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Reduced herbicide doses in field crops: A review 总被引：2，自引：1，他引：2
ROBERT E. BLACKSHAW JOHN T. O'DONOVAN K. NEIL HARKER GEORGE W. CLAYTON ROBERT N. STOUGAARD 《Weed Biology and Management》2006,6(1):10-17
Farmers are becoming increasingly interested in more comprehensive weed management programs that reduce weed populations over time and in the use of reduced herbicide doses that lower their production costs. Research indicates that there is good potential to reduce the number of herbicide applications and utilize lower herbicide doses within competitive cropping systems. Diverse crop rotations, competitive cultivars, higher crop seed rates, reduced row spacing, specific fertilizer placement, and cover crops have been identified as integral components of competitive cropping systems. This review paper explores the potential for successful use of reduced herbicide doses within competitive cropping systems that have a multiyear approach to weed management. The utilization of decision support systems or new methods of assessing active weed growth are discussed in light of further enhancing the successful use of reduced herbicide doses and advising farmers on when (and when not) they might be a viable option. 相似文献
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Avena fatua L. populations from numerous fields in Alberta have simultaneously developed resistance to recommended rates of two dissimilar herbicides, triallate and difenzoquat. We used exogenous applications of gibberellic acid (GA3 ) to investigate the possibility that endogenous gibberellins were involved in the A. fatua 's resistance mechanism. For control plants, without applied GA3 , shoots of the most resistant (R) populations emerged more rapidly and elongated faster than shoots of the susceptible (S) populations. Increases in shoot elongation in response to exogenous GA3 were significantly lower in R populations compared with S populations. This suggests that R populations may have elevated endogenous gibberellin levels, relative to S populations. Additionally, inhibition of S population shoot elongation and shoot anatomical abnormalities caused by relatively low concentrations of triallate and difenzoquat could be prevented by exogenous application of GA3 . These results suggest that there may be a phytohormonal involvement in the mechanism of triallate/difenzoquat resistance in A. fatua . That is, higher endogenous gibberellin levels in R populations may result in meristematic growth that is rapid enough to preclude phytotoxic levels of these herbicides from reaching the shoot meristem, which is the likely site of action. 相似文献
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Field studies were conducted to determine the effect of various densities and duration of interference of Erodium cicutarium (L.) L'Her. ex Ait. on the yield of wheat, oilseed rape, pea and dry bean. The magnitude of yield reductions caused by E. cicutarium differed among the crops. Results indicate that the ranking of crop tolerance to E. cicutarium, when established at their recommended planting densities, was wheat > oilseed rape > pea ? dry bean. Maximum yield reduction occurred at E. cicutarium densities of 100–200 plants m?2 and were 36% for wheat, 37% for oilseed rape, 82% for dry bean and 92% for pea. Crop yield progressively decreased as the duration of E. cicutarium interference increased. Three weeks of E. cicutarium interference after emergence was sufficient to reduce the yield of all crops, indicating the importance of controlling this weed early in the growing season. The mean yield reduction for each week of E. cicutarium interference was 1·6%, 2·7%, 3·6% and 6·3% for wheat, oilseed rape, pea and dry bean respectively. E. cicutarium is therefore a weed that warrants consideration for control in annual cropping systems. 相似文献
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A. CALDERON YUBI J. M. FERGUSON J. P. RENTON S. HARKER M. J. A. HARVEY B. BAGYENJI T. A. DOUGLAS 《The Journal of small animal practice》1987,28(8):753-761
Canine semen was obtained by digital manipulation from two donor dogs and twelve stud dogs. The sperm-rich fraction was diluted with either of two different diluents and the survival of spermatozoa before and after freezing was determined. It appeared that there was no difference in the post-thaw survival rate in either of the diluents used. 相似文献
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The paper explains the organizations set up for control andguidance in the management of forests in private ownership whichform a considerable portion of the entire forest estate in Norway.In the management of the forests the chief concern is the depletionof the growing stock by years of dimension cutting. Other organizationscontrol transport, measurement, marketing, and selling whichincludes price fixation. The paper contains a note on educationand ends with a brief comparison between conditions and controlin Norway and Britain. 相似文献
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JOHANN LANG DR MED VET JEFFREY A. WORTMAN VMD PHD LARRY T. GLICKMAN VMD DR PH DARRYL N. BIERY DVM W. HARKER RHODES VMD M MED SCI 《Veterinary radiology & ultrasound》1986,27(3):74-78
Thoracic radiographs were taken in right lateral recumbent (RLR), left lateral recumbent (LLR), and ventrodorsal (VD) projections in 80 dogs with known or suspected malignant tumors. Radiographs in each projection were interpreted, independently of those in the other two projections, by four veterinary radiologists, and classified as positive or negative for one or more lung metastases. The four radiologists then met, to agree on a diagnosis for each patient by simultaneously reviewing all three views. This panel diagnosis became the standard for subsequently classifying individual views as either true positive or true negative. As determined by a consensus of the panel, 25 dogs had at least one positive thoracic radiograph.
The three radiographic projections differed in sensitivity for the detection of lung metastases. In this study, the RLR view was the most sensitive, and the VD view the least sensitive. The sensitivity of detection improved significantly with multiple readers. From these data we recommend that, for detection of lung metastases in the dog, the RLR view be included in any diagnostic protocol; a minimum of two readers be used; and a three-view protocol be used if only one reader is available. 相似文献
The three radiographic projections differed in sensitivity for the detection of lung metastases. In this study, the RLR view was the most sensitive, and the VD view the least sensitive. The sensitivity of detection improved significantly with multiple readers. From these data we recommend that, for detection of lung metastases in the dog, the RLR view be included in any diagnostic protocol; a minimum of two readers be used; and a three-view protocol be used if only one reader is available. 相似文献
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