Students established an experiment to measure the time-response of 'Palmetto' St. Augustinegrass to varying rates of quick- and slow-release nitrogen sources.  Students also applied fertilizer using a drop spreader at different settings and different grounds speeds.

Fertilizer experiment (sample from 1999) (Results below)

This is a randomized complete block experiment involving twelve fertilizer treatments in two replications (blocks).  The experimental area is a 17-month-old planting of 'Palmetto' St. Augustinegrass under the shade of gumbo-limbo and Bischofia trees.   Plots are 4 feet x 4 feet.  Treatments involve two factors, nitrogen source and rate of N application.

Fertilizers were pre-weighed and applied by hand to each plot, on 31 August 1999.  Students will observe plots each week and objectively assess the response of 'Palmetto' St. Augustinegrass to the different treatments.  Do not bring the plot plan to the plots!  Instead, bring a blank sheet of paper.  Record readings such as "darkness of color" on a 1- to 9 scale, with 9=darkest possible.

Questions:  (1) How many grams fertilizer should have been used per plot?  (2) Why replicate?  (3) If this experiment were repeated for 'Tifway' bermudagrass (419), what would be the anticipated response?  (4) Why not bring plot plans to the plots?  (5) Is this a fair comparison of slow release fertilizer vs. quick release fertilizer?

Drop spreader calibration

A Vigoro DS4000V drop spreader was used to apply three swaths of Milorganite to an adjacent area.  Rain prevented doing more.  Here is the data that was recorded, and a column for converted values to be calculated by students.  The swath size was 50 feet times the width of the spreader, or 18 inches.

Questions:  (1) What were the N application rates?   (2) What was the effect of a larger setting number?  (3) Did walking speed influence application rate?  (4) How would you calibrate a centrifugal ("broadcast" or "rotary") spreader?  (5) What problems did we encounter doing this calibration test, and what could be done to prevent these problems in the future?

Fertilizer experiment results (sample from 1999)

On 21 September 1999, 11 students plus the teacher evaluated St. Augustinegrass color response to the fertilization treatments.  Results were that it was very difficult to see a response.  When analyzed statistically, neither N-source (Milorganite vs. 10-10-10) or rate of application influenced turfgrass color.  When the class results were averaged across individuals and then analyzed, there was a marginal linear trend (P < 0.10) for higher rates of fertilization to promote darker grass.  However, error variability was too great to allow definitive conclusions.

Student remarked that this was a shady site and might not need as much fertilization as turf in the full sun.

The class established another fertilizer experiment, this one on bermudagrass in the full sun.