1. Precision Farming Profitability
Reference G: On-Farm Research
By Sylvie Brouder, Robert Nielsen

2. Precision Farming Profitability, p. 104
Treatment A
Treatment B
Note: Cannot tell if yields reflect something about the treatment, something about the field gradient or some about both factors. A
Treatment A
Treatment B
Replicate number
Note: Completely random assignment of treatments may still result in bias. Here, purely by chance, more of the A treatments are upslope from B Treatments. B
Rep.1
Treatment A
Treatment B C
Rep.2
Rep.3
Rep.4
For most trials, randomization of treatments within each replicate is the best option.
Figure 1a. Side-by-side comparison: no replication. B. Completely randomized design w/4 replicates. C. Randomized block design w/4 replicates.
Precision Farming Profitability, p. 104

3. Precision Farming Profitability, p. 106
Case 1: No difference in yields.
Case 2: No difference in average yields but replicates vary.
Figure 2. Three cases where statistics are not needed to interpret the results from a 2 treatment trial with 4 replicates.
Case 3: Treatment B out-yields Treatment A in every replicate.
Precision Farming Profitability, p. 106

4. Precision Farming Profitability, p. 107
Case 4: Treatment B yields more than Treatment A in 3 replicates but yields are the same in one replicate.
Case 5: Treatment B out-yields A in 3 replicates but A out-yields B in 1 replicate.
Figure 3. Three cases where statistics are most likely needed to correctly interpret the results from a 2 treatment trial with 4 replicates.
Case 6: Results in individual replicates are mixed but Treatment B averages 5 bu/acre more than treatment A.
Precision Farming Profitability, p. 107

5. Precision Farming Profitability, p. 108
Table 2. Understanding the probability.
Precision Farming Profitability, p. 108

6. Precision Farming Profitability, p. 109
Table 3. In each case average yields in Treatment B are greater than A. Test your statistical IQ by figuring the odds that the Treatment B cases are really no different than Treatment A. In cases 6-10 look at only the first 3 replicates of Treatment A.
Precision Farming Profitability, p. 109

7. Precision Farming Profitability, p. 110
Figure 4. Design for an on-farm trial comparing 2 treatments using 4 replicates. Treatments are randomized within each replicate.
Precision Farming Profitability, p. 110

8. Precision Farming Profitability, p. 110
Replicates 2 3 1 4
Treatment A
Treatment B
Treatment C 1
Figure 5. Design for an on-farm trial comparing 3 treatments using 4 replicates. Treatments are randomized withi9n each replicate, and replicates are located so as to avoid known areas of extreme variability.
Precision Farming Profitability, p. 110

9. Precision Farming Profitability, p. 111
Figure 6. Design for an on-farm trial using the “split-planter” approach. This layout shows the equipment passes when planter and combine widths are the same.
Precision Farming Profitability, p. 111