Computer simulation models provide insight into ammonia loss processes and the sensitivity of ammonia loss predictions to environmental and management variables.
As an example of how a simple computer simulation model can inform the Extension guideline development process, the ALFAM (Ammonia Volatilization from Field-Applied Animal Slurry) model was used to...
Organic vegetable growers rely on legume cover crops as an economical source of plant-available N. This research evaluated N contributions to summer vegetable crops by cover crops (CC) residues by monitoring soil nitrate (NO3-N) concentrations during the summer crop growing season. Replicated field plots were established with three CC mixes:...
Peppermint residue consists of the cooked leaves and stems of the peppermint plant after high-temperature distillation to extract oil. This residue has value as a soil amendment. It is often applied to fallow fields in the fall or sold as a soil amendment to gardeners. Research was conducted to determine...
Specialty organic fertilizers used in organic vegetable production are expensive. So, from environmental and economic perspectives, growers want to maximize nitrogen (N) fertilizer use efficiency by the crop. This research was conducted to (1) determine sufficient N fertilizer rates for organic broccoli, (2) evaluate the efficacy of a specialty organic...
Riparian ecosystems, through their unique positions in the agricultural landscape, have the potential to mitigate nutrient loading to streams. This study was conducted to gain a better understanding of N cycling in a poorly drained Grass Riparian Zone (GRZ) and adjacent Perennial Ryegrass seed Field (PRF) in the Willamette Valley,...
Grass seed production in Oregon's Willamette Valley traditionally relied on open field burning for straw residue disposal and nutrient recycling. Changes in residue management from open field burning to methods that remove straw coincided with rapidly declining K soil test values. A survey of grass seed fields showed that many...
Christmas tree needle sampling to evaluate nutrient need is an established practice. Data to support the recommended fall sampling time in Oregon and Washington was not found. In addition, the recommendation for needle sampling of Fraser fir in North Carolina was made without data from winter months. The goal for...
Hare barley (Hordeum murinum ssp. leporinum) is a cool season annual grass that invades pastures and range areas around the world. A documented weed management issue in several Oregon counties, hare barley may infest several thousand acres in western Oregon. This study was conducted to investigate the biology and develop...
Nutrient limitation constrains tree growth in many managed forests. Nitrogen (N) is the most common limiting nutrient, but high N supply can shift limitation to other nutrients, particularly phosphorus (P) and the base cations calcium (Ca), magnesium (Mg), and potassium (K). As different soil minerals have different capacities to supply...
Predicting agronomic rates is important to derive optimum economic and environmental benefits from biosolids fertilizer applications. We conducted this research to 1) evaluate dryland wheat response to biosolids applications over a range of climate zones in the Pacific Northwest and 2) compare agronomic application rates predicted from yield curves with...