Steven J Shirtliffe

University of Saskatchewan | U of S · Department of Plant Sciences

Dormancy in canola (Brassica napus L.) is a complicated process due to many overlapping and interacting factors affecting the absolute dormancy levels. It is unknown if seed dormancy plays a role in the poor stand establishment of planted canola but given that germination and dormancy are two ends of the same continuum, it has been suggested that d...

There is increasing demand for more detailed soil maps to support fine-scale land use planning, soil carbon management, and precision agriculture in Saskatchewan. Predictive soil mapping that incorporates a combination of environmental covariates provides a cost-effective tool for generating finer resolution soil maps. This study focused on mapping...

The application of herbicides in agriculture has significantly increased in recent decades. While many herbicides improve the efficiency and efficacy of weed control, their excessive use at the wrong growth stage can cause crop foliar damage, higher input cost and negative environmental footprints. There are limited techniques to accurately monitor...

Increasing crop trait diversity in oilseed rape (OR, Brassica napus L.) cropping systems by introducing frost-sensitive legume species could improve weed suppression and crop productivity. Intercrops and sole crops were compared over two years in the field in Western France. Winter OR was intercropped simultaneously with either spring faba bean (Vi...

Canola (Brassica napus), with its prominent yellow flowers, has unique spectral characteristics and necessitates special spectral indices to quantify the flowers. This study investigated four spectral indices for high-resolution RGB images for segmenting yellow flower pixels. The study compared vegetation indices to digitally quantify canola flower...

The field pea has both semi-leafless (SL) and leafed (L) types. Mixing these two types together might improve yield by optimizing pea solar radiation interception, reducing lodging, and decreasing disease. However, an optimum mixing ratio has not yet been established, since previous studies mixed two leaf types from two separate varieties. This stu...

Field pea (Pisum sativum L.) has two distinct leaf morphologies: leafed (L) and semi‐leafless (SL). Grown together, semi‐leafless and leafed pea blends have better weed control and higher crop yield than sole crops of either leaf type. Previous studies have only investigated mixing leaf types from two distinct varieties, and therefore the blend cou...

Abstract Advances in high‐throughput platforms such as UAVs (unoccupied aerial vehicles) facilitate rapid image‐based phenotypic data acquisition. However, existing plot‐level data extraction methods are unreliable if field plots differ in size and spacing, as often occurs in early‐generation plant breeding trials. To overcome the limitations of co...

Pea is a grain legume crop commonly grown in semi-arid temperate regions. Pea is susceptible to heat stress that affects development and reduces yield. Leaf pigments and surface wax in a crop canopy make the primary interaction with the environment and can impact plant response to environmental stress. Vegetation indices can be used to indirectly a...

Hailstorms are a frequent natural weather disaster in the Canadian Prairies that can cause catastrophic damage to field crops. Assessment of damage for insurance claims requires insurance inspectors to visit individual fields and estimate damage on individual plants. This study computes temporal profiles and estimates the severity of hail damage to...

Plant breeding experiments typically contain a large number of plots, and obtaining phenotypic data is an integral part of most studies. Image-based plot-level measurements may not always produce adequate precision and will require sub-plot measurements. To perform image analysis on individual sub-plots, they must be segmented from plots, other sub...

To develop new crop varieties and monitor plant growth, health, and traits, automated analysis of aerial crop images is an attractive alternative to time-consuming manual inspection. To perform per-microplot phenotypic analysis, localizing and detecting individual microplots in an orthomosaic image of a field are major steps. Our algorithm uses an...

Stripe rust fungus (Puccinia striiformis) is a major disease problem in all wheat growing areas. Traditional methods of field scouting are time-consuming, labor-intensive and subjective. High-throughput technologies for wheat rust estimation are very limited. Hyperspectral imaging (HSI) captures data in a wide range of spectral bands that can be us...

Due to the relevance of agriculture in economy and human development, the inclusion of technology in this activity is of utmost importance, and moisture content prediction is relevant for assessing the degree of maturity of a crop, which relates to efficient harvesting and quality control. This paper presents an accurate deep learning model for the...

