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Corn 2013 Introduction

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North Carolina State University
College of Agriculture and Life Sciences
North Carolina Agriculture Research Service
Raleigh, North Carolina 27695
Steven Lommel, Director of Research

Crop Science Research Report No. 241
October 2013


With the large number of commercially available and prospective hybrids of corn, it becomes difficult for growers to select a superior hybrid suited for their particular area of the state and their individual farming operations. To make this decision, the growers need up-to-date, unbiased, reliable information. The Official Variety Testing Program, through this report, seeks to provide that type of information.1
This report is concerned with corn hybrids in all production areas of the state. The second section deals with corn silage. Both sections are complete in that they contain information on experimental procedure, location of the tests, a discussion of the data for 2013, as well as summary tables for the past two years.
It is hoped that the organization of this bulletin will provide data in a complete form to those interested in the various crops.
Growers are cautioned against making varietal selection decisions based on an individual location in any one year. True varietal performance may have been masked by the unusual weather conditions experienced at any one location or any one growing season.

Comparing Hybrids

Performance of a hybrid cannot be tested with absolute precision. Although the tests are conducted in a uniform manner, as much as possible, uncontrollable variability exists among experimental plots due to soil type, fertility, moisture, insects, diseases, and other sources of variation. Because this variability exists, statistics are used as a tool to determine differences among hybrids. The size of chance variation is listed in each table as the L.S.D. (least significant difference) and those hybrids which do not differ by more than the L.S.D. are statistically not different. Those hybrids that do differ by more than the L.S.D. are statistically different. The Bayes L.S.D. at the K-ratio of 50 (approximately .10 level of probability) was used.

The coefficient of variability (C.V.) is listed as a general indicator of population variability; it does not, however, always indicate level of precision. The coefficient of determination (R2) is a better measure of the level of precision because it indicates the amount of variation accounted for in the trial. The higher the R2 value, the more precise the trial. Thus, relative precision among various trials can be compared. The standard error of the mean (s.e.) is listed as a general indicator of precision since it reveals how well the true mean was estimated. The formula for the s.e. is the square root of the error variance divided by the square root of the number of replications. The error degrees of freedom (Error d.f.) used to test varieties or hybrids is listed along with the mean of the test.

The hybrids which do not yield significantly less than the highest yielder are denoted by an asterisk (*) next to their yields; the highest yielder is denoted by a double asterisk (**) next to its yield. Other agronomic characteristics may be as equally important as yield.

Based on extensive study of the data over 10 years, the most useful data sets to use in choosing medium-maturing corn hybrids are one-year multi-location averages. This one-year average provides the best prediction of the following year performance while including the latest released hybrids. For early and late-maturing hybrids, the two-year averages across locations provide the best data set to examine in choosing hybrids.

Corn Hybrids

The performance of various corn hybrids in different areas of the state depends on their adaptation to the environmental conditions within the area. The performance of hybrids across the state in three geographic regions of North Carolina is reported in this bulletin.

Entries: Any individual or firm may make application for having hybrids tested. A fee is charged on an entry basis. Personnel of the testing program may also include entries about which further information is desired.
Early in January each year, rules governing the tests for the ensuing year are distributed to all previous participants and to those who make inquiry.
Agencies or individuals entering hybrids in the Official Variety Tests were requested to designate the population and maturity range desired. Because of this, some hybrids may not appear to be in the correct maturity group.

Field Plot Technique

Tests were planted at eight locations across the state. Two tests were located in the Tidewater in Washington and Beaufort County on organic soil (HM). In the Coastal Plain region, four tests were conducted in Columbus, Robeson, Lenoir, and Duplin
counties. In the Piedmont, two tests were conducted in Rowan and Union county. Early, medium and full-season groups were included at all locations. Early-maturing hybrids are approximately 105 to 109 days to maturity, medium-maturing hybrids are approximately 110 to 115 days to maturity, and full-season hybrids are approximately >115 days to maturity. It is important to remember that these are loose groupings, i.e some hybrids may easily fit into either of two maturity groups. Seed companies listed the number of days to maturity for each hybrid. Table 2 lists the cultural practices used and Table 3 lists the soil tests results. In field design a randomized block was used on all maturity groups. Each plot consisted of two rows 22 feet long with a 30, 36, or 38″ row width. The two rows were harvested for yield. Alley width was six feet.
In 2013, all hybrids were planted at the same population within maturity group. The early hybrids were 34,000 ppa while medium and late hybrids were 32,000 ppa.. All hybrids were treated with Poncho (clothianidin) or Cruiser (thiamethoxam) or other systemic insecticides (Table 13).