Steven C. Fransen

Food Waste Compost Effects on Fertilizer Nitrogen Efficiency, Available Nitrogen, and Tall Fescue Yield

and plant-available N release after compost application to land (Sullivan et al., 1998a). Composting of food waste is increasing as composting technologies Composting transforms organic byproducts into drier, improve and as social and environmental pressures demand alternamore uniform, and more biologically stable products tives to disposal in landfills. Few agronomic studies are available to that can act as slow-release sources of plant-available document N availability following food waste compost application. The objectives of this study were (i) to determine food waste compost N. A high-rate compost application also changes the effects on N fertilizer uptake efficiency across a range of N fertilizer soil physical, chemical, and biological properties that rates, (ii) evaluate the effect of food waste composts on grass yield control N availability for many years following applicaand N uptake by tall fescue (Festuca arundinacea Schreb. ‘A.U. tion (Shiralipour et al., 1992; Dick and McCoy, 1993). Triumph’), and (iii) estimate the residual effects of compost applicaUsually, composts supply only a part of the N needed tion on N fertilizer requirements. We used a split-plot design with to produce high-yielding crops; fertilizer N application two compost treatments and a no-compost control as main plots, and is needed for maximum crop yields. NH4NO3 (34-0-0) applied at rates of 0, 17, 34, 50, and 67 kg ha 1 per Most studies on N availability following compost apgrass harvest as subplots. A food waste yard trimmings paper plication have focused on short-term effects. Composts (FYP) compost and a food waste wood waste sawdust (FW) with C:N ratios above 20:1 may reduce crop production compost were applied at rates of approximately 78 Mg ha 1 (870–1000 kg N ha 1 ) before seeding tall fescue. Compost did not affect grass via microbial immobilization of available N during the yield or N uptake in the first year of the study. Compost increased first year after application (Sims, 1990; Shiralipour et grass yield during the second and third seasons after application. Grass al., 1992). For composts with lower C:N ratios, 0 to 25% N uptake increased linearly with fertilizer N application rate in all of the total N usually becomes plant-available during years. Compost did not affect fertilizer N uptake efficiency (the linear the first year after application (Brinton, 1985; Tester, slope describing grass N uptake vs. fertilizer N application). Nitrogen 1989; Dick and McCoy, 1993). The recalcitrant organic fertilizer requirements during the midseason growth period were recompounds present in mature composts probably interduced by 0.22 to 0.37 kg N ha 1 d 1 during the second season after act less with fertilizer N and organic matter N in soil compost application and by 0.13 to 0.26 kg ha 1 d 1 during the third than do most crop residues. Azam et al. (1985) demonseason after compost application. Results of this study suggest that strated that plant residues high in recalcitrant C are N mineralized from compost and N provided by fertilizer can be considered as additive components of N supply for crop growth. usually less active in immobilization–remineralization transformations in soil than residues containing more labile C. The interaction between compost and the cycling of C of food waste is increasing as compostsoil and fertilizer N has been studied over the short ing technologies improve and as social and enviterm with labeled isotopes and factorial blends of comronmental pressures demand alternatives to disposal in post plus fertilizer N. Sikora and Yakovchenko (1996), landfills. Over 100 food waste composting facilities were using 14C-labeled soil organic matter, found that comactive in the USA in 1999 (Glenn and Goldstein, 1999). post did not increase soil organic matter decomposition. Composting in aerated windrows is becoming a widely They found that addition of soil stimulated a small adopted method for rapid composting of wet, putresciamount of compost decomposition and N mineralizable food waste at large composting facilities (Touart, tion. Paul and Beauchamp (1994) reported immobiliza1999; Sikora and Sullivan, 2000). The bulking agent that tion of fertilizer 15N and a very small amount of net N is used to maintain porosity in aerated windrows plays a mineralization in a 12-wk incubation with composted large role in determining final compost N concentration beef cattle manure. Available N from compost was a reliable substitute for up to 50% of fertilizer N supplied D.M. Sullivan, Dep. of Crop and Soil Science, Oregon State Univ., to tall fescue in growth chamber studies (Sikora, 1998; Corvallis, OR 97331; D.R. Thomas, Dep. of Statistics, Oregon State Sikora and Enkiri, 1999). Univ., Corvallis, OR 97331; A.I. Bary, S.C. Fransen, and C.G. Cogger, Because composts contain stabilized organic matter, Dep. of Crop and Soil Sciences, Washington State Univ., Puyallup, WA 98371. Contribution #11550 from Oregon State Univ. Agric. Exp. Abbreviations: ANR, apparent N recovery by tall fescue for midseaStn. Received 13 Dec. 2000. *Corresponding author (Dan.Sullivan@ son growth period; CEC, cation exchange capacity; FYP, compost orst.edu). derived from mixture of food waste yard trimmings paper; FW, compost derived from mixture of food waste wood waste sawdust. Published in Soil Sci. Soc. Am. J. 66:154–161 (2002).

