Albert Boateng Abstract
Nutrient and Metal Fluxes in a Transitional Organic Farming System
Advisor: Dr. K. Kpomblekou-A
Application of inorganic fertilizers in excess of crop needs coupled with pesticide use have resulted in serious environmental and health problems, compromised safe food production, and caused contamination of surface and ground water quality. An alternative to this intensive use of inorganic fertilizers and pesticides in crop production would be a more environmentally friendly approach used in organic farming and includes the use of animal wastes, crop residues, and crop rotation with legumes. According to USDA, the value of retail sales of organic foods was $7.05 billion in 2001 and is projected to reach $20 billion by the 2005 in the U.S. Therefore, research data to support this growing market are critically needed. In addition to macro elements, animal wastes contain trace metals; both macro and trace metals can be released continuously throughout the growing season in leachable forms into soil solution. Knowledge about movement and bioavailability of nutrients and trace metals in the long range in organic farming is urgently needed as nutrient and trace metal loading in agricultural soils increases. Despite the fact that trace metals and nutrients present in animal wastes may have a profound influence on our water resources, research information on nutrient and trace metal leaching through soil profiles in transitional organic farming systems has not been studied. The objectives of this study are to: 1) compare nutrient and trace metal fluxes in the vadose zone in a transitional organic farming system, 2) monitor soil physical and electrical conductivity, and 3) establish relationships between nutrient leaching and soil management practices. The experimental design is a randomized-complete-block with four replications and four treatments examining three cultivars and organic and mineral fertilizations. To homogenize the soil in the experimental field, crimson clover was planted in December 2001, harvested and incorporated into soil in May 2002. Treatments include: 1) control (without a fertilizer), 2) broiler litter, 3) crimson-clover, and 4) NPK fertilization. In December 2002, 48 suction lysimeters were installed in the experimental plots with three on each experimental unit at 30, 60, and 90 cm depths to allow for periodic water sampling. A full weather station with a CSI PC208W data logger software and capacitance probes (Time Domain Reflectometer) were installed horizontally at 30, 60, and 90 cm depths and connected to a data logger (CR 10X, Campbell Scientific) to record digitally rainfall and soil physical properties. The pH of the water collected in each lysimeter at each sampling occasion was measured and the volume recorded in the field, placed in an icebox, transported to the laboratory, and kept in a freezer until analysis. The samples were analyzed for total N and P, inorganic N, sulfate, dissolved reactive P, and trace metals after microwave (MARS 5) acid digestion. Metals in the digest were analyzed by using an ICP/MS. Preliminary results showed presence of nitrate (8.81 to 17.7 mg NO3--N L-) beyond the rooting zone of sweetpotato.