Pre-emergence tillage in field pea effective, but timing critical

Non-Peer ReviewedOn the semi-arid prairies, it is generally recommended to seed field pea early and at a depth of 4 to 7.5 cm. Crops that emerge before weed emergence are more competitive than crops emerging at the same time or after weed emergence. Delayed seeding to control late-emerging weeds and seeding at shallower depths to promote rapid emergence may be an alternative weed management strategy. The objective of this experiment was to identify combinations of seed date, seed depth, and pre-emergent weed control to optimize yield of field pea grown without the use of herbicides

Broadleaf weed control in chickpea (Cicer arietinum) and lentil (Lens culinaris) with fall application of pursuit

Non-Peer ReviewedBroadleaf weed control options in chickpea and lentil are very limited. Preliminary trials found that spring applied Pursuit at rates from 0.25X to 0.5X resulted in severe injury to chickpea in some years. The objective of these trials was to evaluate fall application of Pursuit in chickpea and lentil, at rates from 0.25X to 0.5X, for both crop tolerance and weed control efficacy. A 4-replicate trial was set up at Saskatoon, Sask. in 2000, 2001 and 2002 and at Scott, Sask. and Swift Current, Sask. in 2002. Pursuit was surface applied, with no incorporation, in the fall, at rates of 0.25X, 0.33X, 0.4X and 0.5X. Edge (2000) or Poast Ultra (2001, 2002) were applied to improve grassy weed control. The trials were direct seeded with low disturbance openers. There was excellent crop tolerance to fall applications of Pursuit in both chickpea and lentil at all location-years. Some visual crop injury was evident at the higher rates of Pursuit; however, yield was not reduced. Broadleaf weed control was inconsistent at the 0.25X rate. Rates higher than 0.33X rates resulted in excellent control of stinkweed (Thlaspi arvense L.), wild mustard (Sinapsis arvensis L.), wild buckwheat (Polygonum convolvulus L.), lamb’s-quarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.), Russian thistle (Salsola kali L.) and cleavers (Galium aparine L.) at all location-years. When compared to a post-emergence application of Sencor, fall applied Pursuit at 0.33X to 0.4X rates resulted in similar to 20% higher seed yields in lentil and chickpea, respectively. Fall applied Pursuit at 0.33X to 0.4X rate resulted in consistent broadleaf weed control, low crop injury, and high crop yield

Effect of timing of isoxaflutole application on weed control in desi chickpea (Cicer arietinum)

Non-Peer Reviewe

Interactions of soil residual ALS inhibiting herbicides

Non-Peer ReviewedALS inhibiting herbicides exhibit high bioactivity at low concentrations and may persist in the soil. To examine possible interactions between two different residues present together in the soil, field and lab tests were performed in three contrasting Saskatchewan soils. Field plots using Roundup Ready canola were used to assess residual effects of combinations of ALS inhibiting herbicides applied to peas and wheat in the previous two years. A root length inhibition bioassay based on oriental mustard was used to test for residual herbicide phytotoxicity in samples of soil from field and lab-spiked soils from the three study sites. The field plots were sprayed initially with imazamox/imazethapyr, and followed by imazamethabenz, flucarbazone-sodium, sulfosulfuron, or florasulam in the second growing season. Soil samples were taken from the plots after the second growing season for the bioassay test. To determine the interactions (antagonistic, additive, or synergistic) between the herbicides investigated, Colby’s equation was applied to the bioassay results. In field samples, the results to date have indicated additive and potential synergistic interactions for the same herbicide combinations in different soils