Increased frequency and occurrence of herbicide-resistant biotypes heightens the need for alternative wild oat management strategies. There is an opportunity to exploit the height differential between wild oat and crops by targeting wild oat between panicle emergence and seed shed timing. Two field studies were conducted either in Lacombe, AB, or L...

There is an increasing need for detailed soil property maps to support land use planning, soil carbon accounting, and precision agriculture. While soil maps exist in Saskatchewan, they are at coarse scales (1:100,000), which are not always suitable for detailed soil management. One emerging technique for predictive soil mapping is the use of bare s...

Phenotyping crop performance is critical for line selection and variety development in plant breeding. Canola ( Brassica napus L.) flowers, the bright yellow flowers, indeterminately increase over a protracted period. Flower production of canola plays an important role in yield determination. Yellowness of canola petals may be a critical reflectanc...

Unmanned aerial vehicle (UAV) imaging is a promising data acquisition technique for image-based plant phenotyping. However, UAV images have a lower spatial resolution than similarly equipped in field ground-based vehicle systems, such as carts, because of their distance from the crop canopy, which can be particularly problematic for measuring small...

Identification of optimal pod maturity stage in Canola is key for maximizing seed yield, quality and also an important phenotypic trait in crop improvement programs. The conventional method is via visual inspection of seed color change. Alternatively, hyperspectral sensors have potential to determine physiological status of the crops. Therefore, th...

Farmers rely on desiccants to dry down the crop at maturity that can help with timely harvesting. Traditional methods of screening different herbicides as desiccants are based on visual approaches and often very subjective. The objective of this study was to explore the potential of hyperspectral imaging to determine the efficacy of different herbi...

Some well managed organic soils known to have higher crop yield potential than conventionally managed soils due to the greater soil quality and the ability to tolerate weed competition. However, low available soil mineral N and P in some organic systems may mask such soil quality-related benefits. We hypothesize that when plant-available N and P ar...

The plant microbiome has been recently recognized as a plant phenotype to help in the food security of the future population. However, global plant microbiome datasets are insufficient to be used effectively for breeding this new generation of crop plants. We surveyed the diversity and temporal composition of bacterial and fungal communities in the...

Counting plant organs such as heads or tassels from outdoor imagery is a popular benchmark computer vision task in plant phenotyping, which has been previously investigated in the literature using state-of-the-art supervised deep learning techniques. However, the annotation of organs in field images is time-consuming and prone to errors. In this pa...

The plant microbiome has been recently recognized as a plant phenotype to help in the food security of the future population. However, global plant microbiome datasets are insufficient to be used effectively for breeding this new generation of crop plants. We surveyed the diversity and temporal composition of fungal communities in the root and rhiz...

Wild oat ( Avena fatua L.) is one of the most problematic weed species in western Canada due to widespread populations, herbicide resistance, and seed dormancy. In wheat ( Triticum aestivum L.), and especially in shorter crops such as lentil ( Lens culinaris L.), A. fatua seed panicles elongate above the crop canopy which can facilitate physical cu...

Counting plant organs such as heads or tassels from outdoor imagery is a popular benchmark computer vision task in plant phenotyping, which has been previously investigated in the literature using state-of-the-art supervised deep learning techniques. However, the annotation of organs in field images is time-consuming and prone to errors. In this pa...

Cropping systems experiments are considered vital to devise sustainable strategies to overcome many challenges in weed management. A plethora of cropping systems studies have been carried out to develop weed management solutions for a specified weed problem, or for general weed management. Even though these studies were indispensable to develop wee...

The UAV-based hyperspectral imaging (HSI) has been extensively used in various agriculture applications. The data calibration and pre-processing techniques have been widely studied in the remote sensing research. However, it was ignored that the most important factor affecting the results accuracy is the quality of the spectral data. To acquire suc...

