Seedling emergence as influenced by aggregate size and bulk density

Non-Peer ReviewedProducers in western Canada are becoming increasingly interested in conservation tillage. A thorough understanding of how seedlings interact with the soil surrounding them is required to develop criteria for designing effective furrow openers and packing devices suitable for use in conservation tillage systems. To facilitate interpretation of the results of a field evaluation study of furrow openers for zero tillage seeders,·we conducted a greenhouse experiment designed to assess the impact of bulk density and aggregate size distribution of the seedbed on the emergence of Hard Red Spring Wheat (Triticum aestivum L). Seeds of wheat (c.v. Lancer) were germinated in seedbeds with five aggregate size distributions with geometric mean diameter ranging from 0.44 to 12.67 mm, and four bulk densities ranging from 1.0 to L6 Mg m-3 arranged in a factorial design. The soil used in this study was taken from the Ap horizon of a Swinton silt loam (Orthic Brown Chernozemic). Number of seedlings emerged and speed of emergence were affected by bulk density and aggregate size of the seedbed, and by the interaction of both variables. In general increasing bulk density or aggregate size reduced and delayed emergence, but in seedbeds with high bulk density or with large aggregates, the effect of the other variable was negligible. Increased bulk density delayed emergence mainly by decreasing the volume of voids in the soil. This elevated the interfacial stress to. the elongating coleoptile. The detrimental effect of increased aggregate size was mainly due to increase in the length of the path the coleoptile had to traverse to reach the soil surface, as it elongated through the inter-aggregate voids. Compaction of the seedbed to achieve the higher bulk densities in the coarser-aggregate seedbeds resulted in substantial breakdown of larger aggregates. Consequently, as the interfacial stress was increased by compaction, the path length was decreased, and both effects cancelled each other

Evaluation of furrow openers and packers for conservation tillage

Non-Peer ReviewedProducers in the Canadian Prairies are increasingly adopting conservation tillage systems. A large part of the success of conservation tillage rests on the availability of equipment able to seed into standing stubble. In semiarid environments, wheat yields are often limited by poor stand establishment and low plant density. Consequently, furrow openers and packing systems that promote complete and rapid germination and emergence improve the odds of obtaining good yields. A series of field studies are being conducted at Swift Current to develop protocols for the evaluation of furrow openers and packing systems for reduced tillage systems. The testing protocol consisted of a number of measurements to evaluate the physical properties of the soil within the furrow (bulk density,aggregate size distribution, penetration resistance), estimators of the shape and conformation of the furrow (volume of soil disturbed by the opener, perimeter length, surface roughness, measurement of water status of the soil surrounding the seed (volumetric water content and evaporation rate) estimators of seedling emergence and speed of emergence, measurements of aboveground biomass accumulation by the plants up to the 3 leaf stage, and measurements of the depth of seeding and dispersion of seeds in the furrow area. This presentation will discuss the merits and limitations of the protocol based on the results of an exploratory test of a number of furrow opener-packer combinations

Evaluation of furrow openers and packers for conservation tillage

Non-Peer ReviewedBased on a series of exploratory field studies in 1993 at the Swift Current research station two additional field studies were conducted in 1994 to establish test protocols for the investigation and evaluation of seed furrows formed by direct seeding operations. Measurements of seed furrow physical properties such as soil temperature, soil bulk density, soil moisture, and penetration resistance were repeated. Changes to sampling procedures included a modified soil moisture probe and wave guide connector along with an increased number of soil moisture measurement sites and additional measurements from below the seed furrow. Manual sampling of soil from within the furrow boundaries for soil aggregate determination replaced mechanical core sampling. Furrow profile measurements were carried out on unpacked and packed seed furrows to evaluate the accuracy of lower furrow boundary excavation techniques. To improve the accuracy of correlations between seed furrow characteristics, speed of emergence, plant counts, and above ground biomass row sample lengths were increased from 0.5 to 1.0 meter. This paper discusses the ability of the protocol to quantify significant differences in seed furrow characteristics created by 16 opener and packer combinations and their correlation to crop growth

Towards an effective control programme of soil-transmitted helminth infections among Orang Asli in rural Malaysia. Part 1: prevalence and associated key factors

Background: Despite the continuous efforts to improve the quality of life of Orang Asli (Aborigines) communities, these communities are still plagued with a wide range of health problems including parasitic infections. The first part of this study aimed at determining the prevalence of soil-transmitted helminth (STH) infections and identifying their associated factors among rural Orang Asli children. Methods: A cross-sectional study was carried out among 484 Orang Asli children aged = 6 years (school-age), using unsafe water supply as a source for drinking water, absence of a toilet in the house, large family size (>= 7 members), not washing hands before eating, and not washing hands after defecation were the key factors significantly associated with STH among these children. Conclusion: This study reveals an alarmingly high prevalence of STH among Orang Asli children and clearly brings out an urgent need to implement school-based de-worming programmes and other control measures like providing a proper sanitation, as well as a treated drinking water supply and proper health education regarding good personal hygiene practices. Such an integrated control program will help significantly in reducing the prevalence and intensity of STH in Orang Asli communities