Nitrogen Availability Seven Years After a High-Rate Food Waste Compost Application

Long-term effects of compost application are expected, but rarely measured. A 7-yr growth trial was conducted to determine nitrogen availability following a one-time compost application. Six food waste composts were produced in a pilot-scale project using two composting methods (aerated static pile and aerated, turned windrow), and three bulking agents (yard trimmings, yard trimmings + mixed paper waste, and wood waste + sawdust). For the growth trial, composts were incorporated into the top 8 to 10 cm of a sandy loam soil at application rates of approximately 155 Mg ha−1 (about 7 yd3 1000 ft2). Tall fescue (Festuca arundinacea Schreb. ‘A.U. Triumph’) was seeded after compost incorporation, and was harvested 40 times over a 7-yr period. Grass yield and grass N uptake for the compost treatments was greater than that produced without compost at the same fertilizer N rate. The one-time compost application increased grass N uptake by a total of 294 to 527 kg ha−1 during the 7-yr. field experiment. The greatest grass yield response to compost application occurred during the second and third years after compost application, when annual grass N uptake was increased by 93 to 114 kg ha−1 yr−1. Grass yield response to the one-time compost application continued at about the same level for Years 4 through 7, increasing grass N uptake by 42 to 62 kg ha−1 yr−1. Soil mineralizable N tests done at 3 and 6 yr. after application also demonstrated higher N availability with compost. The increase in grass N uptake accounted for 15 to 20% of compost N applied after 7-yr. for food waste composts produced with any of the bulking agents. After 7-yr, increased soil organic matter (total soil C and N) in the compost-amended soil accounted for approximately 18% of compost-C and 33% of compost-N applied. This study confirmed the long-term value of compost amendment for supplying slow-release N for crop growth.

Fertilizer nitrogen replacement value of food residuals composted with yard trimmings, paper or wood wastes

Composting offers an opportunity to recycle food waste as a soil amendment. A three year growth trial was conducted to determine the fertilizer nitrogen (N) replacement value of food waste composts for cool season perennial grass production. Six composts were produced in a pilot-scale project with two composting methods (aerated static pile and aerated, turned windrow). The aerated, turned windrow method simulated “agitated bay” composting systems, which utilize routine mechanical agitation. Compost bulking agents included yard trimmings, yard trimmings + mixed paper waste, and wood waste + sawdust. Finished composts had Kjeldahl N concentrations ranging from 10 to 18 g N/kg. For the growth trial, composts were incorporated into the top eight to 10 cm of a sandy loam soil at application rates of approximately 155 Mg/ha (about 7 yd3/1000 ft2). Tall fescue (Festuca arundinacea Schreb. ‘A.U. Triumph’) was seeded after compost incorporation, and was harvested repeatedly at a late vegetative growth stage (Apri...

Response of Three Switchgrass (Panicum virgatum) Cultivars to Mesotrione, Quinclorac, and Pendimethalin

