Ground Cover Supplement : GC Supplement - Pastures
GROUND COVER PASTURES 7 WIRRULLA SUMMER WEED TRIAL (LSD 2.25) 0 1 2 3 4 5 6 7 8 9 10 0 Rate % Angel Herald 100 50 A A ANNUAL LEGUMES Upper Eyre Peninsula, SA. Herbicide treatments of metsulfuron-methyl and triasulfuron were applied at 3.5 and 7 grams per hectare and 9 and 18g/ha respectively to simulate a summer sulfonylurea herbicide application (for example, 50 and 100 per cent suggested summer application rates). Herbicide treatments were applied in January and February to allow for an approximate period of three to four months to the normal break of the season. AngelA and HeraldA were then sown dry (2 June 2005) into the prepared soil residues. Results are shown in Figures 1 and 2 with the herbicide effect on the medic assessed by visual scores (24 August) and dry matter cuts (21 September). Although the break to the season did not occur until mid-June, the very dry soil conditions in the interim probably contributed to the persistence of SU residues in the soil. Results from Wirrulla again show the good tolerance of AngelA to SU residues compared to that of HeraldA. In the visual assessment, AngelA’s production was unaffected whereas HeraldA was reduced by more than 80 per cent (Figure 1). The later dry matter cuts confirmed these scores, with HeraldA again reduced by 80 per cent in the 100 per cent treatment (Figure 2). SU herbicides are commonly used to control weeds such as Lincoln weed, caltrop and skeleton weed over summer before going into pasture. The ability of AngelA to tolerate these short-term SU residues will enable it both to survive and to take advantage of the residual moisture and nutrient benefits of weed control whether regenerating or being established for the first time. 3Assessing herbicide options to control AngelA in-crop As a new medic with tolerance to SU residues, questions have been raised about the ability to control AngelA in a cropping system. Trials assessing the effectiveness of various herbicides were conducted in 2004 at Minnipa and Netherton. The most effective control at both sites in 2004 was achieved by 2,4-D, MCPA and dicamba with both cul- tivars controlled by over 70 per cent. The bromoxynil treatment at Netherton also achieved effective control of more than 70 per cent. Of the non-SU herbicides tested, clopyralid was the least effective but still gave reason- able control of 64 per cent compared to the nil plots. The post-emergent SU herbicide options (metsulfu- ron-methyl, chlorsulfuron and iodosulfuron at half and full label rates) provided reasonable to good control of AngelA in-crop with a range of 48 to 80 per cent con- trol. However, while the pre-emergent SU treatments (triasulfuron) achieved control of HeraldA (55 to 83 per cent), they were less effective on AngelA (six to 35 per cent). In 2005, at Walpeup, we tested mixtures of various herbicides and included pre- and post-emergent triasul- furon treatments. All mixtures of either 2,4-D amine, dicamba, MCPA and bromoxynil provided good control of AngelA and HeraldA in-crop ranging from 73 to 92 per cent control, though the diuron/MCPA mixture was less effective (38 to 43 per cent). The pre- and post-emergent triasulfuron achieved control of HeraldA (63 to 80 per cent respectively), but was less effective on AngelA (16 to 32 per cent). We also tested the effectiveness of metribuzin and cyanazine for control of AngelA and HeraldA in field peas with both herbicides proving equally effective upon both cultivars (71 to 75 per cent control). The results from the trial show that AngelA can be effectively controlled to an acceptable level in-crop by a range of commonly used chemicals. These control options include both non-SU and post-emergent SU herbicide applications (excluding triasulfuron). For the first time, growers have a viable pasture legume alternative that can increase productivity through increased dry matter production and nitrogen fixation in the presence of SU residues, which can also be controlled with commonly used in-crop herbicides. AngelA was licensed to Seedmark in 2005. Seedmark plans to sow up to 300 hectares in 2006, targeting an estimated 100 tonnes for commercial sale in 2007. Jake Howie is a senior research officer with the SARDI Pastures Group, SA, and Craig Bell is now an agronomist with PIRSA Rural Solutions, SA. GRDC research code DAS00003 More information: Jake Howie, 08 8303 9407, email@example.com WIRRULLA SUMMER WEED TRIAL (LSD 182) 0 200 400 600 800 1000 1200 0 Rate % Angel Herald 100 50 A A FIGURE 1 Effect of SU herbicide applied at 0, 50 and 100% rate upon AngelA and HeraldA dry matter production at Wirrulla (visual score 0-10). FIGURE 2 Effect of SU herbicide applied at 0, 50 and 100% rate upon AngelA and HeraldA dry matter production at Wirrulla (kg/ha).
GC Supplement - Growers sharing knowledge
GC Supplement - Subsoil constraints