The traditional visual rating system is labor-intensive, time-consuming, and prone to human error. Unmanned aerial vehicle (UAV) imagery-based vegetation indices (VI) have potential applications in high-throughput plant phenotyping. The study objective is to determine if UAV imagery provides accurate and consistent estimations of crop injury from h...

Lodging, the permanent bending over of food crops, leads to poor plant growth and development. Consequently, lodging results in reduced crop quality, lowers crop yield, and makes harvesting difficult. Plant breeders routinely evaluate several thousand breeding lines, and therefore, automatic lodging detection and prediction is of great value aid in...

Lodging, the permanent bending over of food crops, leads to poor plant growth and development. Consequently, lodging results in reduced crop quality, lowers crop yield, and makes harvesting difficult. Plant breeders routinely evaluate several thousand breeding lines, and therefore, automatic lodging detection and prediction is of great value aid in...

Weeds have acquired evolutionary adaptations to the diverse crop and weed management strategies used in cropping systems. Therefore, changes in crop production practices such as conventional to organic systems, tillage-based to no-till systems, and diversity in crop rotations can result in differences in weed community composition that have managem...

Traditional methods of estimating frost damage to crops are labor-intensive and time-consuming. Remote sensing imagery and vegetation indices can be used for condition assessment, however, the utility of using vegetative indices in assessing frost damage specifically is not known. The objective of this study was to estimate the freezing injury usin...

Silene latifolia Poiret of Eurasia has established in North America, prompting this structural study of its mature unisexual buds and flowers. Floral nectaries, anther and stigma changes, and vestigial reproductive structures were studied using light and scanning electron microscopy. In staminate flowers, anthers dehisced before anthesis and >90% o...

With the increasing resistance of wild oat (Avena fatua L.) to herbicides, there is a need to evaluate the potential of alternative cropping systems based on integrated weed management principles. A 5-yr field study at eight sites across Canada was used to evaluate the profitability of alternative cropping systems that have the potential to control...

Interrow cultivation is a selective, in-crop mechanical weed control tool that has the potential to control weeds later in the growing season with less crop damage compared with other in-crop mechanical weed control tools. To our knowledge, no previous research has been conducted on the tolerance of narrow-row crops to interrow cultivation. The obj...

In this paper, we investigate the problem of estimating the phenotypic traits of plants from color images and elevation maps of field plots. We focus on emergence and biomass traits - two important indicators of crop growth and health. We employ a state-of-the-art deconvolutional network for segmentation and convolutional architectures, with residu...

The escalating evolution of weed species resistant to acetolactase synthase (ALS)-inhibitor herbicides makes alternative weed control strategies necessary for field crops that are dependent on this herbicide group. A fully integrated strategy that combined increased crop seeding rates (2X or 4X recommended), mechanical weed control with a minimum-t...

Concern over the development of herbicide-resistant weeds has led to interest in integrated weed management systems that reduce selection pressure by utilizing mechanical and cultural weed control practices in addition to herbicides. Increasing crop seeding rate increases crop competitive ability and thus can enhance herbicide efficacy. However, it...

Canola (Brassica napus L.) often experiences high seed losses prior to and during harvest operations. Pod drop and pod shatter are responsible for pre-harvest seed losses in canola although relatively little is known about the significance of pod drop to total pre-harvest seed losses in canola. This research describes a method to measure the predis...

Legume crops are known to have low soil N uptake early in their life cycle, which can weaken their ability to compete with other species, such as weeds or other crops in intercropping systems. However, there is limited knowledge on the main traits involved in soil N uptake during early growth and for a range of species. The objective of this resear...

Seed shatter of wild oat (Avena fatua L.), green foxtail [Setaria viridis (L.) P. Beauv.], wild mustard (Sinapis arvensis L.), cleavers (Galium spurium L. and G. aparine L.), wild buckwheat (Polygonum convolvulus L.), and kochia [Kochia scoparia (L.) Schrad.] was evaluated in field pea, spring wheat, and canola fields in Saskatchewan in 2014 and 20...