Abstract Annual grass weed control and switchgrass cultivar response to PRE-applied pendimethalin and POST-applied mesotrione and quinclorac was evaluated in 2005 and 2006 near Paterson, WA, in both newly seeded and 1-yr-old established switchgrass. Pendimethalin applied to newly planted switchgrass at 1.1 kg ai ha−1 at the one-leaf stage in 2005 or at 0.67 kg ha−1 PRE in 2006 severely injured and greatly reduced switchgrass stands. Mesotrione applied POST at 0.07 kg ai ha−1 injured newly planted switchgrass, reduced switchgrass height for several weeks after treatment, and reduced final switchgrass biomass by 54% both years. ‘Kanlow’ and ‘Cave-in-Rock’ cultivars were injured less by mesotrione than ‘Shawnee’ in 2005, whereas in 2006, Kanlow was injured less than Shawnee and Cave-in-Rock. Quinclorac applied POST at 0.56 kg ai ha−1 injured newly planted switchgrass less than mesotrione and pendimethalin but reduced final switchgrass biomass by 33% both years compared with treatment with atrazine alone. All three herbicide treatments controlled large crabgrass in the year of establishment. Green foxtail counts were reduced 93% or more by pendimethalin and quinclorac compared with nontreated controls, but mesotrione failed to control green foxtail. Pendimethalin applied PRE at 1.1 kg ha−1 did not injure 1-yr-old established switchgrass or reduce switchgrass biomass. Quinclorac applied POST at 0.56 kg ha−1 to established switchgrass reduced switchgrass biomass of the first harvest by 16% in 1 of 2 yr. Mesotrione applied POST at 0.07 kg ha−1 injured established switchgrass and reduced biomass of the first harvest by 33 and 17% in 2005 and 2006, respectively. Kanlow was injured the least by mesotrione in both years. Established switchgrass suppressed late-emerging annual grass weeds sufficiently to avoid the need for a grass-specific herbicide application. Nomenclature: Mesotrione; pendimethalin; quinclorac; green foxtail, Setaria viridis L. SETVI; large crabgrass, Digitaria sanguinalis L. Scop. DIGSA; switchgrass, Panicum virgatum L. ‘Cave-in-Rock’, ‘Kanlow’, ‘Shawnee’.

Influence of edaphic and management factors on the diversity and abundance of ammonia‐oxidizing thaumarchaeota and bacteria in soils of bioenergy crop cultivars

Ammonia-oxidizing thaumarcheota (AOA) and ammonia-oxidizing bacteria (AOB) differentially influence soil and atmospheric chemistry, but soil properties that control their distributions are poorly understood. In this study, the ammonia monooxygenase gene (amoA) was used to identify and quantify presumptive AOA and AOB and relate their distributions to soil properties in two experimental fields planted with different varieties of switchgrass (Panicum virgatum), a potential bioenergy feedstock. Differences in ammonia oxidizer diversity were associated primarily with soil properties of the two field sites, with pH displaying significant correlations with both AOA and AOB population structure. Percent nitrogen (%N), carbon to nitrogen ratios (C : N), and pH were also correlated with shifts nitrifier population structure. Nitrosotalea-like and Nitrosospira cluster II populations were more highly represented in acidic soils, whereas populations affiliated with Nitrososphaera and Nitrosospira cluster 3A.1 were relatively more abundant in alkaline soils. AOA were the dominant functional group in all plots based on quantitative polymerase chain reaction and high-throughput sequencing analyses. These data suggest that AOA contribute significantly to nitrification rates in carbon and nitrogen rich soils influenced by perennial grasses.

Chemistry and microbial functional diversity differences in biofuel crop and grassland soils in multiple geographies.

We obtained soil samples from geographically diverse switchgrass (Panicum virgatum L.) and sorghum (Sorghum bicolor L.) crop sites and from nearby reference grasslands and compared their edaphic properties, microbial gene diversity and abundance, and active microbial biomass content. We hypothesized that soils under switchgrass, a perennial, would be more similar to reference grassland soils than sorghum, an annual crop. Sorghum crop soils had significantly higher NO3−-N, NH4+-N, SO42−-S, and Cu levels than grassland soils. In contrast, few significant differences in soil chemistry were observed between switchgrass crop and grassland soils. Active bacterial biomass was significantly lower in sorghum soils than switchgrass soils. Using GeoChip 4.0 functional gene arrays, we observed that microbial gene diversity was significantly lower in sorghum soils than grassland soils. Gene diversity at sorghum locations was negatively correlated with NO3−-N, NH4+-N, and SO42−-S in C and N cycling microbial gene categories. Microbial gene diversity at switchgrass sites varied among geographic locations, but crop and grassland sites tended to be similar. Microbial gene abundance did not differ between sorghum crop and grassland soils, but was generally lower in switchgrass crop soils compared to grassland soils. Our results suggest that switchgrass has fewer adverse impacts on microbial soil ecosystem services than cultivation of an annual biofuel crop such as sorghum. Multi-year, multi-disciplinary regional studies comparing these and additional annual and perennial biofuel crop and grassland soils are recommended to help define sustainable crop production and soil ecosystem service practices.

