Field Plots & Agricultural Research

1. Field Plots & Agricultural Research Dr. Bob Kemerait & Dr. Eric Prostko University of Georgia Cooperative Extension Service April 2001

2. SAFETY FIRST

3. Topics • Demonstration plots vs replicated field trials • Importance of replications • Common experimental designs • CRD, RCBD, Split-plot, Factorial • Small plots or large plots? • Plot maintenance • Data analysis & “significance” • Steps for a successful trial

4. Demonstration Plots • Objectives • example/information for growers • simple qualitative comparisons • Advantages • simple to coordinate • simple to assess • Disadvantages • not very useful for quantitative study • may oversimplify issue

5. High Nitrogen Normal Nitrogen Low Nitrogen Demonstration Plotsexample: rates of nitrogen on a field crop

6. Replicated Field Plots • Objectives • desire to statistically compare treatments, varieties, etc. • Advantages • results recognized by scientific community • results suitable for making decisions • Disadvantages • more complicated to conduct

7. Block 1 Block 2 Block 3 Block 4 Replicated Trialexample: effect of different rates of nitrogen

8. How many replications are enough? • Generally, the more, the better! • increased “degrees of freedom” • easier to differentiate similar means • better assessment of variation within plot area • But consider………… • land constraints • time constraints • material constrains • (chemical, plants, etc.)

9. You want how many reps???!!!! • Minimum number varies with discipline and researcher • Absolute minimum: 3 reps • Foliar fungicide programs: we like to see at least 4 reps • For soilborne diseases, including nematodes- we like 5 and even 6 reps • uneven distribution of organisms in the soil

10. Common Types of Experimental Design • There is more than one type! • all of these designs are replicated • completely randomized design • appropriate if no variation in plot area • randomized complete block design • consider ONE source of variation in field!! • split-plot design • two treatment levels, consider interactions • factorial design

11. Completely Randomized Design, 4 reps

12. Randomized Complete Block, 4 reps

14. BLK 1 BLK 2 BLK 3 BLK 4

15. BLK 1 BLK 2 BLK 3 BLK 4

16. Abound in-furrow No in-furrow Abound in-furrow No in-furrow No in-furrow Abound in-furrow Split-Plot Design

17. Plot Maintenance • Importance cannot be overlooked • Uniformity in planting • Careful calibration of spray equipment • Fertility • Weed control • Insect control • Disease control • Field Tours & PRIDE

18. Data Analysis • Statistical analysis can be tricky • consider specialists as references • Statistical Packages/Software • SAS--------MSTAT--------ARM • Analysis of Variance • are treatments significantly different? • Mean Separations • which means are different? • (Fisher’s Protected LSD)

19. What’s so significant about “significance”? • Frequent question • Confusion over meaning • agricultural standard: 95% (usually) • “At the 95% confidence level, we can be sure that these means are different at least 95% of the time.”

20. Getting Started with a Field Trial • Carefully determine your objectives • Decide on (limited) treatments • Develop an experimental design & plot plan • Secure necessary equipment and materials • Identify a conscientious cooperator • Choose your field site CAREFULLY • Remain safety oriented • Keep careful notes • Ask for help

21. GOOD LUCK!