Tag Archives: planting depth

Planting Tips for Profitable Double-Crop Soybean

   Before I get into tips for soybean, I must emphasize one must focus on the entire double-crop wheat-soybean system.  Both crops must contribute to profit; one crop cannot carry the other.  You will may save some input costs such as lime, fertilizer, and rent (making those seasonal cost spread over two crops) with the double-crop system, but certain costs such as soybean seeding rate will increase.  In the end, these inputs roughly equal out with the exception of land rent that can vary greatly over Virginia.

   With that said, the most important thing to insure a profitable double-crop system is yield, yield of both crops.  Without a minimum of 80+ bushel/acre wheat and 33-35+ bushel soybean, the system will not likely be as profitable as the full-season soybean system, especially with today’s low prices. 

Assuming that you will intensely manage both crops during the growing season (note that intensely managing does necessarily not equate to greater input costs, but instead greater attention), the most important thing that anyone can do right now for greater yields is to harvest the wheat crop as soon as possible, and then immediately plant the soybean.  Our 3-year, 5-state (PA, MD, DE, VA, NC) project conducted just a few years ago clearly confirmed that this is one of, if not the most important decision that a double-crop farmer can make.  In that project, we generally showed a rapid decrease in both wheat and soybean yield with delayed harvest and planting after mid-June.  Wheat yield declined anywhere from 0.5% to 2.5% per day, depending on location and year, versus wheat that was harvested at 18-20% moisture.  This was largely due to rapidly declining test weights afterwards.  And we also noted that quality decreased in many test locations. Note that if wheat is harvested this wet, then it will need to be dried almost immediately.  I don’t recommend this unless you have a continuous-flow drier or have a buyer willing to take the high-moisture wheat without severe price dockage. 

Although we found a benefit to the wheat crop, probably the bigger benefit however to harvesting wheat at high moisture is earlier planting of the soybean.  On average the soybean yield began to decrease about ½ bushel/acre per day by mid-June, but this increased to 1-2 bushels per day once we got into late-June (more northerly Mid-Atlantic states) and early-July (more southerly Mid-Atlantic states).   This resulted in a major income difference. 

Just to re-emphasize this most important point, harvesting the wheat and planting the soybean ASAP is the most important thing a farmer can do to make this system as or more profitable than a full-season soybean system.  The current weather is not helping with this (we could have harvested much of our wheat this week), but hopefully next week will bring drier weather.

Here are some other tips that are very important when planting double-crop soybean.

Variety Selection. Select the latest maturing varieties that will mature before the frost.  This will assist with growing as much leaf area and having as many reproductive nodes as possible.  Plant the earlier maturing varieties in this maturity range on your best soils and the later relative maturities on the poorer-yielding land.

Always Plant in Narrow Rows.  I prefer 15 to 20 inch rows seeded with a planter that singulates the seed.  Seed singulation insures uniform seed placement within the row and no big gaps between plants.  The other option is to plant with a drill, which achieves the narrow rows but results in what many refer to today as a “controlled spill”.  This results in many gaps, 2 or 3 seed planted in the same place, and generally lower yields (we proved this in some on-farm double-crop studies in the early 2000s).  Still, a drill is better than 30-inch (or wider) rows at such a late planting date.

Seeding Rate. Beginning next week in Virginia, plant 140,000 to 160,000 seed/acre and increase that rate by 20,000 seed/acre with each successive week.  This will of course put the seeding rate up to 200,000 to 220,00 plants by the first full week of July, sharply decreasing your profit with greater seed costs and lower yields.  Again, this is to insure maximum leaf area and node development.  Note that as one moves north and west, greater seeding rates may be needed due to the shorter growing season (e.g., northwest Virginia may require a greater seeding rate than southeast Virginia, or North Carolina). If using a drill, I suggest increasing these rates by 10%.

Insure Good Soil-to-Seed Contact. First, adequately spread the wheat residue.  No planter will uniformly plant through inches of matted residue. Then make sure the planter is properly set to 1) cut the residue, 2) penetrate the soil to the proper seeding depth, and 3) ensure good soil-to-seed contact.  These steps must take place in order. And they affect each other; a mistake in accomplishing one of the steps can result in mistakes in the other two.  I suggest waiting until late morning to begin planting to insure that the small grain residue to dry – unless the residue is dry, cutting through it will be a problem, resulting in hair-pinning of the residue and prohibiting proper soil-to-seed contact. 

