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Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity. Foundation for Food and Agricultural Research [523926]; Samuel Roberts Noble Foundation; General Mills Published version Foundation for Food and Agricultural Research (grant ID 523926), General Mills, and The Samuel Roberts Noble Foundation.

This study examines consumer preferences and willingness to pay (WTP) for organic and eco-friendly peaches, Prunus persica L., over conventional peaches in Utah. Data were collected at farmers’ markets across Utah, including actual peach purchases coupled with an in-person survey and analyzed using logit models. The results show that farmers’ market shoppers are willing to pay a premium for organic and eco-friendly peaches of $2.10 and $1.41 per pound, respectively. The importance of selected sustainability attributes positively impacted shopper preferences for eco-friendly peaches, while attitudes and lifestyle were associated with stronger shopper preferences for organic peaches. The distinct differences between shoppers who prefer organic and those who prefer eco-friendly, as well as the disparity in premiums, imply that growers should strongly consider their markets and cost of production differences when choosing organic certification over other less expensive differentiation schemes.

Including drought-tolerant crops, such as quinoa (Chenopodium quinoa Willd.), in rotation could benefit growers facing increased water shortages in the western United States. Yet, there are limited...

Maintaining nutrient availability in organic orchards presents challenges. Diverse litter sources may increase nutrient cycling and the efficiency by which microbes utilize carbon (C). Two tree-row treatments: ‘straw-mulch’ (Triticum aestivum L.) and ‘living-mulch’ (Lobularia maritima (L.) Desv.), and two alleyway groundcovers: ‘grass’ (Festuca rubra with Lolium perenne L.) and a legume, ‘Birdsfoot trefoil’ (Lotus corniculatus L.) were compared to an industry standard, tillage with a grass alleyway. Tree-row deposited trefoil biomass contributed 0.2 kg additional total nitrogen (N) per tree annually. Soil from tree-rows with trefoil alleyways had 23% greater organic C (+ 3.1 g kg−1), 17% greater total N (+ 0.3 g kg−1), up to 53% greater microbial biomass (+ 204 mg CO2–C kg−1), 32, 34 and 31% greater dehydrogenase (+ 2.3 µg TPF g−1), alkaline (+ 55.9 µg p-nitrophenol g−1) and acid (+ 106.7 µg p-nitrophenol g−1) phosphomonoesterase enzyme activity, 62% greater soil NO3−N (+ 2.05 µg NO3−1 g−1), and 51% higher nitrification rates (+ 0.22 µg NO2−–N + NO3−–N g−1 soil h−1) than tree-row soils adjacent to grass alleyways. Straw-mulch and living-mulch soils did not differ. Metabolic CO2 quotient (qCO2) values were lowest in trefoil (0.0032) and living-mulch with grass treatments (0.0036), indicating greater microbial growth efficiency. Tillage and straw-mulch with grass alleyway treatments had the highest qCO2 (0.0053 and 0.0048) and the lowest microbial biomass (246.3 and 297.6 mg CO2–C kg−1 soil). Higher potential biochemical activity, and total C and N, suggests orchards with trefoil alleyways cut and deposited into tree-rows, enhances soil organic matter and promotes balanced nutrient cycling and retentive processes.

A whole farm carbon model estimates the emissions of greenhouse gasses (GHGs) based on information for a farm. We analyzed two models, Holos whole-farm and COMET-Farm, by running the models on random inputs and building predictive models from the runs. Holos estimates GHG emissions for a particular year based on crop and animal agriculture input, while COMET-farm adds past and future farm management practices. Users of the models must manually enter farm data through a graphical user interface (GUI), which is a good method for a single farm, but makes it infeasible to calculate GHG emissions over hundreds to thousands of farms. So we automated the interface and generated random farm scenarios within ranges given by experts. We scraped the estimated carbon footprint from thousands of runs of the models and used algorithms to build predictive models that have high accuracy. By reverse engineering the whole-farm carbon models we were able to determine which farm management practices in each whole farm carbon model have the biggest impact on GHG emissions. This can help farmers and rural planners change farm management practices to decrease GHG emissions.

Quinoa ( Chenpodium quinoa Willd.) could provide a high value crop for organic cropping systems in the Intermountain Western US. This study evaluated quinoa in three cover cropping systems [strip crop (SC), undersown clover (UC), or winter cover crop and tillage (T)] with and without compost (+C or −C) in a split-plot with blocks design. Quinoa produced no seed in 2013 and limited seed in 2014, likely due to excessive temperatures during flowering. Compost increased seed yield in 2014, and in both years, increased total biomass and improved soil health measures. Seed and biomass yield was greater in T than UC on a land-equivalent basis but SC was greatest on a per harvest area basis. Cropping system effects on soil health measures were minimal. However, microbial biomass increased in all systems over time, yet was diminished in the tillage system. Quinoa may be an alternative crop for organic systems provided sufficient nitrogen and phosphorous fertility is available, and yields can be stabilized by identifying heat tolerant varieties before widespread adoption of this crop is feasible.

