Tag Archives: Planting Date

Management Recommendations for Frost-Damaged Soybean

Posted on November 1, 2013 by David Holshouser

While most of our double-cropped soybean were planted in a timely manner, many acres were not. And I use the word “timely” very loosely here. This year, “timely” means that they were planted by early- to mid-July. Usually I refer to July planting as “late”, even if the soybean are planted during the first week of July. But, the wet June and July did not allow “timely” planting in many parts of the Commonwealth. Much of Virginia’s double-crop soybean were planted in July and some acres were even planted in early-August.

As a review (maybe a disclaimer?), I did suggest that we continue planting soybean though mid-July because I’ve seen some pretty good yields (in the 30’s) from July-planted soybean. But, planting after mid-July is always risky. With a relatively warm and sunny August and September, late-July and even August-planted beans can catch up and mature before the frost – if the frost waits until early-November. Of course, this year was neither warm or sunny and our first frost came in late-October. Maturity was slowed. The end result is frost- and freeze-damaged soybean.

We are experiencing several scenarios:

Freeze-Damaged Immature Soybean. Soybean were in the R6 stage (green pods and seed) and a hard freeze killed the plant. In this worst case scenario, the crop will not mature and you’ll be left with green seed that you cannot sell. Hopefully very little of our crop experienced this.
Frost-Damaged Immature Soybean. Soybean was in the R6 stage and a frost damaged many of the leaves on the plant (see photo above). In this case, the plants were not killed; therefore, they should continue to mature. But, maturity will be delayed and drying time will be extended. I cannot guarantee that you won’t have some green seed when you harvest, but the number should be much less than for scenario 1. This all depends on how close you were to physiological maturity (R7). And, it’s very likely that the seed will be smaller (photosynthate from the leaves can’t move to the seed if the leaves aren’t there).
Frost/Freeze-Damaged Mature Soybean. Soybean were physiologically mature (R7 stage; at least one pod on 50% of the plants has reached its final brown color). In this case, whether the crop experienced just a frost or a even a hard freeze, the crop will mature but the seed will take a little longer to dry.

Regardless of the scenario you may be experiencing, there are some management tactics that you can use to minimize further damage. Instead of spelling out all of these tactics myself, I’ll borrow an article from Mike Staton, Michigan State University Extension Educator. He is probably more experienced with frost/freeze-damaged soybean than I and he has summarized the issue well.

Management Recommendations for Frost-Damaged Soybeans

Mike Staton, MSU Extension CURE Soybean Educator

This article will help soybean producers reduce the adverse effects of an early frost.

The late planting season combined with some early frost events has increased the potential for frost damage to occur in soybeans this fall. The following recommendations from Michigan State University Extension will help you reduce the adverse impacts in the event that some of your soybean fields are damaged by frost.

Frost-damaged soybeans are generally considered salvageable as long as the plants reached the R6 growth stage at the time the killing frost occurred. The R6 growth stage occurs when the beans completely fill one pod at one of the upper four nodes on the main stem on 50% of the plants in the field. In dense, green soybeans, frost/freeze damage kills the upper leaves but rarely penetrates deeply into the canopy when temperatures remain above 30^oF. However, once the upper leaves have been damaged, subsequent freeze events will penetrate deeper into the canopy. Once the plants reach the R7 growth stage, yield reductions due to frost/freeze injury will be minor. The R7 growth stage occurs when one pod on the main stem has attained its mature color on 50% of the plants in the field.

Combine Adjustment:

Frost-damaged beans will probably be wetter than normal and more difficult to thresh. Your first step in adjusting for this condition is to reduce the concave clearance. If acceptable threshing still does not occur, increase the speed of the cylinder. Make incremental adjustments and check your progress after each adjustment.

Harvest at Higher Moisture Contents:

Soybeans that experienced severe frost/freeze damage extending well into the crop canopy will dry down slowly. In this case, producers should avoid significant harvest delays by harvesting frost-damaged fields at moisture levels between 16 and 18%. Data from the University of Wisconsin showed that shatter losses of 0.2 bushels per acre per day occur after the beans reach 16 to 18% moisture. The beans will need to be dried to a safe moisture level for storage (12% for 6 months). Electronic moisture meters tend to underestimate the moisture levels in green and immature soybeans so remember to add 1.5 percentage points to the moisture meter readings when testing mixtures of green, immature and mature beans and adjust drying times accordingly. In fields where only the upper leaves were damaged by frost, producers should wait and allow the beans to mature and dry to 14 to 15% in the field if possible.

