Torrential downpours in late 2015 and early 2016 left many farmers with underwater fields. Cropland along rivers and other low-lying areas were submerged for several days leaving many fields drenched and unreachable.
Alabama Extension agronomists say soil testing could benefit farmers who plan to plant fields that spent many hours under water. “Soil testing is always important,” Alabama Extension agronomist William Birdsong said. “If there has been a lot of erosion, then fertility is certainly an issue to be addressed. In such a case, grid soil sampling is preferred, but zonal sampling would also be very beneficial.”
Even if the producer has previously sampled the field, Birdsong said it is very likely to have a field with completely different nutrient requirements following a substantial flood.
Flooding Causes Fertility and Weed Issues
Dennis Delaney, Ph.D., an Alabama Extension soybean and conservation cropping specialist, said in addition to nutrient issues, flooding creates problems for nitrogen-fixing bacteria.
“The nitrogen-fixing bacteria that soybeans and other legumes use to fix nitrogen from the atmosphere are susceptible to flooding,” he said. “If a field has had standing water, then it would be a very good idea for a producer planting soybeans, peanuts, clovers or other legumes to apply the proper rhizobia inoculant at planting to be sure there are enough live beneficial bacteria.”
Alabama Extension Specialist Dr. Joyce Treadaway Ducar said there are other concerns about fields post-flood in addition to nutrients and soil bacteria. While seeds for weed species can be brought to the field by travelers and equipment, growers need to be especially aware if they begin to see weed species not present in past years.
“Flooding and excessive rain can bring a host of new weeds to an area by washing of soil from one area to the next, as well as in carrying weed seed in flood waters,” Ducar said. “Depending on how much rainfall is received, we can learn a lot about where weed species originated from.”
Better Safe Than Sorry
Birdsong said it is always better to know the soil nutrient levels in a field before planting.
He said for many farmers, profit margins are tight and discovering an issue after the fact is not an option, as it would be too late to correct a problem and the economics do not justify such errors.
In addition to getting a detailed profile of the soil nutrient needs of a field, Ducar said it is equally as important to scout fields for new weeds and control them before they are mature enough to go to seed.
For more information on soil testing visit the Soil Test Lab webpage. There are soil sampling directions, as well as nutrient recommendations for Alabama crops.