Heather D. Karsten

Predicting weed emergence for eight annual species in the northeastern United States

Abstract A 2-yr experiment assessed the potential for using soil degree days (DD) to predict cumulative weed emergence. Emerged weeds, by species, were monitored every 2 wk in undisturbed plots. Soil DD were calculated at each location using a base temperature of 9 C. Weed emergence was fit with logistic regression for common ragweed, common lambsquarters, velvetleaf, giant foxtail, yellow foxtail, large crabgrass, smooth pigweed, and eastern black nightshade. Coefficients of determination for the logistic models fit to the field data ranged between 0.90 and 0.95 for the eight weed species. Common ragweed and common lambsquarters were among the earliest species to emerge, reaching 10% emergence before 150 DD. Velvetleaf, giant foxtail, and yellow foxtail were next, completing 10% emergence by 180 DD. The last weeds to emerge were large crabgrass, smooth pigweed, and eastern black nightshade, which emerged after 280 DD. The developed models were verified by predicting cumulative weed emergence in adjacent plots. The coefficients of determination for the model verification plots ranged from 0.66 to 0.99 and averaged 0.90 across all eight weed species. These results suggest that soil DD are good predictors for weed emergence. Forecasting weed emergence will help growers make better crop and weed management decisions. Nomenclature: Common lambsquarters, Chenopodium album L. CHEAL; common ragweed, Ambrosia artemisiifolia L. AMBEL; eastern black nightshade, Solanum ptycanthum Dun. SOLPT; giant foxtail, Setaria faberi Herrm. SETFA; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; smooth pigweed, Amaranthus hybridus L. AMACH; velvetleaf, Abutilon theophrasti Medikus ABUTH; yellow foxtail, Setaria glauca (L.) Beauv. SETLU.

The Effect of Weed Density and Application Timing on Weed Control and Corn Grain Yield1

A 2-yr experiment repeated at five locations across the northeastern United States evaluated the effect of weed density and time of glyphosate application on weed control and corn grain yield using a single postemergence (POST) application. Three weed densities, designed to reduce corn yields by 10, 25, and 50%, were established across the locations, using forage sorghum as a surrogate weed. At each weed density, a single application of glyphosate at 1.12 kg ai/ha was applied to glyphosate-resistant corn at the V2, V4, V6, and V8 growth stages. At low and medium weed densities, the V4 through V8 applications provided nearly complete weed control and yields equivalent to the weed-free treatment. Weed biomass and the potential for weed seed production from subsequent weed emergence made the V2 timing less effective. At high weed densities, the V4 followed by the V6 timing provided the most effective weed control, while maintaining corn yield. Weed competition from subsequent weed emergence in the V2 application and the duration of weed competition in the V8 timing reduced yield on average by 12 and 15%, respectively. This research shows that single POST applications can be successful but weed density and herbicide timing are key elements. Nomenclature: Glyphosate; corn, Zea mays L.; forage sorghum, Sorghum bicolor (L.) Moench. Additional index words: Glyphosate-resistant corn, herbicide application timing, postemergence weed control, weed competition, weed density. Abbreviations: POST, postemergence; WAP, weeks after planting.

Effect of Soil Disturbance on Annual Weed Emergence in the Northeastern United States

A 2-yr experiment evaluated the effect of spring soil disturbance on the periodicity of weed emergence. At four locations across the northeastern United States, emerged weeds, by species, were monitored every 2 wk in both undisturbed plots and plots tilled in the spring with a rotary cultivator. Eight weed species including large crabgrass, giant and yellow foxtail, common lambsquarters, smooth pigweed, eastern black nightshade, common ragweed, and velvetleaf occurred at three or more site-years. Spring soil disturbance either had no effect or reduced total seedling emergence compared with undisturbed soils. Total seedling emergence for large crabgrass, giant foxtail, smooth pigweed, and common ragweed were on average, 1.4 to 2.6 times less with spring soil disturbance, whereas eastern black nightshade and velvetleaf were mostly unaffected by the soil disturbance. The influence of soil disturbance on yellow foxtail and common lambsquarters emergence varied between seasons and locations. Although the total number of emerged seedlings was often affected by the soil disturbance, with the exception of yellow foxtail and common ragweed, the periodicity of emergence was similar across disturbed and undisturbed treatments. Nomenclature: Common lambsquarters, Chenopodium album L. #3 CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; eastern black nightshade, Solanum ptycanthum Dun. # SOLPT; giant foxtail, Setaria faberi Herrm. # SETFA; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; smooth pigweed, Amaranthus hybridus L. # AMACH; velvetleaf, Abutilon theophrasti Medicus # ABUTH; yellow foxtail, Setaria glauca (L.) Beauv. # SETLU. Additional index words: Integrated pest management, periodicity of weed emergence, spring soil disturbance.

