Stephen M. Griffith

A hybrid genetic algorithm for multiobjective problems with activity analysis-based local search

The objective of this research was the development of a method that integrated an activity analysis model of profits from production with a biophysical model, and included the capacity for optimization over multiple objectives. We specified a hybrid genetic algorithm using activity analysis as a local search method, and NSGA-II for calculation of the multiple objective Pareto optimal set. We describe a parallel computing approach to computation of the genetic algorithm, and apply the algorithm to evaluation of an input tax to regulate pollution from agricultural production.

High resolution characterization of soil biological communities by nucleic acid and fatty acid analyses

Fatty acid methyl ester (FAME) and length heterogeneity-polymerase chain reaction (LH-PCR) analyses were used to generate ‘fingerprints’ of FAMEs and eubacterial 16S rDNA sequences characteristic of agricultural soil communities. We hypothesized that pooling data from two methods that characterized different components of soil biological communities would improve the resolution of fingerprints characterizing the effects of contrasting tillage and ground cover practices. By using supervised classifications of FAME and LH-PCR, a discriminant analysis procedure distinguished soils from contrasting tillage and ground cover management and predicted the origin of soil samples. Used independently, FAME provided higher resolution of tillage, ground cover, and field location than LH-PCR, but LH-PCR was effective at identifying field location. Pooling data from both methods did not enhance the predictive power. A comparison of linear discriminant analysis, quadratic discriminant analysis, and nonparametric density estimation demonstrated that minimizing assumptions about data distribution improved the capacity of FAME analysis to resolve differences in soil types. Use of a purely statistical Bayesian method to select a subset of fatty acids (FA’s) as variables in discriminant analyses identified FA’s that represented signature FA’s for specific groups of organisms. Published by Elsevier Science Ltd.

Impact of land use patterns and agricultural practices on water quality in the Calapooia River Basin of western Oregon

Agricultural practices, including tillage, fertilization, and residue management, can affect surface runoff, soil erosion, and nutrient cycling. These processes, in turn, may adversely affect (1) quality of aquatic resources as habitat for amphibians, fish, and invertebrates, (2) costs of treating surface and ground water to meet drinking water standards, and (3) large-scale biogeochemistry. This study characterized the surface water sources of nitrogen (N) (total, nitrate [NO3−], ammonium [NH4+], and dissolved organic N) and sediment active within 40 subbasins of the Calapooia River Basin in western Oregon in monthly samples over three cropping years. The subbasins included both independent and nested drainages, with wide ranges in tree cover, agricultural practices, slopes, and soils. Sediment and N form concentrations were tested against weather and agricultural practice variables. Subbasin land use ranged from 96% forest to 100% agriculture. Average slopes varied from 1.3% to 18.9%, and surface water quality ranged from 0.5 to 43 mg L−1 (ppm) total N maxima and 29 to 249 mg L−1 suspended sediment maxima. Total N during the winter was positively related to percentage landcover of seven common agricultural crops (nongrass seed summer annuals, established seed crops of perennial ryegrass [Lolium perenne L.], tall fescue [Schedonorus phoenix {Scop.} Holub], orchardgrass [Dactylis glomerata L.], clover [Trifolium spp.], and newly planted stands of perennial ryegrass and clover) and negatively related to cover by trees and one seed crop, Italian (annual) ryegrass (Lolium multiflorum). Results for NO3− and total N were highly similar. Sediment concentrations were most strongly related to rainfall totals during periods of 4 and 14 days prior to sampling, with smaller effects of soil disturbance. Fourier analysis of total N over time identified four prominent groups of subbasins: those with (1) low, (2) medium, and (3) high impacts of N (up to 2, 8, and 21 mg L−1, respectively) and a strong cyclical signal peaking in December and (4) those with very high impact of N (up to 43 mg L−1) and a weak time series signal. Preponderance of N in streams draining agriculturally dominated subbasins was in the form of the NO3− ion, implying mineralization of N that had been incorporated within plant tissue following its initial application in the spring as urea-based fertilizer. Since mineralization is driven by seasonal rainfall and temperature patterns, changes in agronomic practices designed to reduce prompt runoff of fertilizer are unlikely to achieve to more than ~24% reduction in N export to streams.