Treerow vegetation abundance and biodiversity were measured in response to six orchard floor management strategies in organic peach in northern Utah for three growing seasons. A total of 32 weed species were observed in the treerow; the most common were field bindweed, dandelion, perennial grasses (e.g., red fescue and ryegrass), clovers, and prickly lettuce. Weed biomass was two to five times greater in unmanaged (living mulch) than in manipulated treatments. Tillage greatly reduced weeds for approximately one month; however, vegetation rebounded midseason. Tillage selected for species adapted to disturbance, such as common purslane and field bindweed. Straw mulch provided equivalent weed suppression to tillage in the early season. Straw required annual reapplication with material costs, labor, and weed-seed contamination (e.g., volunteer grains and quackgrass) as disadvantages. Plastic fabric mulch reduced weeds the most, but had high initial costs and required seasonal maintenance. Weed biomass declined within seasons and across the three years of the study, likely due to tree canopy shading. Neither birdsfoot trefoil nor a perennial grass mixture planted in the alleyways influenced treerow weeds. Our results demonstrate several viable alternatives to tillage for weed management in treerows of organic peach orchards in the Intermountain West.Nomenclature: Birdsfoot trefoil, Lotus corniculatus L.; clover, Trifolium; common purslane, Portulaca oleracea L.; dandelion, Taraxacum officinale G.H. Weber ex Wiggers; field bindweed, Convolvulus arvensis L.; red fescue, Festuca rubra L.; perennial ryegrass, Lolium perenne L.; green foxtail, Setaria viridis (L.) Beauv.; prickly lettuce, Lactuca serriola L.; quackgrass, Elymus repens (L.) Gould; peach, Prunus persica L. Batsch.

Onion thrips, Thrips tabaci Lindeman, a primary insect pest of onions, Allium cepa L., worldwide, reduces yield and transmits a devastating Tospovirus, Iris yellow spot virus. Costly and frequent insecticide application and increased resistance of onion thrips to insecticide prompted interest in alternative pest management options. Three trap crops, lacy phacelia (Phacelia tanacetifolia Benth.), buckwheat (Fagopyrum esculentum Moench.), and carrot (Daucus carota L.) planted in commercial onion fields during two growing seasons were evaluated for attractiveness to onion thrips. Abundance of thrips adults, larvae, and eggs were monitored on trap crops and onion plants, and dispersing adults were counted on aerial traps 0, 0.8, 6.4, and 12.8 m from trap crop rows. All trap crops when flowering or with lush vegetation supported all life stages of onion thrips during at least 1 of 2 years; trends in preference by onion thrips varied. Incidence of Iris yellow spot virus was low ranging from 6.6 to 8.2% in year 2; however, in late September of the second year, incidence was greater near trap crops than at farther distances, as measured by enzyme-linked immunosorbent assay (ELISA). Trap crops were attractive to onion thrips adults in June and July which suggests promise for decreasing numbers of thrips on onion during critical periods of bulb sizing and spread of Iris yellow spot virus; however, the short distance of influence suggested need for larger plot sizes or better sampling methods. Potential for planting trap crops along field edges to attract migrating adult thrips early in the season is discussed.

Dual‐use cover/green manure (CGM) crops and animal manure are used to supply nitrogen (N) and phosphorus (P) to organically grown field crops. A comprehensive review of previous research was conducted to identify how CGM crops and animal manure have been used to meet N and P needs of organic field crops, and to identify knowledge gaps to direct future research efforts. Results indicate that: (a) CGM crops are used to provide N to subsequent cash crops in rotations; (b) CGM‐supplied N generally can meet field crop needs in warm, humid regions but is insufficient for organic grain crops grown in cool and sub‐humid regions; (c) adoption of conservation tillage practices can create or exacerbate N deficiencies; (d) excess N and P can result where animal manures are accessible if application rates are not carefully managed; and (e) integrating animal grazing into organic field crop systems has potential benefits but is generally not practiced. Work is needed to better understand the mechanisms governing the release of N by CGM crops to subsequent cash crops, and the legacy effects of animal manure applications in cool and sub‐humid regions. The benefits and synergies that can occur by combining targeted animal grazing and CGMs on soil N, P, and other nutrients should be investigated. Improved communication and networking among researchers can aid efforts to solve soil fertility challenges faced by organic farmers when growing field crops in North America and elsewhere.

Standard commercial soil tests typically quantify nitrogen, phosphorus, potassium, pH, and salinity. These factors alone are not sufficient to predict the long-term effects of management on soil health. The goal of this study was to assess the effectiveness and use of simple physical, biological, and chemical soil health indicator tests that can be completed on-site. Analyses were conducted on soil samples collected from three experimental peach orchards located on the Utah State Horticultural Research Farm in Kaysville, Utah. All simple tests were correlated to comparable lab analyses using Pearson&rsquo, s correlation. The highest positive correlations were found between Solvita&reg, respiration, and microbial biomass (R = 0.88), followed by our modified slake test and microbial biomass (R = 0.83). Both Berlese funnel and pit count methods of estimating soil macro-organism diversity were fairly predictive of soil health. Overall, simple commercially available chemical tests were weak indicators of soil nutrient concentrations compared to laboratory tests. Modified slake tests, Solvita&reg, respiration and soil organism biodiversity counts may be efficient and cost-effective tools for monitoring soil health on-site.

