ftom N form or timing. As a result, there appears to be little basis for selecting hybrids differently based on the N fertilization program, or for fertilizing hybrids differently. Hybrid differences in response to population are fiequently described as a hybrid’s ability to “flex” its cars and produce a larger ear in response to lower populations. Prolific or double-eared hybrids have been promoted as having the ability to produce better at lower populations. Hybrids with these characteristics should be ideally suited to less productive sites, where lower populations may be used or where there may be a greater risk of poor stands. The idea behind this would be that these hybrids could produce a larger ear in response to favorable conditions or reduced populations. Studies in lowa, Wisconsin, and Ohio, however, have indicated optimum populations do not differ greatly among commercial hybrids. These studies have also shown the best hybrids at low populations are generally the best at high populations. Based on this research, it appears that population response should not be an important factor in hybrid selection. Another interaction which has received attention is the adaption of hybrids to high or low yield situations. The question in this issue is whether different hybrids should be selected for high yield and low yield situations. Plant breeders have documented differences among different hybrids in their yield response to different situations (yield stability), and some hybrid testing programs have con- firmed these differences. This is best shown using a stability graph, such as Figure 2, where the yield of two top yielding hybrids is plotted against the average yield of all hybrids tested. In this figure, both hybrids had similar average yields, but hybrid 10 generally performed better in the low yielding sites and hybrid 1 performed better in the high yielding sites. This indicates that differences among hybrids do exist and that there is potential for these differences to be exploited by selecting soim hybrids for higher yielding conditions and other hybridsfor the lower Figure 2. Stability analysis graph tor two hybrids taatad In the 1985 Pennsylvania Commercial Hybrid Com Testa for Maturity Zone 1. The average yields of both hybrids across locations were similar. IHMIRFD C.B. HOOBERA SON, INC. ■ HOOBER EQUIPMENT, INC. Intercourse, PA ■■■■■■■■■■■■■■l Middletown, DE (717) 7184231 ■ ■ TWO LOCATIONS (302)378-9555 (MiMIIII Of aivtfd rijciii iivK OAO^fC JL wmr FURROW FIRMING BOOTS AND POINTS PART # DESC. 91265C1 Std. Point 91265 CR Tungsten Carbide 1277777C1 Std. Boot 1277777C-R...Tungsten Carbide Boot WE SHIP PARTS DAILY Via FED. EXP. - UPS - PPSH - BUS - AIR FREIGHT, ETC. HQUES Mon.-Fn. 7 AM-5 PM; Sat.: 7 AM-Noon I H BIV CALL US... Authorized ItCotlUtoWuHwilf UPS Station Considerations for selecting com hybrids (Continued from Pag* 19) The Saving Place PRICE .$9.01 .$25.25 $22.92 .$34.77 PLANTER & DRILL DISK OPENERS (With Bearings) • Case IH • John Deere • Krause • Great Plains PART# 90850C92.. 90851C92.. 603020R92 1344911C1 DESC. Disk Disk Case IH Drill- Case IH Drill... 141464C92...1H Planter. 8500276... JD Planter... 107-129S...Great Plains Drill NEW 12 WAVE COULTERS FOR PLANTERS AND DRILLS is” $19.00 it $19.75 • KINZE • JOHN DEERE • WHITE • VETTER • GREAT PLAINS 200 180 160 140 120 100 60 80 100 120 140 160 180 Location Mean (Bu/A) yield potential situations. Based on this, there appears to be some basis for placing hybrids on the farm differently depending on the anticipated yield level of a field. In Pennsylvania, one of the main causes of low yield potential is drought stress associated with shallow soils. Thus, a consideration of the yield stability of a hybrid may be important when selecting for such high and low yield situa tions. Unfortunately, only limited data exist on the yield stability of available hybrids, although the seed industry is making an effort to characterize hybrids in this fashion. SOURCES OF INFORMATION Sosd supplier* Commercial seed companies should be able to supply much of the detailed information on hybrid charac teristics. Seed suppliers who have worked with these hybrids in your area should have a basic understand- .$22.54 msTAvm S\ Up Your lone And ice Your Parts Order With t_» Corn Talk, Lancaster Farming, Saturday, April 17,1993—Page Hybrid 1 Hybrid 1 Growing Degree reported on a given day by a morning and afternoon observer have usually occurred on different calendar days. The refined standardization procedure is detailed in North east Regional Climate Center Publication RR93-1. When tested on several sites through out the Northeast, weekly observation time bias was reduced to between 0.5 and -0.5 GDD, (producing no differ- PRICE ...$21.98 ~$21.98 ....$13.99 ....$17.99 STRESS-FREE ROW CROP GUIDANCE • Unique design keeps the implement • Eliminates excessive pull and stress parallel with the rows even when on hydraulic components associated the tractor moves laterally as it with other guidance systems drifts off course Most other • Very few moving parts provide systems oversteer the toolbar smooth, friction-free lateral which adds damaging side pres- movement sure to the stabilizing coulters • Works effectively on all conventional • Automatically compensates for and ndge-ull cultivators, planters and sidehill drift 4-wheel drive articulated tractors CALL FOR DEALER LOCATED NEAREST YOU $19.39 $17.58 539 Falling Spring Road I P O Box 219 I Chambersburg, PA 17201-0219 Phone 717 263 9111 Ryder supply (D®lM TMM MIWO PENNSYLVANIA MASTER COHN GROWERS ASSOC., INC. ing of many of the hybrid traits that are important in your crop production system. They also have access to performance data collected from their own evaluation trials conducted in the regioq. These data are best used for comparing hybrids within a com pany because competitive hybrids often are not included in these trials. Uithrarsity hybrid trials Hybrid performance trials are conducted annually by the Department of Agronomy at Penn State. In this testing program, hybrid evaluations are conducted at five sites in each of the four com maturity zones in Pennsylvania. An average of SO to 60 hybrids are evaluated for grain production in each zone. Data are also collected on moisture, lodging, plant height, ear height, and some diseases. The results are published in the Pennsylvania Commercial Hybrid Com Tests Report which is available at local extension offices. These trials provide a source of independent informa tion on hybrid performance. Hybrid testing reports' are also available from most of the states surrounding Pennsylvania. Strip trials Many strip trials are conducted annually across Pennsylvania by seed suppliers, growers, and extension agents. Nonreplicated strip trials can provide excellent yield performance data when the results of at least several trials are combined to gether. The results of individual trials should be interpreted cautiously. Individual strip trials are best used to evaluate very repeatable traits of hybrids such as harvestability, height, and maturity. Producers who grow sizeable acreages of com should consider evaluating promising hybrids on an annual basis in a strip plot. These are particularly useful for comparing promising new hybrids to those hybrids already in use. On-farm Records Another valuable but often overlooked source of informa tion for hybrid evaluation is on-farm records. Growers who are able to devise a harvest and record keeping system that (Turn to Page 22) (Continued from Page 20) Days ences when rounded to whole GDD values) over observation hours from 6 a.m. to 9 p.m. Dur ing the other unlikely observa tion hours, weekly observation time .bias was reduced to between 1 and 2 GDD. While the residual bias for the unlike ly hours was considerably high er than that of the more com mon observation hours, the cor rected values represent a thrce to four-fold decrease in ihe actual observation time bias. 217
Significant historical Pennsylvania newspapers