Objectives
To evaluate agronomic methods of improving the trash clearance when flax residue has been chopped and returned to the field.
To measure soil moisture and temperature under heavy harrow, low and high disturbance systems.
To measure the decomposition of flax residue as affected by nitrogen and tillage management in the flax crop year.
Project Description
Preharvest glyphosate application did not improve our ability to chop the straw in either year. Application of glyphosate to standing flax in the previous fall resulted in intact flax stems being pressed to the soil surface by the sprayer wheels. These stems were the major source of flax residue being caught on the openers in the spring of 2002. When glyphosate is applied after the flax crop has reached maturity, when application of preharvest glyphosate is recommended, there is limited time for the product to work, and the moisture content of the straw is low. In addition, the standing material dries more quickly, limiting microbial action. Thus, glyphosate application should be used to control weeds and eliminate green straw but should not be expected to improve chopping to a greater extent than swathing.
Removal of the straw resulted in the most appealing looking field after seeding. However, the bunches of straw that did occur were small and did not contain soil. It should be noted that the flax straw was dry at seeding in both season and it is likely that seeding would have been more difficult in moist conditions. Likewise, it has been observed that vertical opener shanks clear residue more easily than the “C shanks” used on most air seeders. Most air seeders have wheels inside the frame and these wheels are where plugging is most common. Spring chopping, just prior to seeding, spread the residues above the surface and improved trash clearance slightly.
We were able to seed into flax stubble without any straw being caught on the openers in any treatment in 2001. In 2002, the amount of flax residue which was caught on the openers ranged from a low of 23 kg/ha to 113 kg/ha and in no case did the openers plug. This was because plant populations were identical in all treatments in both years. In 2001, there were significant differences in wheat yield due to the interaction of seeding direction, straw management and herbicide application but since there were no differences in plant population, it is probable that this was chance.
If producers are going to chop flax rather than remove it by burning or baling the following principles should improve success: 10 do not attempt if the crop has been lodged since this crop will have to be cut very short, 2) direct seed under dry conditions, 3) use a vertical opener shank and 4) use an aggressive chopper at harvest.
A field study was established in 2000, near Brandon Manitoba, to determine the effect of tillage on soil moisture and temperature, and to determine the potential for management of flax residue through fertility management. Decomposition and retting of flax straw were not affected by seeding rate or nitrogen fertility of the crop from which the residue was obtained. The diameter of flax stems and nitrogen content was significantly higher in flax fertilized at 113% compared to 0% of soil test nitrogen recommendations. Future rese4arch should focus on rates of nitrogen fertility in excess of 0% to 166% of soil test recommendations for nitrogen and seeding rates in excess of 67 kg/ha.
