Agronomist Researches Soybean Planting Date

Earlier Planting May Be In Store For Farmers

ST. JOSEPH, LA.
   Dr. Ernie Clawson, an agronomist focusing on cotton and soybeans at Louisiana State University’s Northeast Agriculture Center Research Station, has been working on a threeyear study of soybean planting dates.
   Clawson has recently suggested planting soybeans earlier than was previously recommended. “We have planting dates ranging from mid-March to early June where our previous earliest recommendations were mid-April for any maturity groups,” said Clawson.
   In 2008, Clawson put out two plantings of soybeans one a month earlier than recommended in mid-March and another in late March.
   “We found that you could plant earlier in the conditions that we have had the last two years,” said Clawson. He noted that in 2006, Maturity Group V was especially surprising. “That variety is usually planted the first of May or later but it was the very top yielding variety that we planted in March,” said Clawson.
   “That’s six weeks earlier than usual,” states Clawson, “and it reached its optimal planting date at the very end of March or the beginning of April.” Clawson noted that it was as high yielding at this date as it was at any other date.
   When repeated again in 2008, the study showed very good growth in the early planting date from Group V as it did in the year’s prior. “We haven’t harvested any plots yet this year so I can’t speak on yield,” said Clawson, “but it looks good.”
   The soybeans are irrigated and placed on wide beds, 80 inches from middle to middle. According to Clawson, the soybeans are two-row spacing.
   “In one case, we plant two 40-inch rows on the bed and in the other we plant four 16-inch rows on the bed. The second spacing works out to an average of 20 inches if you account for the space in between the beds,” said Clawson.
   Clawson states that they decided to use 80-inch beds so that they could have a system that used both narrow row spacing and a raised bed for drainage and irrigation.
   Wider beds are being used elsewhere in the region, “80-inched beds are becoming more common in the area,” said Clawson, “they are not always in the exact configuration that we use, but there are a number of different systems where a wide bed is used and used on different crops than soybeans.”
   The Sharkey clay soil used in the test is helpful in furrow irrigating the wide beds. “The moisture appears to be getting all the way through,” said Clawson, “we are in a situation where the water can cross the bed.” Clawson also stated that on Macon Ridge silt loam soils, it can be difficult to get water furrow irrigation to reach the center of a wide seedbed.
   Clawson says that he won’t know until later this year whether the study holds true again but if it does, the recommended planting date for Maturity Group IV and V soybeans may need it to include earlier dates.
   Regarding Maturity Group V soybean results, Clawson stated that it is “somewhat preliminary” because it is only one maturity group variety. He states that it does compare with research that another researcher at the Macon Ridge Research Station has done. “We have confidence in it,” said Clawson.
   Results have yet to be posted, but should be in later this year. To check on Clawson’s progress visit the LSU Ag Center’s website at www.lsuagcenter.com and go to the Northeast Center’s section and look under reports. Δ  

Dr. Ernie Clawson, Agronomist at Louisiana State University’s Northeast Agriculture Center Research Station, details results on a three-year study of soybean planting dates.
Photo by John LaRose