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Crop Update: Soybeans Struggling in Louisiana

ALEXANDRIA, La. - Over the past couple of weeks, the crop situation in Louisiana has gone from good to poor back to good and now mixed depending on where you are in the state. Sub-tropical rainfall or monsoons in some situations are the topics of conversation. In south Louisiana, over the past few days over 9 inches of rain has fallen in some parishes.

Isolated rainfall reports, which have come in, are as much as 20 inches. Most of the heaviest rainfall has been between Interstate 10 and U.S. Highway 90 in south Louisiana. Evangeline, Acadia, St. Landry, Jeff Davis, Lafayette, St. Martin, Pointe Coupee, Rapides, Concordia and Avoylles parishes have been hardest hit. From Alexandria northward, rainfall has been slightly less with about 5 inches reported on average.

As of Monday, our soybean crop is approximately 60 to 70 percent planted with the exception of the wheat acres, which will be planted in the next three to four weeks. Overall, acres are still very hard to assess but soybeans and corn appear to be the predominant crops that have been planted. A large portion of these soybean acres was planted from May 6th to May 11th.

The portion of the crop that was planted earlier is on average 6 to 9 inches tall and has suffered through cold nights and cool soil temperatures. The yellow “appearance” of the crop had diminished due to increased soil and air temperatures but some portions of these early-planted beans have begun to flower.

The soybean crop is struggling with a couple of issues right now. Bean leaf beetle populations are above threshold in several of our earlier-planted fields with most of the reports coming from the northeast. Replant concerns due to general lack of growth, no soil inoculant being used and flooding of fields are the predominant issues that need attention.

In most of the state, cultivating the crop after the soils dry some would not hurt because of the anaerobic conditions that the crop has been subjected to. Cultivation primarily benefits the soil by increasing aeration. According to Jay Stevens, LSU AgCenter Extension soils specialist: “If the sun came out tomorrow, and the water was able to evaporate quickly, that would be best; if not cultivation is about the only option that you have to get some oxygen in the soil and into the plant’s root zone. However, under the type of conditions that the crop is in now, cultivation can offer benefits. If fields have been inundated by subtropical rainfall especially on lighter ground or soils low in organic matter, cultivating can increase root development, which can be stifled after compaction from heavy rains. This increased root development may be what we need to jump start the crop again.”

Another point about soybean production, which cannot be ignored, is the use of inoculant on fields that have not had soybeans in rotation for several years. This practice is still being overlooked in some situations. Additionally, if you have not planted as of yet, which is the case in a couple of hundred thousand acres, do not panic. There is still time. Over the last couple of years, several hundred thousand acres have been planted in late May and early June and have been successful. Many producers last year planted in the second week of June and still harvested 40 to 50 bushels on average.

One question that I will address in a future article is that of harvest aids regarding when to apply and what to apply to meet the August delivery date. If you are planning on delivering beans in August, remember a couple of things. Very simply, stay on top of weed control and insects. Both of these types of pests can be affiliated with delayed maturity if not properly controlled. The fungicide issue of what and when to spray regarding yield enhancement as well as improved seed quality is something that needs attention also.

According to Ray Schneider, a soybean pathologist with the LSU AgCenter, “Fungicide applications before R3 have not been researched and applying a fungicide before R3 might justify a second application due to late season infestations. We do know that applying a fungicide should increase yield by about 4 to 6 bushels an acre. Regarding seed quality, an application at R3 will enhance quality more than a later application at R4 or R5”.

To try and attempt to sum things up, portions of south Louisiana will be looking at replanting some fields from beans not emerging after being planted or fields that have stayed under water for too long. Before making that replant decision, please do stand counts on the fields and see exactly what type of plant populations are left. Soybeans are pretty resilient and forgiving to a point but severe water stress can be pretty hard to overcome. I am telling producers, take one field at a time and make the call.

David Lanclos is Extension corn and soybean specialist with the LSU AgCenter. He is based at the Dean Lee Research Station in Alexandria.


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