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) is a serious virus pathogen in onion bulb and seed crops in the United States and several parts of the world (1). The virus is exclusively transmitted by onion thrips (Thrips tabaci). Besides onion and other susceptible crops such as garlic, leek, chives, and several ornamentals, weeds could be serving as potential reservoir sources of virus inoculum. There are reports of several weeds found naturally infected with IYSV (1,2,4). However, there is no report of IYSV infection of a grass species. Leaves of green foxtail (Setaria viridis (L.) Beauv.) were collected from two naturally occurring plants approximately 30 m apart in a weed trial conducted in commercial onions grown in Box Elder County, UT on 24 September 2008. Notes of IYSV symptoms on green foxtail were made only on the two grass plants sampled. Density of green foxtail in the weed trial was low and was not recorded. Leaves on both plants displayed a range of symptoms that included streaking, purpling, and chlorotic and necrotic lesions along leaf margins oriented along the axis of longitudinal venation. Samples were positive for IYSV by double-antibody sandwich-ELISA with a commercially available kit (Agdia Inc., Elkhart, IN). ELISA values of the grass samples were 2.64 and 2.23 for each plant sampled. Negative and positive control readings were 0.24 and 4.33, respectively. All absorbance readings were made at 405 nm. To provide a contrast of the grass data in context to the onion field where the weed trial was located, final visual assessments of onions in the field were made on 4 September 2009. Approximately 300 onion plants were assessed for incidence and severity of disease. Incidence of the disease among onions was 100% and the severity of iris yellow spot on leaves was 20 lesions per leaf. The average ELISA value over 30 individual onions arbitrarily sampled from the field on the same day was 3.50, and the ELISA values among the samples ranged from 1.37 to 4.38. The negative and positive controls were 0.19 and 4.40, respectively. To further verify the presence of IYSV in the grass specimen, reverse transcription-PCR was performed on total nucleic acid extracts obtained from the symptomatic parts of the leaves. Primers specific to the nucleocapsid (N) gene coded by the small (S)-RNA of IYSV were used (3). The forward and reverse primer pairs, 5′-TCAGAAATCGAGAAACTT-3′ and 5′-CACCAATGTCTTCAACAATCTT-3′, respectively, amplify a 751-nt fragment of the N gene (3). An amplicon of expected size was obtained, cloned, and sequenced. The nucleotide sequence analysis and comparison with known IYSV S-RNA sequences showed that the amplicon from foxtail (GenBank Accession No. FJ652594) samples had the highest nucleotide sequence identity (98%) with the corresponding region of an IYSV isolate from Jefferson County, OR (GenBank Accession No. DQ233479). To our knowledge, this is the first report of natural infection of a grass species by IYSV and the first report of a Tospovirus infecting a grass species. The data suggests grasses may serve as a new host reservoir for IYSV. The increasing number of weed hosts of IYSV warrants further study on the role of these weeds as hosts for onion thrips and in IYSV epidemiology. References: (1) D. Gent et al. Plant Dis. 90:1468, 2006. (2) C. Nischwitz et al. Plant Dis. 91:1518, 2007. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (4) R. Sampangi et al. Plant Dis. 91:1683, 2007.

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) continues to be an economically important pathogen affecting onion bulb and seed production in several parts of the world and the United States (1). Several weeds were reported naturally infected with IYSV (1,2,4). Leaves of Atriplex micrantha Ledeb. (synonym A. heterosperma Bunge) were collected from naturally occurring plants in a weed trial conducted in commercial onions grown in Box Elder County, UT on 24 September 2008. Leaves displayed a range of symptoms including spotting, chlorosis, and necrosis. Symptomatic leaves were preferentially selected for subsequent diagnostic analyses. Samples were positive for IYSV when tested by double-antibody sandwich-ELISA using a commercially available kit (Agdia Inc., Elkhart, IN). For further confirmation, total nucleic acid extracts from the symptomatic parts of the leaves were prepared and tested for the presence of IYSV by reverse transcription-PCR with primers specific to the nucleocapsid (N) gene coded by the small (S)-RNA of IYSV. The forward and reverse primer pair, 5′-TCAGAAATCGAGAAACTT-3′ and 5′-CACCAATGTCTTCAACAATCTT-3′, respectively, amplifies a 751-nt fragment of the N gene (3). An amplicon of expected size was obtained, cloned, and sequenced. The nucleotide sequence analysis and comparison with known IYSV S-RNA sequences showed that the sequence of the amplicon from A. micrantha (GenBank Accession No. FJ493541) shared more than 84% nt sequence identity with the corresponding region of IYSV isolates available in GenBank, confirming the IYSV infection of the new host weed. The highest sequence identity (98%) was with an IYSV isolate from Jefferson County, OR (GenBank Accession No. DQ233479). To our knowledge, this is the first report of IYSV infection of A. micrantha under natural conditions. The role of A. micrantha and other weeds in IYSV epidemiology needs further investigation. References: (1) D. Gent et al. Plant Dis. 90:1468, 2006. (2) C. Nischwitz et al. Plant Dis. 91:1518, 2007. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (4) R. Sampangi et al. Plant Dis. 91:1683, 2007.