Canola (Brassica napus L.) is a high-value summer annual crop grown in the northern Great Plains of Canada and the United States. During the early stages of its life, the crop may lose leaf area as a result of spring hail storms, frost, herbicides, animal grazing, and insects. However, little information is available on the effect of defoliation du...

The increasing occurrence of herbicide resistance, along with no new herbicide modes of action developed in over 30 yr, have increased the need for nonherbicidal weed management strategies and tactics. Harvest weed seed control (HWSC) practices have been successfully adopted in Australia to manage problematic weeds. For HWSC to be effective, a high...

High weed abundance in organic crops is thought to be a key factor contributing to the greater yield loss in organic as compared with conventional cropping systems. However, even with greater weed densities than conventional systems, some organic systems have yields comparable to conventional systems, suggesting that cropping systems might differ i...

Canola (Brassica napus L.) is the main oilseed crop grown in the northern Great Plains (Canada). This species, however, also is associated with significant seed losses before and during harvest. To determine the factors that contribute to on-farm harvest losses in B. napus, an extensive on-farm survey was conducted in four regions across the northe...

In western Canada, more money is spent on wild oat herbicides than on any other weed species, and wild oat resistance to herbicides is the most widespread resistance issue. A direct-seeded field experiment was conducted from 2010 to 2014 at eight Canadian sites to determine crop life cycle, crop species, crop seeding rate, crop usage, and herbicide...

Cow cockle [Vaccaria hispanica (P. Mill.) Rauschert] is an introduced summer annual weed in North America and has been investigated as a potential crop for the Canadian prairies. Seed persistence contributes to volunteers in subsequent crops; therefore, it is undesirable in this prospective crop. To determine whether cow cockle is persistent and fo...

Field pea (Pisum sativum L.) is an important organic crop due to its contribution to soil fertility and other rotational benefits. Leafed (wild-type) pea cultivars tend to be more weed suppressive, but their poor standing ability limits yield compared with semi-leafless cultivars. Crowing mixtures of leafed and semi-leafless cultivars may improve w...

Domestication is the process by which a wild plant evolves into a cultivated plant by undergoing morphological, physiological or molecular changes. These changes may be due to conscious selection (primary cultivated plant) or unconscious selection (secondary cultivated plant) by man. These evolutionary changes need to be studied to understand the t...

Cowcockle, an introduced summer annual weed of the Northern Great Plains, is being considered for domestication because of its high quality starch, cyclopeptides, and saponins. Loss of seed dormancy is one of the key desirable traits for domestication. To determine the potential for domestication of this species, an understanding of the seed dorman...

Seedbank persistence in canola seeds is related to their potential to develop secondary dormancy. This can result in volunteer weed problems many years after canola production. The potential to be induced into secondary dormancy is controlled by both the canola genetics and the environment of the mother plant. However, the effect of time of harvest...

Crown rust (Puccinia coronata Corda f. sp. avenae Eriks.) negatively impacts seed quality and yield in oat (Avena sativa L.) in rust-prone areas of eastern Saskatchewan, Manitoba, Ontario, and Quebec. Genetic resistance is the primary means for controlling this disease, but early seeding and fungicide applications have been suggested to reduce yiel...

Seed loss in canola (Brassica napus) leads to considerable loss of revenue and dispersal of seeds into the soil seedbank. The resulting volunteer canola can create weed problems in subsequent crops and result in further yield loss. The objective of this study was to quantify and compare canola seed loss and seedbank addition from windrowing and dir...

Weed control with herbicides is not possible in several systems including control of wild oat (Avena fatua L.) in tame oat (Avena sativa L.), red rice (Oryza sativa L. var. sylvatica) in rice (Oryza sativa L.), and in organic systems. Competitive crop cultivars can be used to manage weed competition if selective weed control by herbicides is not po...

Seed loss in canola [Brassica napus L., B. rapa L., and B. juncea (L.) Czern. & Coss.], which includes seed shatter and seeds in unopened dropped pods, leads to yield reductions and seed dispersal into the soil seedbank. The volunteer canola can then become a weed in the subsequent crops and cause yield losses. The objective of this study was to ev...