Is Tramlining Weed Seed at Harvest the Silver Bullet to Managing Weeds?
The simple answer is No - it is simply 1 of the tools available to you to manage weeds.
Harvest weed seed management is the last opportunity you have in the season to influence the weed seed bank for the following years crop. It is critical that you take the opportunity to minimise the return of weed seed to the seed bank. Harvest weed seed management won’t cure all troubles if you haven’t managed weeds effectively during the growing season, however forms an important link in the integrated weed management (IWM) chain.
The number 1 aim for any harvest weed seed management option is to get 100% of the weed seed into the harvester. Once weed seeds are captured by the harvester you can control where they go. As soon as you drop away from 100% collection of weed seeds the efficiency of weed seed management drops. Any losses (at the cutting knife) that occur before the seed is captured in the machine will reduce effectiveness of harvest weed seed management.
Ryegrass is probably the most problematic weed to deal with at harvest. Ryegrass has the greatest ability to adapt to changing selection pressures due to its diverse genetic background. For example, by delaying harvest and allowing some ryegrass seed to shed, you are selecting for early shedding biotypes and the process has commenced. These survivors, early shedding types, will cross pollinate the following season and produce progeny that are likely to be very early/early shedding types that make them more difficult to collect at harvest. This process will be repeated in subsequent years and you have a population of early shedding ryegrass that can’t be collected with the harvester. The same for height of harvest, if you increase your harvesting height and miss the low seed heads you are applying a selection pressure for lower seed head or prostate plant structure. The best solution here is to harvest your ryegrass paddocks first, as low as possible, with minimal losses as this maximises benefits of harvest weed seed management.
Having collected the weed seed – what are the best options to manage them?
In my opinion the best option is the Harrington Seed destructor or the Seed Terminator where the seed and chaff are dealt with during harvest operation and distributed back over the area they were collected from. Greater than 97% of the weed seeds are destroyed in the mill. Nothing else left to do – job done. The downside of these pieces of equipment include the capital cost, maintenance costs, extra horsepower required to drive them to list some, but the job is done and done efficiently.
Photo 1. Seed Terminator fitted to a Case IH harvester
Cheaper options for managing the weeds seeds include tramlining and chaff lining. Both strategies work on similar principle of collecting the chaff and weed seeds off the sieves and placing them on the ground in a controlled manner and limit the spread of the seeds to narrow strips behind the harvester. The percentage of weed seeds controlled by tramlining or chaff lines can be variable depending on a number of different factors which vary from site to site, so it is not possible to give an estimate of weeds controlled. Both these methods do have a positive effect on weed reduction.
Tramlining is where the chaff and seeds are placed on one or both permanent traffic tramlines by means of conveyor belts. The chaff lines are left to rot down and minimise the germination of weeds in that rotting mulch. The weeds that do germinate and establish can be controlled with specific management strategies, ie herbicides can be applied, or they are simply left there, and the seed will be harvested and placed back on the same tram line. The capital cost of tram lining is approximately $20k, they are low maintenance, require low horsepower and the job is done at harvest, no follow up work required.
Photo 2. Tramlining conveyors fitted to a JD harvester
Chaff lining is where the chaff and weed seeds are collected and dropped in a single row behind the harvester and the seed is left to rot in the mulch. These chaff lines will be disturbed at the following seeding and viable weed seeds may geminate in these rows. This system generally fits where controlled traffic has not been implemented. The costs associated with chaff lining is very low, chutes can be manufactured for less the $1k, no horsepower is required to run them, and maintenance cost are minimal.
Photo 3. Chaff lining showing how simple the chaff lining chute can be
The final options for harvest weed seed management is windrow burning and chaff carts. I personally don’t think windrow burning is practical in the High Rainfall Zone due to weather conditions not being conducive to achieving thorough and effective burn of all weed seeds in the windrow. Also burning the windrows is another job that has to be done and can be very frustrating when weather conditions are not favourable windrows don’t burn causing complications for the seeding operation and leaving a legacy of weeds to be dealt with over a number of years.
Selectively burning canola windrows is one way to utilise windrow burning efficiently. Canola rows burn very hot, they are easier to manage and control, the downside is that it is only 1 phase of the rotation.
Chaff carts have their advantages in mixed enterprise farming operations as they effectively produce fodder stacks that the stock can utilise. The remnants of the chaff stacks still need to be burnt before seeding to manage weed seed.
Chaff carts have a significant capital cost, they can be problematic to manage during harvest, but the pros and cons need to be weighed up before deciding whether they are for you or not.
Photo 4. Chaff cart ready for action
For further reading on Harvest weed seed management follow this link to the Weed Smart web site
https://weedsmart.org.au/the-big-6/harvest-weed-seed-control-holy-grail/
Each system has advantages and disadvantages, costs structure vary widely between the systems. Please don’t hesitate to contact your friendly Western Ag Agronomist to discuss the pros and cons of each system and which could potentially fit your operation best.
Article produced by - Andrew Heinrich, Western AG Naracoorte