Plant into soil moisture.  If there is plenty of moisture, you can plant as shallow as ¾ inch and get good and rapid emergence.  If a little dry on top, you can plant as deep as 1.5 inches.  With warm soil temperatures, soybean will generally emerge well from this depth and may even emerge from even deeper depths (but I don’t recommend).  Unless you farm in wet, poorly drained soils or are growing continuous soybean, I don’t usually recommend a fungicide seed treatment during June and July due to warm soils.  Double-crop soybean usually emerge quickly if planted into soil moisture and will “out-grow” any seedling disease.

Insure Nitrogen Fixation. If soybean have not been grown in a field for the past 3 years, then be sure to apply inoculate to the seed with the proper bacteria.  This will insure adequate nitrogen fixation by the soybean plant. There is no need to apply nitrogen; definitely don’t apply more than 25-30 pounds/acre or you will inhibit this vital biological process. As a side note, we did find a fairly consistent 1 bushel yield increase with starter N at 25 lbs/acre due to slightly better early-season growth; but this did not pay for the cost of the N – so I don’t recommend.

Fertility (P, K, S, etc.).  Keep in mind that the straw contains quite a bit of nutrients.  If the straw is harvested, make sure that you are replacing those nutrients that are leaving the field.  For more information, see our VCE publication,  The Nutrient Value of Straw.  And make sure that you are being paid more for the straw than these nutrients and organic matter is worth!

Full-Season Soybean Planting Dates, Maturity Groups, Seeding Rates, and Seed Depth

Best Planting Dates & Maturity Groups (MG). If you’ve seen some of my presentations in the past, the best maturity groups will largely depend on location, but also on field productivity. Still, we cannot talk about maturity groups without a discussion on planting date, as they influence each other. Here are some general full-season guidelines:

Planting Date x Relative Maturity Experiment in Caroline County, VA, 2019

Planting Date. On average, there is little advantage, although no disadvantage, to planting in April if using adapted varieties. My data indicate that late-MG 4s and early 5’s are generally the best choice at both planting dates. But note my comments below regarding field productivity.

Location and Maturity Group. On average and most consistently, late-MG 4 and early- to mid-MG 5 varieties have yielded more than other relative maturities when planted in May in most of Virginia. Exceptions are the Northern Piedmont and Eastern Shore. In the Northern Piedmont, late-3s through late-4s yield more than 5s. On the Eastern Shore, early- and mid-4s appear to have the advantage.

Note that these comment are based on relative maturity and planting date studies over the last 3 years and from 10 years of variety test data. This does not mean that you will see similar results every year on every field. There are always exceptions, including the following.

Early planting dates and maturity groups work best on the most productive field. By planting early with an earlier-than-adapted relative maturity will place the most critical time of soybean growth and development, the pod and seed stages, earlier in the year. We generally experience more water and heat stress earlier in the summer; therefore, a more productive field/better soil type will better tolerate the stress (and better take advantage of the longer days).

Later planting dates and later maturity groups work best on less productive soils. By planting later (up to the first week of June) and with later maturity groups (mid- to late-5s), we can avoid the most stressful time of the year, placing the critical pod and seed development into a less stressful time of the year.

Full-Season Seeding Rates: In general, 100,000 to 140,000 seed/acre (assuming at least 75% emergence) is enough to maximize soybean yield when planted in April and May. I’ve even maximized yield with less seed when early-season growth is good. All we are trying to do is grow enough leaves to get 90 to 95% light interception by early pod fill (R3).

A more detailed analysis of my data however revealed that under relatively low-yielding conditions (less than 35 bushels/acre), we need the greater seeding rates. And the lower rates sufficed under higher yielding conditions. Others have found the same thing in the Midwest and South America. What does this mean as far as adjusting your seeding rates?

First, on historically poor-yielding land, use 130,000 to 140,000 seed/acre. On historically better-yielding land, you can reduce that rate down to 100,000 to 110,000.

Note that the later you plant, as you approach June, greater seeding rates will more likely insure maximum yields.

Also note that plant emergence may be less when planted on cold, wet soils; therefore, increase the seeding rate by 10% or so.

Seed Depth. My philosophy on seed depth is plant into moisture at a depth that will give you the best and fastest emergence. Note that the longer the soybean is in the ground, the more likely it will be affected by a seedling disease. I usually recommend 1 inch deep to the bottom of the seed. Under cool and moist soils, plant as shallow as 1/2 to 3/4 inch deep. This will hasten emergence.

Once the soil warms up, you can plant deeper since germination and emergence will take place faster. But, try not to plant over 1.5 inches deep, especially in April or May. Only do so if the soil is very warm and there is little moisture in the top 1 to 1.5 inches.

