Early Maturing Varieties and Soybean Cyst Nematodes: Will this Marriage Work?

Soybean cyst nematode (SCN) is widely distributed in Kentucky\u27s soybean growing areas. The use of SCN-resistant varieties has long been a recommended production practice for infested fields. However, continuous use of such varieties can result in a shift to a race of SCN which is able to vigorously attack previously resistant varieties. For his reason, many states have long recommended that producers periodically grow a crop of SCN-susceptible soybeans within a crop rotation when SCN populations are too low to cause yield reductions. In Kentucky, the UK Plant Pathology Department recommends a four year rotation in SCN-infested fields [PPA3; Wanted: Soybean Cyst Nematode (video)]. Year one should be a nonhost crop (like corn), followed by an SCN resistant soybean variety, then another nonhost crop (corn or milo). Producers would grow an SCN-susceptible soybean variety in the fourth year of this rotation. This is, of course, provided that the three previous years have brought SCN populations down to a safe level

Preliminary Maturity Group II Soybean Variety Trials

On-farm research with early maturing soybean varieties in Kentucky in both 1993 and 1994 has indicated that Maturity Group (MG) II varieties yield competitively with our traditional MG IV varieties. In those tests, four MG II varieties were compared with a single, high yielding MG IV variety (Asgrow A4715) over a range of planting dates on a total of 27 farms across both years. Asgrow A4715 averaged 43 bu/A, while the best MG II variety (Jack) averaged 39 bu/A. Such on-farm strip tests are valuable for comparing varieties under true production conditions. However, strip tests can effectively compare only a handful of the early maturing varieties available. In contrast, the soybean variety trials conducted by Iowa State University routinely include over 200 MG II varieties. In on-station tests at the UK Ag. Experiment Station during the same 2 years, where 12 MG II varieties were compared in four planting dates each year, the best variety averaged 10 bu/A more than the worst variety. However, since we were only able to compare 12 varieties in the on-station tests, both the on-farm and on-station tests could have easily missed some of the best MG II varieties. An alternative which would increase the number of varieties being compared, would be to simply pick the best early maturing varieties from yield tests conducted in the northern locations in which MG II varieties are routinely tested. That strategy assumes that varieties which perform well in the north will continue to perform well when they are moved well south of their normal zone of production. Several soybean breeders, both public and private, have indicated that they feel that some varieties might move south better than others. Traits which have been cited as potentially advantageous for such a southerly move include: 1) taller plant height, 2) higher lodging scores in northern locations (indicating good vegetative growth potential), 3) warmer temperature tolerance, and 4) greater tolerance to pests (such as nematodes, insects, diseases, or weeds). The objective of this research was to compare Kentucky yield performance to northern Illinois yield performance of the same group of commercial and public MG II varieties

Early Maturing Varieties and Soybean Cyst Nematodes: Will This Marriage Work?

Soybean cyst nematode (SCN) is widely distributed in Kentucky’s soybean growing areas. The use of SCN-resistant varieties has long been a recommended production practice for infested fields. However, continuous use of such varieties can result in a shift to a race of SCN which is able to vigorously attack previously resistant varieties. For this reason, many states recommend that producers periodically grow a crop of SCN-susceptible soybeans within a crop rotation when SCN populations are at minimal levels (causing less than a 5% loss in yield). The UK Plant Pathology Department recommends a four year rotation in SCN-infested fields [PPA3; “Wanted: Soybean Cyst Nematode” (video)]. Year one should be a nonhost crop (like corn), followed by an SCN-resistant soybean variety, then another nonhost crop (corn or milo). Producers would grow an SCN-susceptible soybean variety in the fourth year of this rotation. This is, of course, provided that the three previous years have brought SCN populations down to a safe level

An Evaluation of Twelve Maturity Group II Soybean Varieties at Lexington, Kentucky

In both 1993 and 1994, the Kentucky Soybean Promotion Board funded an on-farm test of a small set of Maturity Group (MG) II varieties. Those studies showed that several MG II varieties were competitive with a high-yielding MG IV variety. However, other MG II varieties did not perform as well in those tests, indicating that variety selection is an important management consideration if this early maturing cropping system is to be successful in Kentucky soybean producers\u27 fields. MG II varieties used in past University of Kentucky tests have been chosen based on their performance in university variety trials where such varieties are normally grown. For example, we have used data from Iowa, Indiana, Illinois, and Ohio to make our choices. Such tests often include large numbers of MG II varieties; for example, the Iowa State University trials routinely include over 200 MG II varieties

An Evaluation of Twelve Maturity Group II Soybean Varieties at Lexington, Kentucky

