Submitted to: Agronomy for Sustainable Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2008
Publication Date: 7/21/2008
Citation: Sigua, G.C. 2008. Recycling biosolids and lake-dredged materials to pasture-based animal agriculture: Alternative nutrient sources for forage productivity and sustainability. Agronomy for Sustainable Development. 29(1):143-160. Interpretive Summary: Forage production offers an alternative to waste management since nutrients in the waste are recycled into crops that are not directly consumed by humans. Establishment of an excellent, uniform stand of bahiagrass in a little time period is essential and economical. Failure to obtain an early good stand means the loss of not only the initial investment costs, but production and its cash value. Forage production often requires significant inputs of lime, nitrogen fertilizer, and less frequently of phosphorus and potassium fertilizers. Bahiagrass is a good general-use pasture grass that can tolerate a wide range of soil conditions and close grazing, and withstands low fertilizer input. It has the ability to produce moderate yields on soils of very low fertility and easier to manage than other improved pasture grasses. Land application of lake-dredged materials and biosolids may not only provide substantial benefits that will enhance the environment, community, and society in south Florida, but also in other parts of the world especially those areas having tropical and subtropical climate with forage-based beef cattle pastures. As such, the agricultural or livestock industry could utilize biosolids and lake-dredged materials to produce forages. Lake-dredge materials and biosolids should be regarded as valuable resources, as part of the ecological system. There is still much to be learned whether the environmental and ecological objectives are satisfied over the longer term. Additional research on disposal options of lake-dredged materials and biosolids are much needed to supply information on criteria testing and evaluation of the physical and chemical impacts of biosolids and lake-dredged materials at disposal sites. The first necessary step in evaluating the sludge and lake-dredged materials application alternatives is to determine whether these materials are suitable for use on agricultural land. Therefore, the biosolids and lake-dredged materials should be analyzed carefully and thoroughly to evaluate their quality. The parameters most commonly measured would include percentage total solids, total nitrogen, ammonium and nitrate nitrogen, total phosphorus and potassium and total cadmium, copper, nickel, lead, and zinc, chromium and mercury.
Technical Abstract: Domestic sewage sludge or biosolids and lake-dredged materials are examples of materials that can be used to cut fertilizer costs in pasture-based animal agriculture. Sustainable biosolids and lake-dredged materials management is based upon controlling and influencing the quantity, quality and characteristics of these materials in such a way that negative impacts to the environment are avoided and beneficial uses are optimized. This paper/review examines the following two key questions. Is the use of these materials in an agricultural setting harmless and sensible? Is the use of biosolids secure in all climates, in all soils and is it sustainable over the long term? Recycling biosolids and lake-dredged materials to pasture-based animal production is quite productive as alternative nutrient sources for forage production. Perennial grass can be a good choice for repeated applications of biosolids and lake-dredged materials. Although biosolids and lake-dredged materials supply some essential plant nutrients and provide soil property-enhancing organic matter, land-application programs still generate some concerns because of possible health and environmental risks involved. Repeated applications of biosolids and lake-dredged materials indicate no harmful effects on soil quality and forage quality. Beneficial uses of biosolids and lake-dredged materials are both economical and environmental. The concentrations of soil nitrogen and phosphorus following repeated application of biosolids were far below the contamination risk in the environment. The residual effect of biosolids over the long term can be especially significant in many forage-based pastures where only 50% of the million hectares of pastures are given inorganic nitrogen yearly. Long-term studies have demonstrated the favorable and beneficial effects of added lake-dredged materials on the early establishment of bahiagrass in sandy pasture fields. Often these materials can be obtained at little or no cost to the farmers or landowners. Lake-dredged materials can be used as soil amendments (lime and fertilizer) for early establishment of bahiagrass in beef cattle pastures. Bahiagrass in plots that were treated with biosolids and lake-dredge materials had significantly higher forage yield and crude protein content when compared with those bahiagrass in the control plots or untreated plants.