|Gilbert, Robert - UNIV. OF FL|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 24, 2006
Publication Date: January 1, 2007
Citation: Gesch, R.W., Reicosky, D.C., Gilbert, R.A., Morris, D.R. 2007. Influence of tillage and plant residue management on respiration of a Florida Everglades Histosol. Soil & Tillage Research. 92:156-166. Interpretive Summary: A large portion of the Florida Everglades has been drained for farming. The muck soil that remained after draining the wetlands mostly is made up of decayed plant and animal material (organic matter), which is food for many bacteria and other microorganisms that live in the soil. When microorganisms feed on organic matter, they release carbon dioxide which can be measured. The depth of soil in the drained portion of the Everglades is decreasing mainly due to soil microorganisms feeding on it, and currently, only about two to three feet of soil remain above the bedrock. Tillage practices used for farming may also cause some loss in soil depth through making the soil environment more favorable for these microorganisms to feed, as well as causing an increased release of carbon dioxide from the tilling process itself. However, this has not been well studied, so we designed an experiment to measure the amount of carbon dioxide lost from the soil after deeply tilling the soil with what is called a "switch plow," or tilling to a shallower depth with a disk or tine cultivator. We found that within one day after deeply plowing the soil a very large amount of carbon dioxide escaped from the soil compared to soil that was not plowed. However, when shallow tillage was used, the amount of carbon dioxide lost from the soil was about the same as that from soil that was not plowed. As a result of this research, farmers will benefit from using shallow tillage practices to limit the amount of carbon dioxide lost from the Everglades muck soil, which potentially could help in reducing the amount of soil lost over time if it is to be continually used to grow crops.
Technical Abstract: Subsidence of drained, highly organic matter Histosols in the Everglades Agricultural Area (EAA) of southern Florida is important for sustainability of crop production in this region. Histosol subsidence is primarily due to oxidation of organic matter by aerobic microorganisms, but far less is known about the influence of agricultural practices. The use of shallow tillage, as opposed to deep tillage methods, combined with proper plant residue management, may help to reduce the present rate of subsidence and soil CO2 emissions. The present study was conducted on a Lauderhill soil (euic, hyperthermic, Lithic Haplosaprist) previously cropped in sugarcane (Saccharum spp.). The objectives were to determine the effects of tillage method on short-term CO2 losses in a herbicide-killed weedy residue covered field and another field kept fallow without residue cover, and compare soil respiration measurements made with two different dynamic closed-system portable chamber techniques. Four tillage methods common to the EAA, ranging in depth from approximately 20 to 300 mm, were evaluated. Immediately following tillage, cumulative CO2 loss from the deepest tillage treatment (switch plow; 300 mm deep) was as much as 273 times greater than that from the no-till (control) treatment. The cumulative CO2 losses following intermediate tillage (disk harrow; 78 to 145 mm deep) were as much as 7.8-fold greater than the no-till treatment, but shallower tillage (tine cultivation; 20 to 41 mm deep) was not different. Short-term tillage-induced CO2 losses were primarily related to soil moisture content and soil porosity. Soil respiration measurements made with the two chamber techniques agreed well with each other except for the deepest tillage treatment, where the larger chamber measured CO2 fluxes that were approximately 10 times greater than for the smaller chamber. Results indicate that shallow tillage methods can effectively be used to reduce CO2 emissions and presumably the present rate of subsidence. [GRACEnet Publication]