Precision Farming Profitability

Reference G: On-Farm Research

By Sylvie Brouder, Robert Nielsen

Note: Cannot tell if yields reflect something about the treatment, something about the field gradient or some about both factors.

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.

Treatment A Treatment B A Treatment A Treatment B Rep.1

Rep.2

Rep.3

Rep.4

C Treatment A Treatment B 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 B

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.

Precision Farming Profitability, p. 106 Case 3: Treatment B out-yields Treatment A in every replicate.

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.

Precision Farming Profitability, p. 107 Case 6: Results in individual replicates are mixed but Treatment B averages 5 bu/acre more than treatment A.

Table 2. Understanding the probability.

Precision Farming Profitability, p. 108

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

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

1 1 Replicates 2 3 4

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 Treatment A Treatment B Treatment C

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