Drying Frost-Damaged Soybeans with Ambient Air:

If only 2 to 3 points of moisture need to be removed, the air temperature is above 60^oF and below 75% relative humidity; no supplemental heat is required in drying bins equipped with full perforated floors and fans capable of producing one to two cfm/bu. However, drying will occur slowly. Drying times depend on initial moisture content, air flow, grain depth and weather conditions. Aeration fans should be run continuously as long as the beans are above 15% moisture and the average humidity of the air is below 70 to 75%.

Drying Frost-Damaged Soybeans with Supplemental Heat:

If you plan to add supplemental heat, be careful as soybeans are more fragile than corn and can be damaged by drying temperatures above 130^oF. These temperatures will cause excessive seed coat cracking and split beans. The relative humidity of the drying air should always be maintained above 40% to protect the integrity of the seed coats and prevent splits. Relative humidity is cut in half for each 20 degrees that the air is warmed. Growers can control the heat and humidity of the drying air by using short burner cycles or by changing the burner jets.

Store Frost-Damaged Beans

Green and immature soybeans are included in the total damage factor in the U.S. soybean grading standard. Elevators will discount loads containing green and immature soybeans and in some cases may reject entire loads if the damage levels are high. Discounts can be reduced by screening out the small beans, drying the rest to 12% moisture and storing them in aerated bins for at least six weeks. The green color may fade and marketing concerns should be reduced after this amount of time.

This article was produced by the SMaRT project (Soybean Management and Research Technology). The SMaRT project was developed to help Michigan producers increase soybean yields and farm profitability. SMaRT is a partnership between MSU Extension and the Michigan Soybean Checkoff program.

Soybean Replant Decisions

Posted on June 27, 2013 by David Holshouser

Deciding whether or not to replant can be a gut-retching decision. I readily admit that the choice to leave the present stand or replant is not a simple one. With the ever-increasing cost of Roundup-Ready soybeans and diesel fuel, the profitability of replanting may not seem a good idea. On the other hand, high prices make replanting more appealing. In the end, your decision should be one based on the estimated dollar gain from replanting. This will require a careful evaluation of the soybean stand and an analysis of yield potential of the present and replanted crop.

In general, there is less benefit of replanting if stands are reduced uniformly across the field. Usually replanting can only be justified where stands have been reduced by half. However, poor stands usually include gaps in addition to merely a lower plant population. These gaps must be accounted for. In addition, one may have a 75-80% stand in parts of the field, while other parts of the field may only have 20-25% of the intended plant population; the decision may be to only replant part of the field.

Remember to take into account the yield loss from delayed planting. Up until mid-June, there is very little yield loss from delayed planting. After this, for every day delay in planting yield declines about half a bushel per day. For instance, if replanting in late-June/early-July (about 2 weeks late), your potential yield will have declined by 7 bushels per acre.

A few more questions must be asked before we can proceed with a step-by-step procedure for estimating the profit of replanting. When considering a replant, do you leave plants in the field and plant through them? In many cases, planting through the poor stand is a possibility. If you’re using rows wide enough to fit a tractor tire comfortably between them, then you can split the rows and plant enough new plants to get the final plant population up to 100 to 120 thousand plants for full-season systems (if re-planting before mid-June) or 180 to 200 thousand plants per acre for double-cropped systems (this may require equipment or tractor tire modifications).

On the other hand, a drill will cut up many healthy plants and make them less productive than the ones that you just replanted. Also, if the drill has wide gauge wheels, then you can severely damage a significant number of plants (there’s a significant amount of down pressure on those wheels – enough to crush a plant on hard soil). And a damaged plant can sometimes act more like a weed than a crop. Recognize that the plants growing in the field are going to be higher yielding that any that emerges after replanting. If you destroy or injure those plants, you’ve just writing off some profit. Therefore, I do not suggest planting through the old stand with a drill.

Another issue is that if you decide to replant, do you switch to an earlier maturity group? There is little need to plant an earlier-maturing variety. Here are two general rules of thumbs:

April/May Plantings: A 3-day delay in planting will result in a 1-day delay in planting. Therefore, if planting 30 days later, the crop will mature 10 days later.

June/July Plantings: A 5-day delay in planting will result in a 1-day delay in maturity. Therefore, if planting 15 days later, the crop will mature only about 3 days later.

Most important is to plant a maturity group that would grow as long as possible (therefore producing an adequate canopy for maximum yield) and still mature before the average frost date. If you’re destroying the old crop and starting over, just make sure that the variety you chose will mature before a frost. Alternatively, if you are planting into the old crop, you may want to choose a variety about one-third to half a maturity group earlier (depending on planting date differences) so that harvest maturity of both plantings will be more in sync. For example, if you planted a relative maturity group 5.6 on June 10, then you could choose a relative maturity of 5.2 to 5.4 if replanting on June 25.