Meeting the ‘multi-’ requirements in organic agriculture research: Successes, challenges and recommendations for multifunctional, multidisciplinary, participatory projects

Organic farming is one of the fastest growing agricultural sectors worldwide, and funds to support research and extension activities that address the needs of organic producers are becoming more widely available in the USA. Solutions to problems in ecologically complex systems, such as organic farming systems often exceed the expertise of individual investigators or single disciplines. Further, the complex nature of ecological and social interactions within systems-based agricultural research requires not only more emphasis on information exchange but also synthesis between multidisciplinary teams of academic researchers and organic farmers. Accordingly, federal grant agencies that support organic agriculture research increasingly require that projects encompass multiple academic disciplines, multiple functions (research, outreach, education), and the participation of stakeholders for the ultimate purpose of the integration of knowledge. Many researchers, educators and administrators at land grant universities (LGUs) remain inexperienced in multidisciplinary, multifunctional and participatory research. Using post-completion project interviews of the project investigators on an organic transition project, we identified eight factors that affected the integration of knowledge from a farmer advisory board and the conduct of our multidisciplinary, participatory organic transition project. The first five factors include shared values, balance in technical competence, institutional capacity for research, team capacity for problem solving and institutional resistance. The research team also identified three other factors that evoked confusion and divergence during the project, and include the ambiguity of power and control of knowledge, the proposed experimental plan and terms of team engagement. We considered participatory elements of the project according to Biggs’ linear typology of participation, but found more appropriate Neef and Neuberts position that a linear scale of participatory approach is an inadequate framework for helping agricultural scientists to decide on whether and in which phases they want to, can and should incorporate participatory elements into their research projects. From these findings, we conclude with critical issues for academic research and extension teams to consider during the development and before conduct of these types of projects. We also offer recommendations for LGUs and other research institutions, and funding organizations, to facilitate multidisciplinary, multifunctional, participatory research.

Grass-Based Dairy Production Provides a Viable Option for Producing Organic Milk in Pennsylvania

Abstract More intensive use of pasture and the transition to organic production are being used to reduce production costs and increase profitability of some small dairy farms in Pennsylvania. Farm simulation, supported by case study farm data, was used to compare the economic benefits and environmental impacts of two grazing-based production systems using either organic or conventional practices. Systems using all-grass production with managed rotational grazing and a spring calving herd maintained outdoors throughout the year had lower erosion and phosphorus losses, lower production costs, and up to

Assessment of an Integrated Weed Management System in No-Till Soybean and Corn

200/acre (

Projected climate and agronomic implications for corn production in the Northeastern United States

1.58 to 3.63/cwt of milk produced) greater net return compared to systems using crop production, supplemental grazing, random calving, and winter confinement. With either production approach, substantial economic benefit was found using organic practices, but this benefit was highly dependant upon the price difference between organic and conventional milk. Environmental concerns for organic production were (i) long-term accumulation of soil nutrients due to the use of imported poultry manure for crop fertilization, and (ii) greater soil erosion and runoff loss of phosphorus due to increased tillage for weed control in annual crops. The economic net benefit may encourage more grass-based dairy producers to transition to organic certification, so more attention must be given to identifing strategies that better utilize farm nutrients and reduce losses to the environment.

Corn grain yields and yield stability in four long-term cropping systems.

The objective of this study was to evaluate weed control, crop yields, potential soil loss, and net returns to management of an integrated weed management system in no-till corn and soybean compared to an herbicide-based strategy. The integrated weed management system reduced herbicide inputs by delayed cover crop termination, herbicide banding, and high-residue cultivation (reduced herbicide [RH]), while the other system used continuous no-tillage and herbicides to control weeds (standard herbicide [SH]). Research was conducted within the Penn State Sustainable Dairy Cropping Systems Experiment, where corn and soybean are each planted once in a 6-yr crop rotation. In this 3-yr study, weed density and biomass were often greater under RH management, but weed biomass never exceeded 19 g m−2 in corn and 21 g m−2 in soybean. Corn yield and population did not differ in any year, and net returns to management were

Effect of Drought on Growth, Carbohydrates, and Soil Water Use by Perennial Ryegrass, Tall Fescue, and White Clover

33.65 ha−1 higher in RH corn due to lower herbicide costs and slightly, though not significantly, higher yields. Soybean yield was lower in RH compared to SH in 2 of 3 yr, and was correlated with soybean population and cover crop residue. Net financial returns were

Organic Dairy Production Systems in Pennsylvania: A Case Study Evaluation

43.69 ha−1 higher in SH soybean compared to RH. Predicted soil loss never exceeded T (maximum allowable soil loss) for any treatment and slope combination, though soil loss was 100% greater on a 10% slope under RH management (vs. SH) due to cultivation. Nomenclature: cereal rye (Secale cereale L.); corn (Zea mays L.); soybean [Glycine max (L.) Merr.]