How to Rate Plots By A Numerical Method

System will help you unravel mysteries later.

Published on: Jun 14, 2010

Seed companies use rating systems to get a handle on a number of things, including diseases resistance. Unfortunately, not all seed companies use the same system. Unless you know the rating system that your company uses, seeing a rating of '1' for gay leaf spot on a chart doesn't tell you much. Does a '1' mean it's perfectly clean, the best rating possible, or is '1' the worst rating, meaning it's full of disease.

Dave Nanda, a former plant breeder for 40 years and crops consultant, Indianapolis, Ind., has rated plots for various things during his entire career. He refers back to these ratings today to help explain yield effects that may occur later in the season. While carrying on active breeding research, ratings helped him decide which plants to keep, or which hybrids were worthy of a closer look.

Nanda helped rate plots in the Indiana Prairie Farmer, Tippecanoe County Extension test sponsored by Precision Planting, Tremont, Illinois. The test, consisting of 27 treatments in four replications, is located south of Lafayette in Tippecanoe County, Ind. The variables being examined in the test are down force on planting units, seeding depth and driving speed.

Nanda did his first rating when the plots had been planted for 12 days. Because they were planted May 27, most seedlings have already emerged, with some corn at the two-leaf stage. He was looking to rate the plots, all of one hybrid, supplied by 1st Choice Hybrids, Milton, Ind., for emergence and early seedling vigor. Plant counts were taken at the same time, but that was a numerical rating and didn't influence his rating. He also did not take spacing variability into account because that was more of a function of planting settings, and will be measured as a numerical factor in the near feature.

He was looking for uniform plant height, how tall plants were compared to other plots and related factors. In some plots, he noticed a few plants were bigger, while most were smaller. Obviously something caused those few plants to emerge first. It gave the plots and uneven look, garnering a low rating.

He rated plots from a '1' his highest rating, for plots that he thought were extremely uniform, to a '9', his worst rating, for plots that were barely out of the ground, with uneven height. Several plots scored 5, average, with others going 4 to 7. But he used every rating numeral from 1 through 9 at least once in the plot.

"It's an excellent test which will be fun to watch," Nanda says,. "We have these ratings to know how the plots emerged. It will be interesting to see if some of these differences show up in yield differences at the end of the season."

Nanda is betting that they will. We will keep you up to date on this test.