Genetic diversity and phenotypic variation for drought resistance in alfalfa (Medicago sativa L.) germplasm collected for drought tolerance

Drought is a major environmental factor hampering alfalfa productivity worldwide. Gene banks provide an array of trait diversity, frequently consisting of specific seed collection projects that focused on acquiring germplasm adapted to specific traits such as drought tolerance. These subsets provide a logical starting point to identify useful breeding resources. In the present study, we investigated the genetic diversity and evaluated 18 agronomic, physiological and quality traits associated with drought tolerance in a subset of 198 alfalfa accessions collected for their potential drought resistance. Significant differences were found among accessions for most of the traits evaluated. Water deficit significantly decreased biomass dry yield by 61.9% compared with well-watered control. A positive correlation was found between relative water content (RWC) and drought susceptible index, while negative correlations were found between RWC and leaf senescence (LS), and between RWC and canopy temperature (CT). Alfalfa accessions with high RWC showed relative lower yield reduction, cooler CT and delayed LS. Genetic variation for forage quality was also investigated and the correlation between agronomic and quality traits was analyzed. Biomass yield under drought was negatively correlated with total protein, relative feed value and relative forage quality, suggesting that the efforts to improve yield under drought tend to negatively affect forage quality. Therefore, maintaining forage quality should be considered for breeding alfalfa with drought resistance. Alfalfa accessions with high drought resistance scores and minimum loss of quality were identified in this study and can be used as genetic resources for developing alfalfa varieties with improved drought resistance and water use efficiency while maintaining forage quality.

Ammonia-oxidizing bacteria are the primary N2O producers in an ammonia-oxidizing archaea dominated alkaline agricultural soil: AOB control N2O emissions from an alkaline soil

Most agricultural N2 O emissions are a consequence of microbial transformations of nitrogen (N) fertilizer, and mitigating increases in N2 O emission will depend on identifying microbial sources and variables influencing their activities. Here, using controlled microcosm and field studies, we found that synthetic N addition in any tested amount stimulated the production of N2 O from ammonia-oxidizing bacteria (AOB), but not archaea (AOA), from a bioenergy crop soil. The activities of these two populations were differentiated by N treatments, with abundance and activity of AOB increasing as nitrate and N2 O production increased. Moreover, as N2 O production increased, the isotopic composition of N2 O was consistent with an AOB source. Relative N2 O contributions by both populations were quantified using selective inhibitors and varying N availability. Complementary field analyses confirmed a positive correlation between N2 O flux and AOB abundance with N application. Collectively, our data indicate that AOB are the major N2 O producers, even with low N addition, and that better-metered N application, complemented by selective inhibitors, could reduce projected N2 O emissions from agricultural soils.

Slow-Release Nitrogen from Composts: The Bulking Agent is More Than Just Fluff

One of the goals of byproduct co-utilization is to produce products with increased value, and the amount of slow-release nitrogen (N) supplied by composts for plant growth is one component of compost value. To evaluate the effect of bulking agents on the amount of slow-release N derived from composts, we conducted a three-year field trial with a forage-type tall fescue (Festuca arundinacea Schreb. ‘A.U. Triumph’). Composts were prepared for the field trial from mixtures of food residuals (vegetables, meat, fish, dairy, and bakery by-products) with three bulking agents. Food residuals (33 g N/kg) were bulked with yard trimmings (11 g N/kg), yard trimmings + mixed waste paper (7 g N/kg), and wood chips + sawdust (1 g N/kg). After mixing, the food residual/bulking agent mixtures were composted in a turned windrow supplied with forced air for 70 days, then cured without forced air for 36 days. At the end of curing, total N concentrations in screened compost (< 11 mm) were 17 g N/kg for yard trimmings, 14 g N/kg for yard trimmings + paper, and 8 g N/kg with wood chips + sawdust bulking agent. For the field trial, 155 Mg/ha of compost was incorporated to a depth of 10 cm in a sandy loam soil. Tall fescue was seeded the day after compost application and was harvested 15 times over a three-year period to measure compost effects on grass yield and N uptake. Composts consistently increased yield and grass N uptake in the second and third year after application, demonstrating their slow-release N value. Cumulative apparent N recovery (ANR) over the three-year trial ranged from 7 to 11 % of the compost total N applied. Cumulative ANR was 282 kg N/ha for yard trimmings, 242 kg N/ha for yard trimmings + paper, and 113 kg N/ha for wood chips + sawdust bulking agent. Replacement of wood chips + sawdust bulking agent with yard trimmings more than doubled compost slow-release N value. Thus, yard trimmings are a valuable feedstock when developing compost products with slow-release N value.