Many cultural methods used in soybean production work for one producer and yet don't fit another's production practices. I learned about these differences early because the turn row discussions can be tough if you are not familiar with regional differences in soybean production.
Example of these differences: Why do earlier-maturing varieties really not work out for central and south Louisiana when they do for our neighbors to the north? Why can a planting date be pushed so early in other states and we in Louisiana have not had quite the same success when we are further south and warmer and should be able to plant earlier. Why do particular regions of Louisiana yield so much higher than others?
Louisiana's historical soybean mean yield is about 28 to 30 bushels per acre. If you could take the southwest region out, Louisiana's statewide average would be about 40 bushels per acre.
I am not saying the southwest region is not important to soybean production, because it is. The southwest region accounts for about 25 percent of all soybeans grown in the state. St. Landry Parish alone accounts for about 10 percent of all beans planted annually in Louisiana. St. Landry Parish and southwest Louisiana are where I grew up, so I am still partial to that area.
I am saying southwest Louisiana producers have struggled with many environmental conditions — such as drought, excess rainfall and additional insect pressure — that producers in other regions have not had to deal with the past several years.
Despite differences across the state in planting dates, varieties, maturity groups, soil temperatures and types, and disease, insect and weed incidences, there are consistencies in soybean production that I see as potential yield advantages.
Producers who consistently produce 45- to 65-bushel yields have some things in common.
The first is less disease pressure from aerial blight, frogeye and cercospora leaf blight. From Alexandria northward not many producers usually apply fungicides. If you are just south of Alexandria and do not apply a fungicide, however, losses to diseases can be severe.
The educational efforts for Asian soybean rust have emphasized the benefits of using a fungicide at R3, regardless of where you live. Midwest producers are just realizing the benefits of an R3 application and this year will probably spray more fungicides than ever before.
The second factor is irrigation. Louisiana lags behind other states in irrigation use and efficiency. If the crop is drought-stressed, irrigation will pay for itself. A success story I continue to promote with producers is that of our LSRVP field in Evangeline Parish in 2003 and 2004. It yielded 40 bushels per acre two years in a row because the producer was willing to irrigate.
North Louisiana farmers traditionally irrigate with center pivots or polypipe and enjoy higher yields.
The third factor is narrow rows. Volumes of data prove narrow rows have an advantage over wide rows, especially at early and late dates. But, because of logistics and crop rotation limitations, much of our soybean crop is still planted on row spacings of 30 inches or wider.
I am often asked, “What is a narrow row?” I define it as a row 20 inches or less. Results from research are inconclusive on increasing yield by planting narrower than 20 inches.
The fourth factor is raised beds such as a traditional sugarcane bed or a variation of such. For the raised bed factor, I do not have a lot of data, mainly personal observations. Year-in and year-out, producers who plant on raised beds outyield those who plant on flat or wide rows.
Many farmers tell me they have moved to planting flat to save labor and diesel costs of hipping or bedding rows and to move to narrow row production.
Most farmers in southwest Louisiana will not hip a row because the rice rotation must be planted flat, but every producer there knows that beans planted on busted-out rice levees are the tallest, greenest and highest-yielding areas of a field. Why? In my opinion, because of drainage.
Look at some success stories. Sugarcane producers who have been double-cropping beans consistently average 45 to 60 bushels per acre. I feel the reason has to do with large well-drained beds on good soil and narrow rows. There is a lesson here.
Many sugarcane producers are debating whether three or four rows per bed is superior. The jury is still out on that discussion. Four rows probably give you a slight weed control advantage by closing more of the row more quickly. By planting on these large beds, beans are very well-drained during the season and tend to shed fewer pods. Rarely do I hear about dropped pods in the sugarcane parishes unless we have had an extended drought.
In a previous article, I mentioned a producer in northeast Louisiana who is raising beds 4 to 5 inches and planting on 18-inch spacings. His yields last year were 60 bushels per acre-plus. His biggest advantage is that he can plant corn, soybeans and cotton in this rotation, using this bedding system.
At this point, we do not have much data to support these observations, but we will do more research. For the time being, I am not discouraging anyone who is interested in decreasing row spacings and raising beds. These large raised beds using narrow row spacings produce superior yields.
It really makes sense. We keep promoting and recommending narrow rows and proper drainage. This system provides the best of both worlds, which may be why yields continue to improve using this narrow-row, raised-bed system.
David Y. Lanclos is the soybean, corn and grain sorghum specialist at LSU AgCenter. e-mail: firstname.lastname@example.org