Adequate weed control and nutrient supply are critical for successful establishment of fruit trees. This is of particular concern in organic orchard establishment. In order to determine the best approach for establishing peach trees ( Prunus persica L.) organically in climates characterized by hot dry summers and cold winters such as the North American Intermountain West, seven organic and three integrated and conventional treatment combinations were established in two first leaf orchards at the USU Kaysville Research Farm, Utah, in 2008 and 2009. Treatments consisted of different tree-row and alleyway mulch and fertilizer combinations. Compost or conventional fertilizer (16-16-16 and urea) were applied at a baseline rate of 4.9, 9.6, 19 g and 114 g of available nitrogen (N) per 1st, 2nd, 3rd and 4th leaf tree respectively and adjusted up or down on a plot basis based on tree growth. Compost was supplemented with a feather meal 13-0-0 fertilizer starting in year three to avoid over application of phosphorus (P) and potassium (K). Organic experiment tree growth was initially slowed by living and straw mulches present in the tree-row. By 2011, 3rd leaf trees were largest in treatments with Birdsfoot trefoil alleyways, despite considerable tree-row weed/living mulch pressure. In the integrated experiment, trees were larger in the compost plus conventional herbicide compared to conventional fertilizer and herbicide treatment. Paper mulch depressed tree growth in combination with both compost and conventional N sources, but more so in combination with compost and organic herbicide where weed control was moderate. Weed pressure not lack of N was determined to limit organic tree growth in this study. A trefoil alleyway may alleviate the need for intensive weed control when establishing organic peach orchards.

In the majority of agricultural soils, ammonium (NH4+) is rapidly converted to nitrate (NO3−) in the biological ammonia and nitrite oxidation processes known as nitrification. The often rate-limiting step of ammonia oxidation to nitrite is mediated by ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA). The response of AOA and AOB communities to organic and conventional nitrogen (N) fertilizers, and their relative contributions to the nitrification process were examined for an agricultural silage corn system using a randomized block design with 4 N treatments: control (no additional N), ammonium sulfate (AS) fertilizer at 100 and 200 kg N ha−1, and steer-waste compost (200 kg total N ha−1) over four seasons. DNA was extracted from the soil, and real-time PCR and 454-pyrosequencing were used to evaluate the quantity and diversity of the amoA gene which encodes subunit A of ammonia monooxygenase. Soil pH, nitrate pools, and nitrification potentials were influenced by ammonium and organic fertilizers after the first fertilization, while changes in AOB abundance and community structure were not apparent until after the second fertilization or later. The abundance of AOA was always greater than AOB but was unaffected by N treatments. In contrast, AOB abundance and community structure were changed significantly by ammonium fertilizers. Specific inhibitors of nitrification were used to evaluate the relative contribution of AOA and AOB to nitrification. We found that AOB dominantly contributed to potential nitrification activity determined at 1 mM ammonium in soil slurries and nitrification potential activity was higher in soils treated with ammonium fertilizers relative to control soils. However, AOA dominated gross nitrification activity in moist soils. Our result suggests that AOB activity and community are more responsive to ammonium fertilizers than AOA, but that in situ nitrification rate is controlled by ammonium availability in this agricultural soil. Understanding this response of AOA and AOB to N fertilizers may contribute to improving strategies for the management of nitrate production in agricultural soils.

Compost plays a central role in organic soil fertility plans but is bulky and costly to apply. Determining compost carryover is therefore important for cost-effective soil fertility planning. This study investigated two aspects of nutritive carryover [nitrogen and phosphorus (P)], and an indicator of non-nutritive carryover [soil organic matter (SOM)] to determine the residual effect of a one-time compost application applied at four rates in a corn-squash rotation. Crop yield was measured as an integrated carryover indicator of nutritive and non-nutritive effects. Functional groups of compost and SOM were investigated using FT-IR spectroscopy and soil organic carbon (SOC). While year to year variability was great, compost had a persistent positive effect on crop yields, evident 3 years after application with no reduction in magnitude over time. Soil nitrate was low, and additions of compost at any rate generally did not increase levels beyond the year of application, with the exception of year four. Olsen P was also low, yet was higher in amended soils than in non-amended soils 3 years after application. Pronounced polysaccharide peaks, evident in compost spectra and absent in control soil, were apparent in compost-amended soils 3 years after compost treatment and SOC was greater 2 years afterwards. Compost carryover was most pronounced in year four following the incorporation of a nitrogen-fixing cover crop. These results show that compost can influence nutritive and non-nutritive soil properties many years after incorporation, thereby reinforcing the importance of including compost in organic fertility plans despite the unpredictability of year-to-year response.