Nitrate and ammonium nutrition in ryegrass: changes in growth and chemical composition under hydroponic conditions

Abstract Nitrogen (N) is one of the most critical elements affecting grass seed yield. In soil and cropping conditions of Western Oregon, ammonium‐N may play an important role in the growth and development of ryegrass grown for seed. Our objectives were to determine the physiological and biochemical effects of ammonium and nitrate nutrition on ryegrass vegetative growth and subsequent expression of floral tillers, and changes in plant reduced‐N and carbohydrate composition. Plants were grown in hydroponics (active pH‐controlled) and fed nitrate and ammonium alone or in combination at 10 mM total N. The experiment was terminated at anthesis, which occurred at 68 days after planting (DAP). Changes in plant tiller number, height, dry weight, reduced‐N, and water‐soluble carbohydrates (WSC) were recorded. Vegetative growth rate of plants receiving lower ratios of nitrate/ammonium was up to twice those receiving total nitrate or 75/25 nitrate/ammonium. Total primary tiller number at 68 DAP (anthesis) was 30% g...

Nitrate-nitrogen, land use/land cover, and soil drainage associations at multiple spatial scales.

Managing non-point-source pollution of water requires knowledge of land use/land cover (LULC) influences at altering watershed scales. To gain improved understanding of relationships among LULC, soil drainage, and dissolved nitrate-N dynamics within the Calapooia River Basin in western Oregon, we selected 44 watersheds ranging in size between 3 and 33 km(2) for monthly synoptic sampling of surface water quality between October 2003 and September 2004. Seasonal associations were examined between dissolved nitrate-N and proportion of woody vegetation or poorly drained soils at differing scales (10, 20, 30, 60, 90, 150, 300 m, and entire watershed), which we defined as influence zones (IZs), surrounding stream networks. Correlations between nitrate-N and proportion woody vegetation or poorly drained soil at each IZ were analyzed for differences using the Hotelling-Williams test. We observed negative correlations (r = -0.81 to -0.94) between nitrate-N and proportion of woody vegetation during winter and spring. Poorly drained soils had positive correlations (r = 0.63-0.87) with nitrate-N. Altering the scale of analysis significantly changed correlations between nitrate-N and woody vegetation, with IZs <150 m being stronger than the watershed scale during winter. However, absolute differences in correlation values were small, indicating minimal ecological consequence for significant differences among scales. In contrast, nitrate-N correlations with poorly drained soil were stronger at the watershed scale than the 10- through 90-m IZs during winter and spring, and absolute differences were sufficient to suggest that scale is ecologically important when determining associations between dissolved nitrate-N and poorly drained soils.

Italian ryegrass and nitrogen source fertilization in western Oregon in two contrasting climatic years. I. Growth and seed yield

Abstract Prescription based nitrogen (N) fertilization of crops in a given local environment begins by understanding factors affecting crop N use and relating these factors to a time scale most directly related to crop growth. For these reasons the following objectives were sought for an economically important grass seed crop in western Oregon, Italian ryegrass (Lolium multiflorum Lam.). One, to determine the influence of N source (NH4‐N and NO3‐N) on crop growth and seed yield. Second, to determine the relationship between accumulated growing degree days (GDD) and plant ontogeny and relate these findings to N‐source effects on growth and seed yield parameters. Field plots were established in 1991 and again in 1992. Five N‐source treatments were applied: calcium nitrate (CN), ammonium nitrate (AN), ammonium sulfate (AS), ammonium chloride (AC), and urea‐dicyandiamide (DCD). Nitrogen‐source treatments had no effect on root and shoot dry mass accumulation in either year. Ammonium‐N fertilization increased t...

Remote sensing classification of grass seed cropping practices in western Oregon

Our primary objective was extending knowledge of major crop rotations and stand establishment conditions present in 4800 grass seed fields surveyed over three years in western Oregon to the entire Willamette Valley through classification of multiband Landsat images and multi-temporal Moderate Resolution Imaging Spectroradiometer (MODIS) 16-day composite Normalized Difference Vegetation Index (NDVI). Mismatch in resolution between MODIS and Landsat data was resolved by edging of training and test validation areas using 3 by 3 neighbourhood tests for class uniformity, resampling of MODIS data to 50-m resolution followed by 3 by 3 neighbourhood smoothing to artificially enhance resolution, and resampling to 30 m for stacking data in groups of up to 64, 55 and 81 bands in 2004–2005, 2005–2006 and 2006–2007. Imposing several object-based rules raised final classification accuracies to 84.7, 77.1 and 87.6% for 16 categories of cropping practices in 2005, 2006 and 2007. Total grass seed area was under-predicted by 3.9, 5.4 and 1.8% compared to yearly Cooperative Extension Service estimates, with Italian ryegrass overestimated by an average of 8.4% and perennial ryegrass, orchardgrass and tall fescue underestimated by 10.4, 3.3 and 2.1%. Knowledge of field disturbance patterns will be crucial in future landscape-level analyses of relationships among ecosystem services.

