Systems Agronomic and Economic Evaluation of Cotton Varieties in ...

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Are side-by-side plots more valuable than small-plot replicated trials, or vice versa?Both types of plots can provide good information. The key is to evaluate the reliability ofthe data. It is also important to consider the applicability of the trial to your farmingoperation.When is plot data valid, and when isn’t it?There isn’t a black-and-white answer to that questions. But there are good rules of thumbthat can help guide you. Consider these three field trial scenarios:Scenario 1:A single on-farm side-by-side trial comparing 10 varieties. Each variety is plantedin one strip the width of the harvesting equipment and is 250 to 300 feet long.What you can learn:This trial will allow you to get a general feel for each variety or hybrid in the test,including how it grows and develops during the season. However, this trial, by itself,probably won’t be able to reliably measure differences in yield. This is becausevariability within the field, even if it appears to be relatively uniform, may be largeenough to cause yield variations that mask genetic difference among the varieties.Other varietal characteristics, such as maturity or micronaire in cotton, can also bemasked by soil variation.Scenario 2:Yield data from side-by-side variety trials conducted on the same varieties onmultiple farms in your region.What you can learn:When data from multiple side-by-side trials are considered together, reliabilityincreases. In this case, the more trials comparing the same varieties, the better. Asyou go from three to five to 10 or more locations, the certainty goes up that yielddifferences represent genetic differences and not field variability. Be aware,however, that small differences between treatments (in this case varieties) may stillbe within the margin of random variability of the combined trial and may not indicateactual genetic differences. One treatment will almost always be numerically higher.Statistical analysis helps determine if differences are significant (consistent).159
Scenario 3:A university-style small-block replicated trial comparing the same 10 varieties.What can you learn:Data from such trials, if they are designed well and carried out precisely, generallyare reliable. That is, the results generally determine the yield potential of cropvarieties. However, it is still important to consider whether results are applicable toyour farming operation and are consistent with other research.How do I know whether differences in yield, for example, are real and not caused byfield variability or sloppy research?Scientists use statistical analysis to help determine whether differences are real or are theresult of experimental error, such as field variation.The two most commonly used statistics are Least Significant Difference (LSD) and theCoefficient of Variation (CV), both of which can provide insight on the validity of trial data.If these values aren’t provided with trial results, ask for them.Least Significant Difference (LSD) is the minimum amount that two varieties must differ tobe considered significantly different. Consider a trial where the LSD for yield is four bushelsper acre. If one variety yields 45 bushels per acre and another yields 43 bushels per acre,the two are not statistically different in yield. The difference in their yields is due to normalfield variation, not to their genetics. In this example, a variety that yields 45 bushels peracre is significantly better than those yielding less than 41 bushels per acre. In manyresearch trials, LSDs are calculated at confidence level of 75 to 95 percent. For example,a confidence level of 95 percent means you can be 95 percent certain that yield differencesgreater than the LSD amount are due to genetics and not to plot variability.Coefficient of Variation (CV) measures the relative amount of random experimentalvariability not accounted for in the design of a test. It is expressed as a percent of theoverall average of the test.For measuring yield differences, CV’s of up to five percent are considered excellent; 5.1to 10 percent are considered good; and 10.1 to 15 percent are fair.A high CV means there must be larger differences among treatments to conclude thatsignificant differences exist. The bottom line: When considering yield test data, be skepticalwhen the CV exceeds 15 percent.160
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Systems Agronomic and EconomicEvalu
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Scott Russell, EA-IPM, Terry/Yoakum
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Replicated No-Till LESA Irrigated R
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Agronomic and Economic Evaluation o
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andomized complete block design was
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not significant at this location. H
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Table 1. Inseason plant measurement
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Table 3. HVI fiber property results
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Entry Lint Seed Bur cotton Lint See
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Table 7. Inseason plant measurement
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Table 9. Final plant map results fr
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Table 11. HVI fiber property result
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Replicated LESA Irrigated RACE Vari
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Results and Discussion:Agronomic da
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Replicated Sub-Surface Drip Irrigat
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Replicated LEPA Irrigated RACE Vari
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Replicated No-Till LESA Irrigated R
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Results and Discussion:Acknowledgme
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Replicated LEPA Supplemental (Limit
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lb/acre for FiberMax 2989GLB2. Lint
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Table 2. HVI fiber property results
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Texas Panhandle Cotton Variety Tria
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Biopolymer Research Institue for HV
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Location 2 - DumasAt the Dumas loca
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cotton yields to determine lint and
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Page 122 and 123: Table 1. Final plant map results fr
Page 124 and 125: Entry Lint Seed Bur cotton Lint See
Page 126 and 127: Replicated Dryland Cotton Variety T
Page 128 and 129: Results and Discussion:Significant
Page 130 and 131: Table 2. HVI fiber property results
Page 132 and 133: 125Plains Dryland Systems Variety T
Page 134 and 135: 127Blanco Dryland Systems Variety T
Page 136 and 137: 129Dawson County Dryland RACE Demon
Page 138 and 139: 131Lynn County Irrigated RACE Demon
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Page 146 and 147: Table 1. cont. †BrandVarietyVerti
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Page 150 and 151: Table 2. HVI ratings for varieties
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Page 156 and 157: Table 7. cont.Variety bRel.ValueRan
Page 158 and 159: High Plains (TASS 1N and 1S)Planted
Page 160 and 161: Lubbock Air TemperaturesMay, 2012Te
Page 162 and 163: Lubbock Air TemperaturesSeptember,
Page 164 and 165: Precipitation (inches)4.0LTA20123.0
Page 168: Is a one-year test valid, or are se
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