Finally, realize that you’ll need a higher plant population when planting late. Final stand with a double-crop planting should be at least 180 thousand plants per acre. If replanting in July, increase the seeding rate to insure at least 220 thousand plants per acre.

To estimate the profitability of replanting, follow the guidelines listed below. Be sure to incorporate plant population and gaps in your calculations. We’ve found that 2- to 3-foot gaps cause as much or more yield loss that from low plant populations.

1. Determine the cause of the poor stand. Was the poor stand the result of poor seed quality, cold wet soils, hot dry soils, planting too deep or shallow, soil crusting, herbicide injury, insect or slug feeding, poor soil to seed contact, or disease infection? Determine if the cause can be corrected to avoid a similar situation. If slug or insect feeding or disease is the cause, then you might expect poor stands again.

2. Estimate the stand and percent stand loss due to gaps. Pace off the sections of row 20 paces long in at least 6 areas of the field. Determine (in number of paces) the total length of row lost to 2- to 3-foot gaps. For drilled soybean, this can be interpreted at 2- to 3-foot diameter gaps. Then determine the percent of row lost to gaps. In addition, count and determine average number of plants per foot in sections of row not reduced by gaps. The simplest method is to count the number of healthy plants (capable of recovery) in a length of row equaling 1/1000 of an acre. For instance:

· 36-inch rows = 14.5 feet

· 30-inch rows = 17.5 feet

· 20-inch rows = 26 feet

· 15-inch rows = 35 feet

· 7.5-inch rows = 70 feet

Then, just multiply your counts by 1,000 to get plants per acre.

Or, use the Tables 13.1 or 13.2 to determine remaining plant population. The “hula hoop” method (Table 13.2) is valuable with drilled soybean or when rows cannot be distinguished. This involves placing a circular measuring device such as a hula-hoop on the ground and counting the plants contained within.

Table 13.1. Plant populations of different row spacing with different plant counts per foot.
Plants/ foot	Row Spacing
Plants/ foot	36	30	24	20	15	7.5
	Plant Population (1,000’s/acre)
1	15	17	22	26	35	70
2	29	35	44	52	70	140
3	44	52	65	78	105	210
4	58	70	87	105	139	278
5	73	87	109	131	174	—
6	87	105	131	157	209	—
7	102	122	152	183	244	—

Table 13.2. Hula-hoop method for determining drilled soybean populations.
No. of Plants	Inside Diameter of Hula Hoop
No. of Plants	30”	32”	34”	36”	38”
	Plant Population (1,000’s/acre)^a
6	53	47	41	37	33
10	89	78	69	62	55
14	124	109	97	86	77
18	160	140	124	111	100
22	196	172	152	136	122
26	231	203	179	160	144
^aPlants/acre = no. plants ¸ (3.14 x r2 ¸ 43,560 ft2) where r = radius of hula hoop in feet.

3. Estimate the yield of the poor stand. Use Tables 13.3 and 13.4 to determine percent of yield potential for full-season and double-crop plantings, respectively. Multiply this percentage by the expected yield. This is the yield to expect from the deficient stand.

4. Estimate the yield from replanting. After mid-June, decrease the expected yields an additional half of a bushel per acre per day delay in planting. This is the yield to expect from delayed planting.

5. Determine the gain or loss from replanting. Subtract the expected yield of the poor stand (step 3) from the yield expected from delayed planting. This is the gain or loss in bu/A from replanting. Multiply this number by the expected price ($/bu), using future prices, to obtain gain or loss in $/A.

6. Estimate the cost of replanting. Include per acre cost of tillage, herbicide, fuel, seed, and labor.

7. Determine profitability of replanting. Subtract your cost of replanting from your estimated gain from replanting.

Table 13.3. Yield response (% of maximum) of full-season soybeans to deficit stands^a.
% Stand lost to gaps^b	Remaining Plant Pop (1,000’s/A)
% Stand lost to gaps^b	70	105	140
0	95	97	100
10	93	96	98
20	91	93	96
30	88	90	93
40	83	86	89
50	78	81	84
60	73	75	78
^aSource: Pepper and Wilmot. Managing Deficit Stands. 1991. Illinois Cooperative Extension Cir. 1317. ^bGaps of 12 inches or more; 30-inch rows

Table 13.4. Yield response (% of maximum) of double-crop soybeans to deficit stands^a.
% Stand lost to gaps^b	Remaining Plant Pop (1,000’s/A)
% Stand lost to gaps^b	100	140	180	220
0	80	88	95	100
20	71	79	86	91
40	61	69	76	81
60	48	57	64	69
^aSource: 2001-2004 experiments, Suffolk, VA. ^bGaps of 3 feet; 15-inch rows; MG 4 variety

It’s Time to Increase Soybean Seeding Rates

Posted on June 13, 2013 by David Holshouser

Wheat harvest has begun. Remember that soybean yield potential declines with delayed planting date. During the first two weeks of June, this decline is barely noticeable. After mid-June, expect yield to decline about ½ bushel per acre per day. So to minimize soybean yield loss due to late planting, immediately (or as soon as you can) plant. I like to see the combine and the planter or drill in the field at the same time.