Chemical characterization of chars developed from thermochemical treatment of Kentucky bluegrass seed screenings.

Seed mill screenings would be a considerable biofeedstock source for bioenergy and char production. Char produced from the gasification of residues resulting from cleaning of grass seed and small grains could be recycled to a cropping system as a soil amendment if chemical characterization determined that the gasification process had not produced or concentrated deleterious chemical or physical factors that might harm the environment, crop growth or yield. Previous reports have shown that char derived from the pyrolysis of a variety of biomass feedstocks has potential to enhance soil quality by pH adjustment, mineral amendment, and improved soil porosity. The objective of this research was to characterize char produced from Kentucky bluegrass seed mill screenings (KBss) by a small-scale gasification unit, operated at temperatures between 600 and 650°C, with respect to polycyclic aromatic hydrocarbons, selected heavy metals, as well as other physical and chemical characteristics, and determine its suitability for agricultural application as a soil amendment. We utilized KBss as a model for seed and grain-cleaning residues with the understanding that chemical and physical characteristics of char produced by gasification or other cleaning residues may differ based on soil and environmental conditions under which the crops were produced. Our results support the hypothesis that KBss char could be applied in a cropping system without toxic environmental consequences and serve multiple purposes, such as; recycling critical plant macro- and micro-nutrients back to existing cropland, enhancing soil carbon sequestration, managing soil pH, and improving water holding capacity. Crop field trails need to be implemented to further test these hypotheses.

Italian ryegrass and nitrogen source fertilization in western Oregon in two contrasting climatic years. II. Plant nitrogen accumulation and soil nitrogen status.

Abstract To develop optimum nitrogen (N) fertilization practices with the least impact on environmental quality and with the greatest economic return, it is imperative that a greater understanding of crop and soil N dynamics be sought. This paper reports on research conducted with these objectives: (i) to determine the relationship between plant N and dry matter accumulation and soil N status as affected by N‐source fertilization as a function of accumulated growing degree days (GDD), and (ii) to determine if western Oregon soil conditions favor ammonium (NH4) over nitrate (NO3) nutrition during the period of grass seed crop growth. In a companion paper, plant growth and seed yield component data were discussed in relation to N‐source treatments and climatic year effects. Western Oregon field plots of Italian ryegrass (Lolium multiflorum Lam.) were fertilized with calcium nitrate, ammonium nitrate, ammonium sulfate, ammonium chloride, and urea‐dicyandiamide (DCD) to manipulate soil NH4 and NO3 ratios. Ita...

Nitrogen Mineralization in Riparian Soils along a River Continuum within a Multi-Land-Use Basin

Nitrogen dynamics in riparian systems are often addressed within one land-use type and are rarely studied on watershed scales across multiple land uses. This study tested for temporal trends and watershed-wide spatial patterns in N mineralization and identified site factors related to N mineralization. We measured net N mineralization in situ at monthly intervals for 1 yr at 32 riparian sites along the 124-km length of the Calapooia River, Oregon. We observed seasonal trends of mean net N mineralization with relatively low rates in the fall (29.8 kg N ha ―1 yr ―1 ) and winter (30.1 kg N ha ―1 yr ―1 ) and relatively high rates in the spring (122.1 kg N ha ―1 yr ―1 ) and summer (99.7 kg N ha ―1 yr ―1 ) when conditions for microbial activity and decomposition were likely enhanced. Annual net N mineralization on an area basis ranged from ―13.5 to 234.0 kg N ha ―1 yr ―1 with a mean for all sites of 50.1 kg N ha ―1 yr ―1 . Annual net N mineralization per kilogram of soil ranged from ―16.2 to 207.1 mg N kg soil ―1 yr ―1 with a mean for all sites of 64.4 mg N kg soil ―1 yr ―1 . Regression analysis revealed hardwood basal area and coverage of grass as significant positive predictors of kilograms of N mineralized per hectare. Location along the river explained 22% of the variability of N mineralization per hectare, indicating that riparian areas may function differently along the length of the river.