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After heavy rains: Soybean crop struggles in Louisiana

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. Subtropical rainfall or monsoons in some situations are the topics of conversation.

Most of the heaviest rainfall has been between Interstate 10 and Highway 90. Evangeline, Acadia, St. Landry, Jeff Davis, Lafayette, St. Martin, Pointe Coupee, Rapides, Concordia and Avoylles parishes have been hardest hit. From Alexandria, La., northward, rainfall has been slightly less.

As of May 17, our soybean crop was approximately 60 to 70 percent planted, with the exception of the wheat acres which will be planted in the next two to three weeks.

Soybeans and corn appear to be the predominant crops planted. A large portion of the soybean acres were planted May 6-11. The portion of the crop planted earlier was on average 6 to 9 inches tall and had 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 early-planted beans had begun to flower.

Soybean producers are struggling with a couple of issues. Bean leaf beetle populations are above threshold in several of earlier-planted fields, mostly in northeast Louisiana. The need to replant due to a general lack of growth, no soil inoculant being used and flooding of fields is an issue that needs attention.

In most of the state, cultivating the crop after the soils dry some could help because of anaerobic conditions. Cultivation benefits the soil primarily 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 to get some oxygen in the soil and into the plant's root zone.

“Under the conditions the crop is in now, cultivation can provide 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. Increased root development may be what we need to jumpstart the crop again.”

Another issue is the use of inoculants on fields that have not had soybeans in rotation for several years. The practice is overlooked in some situations.

If you have not planted yet, which is the case on a couple of hundred thousand acres, do not panic. There is still time. Over the last couple of years, several hundred thousand acres planted in late May and early June have been successful. Many producers who last year planted in the second week of June averaged 40 to 50 bushels.

One issue I will address in the future is that of harvest aids — when to apply and what to apply to meet a August delivery date. If you plan to deliver beans in August, stay on top of weed control and insects. Both pests can be associated with delayed maturity.

Which fungicide and when to spray it for yield enhancement and better seed quality also need to be considered.

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”.

Some farmers in south Louisiana will be replanting fields where beans did not emerge and fields that have stayed under water too long. Before making that decision, count stands on the fields to determine plant populations. 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 Y. Lanclos is the soybean, corn and grain sorghum specialist at LSU AgCenter. [email protected].

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