Missouri's rice acres are on the rise. The latest figures available from the USDA -Economic Research Service estimate 160,000 rice acres in Missouri. This represents a record level of planted rice acres for the state.
Some of the additional rice acreage includes soils that are marginal for holding water. Farmers interested in converting to rice are inquiring about the feasibility of growing rice on soils that have never been flooded for rice. Because of the seismic history and the alluvial nature of the soils in southeast Missouri, many of these fields can be less than ideal for rice production.
Providing sound advice for fields that are near the breaking point can be a difficult call. Many of the map units in southeast Missouri have textural variability that include sand boils and lenses. The size and extent of these coarse inclusions are difficult to determine. This fall, the USDA's Natural Resource Conservation Service (NRCS) began evaluating electromagnetic induction and electrical resistivity on rice fields.
"These methods measure vertical and lateral variations in soil at different depths. Soils that contain sand resist electrical current more than soils that contain clay. Because measurements are geo-referenced, they can be used to create detailed maps illustrating spatial distribution of soil properties," says Jim Doolittle, Research Soil Scientist, USDA-NRCS.
The result is a colored site-specific map that indicates relative differences in the field. "This map will be a tremendous advantage for our field personnel," says Doyle Burch, local Resource Conservationist with NRCS. "We will still need to make field inspections, but EM will empower us to make better determinations." With the maps in hand conservationists will be able to identify suspected areas and probe these areas to confirm sand content. "Having the map will provide better sampling points to verify sand content than any random sampling method. We will also be able to estimate the distribution and quantity of sand in each field."
Initial observations with the EM31, EM38, and GEM300 electromagnetic induction instruments were favorable. These devices can be hand-held or attached to All Terrain Vehicles by non-metallic booms. The Veris 3100, a towed implement system, was used to map direct electrical resistivity. For the most part, each device provided similar results. Additional site evaluations are planned for the 2000 growing season.