In search of new herbicide chemistries for the prairies

Non-Peer ReviewedThere are a limited of herbicide groups for use in western Canada so there is a need introduce different modes of action to manage herbicide resistant weeds. In addition, many broadleaf crops such as chickpea have limited broadleaf weed control options. Sulfentrazone, a Group 14 PPO inhibitor has been screened in a number of broadleaf crops. Chickpea has exhibited excellent tolerance to sulfentrazone, while the tolerance of other broadleaf crops can be summarized as follows: sunflower and fababean (fair to good); field pea, and narrow-leaved lupin (fair); dry bean (poor) and lentil (very poor). Isoxaflutole is a Group 27 carotenoid biosynthesis inhibitor that may have potential for use in chickpea, tame buckwheat, and narrow-leaved lupin. Sulfentrazone effectively controls many broadleaf weeds but is weak on cruciferous weeds such as wild mustard. Isoxaflutole also controls a number of broadleaf weeds but does not control wild buckwheat. Both sulfentrazone and isoxaflutole are soil-applied herbicides with potential to carry-over and injure rotational crops. Preliminary results from field trials indicate that combined low rates of sulfentrazone and isoxaflutole can result in excellent broad spectrum weed control in chickpea. Carfentrazone-ethyl, a contact non-residual PPO inhibitor has been shown to be an effective pre-seed burndown partner for glyphosate. This would allow for the control of volunteer Roundup-ready canola prior to the seeding of broadleaf crops

Interactions between the invasive tree Melia azedarach (Meliaceae) and native frugivores in South Africa

The spread of many invasive plants is facilitated through seed dispersal by frugivorous animals. The effectiveness of various frugivores as dispersers of the seeds of Melia azedarach, a highly invasive alien tree species, was evaluated in South Africa in savanna and bushveld vegetation. During 264 h of observation, seven bird species and one bat species were recorded foraging on fruiting trees of M. azedarach. The most common visitors were the darkcapped bulbul (Pycnonotus barbatus) followed by Wahlberg’s epauletted fruit bat (Epomophorus wahlbergi), but both species droppednearly asmany seeds as they dispersed. Knysna turaco (Tauraco corythaix) dispersed the highest number of fruits perminute, but occurred in low abundance in our study sites. Seed germination differed significantly between de-pulped fruits and untreated fruits after 2mo, but was similar after 4mo. Germination success did not differ between animal-handled and hand-depulped fruits. In contrast to the high germination success in the greenhouse, seedlings showed very low recruitment in the field. Thus, M. azedarach seems likely to benefit from frugivores (particularly dark-capped bulbul and Wahlberg’s epauletted fruit bat) dispersing seeds to suitable microsites.Centre of Excellence for Invasion Biolog

Crystal structure of solid Oxygen at high pressure and low temperature

Results of X-ray diffraction experiments on solid oxygen at low temperature and at pressures up to 10 GPa are presented.A careful sample preparation and annealing around 240 K allowed to obtain very good diffraction patterns in the orthorhombic delta-phase. This phase is stable at low temperature, in contrast to some recent data [Y. Akahama et al., Phys. Rev. B64, 054105 (2001)], and transforms with decreasing pressure into a monoclinic phase, which is identified as the low pressure alpha-phase. The discontinuous change of the lattice parameters, and the observed metastability of the alpha-phase increasing pressure suggest that the transition is of the first order.Comment: 4 pages with three figure

High-precision determination of transition amplitudes of principal transitions in Cs from van der Waals coefficient C_6

A method for determination of atomic dipole matrix elements of principal transitions from the value of dispersion coefficient C_6 of molecular potentials correlating to two ground-state atoms is proposed. The method is illustrated on atomic Cs using C_6 deduced from high-resolution Feshbach spectroscopy. The following reduced matrix elements are determined < 6S_{1/2} || D || 6P_{1/2} > =4.5028(60) |e| a0 and =6.3373(84) |e| a0 (a0= 0.529177 \times 10^{-8} cm.) These matrix elements are consistent with the results of the most accurate direct lifetime measurements and have a similar uncertainty. It is argued that the uncertainty can be considerably reduced as the coefficient C_6 is constrained further.Comment: 4 pages; 3 fig

Oscillator strengths with pseudopotentials

The time-dependent local-density approximation (TDLDA) is shown to remain accurate in describing the atomic response of IB elements under the additional approximation of using pseudopotentials to treat the effects of core electrons. This extends the work of Zangwill and Soven who showed the utility of the all-electron TDLDA in the atomic response problem.Comment: 13 pages including 3 Postscript figure