To Plant or Not To Plant Into Dry Soils

Rachel Vann, Extension Soybean Specialist – N.C. State University & David Holshouser, Extension Agronomist, Virginia Tech

Now that the weather has turned hot and dry, and with limited rainfall in the forecast over the next ten days, we are starting to get questions about continuing to plant soybeans or halting planting until we catch a rain. There is no consensus on what to do in this situation, but we aim to discuss the pros and cons of the different approaches in this blog post.

Soybean seed must take in 50% of its weight in water to initiate the germination process. Germination is not affected if the seed has imbibed water for 6 hours (seed is swollen, but seed coat in not broken), then it dehydrates to 10% moisture. If the seed has imbibed water for 12-24 hours (seed coat is broken but no radical has emerged) then dehydrates to 10%, germination may be reduced 35-40%. If the radical has emerged and the seed dehydrates to 10% moisture, few if any seedlings will survive (Holshouser, 2012). What we want to avoid with any approach discussed below is exposing the seed to enough moisture to start germination but not enough for the seed to get out of the ground.

The general optimum planting date range for planting soybeans across North Carolina was identified by Dr. Dunphy as May 1 to June 10. This optimum planting range varies from year-to-year based on rainfall, soil water holding capacity and soybean maturity, but the goal is to get the soybean plants to lap the middles before reproductive growth begins. We still have 10 more days before we get to the end of that optimum range this year and parts of the state have a chance for rain before June 10. Continuing to wait to plant is more of a concern for our growers who still have seed from early maturing varieties to plant (<MG5), as these varieties will have less time for vegetative growth prior to the beginning of reproductive development. The three major options growers in the region are facing are discussed below.

  1. Plant shallowly in the dry and hope for enough rain to get the seed out of the ground. If you decide to take this approach, you want to ensure you achieve uniform seed depth and that you are not allowing the seed access to moisture below the seed that could lead to variable emergence. This approach would be less risky in clean-tilled situation where you are more confident that you have dried the soil out at shallow depths. Dr. Dunphy said he has seen soybeans planted shallowly into dry conditions before that have sat in the ground >5 weeks and still had excellent emergence when rainfall occurred. The biggest risk with this approach is that you catch a small rain that allows the soybean seed to imbibe water but does not provide enough moisture to get the soybeans out of the ground. We would also suggest you exercise caution using this approach in a no-till situation where you would be more likely to see problems with lacking uniformity of moisture across the field leading to variable seed access to moisture and ultimately emergence variability. In many cases, part of the field will have adequate moisture to get the soybeans out of the ground, other parts will be completely dry as in tilled conditions, and much of the field will be in between. Those in-between areas are likely to have enough moisture to swell the seed and/or initiate germination but not have enough moisture to allow the seedling to emerge.    We have had several inquires on the impact of planting into dry conditions on soybean seed treatments. What we can say is that fungicidal seed treatments are less likely needed in this situation where we already have high soil temperatures and lacking soil moisture than they are in earlier planting situations where the soils are cool and wet.
  2. Plant deep to the moisture. Under most conditions, soybeans should be planted 0.75 to 1.5 inches deep. Soil temperatures are high enough right now to germinate and emerge quickly, even at deeper depths than recommended. But soybeans should not be planted deeper than 2 inches. We’ve talked to several growers and County Agents across the region who are not finding soil moisture until 3 to 4 inches deep; we definitely do not recommend planting this deep.  Growers should exercise caution using this approach if your soils are prone to crusting, because a heavy rainfall could seal the soil before the soybeans emerge. In addition, if the planter pushes the soil down a little in tilled conditions, creating a ridge of fluffy soil on each side, a heavy rain will cause this fluffy soil to move into that furrow and possibly add another ½ to 1 inches of soil to your depth.  If you are going to go this route, check the emergence score on the variety.
  3. Keep the seed in the bag until the next time we catch rain. This is the safest approach at this point. Based on historical data, we have another 10 days or so before we start seeing yield declines from delayed planting. Parts of the state have a chance of rain in the next 10 days. Data from recent research throughout the Mid-Atlantic shows that each day delay in planting past mid-June can result in a ½ bu/A or more yield loss and in general these yield declines begin in the second or third week of June; we still have some time before we get to that point.

Whatever decision a grower makes, uniform seed placement in critical to achieve uniform emergence and ensure each seed has as equal of access to water as possible. We have discussed the importance of uniform emergence in soybeans here: https://soybeans.ces.ncsu.edu/2019/04/how-important-is-uniform-emergence-in-soybeans/

In conclusion, there are advantages and disadvantages to each planting option discussed, but we still have time to plant soybeans in our region before we see drastic yield declines. All options discussed will likely result in delayed emergence due to environmental conditions.