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Wally O.S.D.,Nova Scotia Agriculture College | Critchley A.T.,Acadian Seaplants Ltd | Hiltz D.,Acadian Seaplants Ltd | Craigie J.S.,National Research Council Canada | And 4 more authors.
Journal of Plant Growth Regulation | Year: 2013

Seaweeds and their extracts have been used for centuries in agriculture to improve plant growth and impart stress tolerance. There has been historical evidence that phytohormones present in seaweeds lead to these effects, but questions of this mode of action have always been raised. By quantifying phytohormones in seaweed extracts coupled with the use of phytohormone biosynthetic and insensitive mutants, we conclude that the phytohormone levels present within the extracts are insufficient to cause significant effects in plants when extracts are applied at recommended rates. However, components within seaweed extracts may modulate innate pathways for the biosynthesis of phytohormones in plants. Phytohormone profiles of plant tissue extracts were analyzed following root application of a commercial seaweed extract produced from Ascophyllum nodosum (ANE) to in vitro-grown Arabidopsis plants. We found an increase in total concentration of cytokinins (CKs), in particular, of trans-zeatin-type CKs, 24 and 96 h after ANE application, with an increase in cis-zeatin-type CKs observed at 144 h. Concomitantly, increases in abscisic acid (ABA) and ABA catabolite levels were observed whereas auxin levels were reduced. Additionally, the profile of transcripts revealed that CK biosynthetic genes were upregulated, whereas the CK catabolic genes were repressed at 24 and 96 h following ANE application. Not surprisingly, the transcripts of ABA biosynthetic genes were increased whereas the auxin biosynthetic genes were repressed. These corroborated findings are the first to help explain the underlying physiological benefits derived from the application of ANE to plants. © 2012 Springer Science+Business Media New York. Source


Zheljazkov V.D.,Mississippi State University | Cantrell C.L.,Mississippi State University | Astatkie T.,Nova Scotia Agriculture College
Agronomy Journal | Year: 2010

A field experiment was conducted to evaluate the effect of harvest time and drying on Japanese cornmint (Mentha canadensis L.) cultivars Arvensis 2 and Arvensis 3 to optimize technology. Biomass yields were comparable to those reported in the literature. Arvensis 2 had greater oil content (0.78%) than Arvensis 3 (0.59%), while Arvensis 3 had higher concentrations of (-)-menthol (71.9%) and (-)-menthone (13.5%) than Arvensis 2 (61.7 and 9.4%, respectively). Arvensis 3 had higher fresh biomass (34,289 kg ha-1) than that of Arvensis 2 (23,929 kg ha-1). Dried biomass of the two cultivars was not significantly different. Higher oil yields were achieved from the fresh biomass of Arvensis 2 (108.7 kg ha-1), and lower from the dried biomass of Arvensis 2 (78.2 kg ha-1) and the fresh biomass of Arvensis 3 (84.3 kg ha-1). The concentration of (-)-menthol in the cultivars was higher at harvests 4 (69.3%) and 5 (67.7%), and lower at harvests 2 (63.6%) and 3 (64.7%). The yield of (-)-menthol was highest in harvest 4 (116.2 kg ha-1), lower in harvest 3 (78.4 kg ha-1) and lowest in the first harvest (19.1 kg ha-1). In northern Mississippi (or in other areas with similar latitude and environment), cornmint for production of (-)-menthol should be harvested in late July. For highest biomass yields, Arvensis 3 should be harvested in mid-July, whereas Arvensis 2 should be harvested in late July. The essential oil profile of M. canadensis in this experiment was more desirable (with respect to (-)-menthol concentration) than the profile of two commercially available M. canadensis oil samples from other countries, which should make the oil produced in southeastern United States easily marketable. © 2010 by the American Society of Agronomy. Source


Zaman Q.U.,Nova Scotia Agriculture College | Swain K.C.,Nova Scotia Agriculture College | Schumann A.W.,University of Florida | Percival D.C.,Nova Scotia Agriculture College
Applied Engineering in Agriculture | Year: 2010

