The types of experiment that are used in agriculture are often quite complex. This page describes a few real-life examples.
Rice yield and fertiliser
- Aim
- Researchers wanted to determine the effect of two inorganic fertilisers, ammonium sulphate and ammonium phosphate on the yield of paddy rice. A seconary aim was to assess whether the fertilisers have different effects on different varieties of rice.
- Treatments
- Two factors were varied — the variety of rice used (Red Aus, Kashiful and Dudkalama) and the fertiliser applied (ammonium sulphate at 30.4 lb per plot, ammonium phosphate at 40.4 lb per plot and a control level with no fertiliser added)
- Design
- Six blocks of land were used and each was split into nine plots, each measuring (12' by 39'). Within each block, the nine treatments (combinations of rice variety and fertiliser) were allocated at random.
- Response
- The yield was recorded from each plot. (Its units are "chattaks" where 1 chattak is approximately 58 grams.)
- Data
- The table below shows the data that were collected.
Treatment |
Block |
Variety |
Fertiliser |
1 |
2 |
3 |
4 |
5 |
6 |
Red Aus |
Ammophos
Ammosulph
Control |
112
168
106 |
128
116
84 |
118
144
68 |
128
100
156 |
92
100
156 |
152
80
128 |
Kashiful |
Ammophos
Ammosulph
Control |
112
61
97 |
81
98
86 |
108
58
92 |
96
86
80 |
53
65
99 |
48
98
66 |
Dudkalama |
Ammophos
Ammosulph
Control |
134
125
62 |
112
106
60 |
116
110
99 |
114
102
90 |
101
56
58 |
128
110
87 |
- Experimental units
- The experimental units are the 54 plots and the 9 plots within each block may be related — some blocks may have more fertile soil than others.
Calliandra feeding trial
Preliminary work showed that fresh leaves of Calliandra calothyrsus provide a fodder supplement for dairy cattle. Nutritional analysis suggests that 3 kg of Calliandra should be nutritionally equivalent to 1 kg of concentrate.
- Aim
- The experment was conducted in Embu, Kenya, to determine whether Calliandra will substitute (in terms of milk yield) for dairy concentrate at the rate of 3 to 1 when added to the basal diet of cows in Embu.
- Treatments
- 1. Basal diet alone
2. Basal + 3 kg Calliandra
3. Basal + 1 kg concentrate
4. Basal + 3 kg Calliandra + 1 kg concentrate
- Design
- Twelve Farmers, each with a lactating cow, are used in the study. Each cow is allocated to a sequence of treatments — they are on one treatment for a period, and then change to the next. The order of the treatments is varied between cows so that each treatment is used with the same number of cows in each period. A treatment period is 14 days with milk yield assessed during the second seven only.
- Response
- Average daily milk yield (kg) over days 8-14.
- Data
- The table below shows the data that were collected.
|
Period |
Cow |
1 |
2 |
3 |
4 |
1 |
13.88 (T1) |
13.30 (T2) |
12.80 (T3) |
13.25 (T4) |
2 |
10.29 (T1) |
9.33 (T3) |
9.91 (T4) |
8.65 (T2) |
3 |
8.40 (T1) |
9.30 (T4) |
9.80 (T2) |
10.30 (T3) |
4 |
10.70 (T2) |
10.19 (T1) |
10.17 (T4) |
10.10 (T3) |
5 |
15.31 (T2) |
15.07 (T3) |
13.06 (T1) |
13.67 (T4) |
6 |
8.13 (T2) |
9.06 (T4) |
8.36 (T3) |
8.19 (T1) |
7 |
10.50 (T3) |
9.86 (T1) |
10.50 (T2) |
11.12 (T4) |
8 |
8.10 (T3) |
9.40 (T2) |
11.07 (T4) |
10.50 (T1) |
9 |
11.30 (T3) |
12.57 (T4) |
9.37 (T1) |
10.70 (T2) |
10 |
10.06 (T4) |
8.36 (T1) |
9.50 (T3) |
9.15 (T2) |
11 |
12.05 (T4) |
11.83 (T2) |
10.64 (T1) |
11.00 (T3) |
12 |
15.05 (T4) |
13.88 (T3) |
13.72 (T1) |
13.44 (T2) |
- Experimental units
- An experimental unit is a cow over a single 2-week period. These experimental units have some structure — some cows are more productive than others, so the four units for each cow are related. There may be a steady increase or decrease in yield for all cows over the 2 months of the study but the design ensures that this does not affect the conclusions.