Soybean planted after mid-June will not always develop enough leaf area to capture 90-95% of the available sunlight by early pod development (R3). Only if four layers of leaves are formed by that time will yield not be affected. Of course the growing season makes a difference. Last year in many parts of Virginia, even the latest-planted soybean were able to produce enough leaf area. But, on average, June- or July-planted soybean are unable to do so. Therefore it’s important to take actions to minimize this decline.

First, plant as soon as possible. With the recent rains, soil moisture should not be a problem. Even if the soil is dry on top, I suggest to go ahead and plant. You may have to plant a little deeper to hit moisture (don’t plant much deeper than 1.5 inches), but planting depth is not as big of an issue with double-cropped as with full-season soybean.

Second, narrow your row spacing. Narrow rows will produce more leaf area and canopy over faster.

Finally, increase your seeding rates gradually as time goes on. I’m suggesting the following plant populations for Virginia in 2013:

June 2-8 – 120,000 plants/acre
June 9-15 – 140,000 plants/acre
June 16-21 – 160,000 plants/acre
June 23-29 – 180,000 plants/acre
June 30-July 5 – 200,000 plants/acre
After July 5 – 220,000 plants/acre

See the seeding rate chart below to determine the seeds per foot of row needed to obtain a certain number of plants per acre. Note that these seeding rates assume 80% emergence. For different emergence assumptions, divide your desired plant population by the percent emergence that you expect.

	*Desired Plant Population*
*Row Width*	Early-June Planting Date			Late-June/Early July Planting Date
*Row Width*	120,000	140,000	160,000	180.000	200,000	220,000
	(Seed per foot of row assuming 80% emergence)
20	5.7	6.7	7.7	8.6	9.6	10.5
18	5.2	6.0	6.9	7.7	8.6	9.5
15	4.3	5.0	5.7	6.5	7.2	7.9
10	2.9	3.3	3.8	4.3	4.8	5.3
*7.5*	2.2	2.5	2.9	3.2	3.6	3.9
As planting is delayed, increase seeding rate. Use lower seeding rates on more productive soils. Calculation: Desired Plant Pop. ÷ (43,560 sq. ft./acre ÷ row width in ft.) ÷ % emergence Example: = 180,000 ÷ (43,560 ÷ (15 ÷ 12)) ÷ 0.80 = 6.5 seed per foot of row

In addition to planting date, I’ve found that more productive soils will tolerate lower seeding rates, and less productive soils need higher seeding rates; a more productive soil will produce more leaf area than a less productive soil over the same time period.

When Should Soybean Be Planted in Virginia?