Birdsfoot trefoil (BFT, Lotus corniculatus L.) is a nonbloating perennial forage legume well suited to ruminant production on pastures. It is persistent under irrigation in cool, dry western US climates, and has been found to increase meat and milk production compared with other forages. The establishment of BFT pastures was evaluated on five commercial organic dairy farms in southern Idaho and northern Utah. Participating producers broadcast seeded 4-ha BFT pastures between 26 July and 8 September 2011 at a rate of 25 kg pure live seed ha−1. Birdsfoot trefoil and weed densities were systematically sampled 17 to 23 days after first BFT emergence in autumn 2011 and again in spring 2012. On all farms, BFT seedling density was high, averaging 690 plants m−2 in the autumn after planting and 340 plants m−2 the following spring. However, weed density varied between 130 and 750 plants m−2 in the autumn of 2011 and 240 and 410 plants m−2 in the spring of 2012. On the three farms where weed density was equal to or greater than BFT density in the spring of 2012, spring BFT cover averaged less than 10 %. On the two farms where spring weed density was less than BFT density, spring BFT cover was 48 and 66 %. These two pastures produced 6000 to 7600 kg of dry matter ha−1 by 20 June 2012 and were well enough established to support grazing for the remainder of the summer. Birdsfoot trefoil establishment was enhanced under sprinkler compared with flood irrigation.

The USU Student Organic Farm was initiated in April 2008 on 1 acre (0.4 ha) of land at Utah State University (USU). Students plant, weed, harvest, and market the produce on campus. Proceeds support the student farm in terms of operating expenses, equipment purchases, and modest student stipends. Since 2009, the students have operated a community supported agriculture (CSA) program to fund summer internships. Each year the most dedicated volunteers are recruited for the internships and two of the most experienced former interns return as farm managers. Students can also take the Student Farm Practicum for credit. This variable-credit course is offered in the spring, summer, and fall and complements the classroom-based course Fundamentals of Organic Farming. There are no prerequisites for either course, and the goal is to attract students from all disciplines across campus. Both classes are registered as service learning classes with students required to participate in practical activities on the farm and reflect on their experience in writing. The essays were used for content analysis to demonstrate learning as a result of their involvement with the student farm. Students learned group work, decision making, personal initiative, research, and communication skills. Students working at other student-run organic farms could write journal entries or reflective papers that describe what they learn so that the benefits of experiential learning on student-run farms can be better documented.

a b s t r a c t Onion thrips and Iris yellow spot virus (IYSV) are two primary yield reducing factors in onion production worldwide. Current management practices rely on heavy use of insecticides and fertilizers, threatening the sustainability of onion systems. Little is known about how cultural practices such as reduced fer- tility, soil biostimulants, and crop rotation affect onion yield, thrips densities, soil properties, and IYSV incidence. In a replicated field experiment, reduced nitrogen (N) (134 kg N ha−1, one-third the standard grower rate), slightly decreased yield and onion size. Adult thrips populations were 23 to 31% lower in the reduced as compared to standard N (402 kg N ha −1 ) and biostimulant treatment, respectively. Growing onions following a one year cycle in corn rather than wheat reduced onion thrips in one of two years. The addition of a biostimulant had no effect on soil properties, but may have slightly increased yield, attracted adult thrips, and increased thrips populations. IYSV incidence was not influenced by fertilizer rate or crop rotation. Soil microbial biomass and readily mineralizable carbon were greater following wheat, while soil nitrate (NO3 −) accumulation was greater in standard N treatments. Soil microbial activity, as mea- sured by dehydrogenase enzyme potential, may have been adversely affected by high N rates. Results suggest that reduced N, without biostimulant, sustained onion yields, decreased onion thrips densities and potential for IYSV incidence, created a more favorable soil environment for microbial activity, and reduced the risk of NO3 − leaching

Fruit production in Utah and throughout the US Intermountain West has come under increasing pressure due to rising input costs, diminishing water supplies, loss of export markets, and urban encroachment. These challenges also present considerable opportunity in the form of increased local and value-added marketing potential. Organic production may help growers to access new markets and cut production costs through enhanced synergies between ecosystem services and production goals. A peach (Prunus persica) orchard was established in 2008 with six organic treatment combinations: 1) straw mulch and grass alleyway; 2) straw mulch and legume (birdsfoot trefoil, Lotus corniculatus) alleyway; 3) living mulch (low-growing shallow rooted alyssum, Lobularia maritime) and grass alleyway; 4) living mulch and legume alleyway; 5) woven plastic mulch and legume alleyway; 6) tillage and grass alleyway. Paunch manure compost was applied at a baseline rate of 25, 48 and 96 g total N per tree in the first, second and third years of establishment and adjusted up or down relative to the baseline rate against tree growth. Tree growth as measured by trunk cross sectional area was initially slowed in living and non-living mulch treatments; by the end of 2011, trees were largest in legume alleyway treatments despite considerable tree row weed pressure. The ultimate goal of the research was to quantify the benefits and/or tradeoffs between different organic management scenarios on water use, pest dynamics, and fruit and soil quality in order to assist growers in making both economically and environmentally sound organic management practice decisions.

