title: A comparison of in situ methods for measuring net nitrogen mineralization rates of organic soil amendments.
abstract: In situ incubation methods may help provide site-specific estimates of N mineralization from land-applied wastes. However, there are concerns about the reliability of the data generated by the various methods due to containment artifacts. We amended a sandy soil with either poultry manure, biosolids, or yard-waste compost and incubated the mixtures using four in situ methods (buried bags, covered cylinders, standard resin traps, and "new" soil-resin traps) and a conventional laboratory technique in plastic bags. Each incubation device was destructively sampled at 45-d intervals for 180 d and net N mineralization was determined by measuring the amount of inorganic N that accumulated in the soil or soil plus resin traps. Containment effects were evaluated by comparing water content of the containerized soil to a field-reference soil column. In situ incubation methods provided reasonable estimates of short-term (< 45 d) N mineralization, but long-term (> 45 d) mineralization data were not accurate due to a variety of problems specific to each technique. Buried bags and covered cylinders did not retain mineralized N due to water movement into and out of the containers. Neither resin method captured all of the mineralized N that leached through the soil columns, but the new soil-resin trap method tracked field soil water content better than all other in situ methods evaluated. With further refinement and validation, the new soil-resin trap method may be a useful in situ incubation technique for measuring net N mineralization rates of organic soil amendments.
authors.affiliation: Soil and Water Science Department, 106 Newell Hall, University of Florida, Gainesville, FL 32611-0510, USA. taha@mail.ifas.ufl.edu
authors.forename: Travis A
authors.initials: TA
authors.lastname: Hanselman
authors.forename: Donald A
authors.initials: DA
authors.lastname: Graetz
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Obreza
mesh_terms: D000818:Animals; D005308:Fertilizers; D008372:Manure; D009584:Nitrogen / Q000032:analysis / Q000737:chemistry*; D011200:Poultry; D015203:Reproducibility of Results; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D005308:Fertilizers; D008372:Manure; D012989:Soil Pollutants; D009584:Nitrogen