimize explanation of why—that can go in the Discussion section. Soil nitrate You received a table of these data. a) Calculate mean & standard error (SE = SD / v n*) for each treatment rep, at each sampling date. You can do this on a calculator or in an Excel spreadsheet. In Excel, the formulae are: =AVERAGE(cell X: cell Y) =STDEV(cell X: cell Y)/SQRT(n*). *n = the # of observations (4 or 5, put this number in the formula) Once you type both formulas into the spreadsheet, you can copy/paste them, but if the number of means changes, then you need to correct your formula. Double-clicking on the formula produces a blue box around the data. Be sure the data range is correct. Include this table with raw data in the report, just to show me that means and standard errors are calculated correctly. To actually display the soil nitrate data in your report, follow (b) below. b) Display the data (means only) to best show any significant trends. This could be a line or bar graph– you decide. Note: if you prepare a line graph, check that on the x-axis, the intervals between sampling dates are correct. Better to use week # rather than sampling # as your x-variable. In Excel, selecting a scatter graph and then the line option, is the best way to achieve this. c) Ideally, standard errors are displayed as error bars on your graph. Not required, but I can demonstrate how. Be sure to select the “custom” option so that you provide the S.E. values for Excel to use. Soil respiration (Lab 9) A data table was provided. Calculate means and standard errors. You can append this table and/or make a bar graph. Very good idea to show standard error bars on the graph, but not required. Soil tilth (Lab 12) Refer to the definition of soil tilth in Lab 12 packet. Tilth cannot be measured directly, so instead we measured soil aggregate stability which is one of several properties that contributes to good soil tilth. This test is somewhat rudimentary and large differences amongst the treatments may not be observed, in part because several years of organic matter incorporation are often required for a measurable change. A data table will be provided. Calculate means and standard errors. You can append this table and/or make a bar graph. Try to show the standard error bars on the graph. General comments for Results section • Soil nitrate is the largest data set—spend more time describing these results. However, you must also report and describe data for soil respiration and for soil tilth. Soil tilth will be the shortest section and may be more qualitative. • Compare only treatment means (averages). Results for individual reps (soil boxes) are not usually described—unless one was highly different and worth commenting on. • Be sure that you comment on results for all four treatments (control, legume, cereal and straw). However, in some cases, you might compare “unamended” (control) soil to the entire group of “amended soils”. This would be for the text, but not for tables or graphs. • Describe the results and after the first sentence of this description, put the figure or table number, e.g. (Fig. 1), in parenthesis at the end of the sentence. This directs the reader to the data figures or tables where those results are found. Do not include a sentence such as “Figure 1 shows the data for…….”. • Label graphs as Fig. 1, 2, etc. so that you can reference them in the text (as described in bullet above). Be sure that all axes are labeled, including the unit. • 3 significant digits is sufficient! Avoid having numbers like 2.37415 in your data table. Listing it as 2.37 (fewer digits) makes the table easier to read. Use the “decrease decimal” icon in Excel to reduce the # of decimals. • Graphs and/or data tables do not have to be imbedded….can be appended as separate pages at the end. If you wish to imbed, that is good, too. 5. Discussion Discuss the results and their implications in light of the objectives of the experiment (stated in the Intro) and the background information (week 1 packet). 6. Conclusion A brief (few sentence) summary of the outcome of this experiment.