Agron 503/541 © 2007 Center for Agricultural Instruction & Technology Transfer Iowa State University Duplication of this product is prohibited. For more information, call Lab 1-2: Yield Trend

Agronomy 503/541 Elwynn Taylor

Agronomy 503/541 Lab 1-2: Graphing Crop Yield

Assignment 1-2: 01 Access the USDA NASS site and locate the US Yield by Year. (at the time this was written the data are found by: click “Crops and Plants” then Click “Charts and Maps” then under Field Crops Corn click “ Yield by Year, US”) Obtain national crop yield data for corn Produce a graphic much like the USDA graph TURN IN THIS SPREADSHEET Helps follow in the next several slides:

Obtain Historic Corn Data Under “Quick Stats”, “U.S. and State Data” Choose US * State – Crops Go 1- Planted, Harvested, Yield, etc 2- Corn for Grain United States 5- Add 6- Get Data 7- At top of data record choose “Units as a separate column” 8- Select (highlight) from the lower right cell of the table to the upper left [where it says “Commodity….”] Right click and COPY 9- Having opened Excel…. Place the cursor in cell A-1 and PASTE

Sample data set The upper left corner of your work sheet should look like this: Commodity ↑ YearState Planted All Purpo ses Planted All Purpo ses_u nitHarvested Harvested_ unitYield Corn For Grain1977 United State s84,328 thousand acres71,614 thousand acres90.8bushel Corn For Grain1978 United State s81,675 thousand acres71,930 thousand acres101bushel Corn For Grain1979 United State s81,394 thousand acres72,400 thousand acres109.5bushel Corn For Grain1980 United State s84,043 thousand acres72,961 thousand acres91bushel Corn For Grain1981 United State s84,097 thousand acres74,524 thousand acres108.9bushel

Make a Graph At the top of your spreadsheet data table “left click” to highlight the “B” the entire “B” column should now be highlighted. Hold down the “Ctrl” and “left click” on the “H” You now have columns B and H highlighted “Chart Wizard” should be displayed in the Excel Tool bar…. Click it The 4 th down graph type should be “x-y (scatter)” click it The chart sub-type (3 rd down) to click is points connected by lines. Click “Next” and a graph should appear. Click “Next” again. Add Titles and under Gridlines select the “Major” for X and Y axis Click “Finish” Place the cursor on a data point on your graph and “left” click (some points light up) Right click on a point and “Add Trendline (linear), click Options and select “display equation on chart” click OK

Rough Graph with Equation Your graph should look something like this, you can move things around and dress it up quite a bit, format the axis if you wish, etc. NOTE: This example is for reference, it is off by one year from the assignment.

Compute the Trend Find the trend yield for the year 2008: (you use the year in place of the “x” in the equation) (use your equation, not the one in slide #9)

This is a non- linear trend, & includes +10% & -10% curves.