Submitted to: Agro-Environment Symposium
Publication Type: Proceedings
Publication Acceptance Date: 3/3/2008
Publication Date: 4/27/2008
Citation: Norton, L.D. and Acuna, S.F. 2008. Improving Water Quality Using Soil Amendments in Conservation Tillage. In: Natural Resources Conservation, Use and Sustainability. Proceedings of the 6th International Symposium Agro-Environment, April 28-May 1, 2008, Antalya, Turkey. p. 9-13.
Technical Abstract: Water quality is a major problem in many parts of the world. Agriculture has been blamed for adverse water quality problems because of the considerable inputs of nutrients and pesticides in high production modern agricultural systems. When runoff occurs both soluble forms and those attached to soil particles are transported to water ways which can travel great distances to cause algal blooms, hypoxia and adversely affect drinking water quality. Conservation tillage has been promoted as a best management practice to reduce runoff and erosion on highly erodible lands and is the basis on many farm programs in the USA. However, in no-till, per se, all the chemicals are applied at or near the soil surface in soluble forms. When runoff does occur there exists the potential for high concentrations of both soluble and attached forms of nutrients and pesticides. We conducted a three year rainfall simulator experiment on field plots farmed with a modified no-till system in a corn/soybean rotation to determine if soil amendments could reduce runoff and improve water quality. One m wide by 6 m long plots on a Blount loam soil with 4-6 % slope received a 64 mm hr-1 target rate of simulated rainfall until steady state conditions were obtained. Samples of runoff were collected in 5-min intervals for runoff volume, sediment concentration, nutrients and pesticides. The filtered and unfiltered nutrient and pesticide samples were frozen until analyzed in the laboratory. In each year of the study the experiment was performed in the spring on remaining soybean residue with two year old corn residue following planting to corn. All pesticides and nutrients had been applied as part of the normal farming system prior to conducting the experiments. Treatments varied depending on the year but always included the modified no-till system, widely used as the conventional conservation tillage system, with and without a surface application of gypsum soil amendment. Poultry manure application is a common practice in the area and it was also included as a treatment with and without addition 1 ton ha-1 of gypsum. We found that addition of gypsum to the no-till system did not significantly reduce runoff volume but did reduce the sediment concentration, the concentration of soluble reactive phosphorous, total phosphorous and total nitrogen, especially in the plot receiving 1 ton ha-1 of poultry manures. Application of gypsum did not significantly reduce concentrations of atrazine, glyphosate of nitrate, therefore, other methods will need to be explored to reduced the threat to water quality from these very soluble compounds. The practical application of these results are that application of gypsum to a conservation tillage can significantly reduce the offsite pollution due to nitrogen and phosphorous especially where poultry manure is applied.