Dose-response analysis can be carried out using multi-purpose commercial statistical software, but except for a few special cases the easily becomes cumbersome as relevant, non-standard output requires manual programming. The extension package drc environment R provides flexible and versatile infrastructure dose-response analyses in general. present version of package, reflecting extensions modifications over last decade, user-friendly interface to specify model assumptions about...

We describe an add-on package for the language and environment R which allows simultaneous fitting of several non-linear regression models. The focus is on analysis dose response curves, but functionality applicable to arbitrary Features illustrated in examples.

Advances in statistical software allow methods for nonlinear regression analysis of dose-response curves to be carried out conveniently by non-statisticians. One such is the program R with drc extension package. The package can: (1) simultaneously fit multiple curves; (2) compare curve parameters significant differences; (3) calculate any point along at response level interest, commonly known as an effective dose (e.g., ED30, ED50, ED90), and determine its significance; (4) generate graphs...

Surveys of the weed flora in Danish arable fields were conducted 1967-70 and 1987-89. Frequencies 67 common species spring barley, rape, winter rye, wheat grass ley compared. The comparison showed that occurrence has generally decreased during last 20 years. frequency some such as Anagallis arvensis, Arenaria serpyllifolia, Atriplex patula, Cerastium caespitosum, Galium aparine, Plantago major Silene noctiflora remarkably, possibly because intensive chemical control. dominating 1987-89...

Summary One of the most commonly used techniques to assess efficacy herbicides is apply principle bioassays. A bioassay defined as an experiment for estimating potency a herbicide by analysis reaction that follows its application living organisms. The variance central applications statistical methods in experiments. This true bioassay, but perhaps fundamental importance regression and related concepts here particularly apparent. purpose this presentation quantify herbicidal effects applying...

During the past two decades, phenomenon of hormesis has gained increased recognition. To promote research in hormesis, a sound statistical quantification important parameters, such as level and significance increase response range concentration where it occurs, is strongly needed. Here, we present an improved model to describe hormetic dose-response curves test for presence hormesis. Using delta method freely available software, any percentage effect dose or can be derived with its...

This paper evaluated the frequency, magnitude and dose/concentration range of hormesis in four species: The aquatic plant Lemna minor, micro-alga Pseudokirchneriella subcapitata two terrestrial plants Tripleurospermum inodorum Stellaria media exposed to nine herbicides one fungicide binary mixtures thereof. In total 687 dose-response curves were included database. study showed that both frequency hormetic response depended on endpoint being measured. Dry weight at harvest a higher larger...

Summary Weeds cause yield losses and reductions in crop quality. Prior to the introduction of selective herbicides, drudgery manual weeding forced farmers adhere a suit weed management tactics by carefully combining rotation, appropriate tillage fallow systems. The herbicides late 1940s constant flow new succeeding decades provided with tool, ‘the chemical hoe’, putting them position consider control more independently production system than hitherto. reliance on for control, however,...

As cases of resistance to herbicides escalate worldwide, there is increasing demand from growers test for weed and learn how manage it. Scientists have developed resistance-testing protocols numerous species. Growers need immediate answers scientists are faced with the daunting task testing an increasingly large number samples across a variety species herbicides. Quick tests been, continue be, address this need, although classical still norm. Newer methods involve molecular techniques....

Summary Small unmanned aerial systems ( UAS ) with cameras have not been adopted in weed research, but offer low‐cost sensing high flexibility terms of spatial resolution. A small rotary‐wing was tested as part a search for an inexpensive, user‐friendly and reliable aircraft practical applications imagery research. In two experiments post‐emergence harrowing barley, the crop resistance parameter, which reflects response to harrowing, unaffected by image capture altitude range from 1 50 m....

A range of 111 rice cultivars was studied for weed‐suppressing ability in field experiments with a sown infestation Echinochloa crus‐galli. Cultivars differed significantly their to suppress the growth E. crus‐galli , and differences were reasonably reproducible over three seasons. The same tested laboratory screening allelopathic potential, which showed significant reduce root . Correlation between that performance could be described some extent by length reduction laboratory. Plant height...

Abstract Widely used herbicides sometimes inadvertently contaminate surface waters. In this study we evaluate the toxicity of to aquatic plants and algae relate it environmental herbicide concentrations exposure scenarios, formulation mode action. This was done experimentally for ten herbicides, using macrophyte Lemna minor L. green alga Pseudokirchneriella subcapitata (Korshikov) Hindak, supplemented with a database comprising data 146 herbicides. The laboratory showed that formulations in...

Summary: The distribution of 37 common weed species in eight Danish crops response to seven edaphic factors was evaluated using linear logistic regression with adjustment for over‐dispersion. main effects soil properties on were adjusted crop type and sample year by the regression. Crop clay content generally those explanatory variables that had greatest influence occurrence species, but all other examined (sample year, loss ignition, pH, P, K, Mg Mn) also an effect some species.

Mixing herbicides is a common practice in agriculture, to optimize farm management practices, widen the weed control spectrum, enhance application efficiency, and manage herbicide resistance. Interactions between can occur within spray tank, on leaf surface, and/or inside plant, resulting physicochemical physiological interactions. Additive, synergistic, or antagonistic effects result from these Given range plant response potential for negative positive outcomes management, predicting...

Although the ecological significance of mixtures phytotoxins is recognized in research on chemical plant interference (allelopathy), few studies convincingly demonstrate joint action phytotoxin mixtures, key to understanding impact these materials, using established models from other biological disciplines, e.g. toxicology and pharmacology. Addressing this need, present study investigates phenolic acids, p-hydroxybenzoic, p-coumaric ferulic acids root growth inhibition perennial ryegrass...

SUMMARY Transformation and weighting techniques are applied to dose-response curve models. In particular, methods derived from a controlled-variable, random-effect model closely related random-coefficient studied. These two models correspond additive multiplicative effects of variations in the dose, both lead variance components proportional square derivative response function with respect dose. When is nonlinear typically identifiable even without replicate measurements bioassay example fit...

(1980). Models for Curve-fitting Herbicide Dose Response Data. Acta Agriculturae Scandinavica: Vol. 30, No. 1, pp. 59-64.

Abstract Theoretically, the effect of two independently acting compounds in a mixture will depend on slope dose‐response curves individual if evaluated relation to model concentration addition (CA). In present study, we explored development shape relationship for four different recommended endpoints (surface area, frond number, fresh weight‐specific, and dry weight‐specific relative growth rates [RGR A , RGR F FW DW respectively]) differently herbicides (metsulfuron‐methyl terbuthylazine)...