Soybean population dependent upon various factors

By David G. Hallauer

Meadowlark District Extension Agent, crops, soils, horticulture

The components of soybean yield consist of plants per acre, pods per plant, seeds per pod, and seed weight. Most all of these depend up variety, moisture, or other environmental factors. The factor that you as a producer can control--plants per acre--is an even greater concern, particularly as seed costs rise.

Over the past couple of years, 26 experiments on producer fields and university research sites have looked at soybean populations in north central and north east Kansas. While the trials encompassed a number or row spacings, yields, etc., the trend--yields tended to increase in response to increasing population, but only up to a point. After that optimum population level, increasing the number of plants per acre had no effect on yield one way or the other. So, what's the optimum--usually, a population of 100,000 plants per acre is sufficient to maximize yield, even at yields greater than 70 bushels per acre. In very low-yield environments, yields plateau at a population of about 70,000 to 80,000 plants per acre, but at those population levels, producers may run the risk of missing out on greater yields if conditions are better than expected. In very high-yielding situations, producers may need more plants per acre to maximize yields. However, some of the highest yields (close to 80 bushels per acre) were achieved at an irrigated location in which yields leveled out at a seeding rate of 105,000 seeds per acre.

Soybeans adjust to different population levels by increasing or decreasing the amount of branching and the number of pods per plant. When populations are higher than the optimum level, the plants simply produce fewer pods per plant. The total number of pods per acre, however, stays about the same.

So, a final plant population of 100,000 is what you're shooting for. Next week, what do we plant to get 100,000?

Asian lady beetles appearing in homes

Most people are familiar with lady beetles and know they are beneficial because they feed on certain insect pests such as aphids. Though the Asian lady beetle does feed on other insects, as do other lady beetles, it differs from its cousins in ways that can make it a nuisance. While lady beetles usually cluster together when overwintering, only the Asian lady beetle tends to do so around (or in) buildings. And this being the time when they emerge from hiding and head outside, this is also the time when they tend to express their nuisance behavior.

When disturbed, Asian lady beetles emit a yellow-orange liquid (their blood) that produces a foul-smelling odor. This material can stain the walls and home furnishings they land upon. More beetles means a more intense smell. The beetles can also pinch when they land on bare skin. Fortunately, they are unable to break the skin's surface.

Control of these insects is practically impossible in the spring. A vacuum can be used to control those that are in the open but the bag must be sealed after use to prevent escape. Eventually the problem will go away after all the lady beetles have emerged.

4/7/08
1 Star WK\5-B

Date: 4/3/08

	Web hpj.com

Copyright/Privacy
Copyright 1995-2011.  High Plains Publishers, Inc.  All rights reserved.  Any republishing of these pages, including electronic reproduction of the editorial archives or classified advertising, is strictly prohibited. If you have questions or comments you can reach us at High Plains Journal 1500 E. Wyatt Earp Blvd., P.O. Box 760, Dodge City, KS 67801 or call 1-800-452-7171. Email: webmaster@hpj.com