Multilocus genotyping of giardia duodenalis in Malaysia. Infection, genetics and evolution

Giardia duodenalis is considered the most common intestinal parasite in humans worldwide. In Malaysia, 26 many studies have been conducted on the epidemiology of giardiasis. However, there is a scarcity of 27 information on the genetic diversity and the dynamics of transmission of G. duodenalis. The present study 28 was conducted to identify G. duodenalis assemblages and sub-assemblages based on multilocus analysis 29 of the glutamate dehydrogenase (gdh), beta-giardin (bg) and triose phosphate isomerase (tpi) genes. Fae- 30 cal specimens were collected from 484 Orang Asli children with a mean age of 7 years and examined 31 using light microscopy. Specimens positive for Giardia were subjected to PCR analysis of the three genes 32 and subsequent sequencing in both directions. Sequences were edited and analysed by phylogenetic 33 analysis. G. duodenalis was detected in 17% (84 of 484) of the examined specimens. Among them, 71 were 34 successfully sequenced using at least one locus. Genotyping results showed that 30 (42%) of the isolates 35 Q2 belonged to assemblage A, 32 (45%) belonged to assemblage B, while discordant genotype results were 36 observed in 9 specimens. Mixed infections were detected in 43 specimens using a tpi-based assemblage 37 specific protocol. At the sub-assemblages level, isolates belonged to assemblage A were AII. High nucle- 38 otide variation found in isolates of assemblage B made subtyping difficult to achieve. The finding of 39 assemblage B and the anthroponotic genotype AII implicates human-to-human transmission as the most 40 possible mode of transmission among Malaysian aborigines. The high polymorphism found in isolates of 41 assemblage B warrants a more defining tool to discriminate assemblage B at the sub-assemblage level

Toxicity of naturally occurring Bio-fly and chitosan compounds to control the Mediterranean fruit fly <i>Ceratitis capitata</i> (Wiedemann)

<div><p>The efficacy of five compounds of a biopolymer chitosan and Bio-fly (<i>Beauveria bassiana</i> fungus) as biopesticide was evaluated on <i>Ceratitis capitata</i> under laboratory conditions. The inhibitory effects on acetylcholinesterase (AChE) and adenosinetriphosphatase (ATPase) as biochemical indicators were also determined <i>in vivo</i>. The results indicated that <i>B. bassiana</i> based Bio-fly exhibited significant toxicity against <i>C. capitata</i> (LC₅₀ = 3008 and 3126 mg/L after 48 h in females and males, respectively) followed by the derivatives of chitosan, <i>N-</i>(4-propylbenzyl)chitosan and <i>N-</i>(2-nitrobenzyl)chitosan. Bio-fly displayed remarkable inhibition of AChE activity (IC₅₀ = 2220 mg/L) while <i>N-</i>(<i>2-</i>chloro,<i>6-</i>flourobenzyl)chitosan, <i>N-</i>(<i>4</i>-propylbenzyl)chitosan and <i>N-</i>(3,4-methylenedioxybenzyl) chitosan had no significant difference in inhibitory action. In adult males, <i>N-</i>(<i>2-</i>nitrobenzyl)chitosan exhibited the highest inhibitory action (IC₅₀ = 6569 mg/L). In addition, the toxic effects of the tested compounds on the activity of ATPase indicated that highly significant inhibition was found with <i>N-</i>(4-propylbenzyl)chitosan with an IC₅₀ of 8194 and 8035 mg/L, in females and males, respectively.</p></div

Multi locus genotyping of Giardia duodenalis in Malaysia

Giardia duodenalis is considered the most common intestinal parasite in humans worldwide. In Malaysia, many studies have been conducted on the epidemiology of giardiasis. However, there is a scarcity of information on the genetic diversity and the dynamics of transmission of G. duodenalis. The present study was conducted to identify G. duodenalis assemblages and sub-assemblages based on multilocus analysis of the glutamate dehydrogenase (gdh), beta-giardin (bg) and triose phosphate isomerase (tpi) genes. Faecal specimens were collected from 484 Orang Asli children with a mean age of 7 years and examined using light microscopy. Specimens positive for Giardia were subjected to PCR analysis of the three genes and subsequent sequencing in both directions. Sequences were edited and analysed by phylogenetic analysis. G. duodenalis was detected in 17 (84 of 484) of the examined specimens. Among them, 71 were successfully sequenced using at least one locus. Genotyping results showed that 30 (42) of the isolates belonged to assemblage A, 32 (45) belonged to assemblage B, while discordant genotype results were observed in 9 specimens. Mixed infections were detected in 43 specimens using a tpi-based assemblage specific protocol. At the sub-assemblages level, isolates belonged to assemblage A were AII. High nucleotide variation found in isolates of assemblage B made subtyping difficult to achieve. The finding of assemblage B and the anthroponotic genotype All implicates human-to-human transmission as the most possible mode of transmission among Malaysian aborigines. The high polymorphism found in isolates of assemblage B warrants a more defining tool to discriminate assemblage B at the sub-assemblage level. (C) 2013 Elsevier B.V. All rights reserved