May 9, 2013

Management Decisions for Late-Planted Soybeans in 2013

In my previous writings, I have touted the yield and economic advantages of early planting of early-maturing soybean varieties in the midsouthern US. However, in 2013, nearly continuous rainfall and resulting wet soil have prevented the planting of the majority of the intended April and early May plantings. Thus, those acres are being pushed into a later planting window.

To underline just how serious this is, the May 6, 2013 NASS crop progress report estimates that only 15% of the projected Mississippi soybean crop of ~2 million acres had been planted by May 5. This compares to last year’s average of 72% and the 5-year average of 60%. Thus, over 1.5 million acres of soybeans remain to be planted in Mississippi as of May 5.

As of this posting (May 10), two things will happen.

The rain will stop and much of the intended soybean acreage will be planted by May 15.

The intermittent rainfall will continue, further delaying planting of many of these acres into late May and early June.

This article will deal with the ramifications of the latter happening. The items addressed in this article will be based on the fact that later-than-normal plantings in the midsouthern US will require a management strategy that is different from that for earlier plantings.

It is a foregone conclusion that late-planted soybeans in the midsouthern US will yield less than early-planted counterparts. That yield penalty cannot and will not be overcome by increased management of the later plantings. Thus, the below general management hints should be used as a guide to ensure that the maximum though reduced yield potential is realized from later plantings.

Long-term and recent reseach indicate that MG IV varieties can be planted with maximum though reduced yield expectation through about May 20-25. They should be planted in narrow rows during this later period.

Long-term and recent research indicates that Late MG V or early MG VI soybean varieties are the best fit for late May and early June plantings. It is presumed the greater yields result from their longer vegetative period (CM 2005).

A MG IV variety planted in late May/early June will typically take about 35-38 days to reach beginning bloom and 100+ days to reach maturity or R8. A MG V variety planted in late May/early June will typically take about 50 days to reach beginning bloom and about 120-125 days to reach maturity or R8 (CM 2005). The much shorter vegetative period for late-planted MG IV varieties will necessarily mean they will be short and therefore will not canopy in wide rows.

Preventing and/or alleviating short-term stresses during early vegetative development is more critical with later plantings. Therefore, seed treatments should be used, even though the threat of seedling diseases associated with cool, wet soils is not considered as serious with later planting. Using a combination product that contains both fungicides and an insecticide is a relatively inexpensive insurance to prevent stand losses and the early-season stresses caused by seedling diseases and insects. See the article on this website for results from a study that was conducted behind the 2011 flood.

Planting late that results in later calendar-date maturity will necessarily mean a higher probability of detrimental infestations of both foliage and pod-feeding insects during reproductive development. This will result in either increased cost associated with more spraying or unacceptable yield loss if control measures are not applied. Up-to-date information and advisories about pest outbreaks during the growing season are available from AgFax Media and the Mississippi Crop Situation blog.

Planting late results in a higher risk of detrimental effects from drought during both vegetative and reproductive development. In irrigated plantings, this potentially means more irrigation before and/or during reproductive development with subsequent higher input costs. Information in the Irrigation White Paper posted on this website will help with irrigation decisions for late plantings.

The threat of soybean rust to the midsouthern US soybean crop is always a major concern. Rust usually is detected in soybean sentinel plots in the extreme southern part of the region no earlier than late July/early August, which coincides with beginning bloom or R1 of MG V and VI varieties planted in late May/early June.

Since these plantings will not reach R6 until about mid-September, they are susceptible to rust incursions during their entire reproductive period. Thus, they are more likely to require treatment to prevent or control late-season rust infestations that may occur. Up-to-date information and advisories on the occurrence and expected movement of soybean rust in the US are available from the soybean rust pest information platform.

Late plantings will have less time to recover from stresses, especially during reproductive development. Therefore, it is critical that manageable stresses caused by pests, weeds, and drought are either prevented or are quickly identified so that remedial measures can be applied as soon as possible. This will require more frequent scouting.

Later-maturing varieties used in later plantings will be ready for harvest in October and later when there is a greater probability of wet soil. Harvesting at this time usually results in some level of rutting that may require remedial tillage. This may interfere with a continuous no-till system in some years, but as stated in the Tillage White Paper on this website, this occasional tillage does not necessarily compromise the long-term goals of a no-till system.

Other important points to consider are:

Do not till prior to planting. This will result in the earliest possible planting after soil dries, possibly planting before weed emergence, and conservation of soil moisture.

Plant in narrow rows, preferably less than 20 inches. Forming a crop canopy as quickly as possible in these later plantings is critical for success.

Use a broad-spectrum seed treatment and inoculate seed with nitrogen-fixing bacteria. See the article by Dr. Tom Allen for a list of seed treatment and inoculant products.

Do not apply starter nitrogen fertilizer. Inoculants are cheaper.

Ensure a weed-free seedbed at planting. This may mean additional burndown and/or residual herbicide applications since those applied in anticipation of early planting will have lost their effectiveness. Any early-season competition from weeds will be more critical in later plantings. A reasonable option is to apply a tankmix of a burndown/residual herbicide combination (see following point).

Using pre-emergence herbicides that require rainfall for activation will be a higher-risk practice because of the lower probability of summer rain following planting on these later dates. If pre-emergence herbicides are used, be sure to match the herbicide rate with the soil texture to prevent any early-season stunting.

Prevent any early-season weed competition with the soybean crop after emergence. This means more intense scouting for weed emergence and more timely post-emergence herbicide applications following soybean emergence if residual herbicides are not used or are not activated by rainfall or irrigation.

Finally, remember that nonirrigated yields will be low from these plantings and may not be profitable if expensive inputs for weed and pest control are necessary.

I re-emphasize three important points.

If you haven’t already, bookmark the pest advisory links I have provided. Their information will be invaluable to you in planning pest management activities in later plantings. Also, by following the advisories they give, you will save time and money by avoiding applications of unnecessary control measures for the major soybean pests.

I regret that I can only provide broad estimates of occurrences or activities for later plantings. The lack of this type of information is the reason that the Mississippi Soybean Promotion Board contributes to the Midsouth Soybean Board’s multi-state project that is being conducted to provide definitive answers on this topic. The first year of this study was completed in 2012.

Finally, if you are looking for an average daily yield loss estimate for soybeans that are planted after a certain date, you won’t find it here. I place neither value nor credibility on these calculations because they do not represent what will occur in any given year. As you know, the yield from these later plantings will be depend on their subsequent management and the growing conditions that follow the planting no matter what the date is.

Articles that can provide useful information on this subject are: