Jennifer R. Reeve

Fruit and Soil Quality of Organic and Conventional Strawberry Agroecosystems

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.

Influence of biodynamic preparations on compost development and resultant compost extracts on wheat seedling growth.

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.

Agroecological Principles from a Bibliographic Analysis of the Term Agroecology

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.

Mulch and organicherbicide combinations for in-row orchard weed suppression

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 beginning and end of the season. Weed biomass and percent weed cover were collected at the end of the 2010 season. Mulches each provided significant weed suppression in the first year, but each mulch presented unique challenges over time. For example, paper mulch effectiveness decreased over time as cracks developed during wet-dry cycles allowing weed seedlings to emerge. Volunteer barley became problematic in straw mulch plots in the first year of each trial, and annual weed seed germination on top of the wood chip mulch became problematic in the second year. The straw mulch consistently provided among the highest weed control and the least end-of-season weed biomass. Glyphosate and pelargonic acid gave near 100% weed control among all mulch treatments, including the non-mulched plots. Lemon oil and clove oil displayed the same weed control ratings as the no-herbicide treatment in the three mulches (straw, wood chip, and paper), but displayed 41–95% weed control when applied without mulch. While organically certified herbicides generally did not provide sufficient weed control alone, some mulches and organic herbicide combinations provided weed suppression similar to conventional herbicide application.

Soil enzyme activities and abundance of microbial functional genes involved in nitrogen transformations in an organic farming system

Organic farming systems receive organic amendments to maintain soil fertility and supply nutrients for plant growth. This study investigated the effect of organic fertilizers (no amendment as control, compost, and manure), and their interaction with cover crops (millet, buckwheat, and black turtle bean) on soil enzyme activities, N transformation rates, and functional gene abundances under an organic production system. Organic N fertilizers had a stronger effect than cover crop type on soil function and functional gene abundances. Soil enzyme activities were increased by both compost and manure, but there were few differences between these treatments. Nitrification potential, nitrite oxidation potential, and denitrification potential were significantly higher in manure-treated than in control and compost-treated soils, indicating application of manure had a higher N loss potential than compost application in this organic farming system. Organic N fertilizers significantly increased the abundance of some genes involved in N mineralization, ammonification, and nitrification (sub, ureC, bacterial amoA and nxrB). The activity of ammonia-oxidizing bacteria and archaea were both increased by organic N fertilizers, and their activities were higher in manure-treated than in compost-treated soils. Overall, the abundance of functional genes was significantly correlated with their corresponding enzyme activity. However, functional gene abundance was less important than soil chemical and microbiological properties in explaining the variation in the corresponding enzyme activity.

Effects of Floor Vegetation and Fertility Management on Weed Biomass and Diversity in Organic Peach Orchards

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.