In 1993, an on-farm study funded. by the Kentucky Soybean Promotion Board showed that the best Maturity Group (MG) II variety tested was quite competitive with the best available MG IV variety. However, other MG II varieties did not fare as well, indicating that careful variety selection will be essential for on-farm success with this MG II cropping system. MG II varieties used in past University of Kentucky tests have been chosen based on their performance in university variety trials where they are normally grown, for example, in Iowa, Illinois, Indiana, and Ohio. Such tests include relatively large numbers of MG II varieties. For example, Iowa routinely tests up to 200 such varieties at multiple locations. Thus, it would seem that Kentucky growers ought to be able to simply use the Iowa results to choose MG II varieties to plant in Kentucky. However, some growers have expressed interest in obtaining yield performance data for MG II varieties grown under Kentucky conditions. Some suspect that our warmer temperatures, heavier insect and disease pressures, and more prevalent soybean cyst nematodes might alter the relative yield ranking of varieties moved well south of their intended growing area. However, recent cooperative work between the University of Kentucky and the University of Minnesota showed no evidence that some early maturing varieties are better suited to move south than other varieties. Thus, northern data ought to be suitable for use in MG II variety selection in Kentucky

On-Farm Testing of Early Maturing Soybeans

Maturity Group (MG) II soybean varieties have performed well in University of Kentucky tests over the past several years. Six tests from 1986 to 1989 showed MG II varieities to outyield MG I, III, or IV varieties. During those relatively dry years, MG II may have been able to better utilize limited soil moisture than did later maturing varieties. Across the years 1990 to 1993, four planting date tests showed continued strong performance by MG II\u27 varieties, although MG III and IV varieties had slightly higher yield averages during those wetter years. In summary, over the last eight years of UK testing, MG II varieties have produced average yields virtually identical to those of MG III or MG IV varieties. Thus, growers could plant a portion of their soybean acreage to MG II varieties and gain the advantages of earlier harvest, more fall planting options, and perhaps profit from higher early fall cash market prices

On-Farm Testing of Early Maturing Soybean

Maturity Group (MG) II soybean varieties have performed well in University of Kentucky tests over the past several years. Early planted (late April/early May) tests in the relatively dry years of l986 through 1989 showed MG II yields to exceed those of MG III or MG lV. Over the generally wetter years 1990 through 1993, MG III and lV yields were slightly better than those of MG II varieties. Across eight years of data, MG II yield averages were virtually identical to those of MG III and lV. Perhaps growers could plant a portion of their soybean acreage to MG II varieties and gain the advantages of earlier harvest, such as more fall planting options and slightly higher early fall cash market prices, while obtaining similar yields as they could with MG lV varieties

Growth of Early Maturing Soybean

Production of early maturing soybean varieties has grown in popularity across the southeastern US in recent years. Many growers in Mississippi, Arkansas, and Texas have seen this system as a way to avoid late season drought. However, several Kentucky growers have had good success with the use of Maturity Group (MG) II soybeans in the recent seasons which had generally good rainfall patterns. Some growers are glad to get competitive yields from MGII soybean while gaining the opportunity to harvest some of their soybean acreage before corn is ready to harvest

Potential Use of Ethephon to Control Lodging of Soybeans

Lodging is sometimes a serious problem with soybeans in Kentucky, especially with the full season crop. However, under, excellent growing conditions, or if planting rates are too high, substantial lodging of double crop soybeans can also occur. If lodging occurs early during seed fill, it can reduce yields directly by causing poorer light use and increasing diseases. If lodging occurs late during seed fill, it will have little direct effect on yield, but may have an indirect effect by slowing down harvest and increasing harvest losses. Thus, the use of an inexpensive chemical to reduce soybean lodging is attractive. Our primary objective in this study was to determine if ethephon (Cerone) could reduce lodging of soybeans. Since we suspected that the shorter plants resulting from ethephon treatment might have set pods closer to the ground, our secondary objective was to determine if ethephon would have a detrimental effect on yield by causing greater harvest losses. While ethephon is not labeled for use on soybeans, we wanted to study its potential use for this important Kentucky crop

Planting Dates For Early Maturing Soybean

Early maturing soybean cropping systems have been gaining in popularity with producers across the southeastern US, as well as in Kentucky. To our south, some producers in Texas, Arkansas, and Mississippi are using varieties that are two or three Maturity Groups (MG) earlier than those traditionally grown. The main intent in those states has been to avoid late summer drought by using early maturing varieties coupled with early planting. Previous Kentucky research in this area has also emphasized early planting(late April). However, a number of Kentucky growers have had good success using later planting dates for early maturing varieties, particularly in the wetter years we have seen so far in the 1990s