Interest in unheated plastic film-covered high tunnels to extend the growing season of high-value fruits and vegetables is growing rapidly, but sustainable soil management in intensively managed high tunnels is challenging. Yields, fruit quality, and soil quality in transition organic and conventional tomato were measured over the course of three growing seasons. Nitrogen (N) was applied at the rate of 112, 168, and 224 kg total N/ha in the form of chicken manure compost to the organic treatments and a polymer-coated slow-release urea fertilizer in the conventional treatments. Marketable yield of organically grown tomatoes was lower in Year 1 but equaled conventional tomatoes in Years 2 and 3. Soil quality as measured by total carbon (C) and N and microbial activity was significantly greater in organic tomato production at the end of the study. Significant phosphorus (P) and potassium (K) applied with the composted manure resulted in high soil P and K levels in organically managed high tunnels after just 3 years of application. Although compost is the most economical organic fertilizer and results in significant benefits in soil quality during the transition phase to organic production, a maintenance fertility plan is needed once available soil P reaches adequate to high levels. Combinations of compost and high N, low P organic fertilizers are needed for optimum maintenance fertility strategy for organic tunnel house production.

Trials were established at two locations to evaluate weed control provided by mulches and organic herbicides alone or in combination. Mulch treatments included barley straw, pine wood chips, paper, and no mulch (bare-ground control). Herbicide treatments included three organically certified herbicides: lemon grass oil (14% v/v), clove oil (8% v/v), and two rates of acetic acid (10 and 15% v/v). Other treatments included pelargonic acid (7% v/v), glyphosate (1.06 kg ai/ha), and no-herbicide (control). Individual herbicide treatments were applied according to weed pressure and were determined every 7 to 10 days. Herbicide applications were made two and three times in 2009 at Logan and Kaysville, respectively. Treatments were carried out for a second year at both locations with herbicide treatments applied a maximum of four times. A third trial was established in 2010 at Kaysville with four application times. Weed control evaluations were made once a month, and weed population densities were evaluated at the...

Overreliance on fossil fuel based inputs, and transport of inputs and products is seen by many as a threat to long-term agricultural and food system sustainability. Many organic, biodynamic, and low-input farmers limit off-farm inputs, attempting instead to farm within the carrying capacity of their land or local environment. These farmers often accept lower farm productivity because they see reduced reliance on non-renewable inputs as more sustainable. Documentation of low-input agricultural systems through both replicated research trials and case studies is needed in order to better understand perceived and real advantages and tradeoffs. The goal of our study was twofold: (1) to compare liming and biodynamic (BD) preparations in improving pasture on a moderately acidic pasture soil through stimulation of soil microbial activity; (2) to place these findings within the context of a whole farm analysis of economic, plant, and animal health. Treatments included lime, the Pfeiffer Field Spray plus BD compost preparations, and untreated controls. Soil pH, total C and N, microbial activity, forage biomass, and forage quality were evaluated over two growing seasons. Both lime and the Pfeiffer Field Spray and BD preparations were only moderately effective in raising soil pH, with no effect on soil microbial activity or forage yield. Lime significantly reduced forage crude protein but the practical implications of this are questionable given the overall low quality of the forage. While the farm is profitable and economically stable and the animals healthy, the need for future targeted nutrient inputs cannot be ruled out for sustainable long-term production.

Current guidelines for the use of compost in organic agriculture are based on nutrient targets, which represent the conditions needed for maximum yield. Due to the high cost of inputs, however, a maximum-yield strategy may be far from economically optimal in some organic cropping systems. In this article we formulate a theory of economically optimal rates (EORs) for compost that incorporates the effects on yield in the years after application. When carryover is neglected, it is well known that the slope of the yield response at the EOR equals the fertilizer/crop price ratio. We show that when carry-over effects are modeled with a decay series, the critical slope is reduced by the sum of the decay series, and this criterion holds for each crop in a rotation. To demonstrate the application of these theoretical results, we used data from a previous study in which the dryland wheat yield response to compost was measured on organic farmland in northern Utah. Since a decay series was not measured, EORs are presented for a range of values of the cumulative carryover, as well as for different compost/wheat price ratios. The EOR for compost sold by one of the region's main composting facilities was predicted to be zero, which highlights the challenging nature of organic fertility management in northern Utah's dryland agriculture. Confidence in the EOR was hindered by our limited understanding of carryover in dryland systems, which should be a priority for future research.

