Continous Soybeans? Does Grade and Weight Matter?  01/17/17 3:05:03 PM

Key Dates
Seed Discounts—January 20th, 2017—12% Volume, 6% Cash Seed Discount Ends
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Storm Date January 31st 2017                                               
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Yield Info.—2016 Yield Grids are complete! Visit the lobby for the complete genetics X environment version or our website for the summaries.
Continuous Soybean Management Decisions
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Growers might be considering planting soybeans after soybeans because it is cheaper to plant soybeans than it is to plant corn. Every year there is this discussion and given the current/on-going commodity market situation, some folks are thinking about this.  There are some things to consider in monoculture soybeans. However, certain management practices can be used to lessen the negative impact of continuous soybeans

  1.  A yield loss of 5 to 15% is realistic from continuous soybeans when compared to a corn-soybean rotation. 


Crop Rotation effects on Soybean Yields  1985-2005

Yield (Bushels/Acre)








Source:  Duffy, M. Where will the Corn Come from?  Iowa State Univerisity Ext. Nw 2006

You may not experience that much yield loss every year, but some decrease in yield potential is a near certainty. The yield penalty is believed to be a result of a buildup of pest problems and a reduction in soil quality over time. The yield penalty for continuous soybeans is less with better environments for crop growth. Choose fields that have not had a history of insect and disease problems in soybeans. More problems with soybean cyst nematode (SCN) occur in continuous soybeans. SCN is effectively managed through crop rotation. If you know the field has a history of SCN, do not take the field out of rotation. Fields with soybeans year after year have the potential for having the highest SCN egg levels. Sample fields for SCN to determine egg population levels. Rotate genetics and choose an adapted variety that has a different source of resistance.

  1. Manage Diseases. Wet fields are more prone to disease development, especially pythium and Phytophthora root rot. Select varieties that exhibit high levels of partial resistance to Phytophthora root rot and use soybean seed treatments. The buildup of disease inoculum on crop debris occurs with continuous soybeans. This results in more disease and a greater severity in seasons with environmental conditions favoring disease development. Frogeye leaf spot and Brown stem rot (BSR) can be more of a disease problem in continuous soybeans. Choosing resistant varieties helps with their control, but the genetic sources of BSR resistance are limited. Strategies for fields with a history of BSR may include planting later in the season or planting shorter relative maturity varieties. Watch for leaf diseases and consider appropriate foliar fungicide treatments.


  1. Prevent Problem Weeds. Weed control is more difficult in continuous soybeans. Weeds, like other pests, are constantly kept off balance when crops are rotated. It is not as easy to rotate herbicide modes of action in a continuous soybean system. There is more potential for weed resistance or a shift to more tolerant weeds when growing soybeans year after year.  A residual herbicide along with Roundup® agricultural herbicide in a Roundup Ready® weed control system provides multiple modes of action and helps manage the potential for weed population shifts or resistance to develop. Use residual herbicides that control the problem weed species in the field


  1. Soil and Other Considerations. Maintain good soil fertility and pH levels. The soil should be tested and recommended amounts of lime and fertilizer should be applied. Soil pH should be maintained in the 6.5 to 7.0 range. Soybeans use a large amount of potassium, most of which is taken up within 2 to 3 months after emergence. Potassium deficiency restricts soybean grain development by reducing the size and weight of the beans Sandy-textured soils in particular do not have the capability to hold potassium. Spring applications of potash should be considered on soils that tend to tie it up. Split applications of potash during the early growth stage of soybeans can also help to maintain yield potential. Soybean plants produce small amounts of residue. This can lead to increased soil erosion and a decrease in soil structure and organic matter. The use of winter cover crops and no-tillage can be helpful in maintaining soil quality. A cover crop planted in the fall immediately after soybean harvest improves soil structure and reduces erosion. It may also provide a yield benefit for continuous soybeans. Seedling mortality increases in continuous soybean fields. Maintain seeding rates and consider using seed treatments for better odds of a good stand.

Source: Raising Non-Rotation Soybean. Palle
Pedersen et al. Dept. of Agronomy, Univ. of WI
Rounds or Flats: Which Corn Seed is Better?
“My planter works best with 45 lb AR seed”  OK.  Everyone has their reasons.   Equipment today, continues to make strides towards decreasing the impact of the size and weight of the seed and impact it might have for stand establishment, etc.   Corn seed size and shape on the same ear will vary due to genetics, the environment, and location of kernels on the ear.


Size Description

Approx. Bag Weight*


AF AccuFlat


AF2 AccuFlat


AR AccuRound


AR2 AccuRound


* Estimate provided as bag weight can vary among

corn hybrids.

Genetic Potential. Numerous studies have been conducted over the years that well document Hybrid corn seed size or shape has nothing to do with the genetic yield potential of the hybrid. Small corn seed has been associated with slight delays in tasseling or silking, but this has seldom translated into yield losses.
Seed Quality. Crop stress including high temperature, low soil moisture, or low fertility can decrease hybrid seed size. Additionally, placement of seed on the ear affects both seed size and viability because of the sequential development of the corn ear from the base to the tip and the variation in photosynthate availability to each kernel, seed from a single ear can fall into many size/shape categories. Large-round classes usually come from the base of the ear, flats from the center, and small-round seed from the tip.
Results from a wide variety of scientific field studies suggested that corn producers should focus on genetic potential and seed quality rather than specific seed sizes or shapes when selecting corn hybrids.
Plantability. The most important factor involving seed size effects on yield relates to plantability issues. Plantability problems often occur if planters are not adjusted for the seed size being used. Excessive numbers of doubles (two seeds dropped at the same time) or skips can easily reduce grain yield by 3 to 10 bushels per acre. Therefore, get the most out of the seed corn you purchased this year and calibrate each seed lot separately before the hectic planting season starts. Your corn yields will like you for it!
Sources: R. Nielsen. 1996. Seed size, seed quality, and
planter adjustments. Online source:
Graven, L.M. and P.R. Carter. 1990. Seed size, shape, and
tillage system effect on corn growth and grain yield. Journal of
Production Agriculture 3: 445-452.
John W. McNamara
Wiles Bros. Inc.
606 Wiles Road
Plattsmouth NE. 68048
(402) 298-8550--Office
(402) 499-3870--Cell
(402) 298-7174--Fax

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