Evolutionary-thinking in agricultural weed management

Agricultural weeds evolve in response to crop cultivation. Nevertheless, the central importance of evolutionary ecology for understanding weed invasion, persistence and management in agroecosystems is not widely acknowledged. This paper calls for more evolutionarily-enlightened weed management, in which management principles are informed by evolutionary biology to prevent or minimize weed adaptation and spread. As a first step, a greater knowledge of the extent, structure and significance of genetic variation within and between weed populations is required to fully assess the potential for weed adaptation. The evolution of resistance to herbicides is a classic example of weed adaptation. Even here, most research focuses on describing the physiological and molecular basis of resistance, rather than conducting studies to better understand the evolutionary dynamics of selection for resistance. We suggest approaches to increase the application of evolutionary-thinking to herbicide resistance research. Weed population dynamics models are increasingly important tools in weed management, yet these models often ignore intrapopulation and interpopulation variability, neglecting the potential for weed adaptation in response to management. Future agricultural weed management can benefit from greater integration of ecological and evolutionary principles to predict the long-term responses of weed populations to changing weed management, agricultural environments and global climate

Choosing Book Friends

PDF pages: 3

Organic Spring Wheat Weed Control Strategies Report

Many organic cereal grain growers struggle with weed issues, especially in spring wheat. Weed competition is one of the major issues in spring wheat due to many factors. Some of those factors include weed seed flushes from spring tillage and weed germination at the same time as crop germination. With this in mind, the University of Vermont Extension has begun conducting trials to evaluate the effects of different weed control methods in spring wheat. In 2012, the study was continued to develop strategies that will minimize weed competition while maintaining yield and quality parameters to successfully produce high-quality bread wheat. The management practices evaluated include variable row spacing and mechanical cultivation with a tineweeder or inter-row hoe

Brassica cover crops for weed control in organic vegetable production

Cover crops (or green manures) are commonly used by organic vegetable growers for soil fertility building and other benefits including weed control. Brassica crops have been reported to control weeds in subsequent crops, usually attributed to the allelopathic effects of glucosinolates (GSL) in the brassica residues, although the effects are inconsistent. New brassica varieties with high GSL levels (Brassica juncea cv. Fumus and Raphanus sativus cv. Weedcheck) were tested in combination with mechanical weed control and another locally grown forage crop (Lolium multiflorum cv. Conquest) for their effects on weed growth during the pre-crop phase and subsequent weed and lettuce growth during the in-crop phase. The cover crops and bare fallow controlled weeds effectively during the pre-crop phase, but did not affect weed and lettuce growth in the following in-crop phase. The cover crops provided better on-going weed control than the bare fallow. Reducing the delay between the pre- and in-crop phases from four weeks to one day did not affect weed and lettuce growth. Weed control was closely related to the amount of light reduction by the cover crops, while competition for nutrients and water appeared to be less important in weed suppression by the cover crops. The use of cover crops requires careful selection of appropriate varieties, attention to good cover crop husbandry (particularly establishment) and an awareness of prevailing weed seed bank levels

Uncoupled isotonic regression via minimum Wasserstein deconvolution

Isotonic regression is a standard problem in shape-constrained estimation where the goal is to estimate an unknown nondecreasing regression function $f$ from independent pairs $(x_i, y_i)$ where $\mathbb{E}[y_i]=f(x_i), i=1, \ldots n$. While this problem is well understood both statistically and computationally, much less is known about its uncoupled counterpart where one is given only the unordered sets $\{x_1, \ldots, x_n\}$ and $\{y_1, \ldots, y_n\}$. In this work, we leverage tools from optimal transport theory to derive minimax rates under weak moments conditions on $y_i$ and to give an efficient algorithm achieving optimal rates. Both upper and lower bounds employ moment-matching arguments that are also pertinent to learning mixtures of distributions and deconvolution.Comment: To appear in Information and Inference: a Journal of the IM

Sharp asymptotic and finite-sample rates of convergence of empirical measures in Wasserstein distance

The Wasserstein distance between two probability measures on a metric space is a measure of closeness with applications in statistics, probability, and machine learning. In this work, we consider the fundamental question of how quickly the empirical measure obtained from $n$ independent samples from $\mu$ approaches $\mu$ in the Wasserstein distance of any order. We prove sharp asymptotic and finite-sample results for this rate of convergence for general measures on general compact metric spaces. Our finite-sample results show the existence of multi-scale behavior, where measures can exhibit radically different rates of convergence as $n$ grows

Tolerance to weed harrowing in spring barley genotypes

Controlling weeds in spring cereals grown under organic conditions is mostly done by post emergence weed harrowing, where spring tines of the weed harrow control weeds by uprooting and/or covering small weeds plants with soil. In situations with relatively large weed plants and relatively small crop plants, there are increased risks for crop damages by soil coverage or other mechanical damages of the crop leaves. These damages are increasing with increasing weed control intensity, and are resulting in reduced crop growth immediately after weed harrowing. There are risks that the reduced growth reduces final crop yield too. However, there is some evidence that there are varietal differences in the tolerance to weed harrowing. The aim of this study was to estimate the damages by weed harrowing in four pure genotypes and three two- or one three-component mixtures of spring barley, and to analyze if there were differences in tolerance to weed harrowing between the genotypes and mixtures. Results from a two-year field study showed that there were varietal differences in the tolerance to mechanical weed control in the immediate effect as well as the short term effect, however there were marked differences in the immediate and short term effect between the two years. Regarding the long term effect of weed harrowing on yield, there were no significant differences in 2003 but in 2004, Brazil and the three component mixture suffered significantly from weed harrowing while Modena, Otira and Modena+Orthega mixture, seems to benefit from weed harrowing. The reason for these differences is probably due to differences in growth habit at the time for weed harrowing