The presence of weeds, bare spots, and variation in fruit yield within wild blueberry fields emphasizes the need for yield mapping for site-specific application of agrochemicals. An automated yield monitoring system (AYMS) consisting of a digital color camera, differential global positioning system, custom software, and a ruggedized laptop computer was developed and mounted on a specially designed Farm Motorized Vehicle (FMV) for real-time fruit yield mapping. Two wild blueberry fields were selected in central Nova Scotia to evaluate the performance of the AYMS. Calibration was carried out at 38 randomly selected data points, 19 in each field. The ripe fruit was hand-harvested out of a 0.5- × 0.5-m quadrant at each selected point and camera images were also taken from the same points to calculate the blue pixel ratio (fraction of blue pixels in the image). Linear regression was used to calibrate the actual fruit yield with percentage blue pixels. Real-time yield mapping was carried out with AYMS. Custom software was developed to acquire and process the images in real-time, and store the blue pixel ratio. The estimated yield per image along with geo-referenced coordinates was imported into ArcView 3.2 GIS software for mapping. A linear regression model through the origin (y = bx) was highly significant in field 1 (R2 = 0.90; P < 0.001) and field 2 (R 2 = 0.97; P < 0.001). The correlation between actual and predicted fruit yield (validation, using the equation from field 2) in field 1(R 2 = 0.95; P < 0.001; RMSE = 3.29 Mg/ha) and field 2 (validation, using the equation from field 1) (R2 = 0.97; P < 0.001; RMSE = 2.69 Mg/ha) was also highly significant. The best results were obtained by using site-specific calibration of <20 points for every field, using a representative range of fruit yield. Maps showed substantial variability in fruit yield in both fields. The bare spots coincided with no or low yielding areas in the fields. The yield maps could be used for site-specific fertilization in wild blueberry fields. © 2010 American Society of Agricultural and Biological Engineers. Source


Zhang F.,Zhejiang University | Zaman Q.U.,Nova Scotia Agriculture College | Percival D.C.,Nova Scotia Agriculture College | Schumann A.W.,University of Florida
Applied Engineering in Agriculture | Year: 2010

Wild blueberry fields are developed from native stands on deforested land by removing competing vegetation. The majority of fields are situated in naturally acidic and non-fertile soils that have high proportions of bare spots, weed patches, and gentle to severe topography. Producers presently apply agrochemicals uniformly without considering bare spots. The unnecessary or over-application of agrochemicals in bare spots may increase cost of production and environmental pollution. An automated cost-effective machine vision system using digital color photography was developed and tested to detect and map bare spots for site-specific application of agrochemicals within wild blueberry fields. The experiment was conducted at a 4-ha wild blueberry field in central Nova Scotia. The machine vision system consisting of a digital color camera, differential global positioning system, and notebook computer was mounted on a specialized farm vehicle. Custom software for grabbing and processing color images was developed in Delphi 5.0 and C++ programming languages. The images taken by the digital camera were stored in the notebook computer automatically and then processed in red, green, and blue (RGB), and hue, saturation, and value (HSV) color spaces to detect bare spots in real-time within blueberry fields. The best results were achieved in hue image color space with 99% accuracy and a processing speed of 661 ms per image. The results indicated that bare spots could be identified and mapped with this cost-effective digital photography technique in wild blueberry fields. This information is useful for site-specific application, and has the potential to reduce agrochemical usage and associated environmental impacts in the wild blueberry production system. © 2010 American Society of Agricultural and Biological Engineers. Source


Farooque A.A.,P.A. College | Zaman Q.U.,P.A. College | Schumann A.W.,University of Florida | Madani A.,P.A. College | Percival D.C.,Nova Scotia Agriculture College
Applied Engineering in Agriculture | Year: 2012

The concept of management zones has been proposed as a solution to the problems associated with the soil variability to more efficiently apply agricultural inputs on a site-specific basis. This study was designed to characterize and quantify the spatial variation in soil properties and wild blueberry fruit yield and to delineate management zones for site-specific fertilization. Two wild blueberry fields were selected in central Nova Scotia, and a grid pattern (15×15 m) was established at experimental sites to collect soil and fruit yield samples. The soil samples were analyzed for ammonium nitrogen (NH 4 +-N), nitrate nitrogen (NO 3 --N), pH, electrical conductivity (EC), texture, and soil organic matter (SOM). The volumetric moisture content (θ v) and ground conductivity data including horizontal coplanar geometry (HCP) and perpendicular coplanar geometry (PRP) were also recorded at the same grid points. The location of the sampling points were marked with a differential global positioning system (DGPS), and field boundary, bare spots, weeds, and grass patches were also mapped. The cluster analysis was performed to group the soil and fruit yield data into five zones termed as 'very poor,' 'poor,' 'medium,' 'good,' and 'very good' without prior knowledge of productivity potential with the internal homogeneity and external heterogeneity at a similarity level of greater than 70%. The coefficient of variation, geostatistical range of influence, and kriged maps suggested moderate to high variability of soil properties and fruit yield except soil pH and silt. The results of correlation matrix suggested significant relationships among the fruit yield and the soil properties. The results of ANOVA indicated that the fruit yield, HCP, PRP, θ v, SOM, and inorganic nitrogen were significantly different in developed management zones except poor and very poor zones. The significant positive correlations of HCP and PRP with soil properties and fruit yield suggested that the ground conductivity data can be used to develop management zones for site-specific fertilization. © 2012 American Society of Agricultural and Biological Engineers. Source

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