Part of Lesson Plan: Nitrogen Cycle in Agriculture- Jennifer Terpstra

Activity Overview / Details

  Students will work through their Legume Scenario Sheets. They must construct a graph from the first data table. There are two options as far constructing the graphs. Either is acceptable depending on the resources available. The easy option is giving the students graph paper and then letting them graph the information by hand. The other option, is to have them use Microsoft Excel to graph the data. To model that activity, use a projector so students can see your computer screen on a screen at the front of the classroom. Use a sample set of data to show students how to first enter the data in a table form, then select the table and choose the Chart Wizard function. Excel will allow them to choose a graph and revise it as they see fit. This gives them many creative options; students can change background colors, fonts, etc. Excel is widely used on our campus, but any type of data processing computer application program will work. Even Microsoft Word has a basic version to make tables and graphs. Anytime the opportunity comes up to use technology, students jump at the chance to work with computers. It is very comfortable for them. Either option, by hand or by computer, the student must choose the graph that works best for the data presented to them on the activity sheet. Remind them that it is their responsibility to choose the type of graph that best represents the data (a bar graph). Remind them to include a title and label each axis. They should also provide a key.
   The second activity that needs modeling would be the nitrogen test. Any nitrogen test kit will work. They can be purchased through scientific catalogs or the local home improvement store. I prefer to use Rapitest, which can be found at Orchard Supply Hardware. Show students how to test the soil for nitrogen. Rapitest requires that a soil sample be mixed with water and set for 24 hours. Then the water from the soil is tested for nitrogen by adding a nitrogen indicator; the result is matched with a color key showing the nitrogen level. A scientific supply company like Ward's Biology sells more sophisticated kits that give results in part per million and parts per billion.  I suggest using a kit that best suits the ability of the class and knowledge of the teacher.  Set the lab up so that each soil students test represents soil from each of the test plots in the activity (i.e. Monantha vetch, Austrian peas, etc.). The three soils that had legumes grown on it should have higher nitrogen in it than the control ("none" plot) or the rye grass plot. In fact, the control plot should have more nitrogen than the rye grass plot. If finding five different soils with varying levels of nitrogen is difficult, a slight amount of nitrogen fertilizer can be added to the soil samples to make the results more easily seen by students. It is the teacher's responsibility to determine how much nitrogen to add to the soil, as soils will vary according to geography; so I will not give you a set amount.  Also, nitrogen strengths vary by brand/source, and the best way to determine how much is through prior testing on the part of the teacher.  It is easy- just make sure nitrogen readings show the following from highest to lowest:  Austrian Peas, Monantha Vetch & Hairy Vetch (they will be similar), the bare land, and then the rye should have the least nitrogen in its soil.  Before allowing students to begin, explain what the expectations are for safety and cleanup: 1. All students should wear safety glasses 2. At the conclusion of their soil test, students should empty their used material in the waste collector- not dumped down the sink!