Biodynamic (BD) agriculture, a form of organic agriculture, includes the use of specially fermented preparations, but peer-reviewed studies on their efficacy are rare. Composting of a grape pomace and manure mixture was studied in two years (2002 and 2005) with and without the BD compost preparations. Water extracts of finished composts were then used to fertigate wheat seedlings, with and without added inorganic fertilizer. BD-treated mixtures had significantly greater dehydrogenase activity than did untreated (control) mixtures during composting, suggesting greater microbial activity in BD-treated compost. In both years there was a distinct compost effect on wheat shoot and root biomass irrespective of supplemental fertilizer. Shoot biomass was highest in all treatments receiving 1% compost extract. Wheat seedlings that received 1% compost extract in 2005 grew similar root and shoot biomass as fertilized seedlings, despite only containing 30% as much nitrogen as the fertilizer treatment. In both years seedlings that received fertilizer plus 1% compost extract produced 22-61% more shoot biomass and 40-66% more root biomass than seedlings that received fertilizer alone, even at higher rates. In 2002 a 1% extract of BD compost grew 7% taller wheat seedlings than did 1% extract of untreated compost. At 0.1% only BD extract grew taller plants than water, but in 2002 only. No effect on shoot or root biomass was seen at 0.1%. Our results support the use of compost extracts as fertilizer substitutes or supplements, testimonial reports on the growth promoting effects of compost extracts, and the occasional superiority of BD compost to untreated compost.

Relationships between soil microbial diversity and soil function are the subject of much debate. Process-level analyses have shown that microbial function varies with soil type and responds to soil management. However, such measurements cannot determine the role of community structure and diversity in soil function. The goal of this study was to investigate the role of gene frequency and diversity, measured by microarray analysis, on soil processes. The study was conducted in an agro-ecosystem characterized by contrasting management practices and soil types. Eight pairs of adjacent commercial organic and conventional strawberry fields were matched for soil type, strawberry variety, and all other environmental conditions. Soil physical, chemical and biological analyses were conducted including functional gene microarrays (FGA). Soil physical and chemical characteristics were primarily determined by soil textural type (coarse vs fine-textured), but biological and FGA measures were more influenced by management (organic vs conventional). Organically managed soils consistently showed greater functional activity as well as FGA signal intensity (SI) and diversity. Overall FGA SI and diversity were correlated to total soil microbial biomass. Functional gene group SI and/or diversity were correlated to related soil chemical and biological measures such as microbial biomass, cellulose, dehydrogenase, ammonium and sulfur. Management was the dominant determinant of soil biology as measured by microbial gene frequency and diversity, which paralleled measured microbial processes.

For organic farmers who use manure or compost to maintain soil fertility, a pressing question is how much should be applied. Although many factors influence this decision, an important consideration is that manure and compost continue to fertilize for many years after their application. In conventional agriculture, the carry-over effects of manure have traditionally been quantified in terms of N fertilizer equivalents, that is, through a decay series. Nitrogen decay series may also be used by organic farmers trying to meet N fertilizer recommendations with manure and/or compost. However, this creates an unsustainable paradigm for organic fertility management because N fertilizer equivalency experiments cannot be conducted on organically certified land. We propose a new type of decay series compatible with organic regulations in which the carry-over effects of manure/compost are measured, not against N fertilizer, but against new applications of the amendment. The result is a decay series in manure/compost equivalents, which, although conceptually straightforward, is not as readily estimated as a N decay series. The methodological challenges of this approach were explored using data from a continuous corn (Zea mays L.) system fertilized with manure slurry. Regression analysis revealed that 1 unit of manure slurry had the same effect on yield as 0.21, 0.16, and 0.13 units of new slurry after 1, 2, and 3 yr, respectively. By quantifying the nutritive and non-nutritive carry-over effects of manure/compost, this new decay series has the potential to fully credit organic matter in fertility planning.

Plants take up nitrogen principally in the form of nitrate and ammonium; however, evidence is growing that they can also use organic N in the form of amino acids. Selecting varieties that better use organic N could be important in maximizing productivity in organic and low-input systems because these varieties may access a wider pool of available nutrients. We tested amino acid-N uptake by wheat (Triticum aestivum L.) seedlings over 24 h over a range of soil glycine concentrations. Wheat was grown in 5 ml pipette tips for 10 days prior to labeling with 14C-labeled glycine. In a second experiment, uptake of amino acid-N relative to nitrate and ammonium was tested in three pre-1940 wheat varieties (Arco, Idaed, and Red Fife), three modern varieties (Alpowa, Madsen, and Zak), and one perennial wheat variety (unreleased). Glycine-N was detected in all shoots (with the exception of the lowest soil concentration) and increased with increasing soil concentration. There were few differences in uptake between individual varieties tested but seedlings of modern varieties were more efficient at capturing organic N than classic varieties. Glycine-N constituted between 3.9% and 8.1% of total N uptake over 24 h and constituted a significantly greater proportion of total N in perennial wheat than annual wheat varieties. These results show that there may be sufficient varietal differences in organic N uptake in wheat to warrant selection for this trait in breeding programs targeted to improving N use efficiency.

