Empowering Students to Apply Mathematics to Soil Science: Using Spreadsheets to Solve Fertilizer Selection Problems.

Undergraduate students frequently come into soils courses with limited numerical problem-solving capacity. This becomes a serious practical limitation when they are asked to calculate chemical, nutrient application rates, fertilizer selections, etc. This limitation also limits capacity to understand, control, and manage nutrient, chemical, and amendment applications. A spreadsheet example was developed in Excel to be used to help students learn to think about problems with calculations and to facilitate their solution and increase understanding. The set of spreadsheets uses a problem-solving structure introduced at Purdue University, Dep. of Biosystems Engineering (Buckmaster, 2006). Experience introducing and using the spreadsheet at Eduardo Mondlane University, Maputo, Mozambique, UniZambeze, Mocuba, Mozambique, and at the University of Hawai`i at Manoa, Honolulu, Hawaii, indicates that students quickly learn to use the spreadsheet and can learn the problem solving structure and apply it to other problems. Exercises have been carried out with students in their first course in soils as well as with upper level undergraduate and graduate students. Upper level undergraduates and graduate students learn the problem-solving technique by writing Excel programs based on the problem-solving structure. The example deals with how to select, blend, and compare costs of fertilizers to arrive at a specified N, P2O5, and K2O recommendation. The exercise encourages students to use information technology to conceptualize and solve problems, use software to compare scenarios, learn to conduct sensitivity analyses, all with readily available software.