My research has focused on understanding N and C cycling in soils at small scales. Isotope dilution methods commonly used to estimate gross rates of soil chemical transformations assume homogeneous distribution of label. I explored the effects of diffusion limitations on isotope dilution experiments in soil aggregates using spherical diffusion-reaction...
Intimate associations with reactive metal species permanently protect soil organic matter (SOM) from microbial access and oxidation, contributing to the build-up of organic carbon (C) stocks in soils. It is increasingly recognized, however, that such associations can be reversible and that reactive metal species might even facilitate the oxidation of...
Twelve Sri Lankan Alfisols were characterized for P. Soils
were incubated for three weeks with sufficient P applied
(P2) to elevate soil solution P to 0.2 ug P/g solution as
determined by sorption curves, with 75 percent of P2 (P1),
and without P (P0). For PO treatments, (a) organic P,...
In order to properly utilize organic amendments as nitrogen sources, reliable methods
to estimate plant-available nitrogen (PAN) are needed. The objectives of this study
were to (1) evaluate the use of crop and soil responses in fertilizer N equivalence
(FNE) calculations, (2) examine the relationships between the C/N ratio, total...
Changes in the type and amount of plant inputs can occur gradually, as with succession, or rapidly, as with harvesting or wildfire. With global change it is anticipated that both gradual and immediate scenarios will occur at increasing frequency. Changes in vegetation inputs alter the quality and quantity of soil...
The Federal Water Pollution Control Act Amendments of 1972
prohibits the discharge of seafood processing solid wastes into
navigable waters after July 1, 1977. Oregon shrimp and crab processors
must use other methods of disposal for the 15 to 30 million
pounds of solid waste generated annually. The application of...
Decomposition of forest litter is a complex process
involving interactions between physical, chemical and
biological factors. As litter decomposes it is chemically
altered. Cation exchange capacities of litter represent a
means of characterizing the number of hydrophilic acid
groups. Some kind of soil-root ion exchange mechanisms are
utilized by the...
Nitrogen availability in agricultural soils from fertilizer, plant residue inputs, and soil organic matter has important implications beyond crop yield. Legume winter cover crops and one fourth the recommended N rate on sweet corn resulted in yields equivalent to those at the recommended rate in the Willamette Valley of western...
Dust deposition on ecosystems with highly weathered soils may provide vital rock-derived nutrients that maintain ecosystem productivity. Because of the difficulties in measuring temporally and spatially heterogeneous dust deposition over ecologically meaningful timescales, evaluations of the spatial variability in dust deposition are extremely rare. In the Luquillo Mountains of Puerto...