Posted on April 9, 2012 by David Holshouser

We must remember a main goal of many pre-plant and at-planting decisions is obtain adequate canopy and leaf area that captures 90% or more of the sunlight by the R2 (full bloom) to R3 (beginning pod) stages. A secondary goal related to planting date is to position the most critical time of crop growth, the pod (R3-R4) and seed (R5-R6) development stages, during a time of the season where there are sufficient resources (water, light, nutrients, CO2, and O2) to maximize yield.
We might assume that the earlier that we plant, the sooner the crop emerges; therefore, earlier emergence means faster canopy closer and more leaf area development. Furthermore, the earlier we plant, the sooner the crop will reach first flower (R1); therefore, the critical R3-R6 development stages will take place at a time when days are longer and there is more sunlight. While these assumptions are mostly true, the end result will not always contribute to final yield.
Let’s examine the first assumption that earlier planting means more leaf area. This is generally true, but how much leaf area do we really need? Soybeans need enough leaf area to capture 90 to 95% of the sunlight by the R2/R3 stages. This minimum requirement can usually be met by planting in April, May, and even early-June. So, adequate canopy development is not usually an issue until we double-crop the soybean after wheat harvest
Of course canopy development is affected by the environment in which the crop is growing, mainly by soil moisture and temperature. If soil moisture is lacking, growth will be slowed but usually not enough to prevent adequate canopy development, even with late-May and early-June planting dates. Besides, early-season soil moisture is usually not a problem with full-season no-till production unless a cover crop has removed most of it during a dry spring. Even if this were to occur, it can be alleviated by killing the cover crop earlier than planned during dry springs and when continued drought conditions are forecast. Low water-holding capacity soils may also affect canopy development even when there is adequate soil moisture at planting, but other cultural practices can make up for the lower leaf area in these situations (discussed later). I reemphasize that it is rare that leaf area requirements are not met with full-season plantings.
In addition, there is not as much to be gained (from a leaf area perspective) from planting between April and early-June. Why? Growth during April and early-May is slow due to cooler temperatures. Therefore, there is little difference in vegetative soybean growth between an April planting (cooler conditions) versus a May planting versus an early-June planting (warmer conditions). When planted in April, soybean may take up to three weeks to emerge and growth will generally be slow until mid-May. On the other hand, when planted in early June, the crop will emerge within 3 to 5 days and, if soil moisture is adequate, will grow rapidly. Therefore the time between planting dates will be much greater than the difference in the subsequent growth of the crop. In summary, I see few benefits, at least from the standpoint of canopy development, in planting soybean before mid-May to early June in Virginia.
An exception may be if you are planting an earlier-than-recommended maturity group (MG) for your area (MG III or early IV). In Virginia, late MG IV’s and MG V’s are the best adapted varieties, with IV’s doing better in the northern half and V’s doing better in the southern half of the state. If you stick with late IV’s and V’s, there should be no issue with canopy development when planted in April or May. On the other hand, a MG III planted in late-May to early-June may suffer as shown in the below graph. This is because there is not enough time between planting and flowering to allow adequate leaf area development. Still, note that yield suffered only when the MG III variety when planted in early June. The yield response does not always look this way due to rainfall patterns, soil type differences, etc. Sometimes MG III varieties will show a similar response as the later-maturing soybean. But, I think that it is safe to say that if planting early-maturing varieties, you should try to get those planted by mid-May to reduce the risk of low leaf area.
Of course, when planting double-crop soybean, canopy development will suffer. Therefore, other cultural practices such as narrow row spacing and greater seeding rates must be implemented to minimize low leaf area effects. Late-planting and double-cropping will be discussed in next month blog.

So, what about the second assumption that the earlier we plant, the sooner the crop will reach R1; therefore, the critical R3-R6 development stages will take place at a time when days are longer and there is more sunlight. The reasoning is that the longest day of the year is during late-June. With more daily radiation during pod and seed development, there is more energy being put into yield. So, it stands to reason that if we were to plant in April, we could push the pod- and seed-development stages into an environment where we can capture more light. This may work as long as the crop is running full speed ahead and there is no other stress to slow it down. But, is this the case in Virginia? Will there be adequate moisture and temperatures lower than 90O F during July and August? I doubt it.
Let’s examine this a bit further. For April and May plantings, a 3-day delay in planting results in about a 1 day delay in maturity. Therefore, planting in mid-April instead of mid-May will allow the plant to reach flowering (R1/R2) about 10 days earlier. Instead of the first flower being on the plant during the last 10 days of July, it’ll be there during mid-July. Instead of reaching R5 (beginning seed) by the last week in August and R6 (full seed) in early September, the crop can reach theses stages by mid- to late-August. But, is this really a good thing? Do we really want to shift the R4 to R6 stages into typically the hottest and driest time of our season? Even if you irrigate, you’ll have the heat to contend with. And it’s much more expensive to irrigation when the temperatures are higher.
Some may suggest that we should take this a step further and use an earlier maturing variety when planting in April. This is sometimes referred to as the Early Soybean Production System. OK, let’s use a variety with a relative maturity of 3.7 instead of one with a relative maturity of 5.2. This will shift the maturity of the crop 12-15 days earlier. So, we are now putting the critical R4 to R6 stages right into July and two weeks of August. Although the crop is experiencing longer days, it’s also experiencing higher temperatures and, likely, lower soil moisture. The Early Soybean Production System will work if you have a consistent August drought. However, our droughts in Virginia are intermittent. We are just as likely to have a drought in June as we are as in July as we are in August. We can’t predict it. However, it is usually hotter in late-July and August than it is in September. So, in the long run, it’s better to push soybean development in Virginia to a later part of the season, even though we cannot gather as much sunlight during the day. Maybe that’s one of the reasons that soybean following our barley crop usually yields as well or better than soybean planted in May.
To conclude, planting soybean early will have little effect on yield in Virginia. Plus, it could be detrimental, especially on low water-holding capacity soils. My suggestion is that you adjust planting dates to suit and spread out labor and equipment needs, but not to increase yield.