Evidence is growing that amino acids can be an important source of plant N in nutrient limited natural ecosystems, but relatively little is known about the effect of agricultural management on soil amino acid pools and turnover. Organic management in particular relies on slow-release organic inputs as fertilizer, which could result in greater pools of soil amino acids available for plant uptake. Moreover, we know little about potential differences in amino acid uptake ability within plant families and whether this ability may have been lost during domestication. In order to determine the relative effects of soil type and management on amino acid turnover, we measured the effect of fine- versus coarse-textured soil and organic versus conventional management on free amino acids and proteolytic activity in the field. Secondly, we conducted greenhouse experiments to determine the ability of domestic and wild strawberry to utilize amino acid-N. Fine-textured and organically managed soils contained significantly higher total C and N than coarse-textured and conventionally managed soils. There were no significant differences in free amino acids or protease activity in relation to texture or management. Amino acid turnover was calculated at 0.7-1.5 h. Turnover time was significantly greater in fine-textured soils. Turnover time as a result of substrate additions was significantly shorter in coarse-textured soils; in fine-texturedsoils turnover time was shorter under conventional management. This suggests less competition for amino acids in soils with greater C, N and/or cation exchange capacity (CEC), such as fine-textured and organically managed soils. Two wild species of strawberry, Fragaria virginiana and Fragaria chiloensis, took up significantly more 14C labeled glycine than the domesticated species, Fragaria fragaria. More research is needed to determine whether strawberry cultivars could be selected or bred for their ability to capture amino acid-N, thus improving N-use efficiency in farming systems relying on the breakdown of organic matter as a N source.

Agricultural developments over the previous half-century have highly increased food, feed and fiber production. Yet, global food output and distribution still falls short of feeding the world with unintended harm to the environment and society. Agriculture requires new approaches that meet the challenges of sustainable and equitable food production. One prevailing alternative, agroecology, is an approach that promotes environmental conservation, ecosystem health and social equality in the global food system. However, the field of agroecology remains disjointed by a number of working definitions and conflicting agendas. Lack of a clear definition of the term can lead to misuse or overgeneralization that hinders effective dialog, collaboration, and development of the discipline.

That the health of soils, plants, animals, and people are linked is an ancient idea that still resonates. Growing evidence links farm management, soil health, and plant health but relationships among soil health, food crop nutritional quality, and human health are less understood. Numerous studies compare organic with conventional farming in order to shed light on these links. Organic farming systems utilize carbon-based amendments, diverse crop rotations, and cover crops to build soil fertility. These practices increase biologically available soil organic matter and beneficial soil microbe and invertebrate activities, improve soil physical properties, reduce disease potential, and increase plant health. To date, comparisons of nutrient content between organic and conventional foods have been inconsistent. Recent evidence suggests that organically grown fruits and vegetables contain higher levels of health promoting phytochemicals, possibly linked to greater plant stress, rhizosphere microbial communities, and/or lower available nitrogen. But the overlap in management practices among farming systems make broad generalizations difficult. Moreover, environmental and crop species and/or cultivar interactions may exert stronger effects than management. Here we summarize the known factors influencing soil and plant health and link these with food-crop quality and human health. Though this paper draws primarily from research on organic farming, management practices that enhance soil, plant, and human health remain an important goal for all sustainable food production systems.

Background Sale of organic foods is one of the fastest growing market segments within the global food industry. People often buy organic food because they believe organic farms produce more nutritious and better tasting food from healthier soils. Here we tested if there are significant differences in fruit and soil quality from 13 pairs of commercial organic and conventional strawberry agroecosystems in California. Methodology/Principal Findings At multiple sampling times for two years, we evaluated three varieties of strawberries for mineral elements, shelf life, phytochemical composition, and organoleptic properties. We also analyzed traditional soil properties and soil DNA using microarray technology. We found that the organic farms had strawberries with longer shelf life, greater dry matter, and higher antioxidant activity and concentrations of ascorbic acid and phenolic compounds, but lower concentrations of phosphorus and potassium. In one variety, sensory panels judged organic strawberries to be sweeter and have better flavor, overall acceptance, and appearance than their conventional counterparts. We also found the organically farmed soils to have more total carbon and nitrogen, greater microbial biomass and activity, and higher concentrations of micronutrients. Organically farmed soils also exhibited greater numbers of endemic genes and greater functional gene abundance and diversity for several biogeochemical processes, such as nitrogen fixation and pesticide degradation. Conclusions/Significance Our findings show that the organic strawberry farms produced higher quality fruit and that their higher quality soils may have greater microbial functional capability and resilience to stress. These findings justify additional investigations aimed at detecting and quantifying such effects and their interactions.